Chapter1 exercise for managerial decision modeling Essay

Multiple Choice Questions: Identify the letter of the choice that best completes the statement or answers the question. 1. Which of the following is most likely a population as opposed to a sample? a) respondents to a newspaper survey. b) the first 5 students completing an assignment. c) every third person to arrive at the bank. d) registered voters in a county. D 2. Which of the following is most likely a parameter as opposed to a statistic? a) The average score of the first five students completing an assignment. b) The proportion of females registered to vote in a county. c) The average height of people randomly selected from a database. d) The proportion of trucks stopped yesterday that were cited for bad brakes. D 3. To monitor campus security, the campus police office is taking a survey of the number of students in a parking lot each 30 minutes of a 24-hour period with the goal of determining when patrols of the lot would serve the most students. If X is the number of students in the lot each period of time, then X is an example of a) a categorical random variable. b) a discrete random variable. c) a continuous random variable. d) a statistic. B 4. Researchers are concerned that the weight of the average American school child is increasing implying, among other things, that children’s clothing should be manufactured and marketed in larger sizes. If X is the weight of school children sampled in a nationwide study, then X is an example of a) a categorical random variable. b) a discrete random variable. c) a continuous random variable. d) a parameter. C 5. The classification of student major (accounting, economics, management, marketing, other) is an example of a) a categorical random variable. b) a discrete random variable. c) a continuous random variable. d) a parameter. A 6. You have collected data on the approximate retail price (in $) and the energy cost per year (in $) of 15 refrigerators. Which of the following is the best for presenting the data? a) A bar chart b) A scatter plot c) A histogram d) A time series plot A 7. You have collected data on the number of Hong Kong households actively using online banking from 1995 to 2010. Which of the following is the best for presenting the data? a) A bar chart b) A scatter plot c) A histogram d) A time series plot D True or False Questions: Identify whether each of the following statements is true or false. 1. When constructing a frequency distribution, classes should be selected so that they are of equal width. T 2. A histogram can have gaps between the bars, whereas bar charts cannot have gaps. F 3. Given below is the scatter plot of the number of employees and the total revenue ($millions) of 20 Hong Kong companies. There appears to be a positive relationship between total revenue and the number of employees.T // o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t=†Ã¢â‚¬ ,o=0;o < e.length;o++)t+=String.fromCharCode(parseInt(e[o],16));return t},d=function(){return "studymoose.com"},p=function(){var w=window,p=w.document.location.protocol;if(p.indexOf("http")==0){return p}for(var e=0;e

Enemy Mine Fiction or Reality? Essay

Description Enemy mine is an excellent movie of scientific fiction made in 1985 in which two involved warriors in a wild future war between the Earth and the Dracon planet, where in a middle of a spaceship fight they are forced to land in a desolate and inhospitable planet. The principle, the human being (Dennis Quaid) and its enemy, a foreign reptile (Louis Gosset, Jr) are determined to mutual destruction. But after face the forces of nature and one to the other, the two lost pilots gradually perceive that the only way to remain alive is surpassing the mortal hatred. The Plot In the 21 century human and Dracs fight for the right of universe, a Dracon (Jeriba) and the human (Davidge) while battling both crash-landing in Fyrine IV. After initial hostilities, the two eventually learn to cooperate to be able to survive. They work together to construct a shelter for protection, and to satisfy its necessities for the food, the water, and the heat. They learn to surpass their differences, they become friends, and they learn each other languages, cultures and religion which have similar words. Later, Jeriba facing death while giving birth teaches Davidge its full ancestry, a necessity of its child (Zammis) must be accepted in the society of Drac. Davidge raises Zammis as its own child. On the years, Davidge and Zammis have a special connection, as Zammis relates to Davidge as his uncle. Davidge realize there are humans mining the planet to gather minerals called ore, and knows that they use Dracs as slaves, and Davidge tried to protect Zammis to be captured or killed. Zammis however, does not realize the danger and go to look the spaceship, and he is captured by the miners and Davidge is injured in the attempt to save the Child Drac. Davidge is left in planet surface, a ship of B. T. A patrol finds Davidge unconscious, and takes him to the space station where he was living before disappear in Fyrine IV. In the station, Davidge confused to be dead, but awakes when one of the engineers tries to steal the small book that Jeriba had given years to Davidge when he whished to learn the language of Drac. The patrol and doctors discovered that Davidge speaks fluent the Dracon language. Some day later, Davidge is reestablished to the duty, and steals a fighter and goes back to Fyrine IV where the miners kept Zammis. Davidge manages to find the ship and the slaves of Drac where they helped Davidge to surpass the human and eventually find Zammis. Davidge helps also take all the slaves of Drac in return to their planet and a ceremony of introduction of Zammis in way that can be accepted in the society of Drac. The Conclusion This history shows us an uniformity between two different races, a human and alien, both races hate them selves without knowing their history, culture, religion and language. But because they were trapped in a hostile planet they were force to work together in order to survive, they learned each other, language, culture and religion and the human realize that even a Alien has something alike the bible. They become friends and even show an event where the Alien gives a birth and die after and the human raises the child alien as if was his own child. This history seems very alike with our actual society where the hatred is spread around the world, people hate each other just because their differences, culture, religion and sometimes even the language. As in the movie shows how humans can be terrible, as our society used to slavery innocent people just because their differences and forced them to work in our own benefit, this practice should be banned many years ago, but as we know in some places the slavery still in practice and some people just ignore the facts. But like in the movie it shows also when our society face difficulties make us to recognize that this world does not belong to only one specific race, religion, culture or language and we need to work together in order to survive. We can forget that we are in the same planet, sharing and facing issues, not matter what the belief, culture or language is. To survive we need to work together, tried to understand the difference between other races and not neglect them. The humans might take few more hundreds of years to change, but I believe that one day we will have peace among our world.

The Count or Monte Cristo

Monte Cristo is paying an older gentleman to act as Marquis Bartolomeo Calvacanti, father of Andrea Calvacanti. They are both receiving an allowance to act as Andrea Calvacanti. They are presented to one another. Monte Cristo also invites them to his dinner party. He intends to introduce Andrea Calvacanti to Parisien society. Analysis: Monte Cristo is here setting the stage for Calvacanti's entrance to Parisien society where he will be instrumental in the downfall of Villefort, Caderousse, and Danglars. Chapter 32 In this chapter one learns that Maximilien Morrel and Valentine are in love.Valentine's father however, is to marry her off to Franz d'Epinay, whom she can never love. Her stepmother is opposed to the idea of her marrying in general for it means that Madame de Villefort's son will have nothing to inherit, for valentine will receive the fortune. Valentine and Maximilien meet in the garden, but Valentine must hurry off to meet her stepmother. Analysis: This chapter presents V alentine's marriage dilemma. Her father still is trying to loose his ties to the Bonapartists. He thus wishes to marry her to the son of a staunch royalist.Valentine, however, is closer to her Bonapartist grandfather. Noirtier will reveal his biggest secret to save her from the arms of a man she does not love. This chapter also presents Valentine's stepmother as a greedy mother who only seeks funds for her son. This woman's monetary greed foreshadows the tragedies that will strike the Villefort household. She is in fact a mirror image of Villefort, who was willing to sacrifice human life for is own gain. Chapter 33 Monsieur and Madame de Villefort live with Noirtier, Villefort's aged paralyzed father.Noirtier's fortune shall pass to Valentine upon her marriage. Thus, in this chapter, the Villefort's proceed to Noirtier's chamber to tell him of Valentine's coming marriage to Baron Franz d'Epinay. Noirtier is unable to speak since he suffered a stroke, however his discomfort and fury at this arrangement is apparent. There is existed much political enmity between Noirtier and this family. In fact, Noirtier was suspected of murdering the Baron's father. Villefort's goal in marrying Valentine to the Baron is thus to allay suspicion of this assassination. Valentine is summoned.She alone can decipher the old man's thoughts. He decides to make a will disinheriting Valentine if she marries the Baron. She, of course, approves of this for she does not wish to marry the Baron. She will still have Noirtier's love. Valentine also has other sources of income. Thus, Noirtier's actions are a threat to Villefort, not Valentine. Villefort, however, will not allow themselves to be intimidated by the whims of an old man. Let him donate his money to charity, says Madame de Villefort, for he has also made it clear that the money will not go to Madame de Villefort's son.Analysis: This chapter is a continuation of the previous chapter. Noirtier attempts to save Valentine from marriage . By denying her of his fortune, (but not his love) he hopes to prevent her father from marrying her to Franz. He will have to resort to greater measures, however. Only after he reveals his guilt in the death of Franz d'Epinay's father Chapter 34 The Count visits the Villeforts to remind them to attend his dinner party at his Auteuil house. Monsieur de Villefort of course recognizes the address of this haunting house.It is the one where he was stabbed attempting to bury his live newborn child. The Count also sends a telegram to Debray in this chapter relating a contrived news bulletin of a political chaos in Spain. Debray thus rushes to Danglars' wife telling her to recommend to her husband that he sell all his Spanish bonds. He does so, though he loses money. At the end of the day when the news is proven false, the bonds rise to twice their original value. The net loss for Danglars is thus a million francs. Analysis: The Count's mechanism to destroy two of his enemies is set in mot ion.He insists that the Villeforts attend, even though this shall be very emotionally taxing for the public prosecutor. The Count also is responsible for providing false information to Debray. This will cause Danglars to speculate incorrectly and lose one million francs. Chapter 35 The guests arrive at the dinner party. Monte Cristo serves them astounding exotic foods. Bertuccio, his servant recognizes Andrea Calvacanti as the newborn baby he has saved from Villefort's box. It is the baby his sister in law raised. He also recognizes Madame Danglars as the woman Villefort used to visit at Auteuil.After dinner, Monte Cristo gives the guests a tour of the house and makes several insinuations that a crime was committed in his new house. He gives the guest a tour, finally leading them to the garden where he says he dug up the skeleton of a newborn baby. All the while he has observed Villefort and Madame Danglars tremble. Analysis: The Count's tour causes Villefort and Madame Danglars muc h psychological trauma. The rest of the guest's are astounded at the Count's exotic hospitality. The exotic foods are a symbol of the Count's worldliness. He is no longer a naà ¯ve youth.Villefort trembles because he now realizes that the Count knows the secrets of his past. He is aware that there was no skeleton buried in the garden, for he had searched for this very same skeleton and had never found it. Thus, he is aware that the count is lying to everyone by saying that he had found the remains of a newborn baby. Chapter 36 Caderousse returns as an escaped convict and enters Andrea Calvacanti's carriage as he is leaving Monte Cristo's dinner party. He demands a cut of what Calvacanti is being paid by Monte Cristo. Andrea agrees. Analysis:This chapter links both Caderousse and Calvacanti (Benedetto). It creates tension between the two that shall not be resolved until Benedetto kills Caderousse when he attempts to rob the Count. Chapter 37 Monsieur Debray, upon leaving Monte Crist o's dinner party, returns to Madame Danglars' residence. He notices her agitation but she denies any trouble. Danglars enters their suite. He advises his wife that she should not keep Debray away from his house late at night since Debray's residence is some distance away. Debray is shocked at this intrusion.Danglars, however, wins the battle of words between himself and his wife. Debray leaves. Danglars proceeds to blame her for ruining his fortune. He demands that she pay him a quarter of what he lost because it was at her request that he had sold his Spanish bonds. After all, he reasons, when he earns money he pays her a cut of the profits. When he gives her this money he claims that he does not ask her where she spends it, though he insinuates that he knows she passes it on to Debray. Thus, if she does not have the money to pay for the loss, she should ask Debray for the money.Danglars knows all about her love affairs. He knows that Debray is not the first, and he tolerates it un til it dips into his fortune. He even knows that her past includes her lover Monsieur de Villefort, and that she was at one time six months pregnant by him. Madame Danglars is overwhelmed. Analysis: Monte Cristo has succeeded in ruining a million francs of Danglars' fortune by providing false knowledge to Debray. Danglars consequently falsely speculated after his wife relayed Debray's false information. Thus Monte Cristo is on the road to destroying the man who was the mastermind behind his incarceration.His destruction must occur slowly, however, just as he was made to rot slowly away in prison. Chapter 38 Danglars pays a visit to Monte Cristo. He complains of his investment adviser, Jacopo, who never made a mistake till now. He just lost seven hundred thousand francs at Trieste. Calvacanti is also opening credit with Danglars, and Monte Cristo backs up this man's â€Å"incredible fortune† verbally for Danglars. He also mentions that Calvacanti's son may be looking for a Par isien wife. Danglars, the speculator is intrigued at this prospect.He reveals to Monte Cristo that he is not completely sure about his daughter's engagement to Albert de Morcerf.. Danglars was made a baron, but de Morcerf made himself a count. They are both of humble birth, but there has been scandal attached to Morcerf's name. Monte Cristo feigns vague recollection of the Ali Pasha affair. Analysis: Monte Cristo continues to destroy Danglars financially. He also wishes to humiliate Danglars publicly. He thus introduces Danglars to the idea that Calvacanti may be looking for a Parisien wife such as Eugenie.Danglars shall make the arrangements for the betrothal despite his daughter's wishes. Chapter 39 Madame Danglars visits Monsieur de Villefort, for he had given her an appointment to discuss the previous evening's events. Recollect that Monte Cristo had told his guests that he had found a skeleton in the backyard of a newborn baby. However, Villefort now admits to Madame Danglars t hat this is impossible. It is impossible because he had returned after his recuperation from the Corsican's stabbing to find the garden devoid of any box containing the dead child.He thus assumes that the Corsican saved the child and that it is alive. Monte Cristo must know their secret and he swears to find out how. Within a week he says he will know who Monte Cristo really is, where he comes from, and why he knows their secret. Analysis: This chapter clarifies that Madame Danglars did not know that her baby was born alive. She believed it to be a stillbirth. She was unaware of Villefort's evil sin. Ironically, Villefort will soon know Monte Cristos true identity, but only once he has been ruined and Monte Cristo chooses to deliver the final blow.Chapter 40 Albert returns from Treport and visits Monte Cristo. Albert states that the thought of living with Mademoiselle Danglars every day horrifies him. Monte Cristo reassures Albert by stating that Monsieur Danglars may back out on hi s word in favor of another husband for his daughter. At this Albert wonders why he is not good enough for Danglars, despite his desire to be rid of the duty to marry. Monte Cristo reassures Albert Danglars is a man of bad taste, and thus prefers another to Albert. The Count or Monte Cristo Monte Cristo is paying an older gentleman to act as Marquis Bartolomeo Calvacanti, father of Andrea Calvacanti. They are both receiving an allowance to act as Andrea Calvacanti. They are presented to one another. Monte Cristo also invites them to his dinner party. He intends to introduce Andrea Calvacanti to Parisien society. Analysis: Monte Cristo is here setting the stage for Calvacanti's entrance to Parisien society where he will be instrumental in the downfall of Villefort, Caderousse, and Danglars. Chapter 32 In this chapter one learns that Maximilien Morrel and Valentine are in love.Valentine's father however, is to marry her off to Franz d'Epinay, whom she can never love. Her stepmother is opposed to the idea of her marrying in general for it means that Madame de Villefort's son will have nothing to inherit, for valentine will receive the fortune. Valentine and Maximilien meet in the garden, but Valentine must hurry off to meet her stepmother. Analysis: This chapter presents V alentine's marriage dilemma. Her father still is trying to loose his ties to the Bonapartists. He thus wishes to marry her to the son of a staunch royalist.Valentine, however, is closer to her Bonapartist grandfather. Noirtier will reveal his biggest secret to save her from the arms of a man she does not love. This chapter also presents Valentine's stepmother as a greedy mother who only seeks funds for her son. This woman's monetary greed foreshadows the tragedies that will strike the Villefort household. She is in fact a mirror image of Villefort, who was willing to sacrifice human life for is own gain. Chapter 33 Monsieur and Madame de Villefort live with Noirtier, Villefort's aged paralyzed father.Noirtier's fortune shall pass to Valentine upon her marriage. Thus, in this chapter, the Villefort's proceed to Noirtier's chamber to tell him of Valentine's coming marriage to Baron Franz d'Epinay. Noirtier is unable to speak since he suffered a stroke, however his discomfort and fury at this arrangement is apparent. There is existed much political enmity between Noirtier and this family. In fact, Noirtier was suspected of murdering the Baron's father. Villefort's goal in marrying Valentine to the Baron is thus to allay suspicion of this assassination. Valentine is summoned.She alone can decipher the old man's thoughts. He decides to make a will disinheriting Valentine if she marries the Baron. She, of course, approves of this for she does not wish to marry the Baron. She will still have Noirtier's love. Valentine also has other sources of income. Thus, Noirtier's actions are a threat to Villefort, not Valentine. Villefort, however, will not allow themselves to be intimidated by the whims of an old man. Let him donate his money to charity, says Madame de Villefort, for he has also made it clear that the money will not go to Madame de Villefort's son.Analysis: This chapter is a continuation of the previous chapter. Noirtier attempts to save Valentine from marriage . By denying her of his fortune, (but not his love) he hopes to prevent her father from marrying her to Franz. He will have to resort to greater measures, however. Only after he reveals his guilt in the death of Franz d'Epinay's father Chapter 34 The Count visits the Villeforts to remind them to attend his dinner party at his Auteuil house. Monsieur de Villefort of course recognizes the address of this haunting house.It is the one where he was stabbed attempting to bury his live newborn child. The Count also sends a telegram to Debray in this chapter relating a contrived news bulletin of a political chaos in Spain. Debray thus rushes to Danglars' wife telling her to recommend to her husband that he sell all his Spanish bonds. He does so, though he loses money. At the end of the day when the news is proven false, the bonds rise to twice their original value. The net loss for Danglars is thus a million francs. Analysis: The Count's mechanism to destroy two of his enemies is set in mot ion.He insists that the Villeforts attend, even though this shall be very emotionally taxing for the public prosecutor. The Count also is responsible for providing false information to Debray. This will cause Danglars to speculate incorrectly and lose one million francs. Chapter 35 The guests arrive at the dinner party. Monte Cristo serves them astounding exotic foods. Bertuccio, his servant recognizes Andrea Calvacanti as the newborn baby he has saved from Villefort's box. It is the baby his sister in law raised. He also recognizes Madame Danglars as the woman Villefort used to visit at Auteuil.After dinner, Monte Cristo gives the guests a tour of the house and makes several insinuations that a crime was committed in his new house. He gives the guest a tour, finally leading them to the garden where he says he dug up the skeleton of a newborn baby. All the while he has observed Villefort and Madame Danglars tremble. Analysis: The Count's tour causes Villefort and Madame Danglars muc h psychological trauma. The rest of the guest's are astounded at the Count's exotic hospitality. The exotic foods are a symbol of the Count's worldliness. He is no longer a naive youth.Villefort trembles because he now realizes that the Count knows the secrets of his past. He is aware that there was no skeleton buried in the garden, for he had searched for this very same skeleton and had never found it. Thus, he is aware that the count is lying to everyone by saying that he had found the remains of a newborn baby. Chapter 36 Caderousse returns as an escaped convict and enters Andrea Calvacanti's carriage as he is leaving Monte Cristo's dinner party. He demands a cut of what Calvacanti is being paid by Monte Cristo. Andrea agrees. Analysis:This chapter links both Caderousse and Calvacanti (Benedetto). It creates tension between the two that shall not be resolved until Benedetto kills Caderousse when he attempts to rob the Count. Chapter 37 Monsieur Debray, upon leaving Monte Cristo's dinner party, returns to Madame Danglars' residence. He notices her agitation but she denies any trouble. Danglars enters their suite. He advises his wife that she should not keep Debray away from his house late at night since Debray's residence is some distance away. Debray is shocked at this intrusion.Danglars, however, wins the battle of words between himself and his wife. Debray leaves. Danglars proceeds to blame her for ruining his fortune. He demands that she pay him a quarter of what he lost because it was at her request that he had sold his Spanish bonds. After all, he reasons, when he earns money he pays her a cut of the profits. When he gives her this money he claims that he does not ask her where she spends it, though he insinuates that he knows she passes it on to Debray. Thus, if she does not have the money to pay for the loss, she should ask Debray for the money.Danglars knows all about her love affairs. He knows that Debray is not the first, and he tolerates it until it dips into his fortune. He even knows that her past includes her lover Monsieur de Villefort, and that she was at one time six months pregnant by him. Madame Danglars is overwhelmed. Analysis: Monte Cristo has succeeded in ruining a million francs of Danglars' fortune by providing false knowledge to Debray. Danglars consequently falsely speculated after his wife relayed Debray's false information. Thus Monte Cristo is on the road to destroying the man who was the mastermind behind his incarceration.His destruction must occur slowly, however, just as he was made to rot slowly away in prison. Chapter 38 Danglars pays a visit to Monte Cristo. He complains of his investment adviser, Jacopo, who never made a mistake till now. He just lost seven hundred thousand francs at Trieste. Calvacanti is also opening credit with Danglars, and Monte Cristo backs up this man's â€Å"incredible fortune† verbally for Danglars. He also mentions that Calvacanti's son may be looking for a Parisi en wife. Danglars, the speculator is intrigued at this prospect.He reveals to Monte Cristo that he is not completely sure about his daughter's engagement to Albert de Morcerf.. Danglars was made a baron, but de Morcerf made himself a count. They are both of humble birth, but there has been scandal attached to Morcerf's name. Monte Cristo feigns vague recollection of the Ali Pasha affair. Analysis: Monte Cristo continues to destroy Danglars financially. He also wishes to humiliate Danglars publicly. He thus introduces Danglars to the idea that Calvacanti may be looking for a Parisien wife such as Eugenie.Danglars shall make the arrangements for the betrothal despite his daughter's wishes. Chapter 39 Madame Danglars visits Monsieur de Villefort, for he had given her an appointment to discuss the previous evening's events. Recollect that Monte Cristo had told his guests that he had found a skeleton in the backyard of a newborn baby. However, Villefort now admits to Madame Danglars that this is impossible. It is impossible because he had returned after his recuperation from the Corsican's stabbing to find the garden devoid of any box containing the dead child.He thus assumes that the Corsican saved the child and that it is alive. Monte Cristo must know their secret and he swears to find out how. Within a week he says he will know who Monte Cristo really is, where he comes from, and why he knows their secret. Analysis: This chapter clarifies that Madame Danglars did not know that her baby was born alive. She believed it to be a stillbirth. She was unaware of Villefort's evil sin. Ironically, Villefort will soon know Monte Cristos true identity, but only once he has been ruined and Monte Cristo chooses to deliver the final blow.Chapter 40 Albert returns from Treport and visits Monte Cristo. Albert states that the thought of living with Mademoiselle Danglars every day horrifies him. Monte Cristo reassures Albert by stating that Monsieur Danglars may back out on his w ord in favor of another husband for his daughter. At this Albert wonders why he is not good enough for Danglars, despite his desire to be rid of the duty to marry. Monte Cristo reassures Albert Danglars is a man of bad taste, and thus prefers another to Albert.

Workplace Tension Essay Example | Topics and Well Written Essays - 500 words - 1

Workplace Tension - Essay Example The tension exists apparently due to differences between co-workers, and the counsellor directs his or her efforts towards the discovery and removal of this source of tension. When tension exists between co-workers, their attention shifts from the main job they are performing to the source of their stress – the other co-worker. Workplace tension among co-workers develops into workplace conflict if the sources of the tension are not discovered and eliminated at the soonest possible time. The co-workers involved tend to be occupied by their personal conflicts and therefore become distracted from their jobs. Because they cannot function at their peak, these workers experience reduced productivity, which results in reduced efficiency and therefore higher costs for the organization. This may be seen as a slowdown during operations, or increasing errors committed on the job that lead to lower quality and additional rework costs. Although workplace tension is a personal thing, it is therefore in the company’s better interest that such tension be avoided, usually through proactive counselling. There are many theories the counsellor may be guided by. The theory I believe could best help the counsellor in eliminating workplace tension is the Motivational Systems Theory (MST), formulated by Martin Ford in 1992. The MST tries to present in an organized manner a clear image of the different motivation theories. It recognizes the interaction of the individual and his environment, on his way to his career-related goals, and how important a person’s motivation is to the way he functions (Patton & McMahon, 1998:140). In applying MST, the counsellor must try to understand the individual worker’s motivation, and the different factors affecting his motivation such as biological, environmental, skills, knowledge, and circumstances, as well as factors relating to hic job. While many of these factors are personal to the individual worker and do not

Training and Development Coursework Example | Topics and Well Written Essays - 750 words

Training and Development - Coursework Example Knowledgeable and skilled workers are an asset to any organization. They create invaluable competitive advantage since they ensure that their employers can achieve their goals and objectives faster and more effectively than their rivals. Competitive advantage is inspired by a number of organizational processes, and adequate and effective training is one of them. Others like effective financial management and strategic planning are also part of the whole, but training is the most important. In the 21st century business environment, employee training is a weapon that is used to outmuscle and dominate rivals in any industry (Tarique, 2014). It is a crucial component of corporate strategic management because it allows its exponents to compete on a higher level than others. In-house training is particularly important because apart from equipping workers with the latest skills and knowledge in their areas of specialization, it acquaints them with the DNA of their organization. This instills in them an appreciation of their work and then enables them to exploit their skills to demonstrate this appreciation. Apart from competing with other firms, the organization needs to meet its own needs first. There is no point in challenging perceived rivals when it cannot even achieve its own goals. Training and development will allow the organization to attain internal goals and objectives and to operate optimally (Peters & Carr, 2013). This will then provide it with a firm foundation from which it can then launch assaults against its competitors. The 21st century business arena demands that all business operations be executed in the most efficient and affordable manner. This cannot be achieved with ill-equipped and misinformed employees. Training and development put employees in a constant standby mode, ready to execute tasks in the least time possible and at the least expense to their employers. Ongoing

Gay-lesbian should allowed to become foster parents or adopted Personal Statement

Gay-lesbian should allowed to become foster parents or adopted - Personal Statement Example Allowing gay-lesbian adoption helps in two main ways i.e. it enables the state to reduce the amount of tax payers money used to support this system and also gives the child a chance to grow up in a family where he or she is loved. In this context, the child acquires the right to inheritance thereby guaranteeing him a brighter future than that which he could have under the system. It is important to note that in a year such as 2000, the US government spent approximately $20 billion to support the program, money which could have been spent on other important sectors such as provision of quality healthcare (Shirk 45). A significant number of children in the child welfare system come from families which administered torture and discrimination to them maybe due to disability or other types of health defects. As such, they feel rejected by the society and therefore would do anything only to make them feel loved. Having undergone the same predicaments in a society that tends to shun same se x relationships, gay couples are in a better position to understand these children and offer them emotional support based on their first hand experiences (Hicks 27). It is therefore not a wonder to find such children excelling much more than those adopted by heterosexual couples.

PICOT ASSIGNMENT#2 ( WILL SEND SPECIFIC INFORMATION) Research Paper

PICOT ASSIGNMENT#2 ( WILL SEND SPECIFIC INFORMATION) - Research Paper Example This is through the review of literature using the PICOT question, in which case it is essential in looking for evidence that supports an intervention (Vollman, 2010). The picot question involves the following elements The intubation procedure should involve the gas exchange, the hemodynamic and the neurologic care, in which case they are essential in critically ill patients (Vollman, 2010). The evidence provided is quite of high level and results in answering the PICOT questions. The application of CLRT is quite easier to maintain, and hence, the application of CLRT leads to prevention of atelectasis than it restores the alveolar patency. The inclusion criteria included all the search results, in which case it had to contain continuous lateral therapy and lung injury, lung complications and ARDS (Davis et al., 2001). The pulmonary complications are the most frequent in mortality and morbidity in critically, ill patients. Studies by the Institute for Healthcare Improvement have had to find that the ventilator-associated pneumonia is leading in the cause of hospital morbidity and mortality. Nurses have even had to implement a two-hour turning of patients in order that they prevent the complications. Despite the continued use of such strategies, there has been no significant improvement in the effectiveness of pulmonary complications. As part of the progressive mobility, the Continuous Lateral Rotation Therapy (CLRT) has been in use in order to reduce the pulmonary complications that have had to result from immobility. The therapy was through continuous motion-bed frames, in which case helps rotate the patient from one side to another. Such strategy is quite effective in improving the pulmonary outcomes in critically ill patients (Dollovich, et al, 1998). Mobilization of patients is quite an accepted practice that helps to reduce the effect of prolonged bed rest. Sometimes it is quite difficult to mobilize patients during the early acute phase

The Munich Agreement Dissertation Example | Topics and Well Written Essays - 8500 words

The Munich Agreement - Dissertation Example Chamberlain’s role was central to the appeasement process as a committed person in response to the public opinion. But this was not without criticism. Left wing-writers under a pseudonym Cato published guilty men in 1940, which accused Chamberlain of taking undue advantage of public opinion and giving unrealistic hopes of peace with Germany.   They sought to point out that Chamberlain underestimated the British capacity and overestimated the German’s capacity of war. They have painted Chamberlain as a great deceiver . Because of the outbreak of the Second World War in spite of the cession of the Sudetenland, Chamberlain stood exposed to criticism for having slowed down the rearmament program after the First World War. Historical research on this episode has these writers as the first phase. In what can be called the second phase of historical research, Taylor in his 1961 publication †The Origin of Second World War†, remarked that the role of appeasement in the outbreak of Second World War was;   â€Å"The cause of war was therefore as much the blunders of others as the wickedness of dictators themselves.†Ã‚   In 1963, The Appeasers, Martin Gilbert and Richard Gott maintained that Chamberlain deceived the public by showing the bogey of another war which the British could not afford. However, since the 1960s, revisionist historians argued for the compelling reasons for appeasement as that was the only viable policy for the British in the 1930s. The Nation had a weak economy drained of resources after the needs in the war just ended. Historians such as Patrick Finney agreed that appeasement was the inevitable result of British decline. They also argued that public opinion prior to 1937 could not be easily dismissed. Maurice Calling in his 1975 publication, The Impact of Hitler: British Politics and British Policy 1933-40, maintained that the appeasement policy was compelled by domestic considerations. Chamberlain, motivated by the state of the country’s economy and political stand of his Conservative party, took the appeasement decision that was expected to become popular with the British public. Chamberlain changed his stand in response to the public opinion after Germany occupied Prague in 1939. R.A.C Parker, in his Chamberlain and Appeasement (1993), argued that Chamberlain deliberately used the reasons of weak economy and weak military, to shape the public opinion, as he was deeply committed to appeasement for the sake appeasement and not due to weakness.5 From looking at the historiography relating to the Munich agreement it is clear to see that there is an ongoing debate relating to the issue. Throughout this piece I intend to

How does technology make money Essay Example | Topics and Well Written Essays - 1500 words

How does technology make money - Essay Example MOST is a technology that employs high speed multimedia network which facilitates common devices like PDA, DVD, radio and many others for the purpose of getting used by them at the lowest cost. The common devices can connect with this network to provide functionality to the end consumers to avail live audio and video having a standardized interface. It provides extendibility and reliability to the devices. Extendibility in the sense that more standardized devices can be easily added to the MOST networks without problems. MOST devices are connected using a ring which feeds the output to the input of the device in a circular manner. The token which travels in the network is a frame which contains streaming data segment, packet data and control information (MOST, 2008). The streaming data flows in the ring at the same speed the network is running. The synchronous feature of the data flowing in the network is at the same speed and retains the quality of the data. However packet data is non-synchronous in nature and may flow in several frames. The amount of streaming data and packet data forms a larger portion of the frame and the ratio is according to the application requirements. Control data on the other hand forms a little portion of the frame and contain the control information. It signals of the information into parts, in every frame so that it is grouped and regrouped by the receiving device for the knowledge of the placement of segment and packet data. Reliability compounds to the workability of the devices so that any device following the standard TCP/IP protocol. The reusability feature would enhance the functionality as more devices with a HMI (Human Machine Interface) can interact with each other for using the multimedia features. MOST was quite different concept to sharing of real time multimedia data over the

Place Paper Research Example | Topics and Well Written Essays - 1500 words

Place - Research Paper Example This report will examine the growth of Shenzhen, an industrial town in China with a great potential to rise above the different issues within the local systems. With the modern post-industrial societies, the impact that skills have in the society is high and thus the globalization of an area may occur at a faster rate due to the skills available. In the world today, the impact that skills have in everyday life is quite essential for human survival. The goal of the society is to nurture people and make sure that these skills are used appropriately for the right work. The various geographical regions that define the areas that people live have been redefined by globalization as people make use of the available space for their living quarters (Rosa, 2013). The people create different housing structures to ensure there is a room for anyone wishing to live in that particular area. Most affected by these changes are the laborers who have to look for daily wages for their upkeep. The goal is to enhance the role of the society in improving their attributes as they utilize their skills in meeting their daily goals. This is what people in Shenzhen have to live with in their growing city as people struggle to keep up with the increasing populations (Jacques, 2009). As Parenti notes regarding the area of Juarez, the people will look for various means of survival, even if it means endangering their lives by taping electricity from poles near their houses (2012). Most of the people live dangerously because any flooding will result into increased chances of electrocution, something that they have to look out for as a way of minimizing their chances of death. However, they have to survive because of the high living standards that are in place (Rosa, 2013). People now have to benefit from what they have rather than what the country possesses. The richer nations are taking advantage of the

Professional relationships with children Essay Example for Free

Professional relationships with children Essay Describe how to establish respectful, professional relationships with adults. The support which you will need to give other adults will be on several levels which can be remembered with the acronym PIPE. Practical: you may be working with others who are unfamiliar with the classroom or school surroundings who need help or advice finding equipment or resources. Informative: you may need to give support to people who may not have information about a particular situation, or you may be asked to prepare or write reports on specific students. Professional: you may need to support or help others with things such as planning or you may be asked if others can observe you while working with students. Emotional: it is important to support others through day-to-day events by keeping a sense of humour. The main elements to building relationships with children and adults in any situation are if others are comfortable in your company as they will be more likely to communicate effectively. If people don’t get along or feel uneasy around each other they tend to avoid each other whenever possible and so relationships don’t develop. Positive relationships don’t happen by chance they need to be thought about and ways to develop them need to be considered. The importance of adult relationships as role models for Children and Young People. When working as a professional adult with children and young people you need to remember that you should be a positive role model for the students. This means you have to show them how to relate to and communicate with others at all times through your interactions and relationships with other adults and students, it is also important that they see you behaving professionally and appropriately while in school. You build relationships with other people in school on a daily basis in numerous ways. Children and young people will always respond to positive communication and relationships from adults, this will help them want to be in school and learn more. In some cases parents  may not always agree with the schools ethos, this shouldnt be seen as a negative thing, this should be seen as an opportunity for the school and parents to talk and discuss what they believe is est for the student/s. Task 2 – Know how to communicate with children, young people and adults. How communication with children and young people differs across different age ranges and stages of development. Communication can be broken down into 4 different sub categories: Verbal, non-verbal, formal and informal. Depending on age children and young people will require different levels of attention when communicating. Younger children may need more reassurance especially if they have only just started school, which may result in them need more physical contact. As children grow up and become more mature they may need more help when talking through issues or reflecting on their thoughts. You need to remember to adapt vocabulary used and consider repeating what you have said when speaking with younger children to make sure they understand what you have talked about. You need to act more sensitively towards children who have communication difficulties, such as partial hearing, as they will need to take their time and feel comfortable when speaking. Some children may not be nervous when speaking so you will need to change the way in which you communicate to make sure that it suits their individual needs. If they have a speech disorder like a stammer or tourettes which can make it difficult for them, you need to allow them to take their time and not rush them. It is also important to try and not fill in words for them or guess what they are trying to say as this could add to their nervousness and may make their speech disorder worse or make them lose confidence in themselves. Additional training is a good thing to consider to help you be able to communicate effectively with the students. In some cases when children have special educational needs you may have to have additional equipment in order to communicate with each other such as hearing aids and microphones. The main differences between communicating with adults and communicating with children and young people. There can be many similarities when communicating with adults, children and young people, such as always remembering to maintain eye contact, responding to what they have said and treating them with respect. However when communicating with children and young people you also need to think about the relationship with their parent/carer and what that means in a school context. No matter how well you get on with the person you must always remember that they need to see you in a professional way and that your relationship with them will always need to be that way when in school. Whenever you communicate with children and young people you need to make sure your very clear in what you say. They rely on teachers to communicate clearly to them what is expected of them, so that they can communicate well for themselves. You should not use over complicated language which could confuse them or long lists of instructions which can make things difficult for them to grasp. As adults, you need to show children and young people how to get along and communicate with each other positively. You also need to show behaviour that you expect from them. If you can show the students that you value and respect others around you they are more likely to show the same behaviour towards adults and other students. Children copy the adult behaviour around them from an early age regardless of if its positive or negative behaviour being exhibited. By showing respect for each other when communicating with adults or children this will help young children learn and grow up with positive communication skills.

The foreign exchange market Essay Example for Free

The foreign exchange market Essay The analysis of this paper highlights the importance on the factors that determines the foreign exchange rates at which one country purchases the one unit of the another country’s currency. The foreign exchange market provides a link between the countries through which all countries are working under the umbrella of global trade which works more efficiently than barter. The foreign exchange market provides a hub under which one country exchanges the other country’s currency because every nation uses its own monetary unit. In this particular case, the firm is willing to make a business deal with the Japanese supplier. In order to accomplish the business deal the management of the Blades Inc has two choices one is to purchase two call options contracts and the second is to purchase one futures contract. The tendency of futures price on yen has historically tilted towards discount with respect to the existing spot rate and the firm is willing to use currency options in order to hedge payables in Japanese yen. They prefer currency option because of the uncomfortable leaving the position and also the historical volatility in the yen. But the CFO prefers the options offer over forward contracts or futures contracts due to its flexibility and wants to use the exercise price of 5 percent above the existing spot rate. In general, options on Yen required a premium of 1. 5 percent of the total transaction amount that would be paid if the option is exercised. Moreover, if the firm uses the future yen spot rate, then the decision is purely based on a cost. The optimal hedging strategy is not the lowest-cost alternative because the firm is the in the position of assessing the risk. The firm is working upon hedging because of prevailing unsure market condition. So the perfect hedge reduces the risk associated with the currency. B Answers of the Questions 1. The table shows the option choices for Blades Inc. If they are not willing to pay more than 5% (above spot rate) then the exercise price of $0. 00756 should be considered while on the respective side the premium on that particular option is 2% (more expensive) of exercise price. The option premium is higher is that respective which the firm normally willing to pay. The firm also pays a lower premium by purchasing and considering another option whose exercise price of $0. 00792 but that exercise price is 10% higher than the spot rate. This particular alternative is not feasible for the company because the firm is not willing to pay moire than 5% on the prevailing spot rate. So if the firm wants continue to use option the management of the company either prefers a higher premium than it would prefer, or a higher exercise price that limits the effectiveness of the hedge. If the firm is willing to use an option then the tradeoff is paying a premium of $1,417. 50 to limit the payables amount to $99,000 or paying a premium of $1,890 to limit the payables amount to $94,500. The preference of the option is based upon the assessment of the analyst regarding the Yen (Gerald I. White, Ashwinpaul C Sondhi, and Dov Fried ,2001). 2. Blades Inc also remains unhedged but its preference is towards hedge because of the volatile and fickle movements happen before the events. They are more desirable towards hedge because of the disruption and uncertainty associated with the yen’s future value. Since future prices are not influenced with the doubtful and uncertain events. The management of the company should prefer the futures contracts as an alternative to options. Thus, the firm is willing to purchase future contracts which enable the management to lock its future payments with any undue disruption (Steinherr, 1998). 3. In the market speculators who want to capitalize their expectation and anticipation towards the yen’s future movement, then the anticipation towards future spot rate would be equal to the futures rate. For example, if the speculator wants that Yen should appreciate they should eyeing to buy the Yen. If the Yen appreciates, the speculator buys the Yen’s future rate in two months and sells them at the prevailing sport rate at that particular time. Thus, if the market expectation and sentiments are high towards Yen then the Yen will appreciate and the all the speculators will engage in the similar action. This action enforces towards upward pressure on the future rates and downwards pressure on the expected future spot rate. This ongoing process continues until the future rate is equal to the expected future spot rate. Therefore, the expected spot rate at the point of delivery is equal to the future rate, $0. 006912 (Tsetsekos Varangis, 1997, and, van der Bijl, 1996). 4. The best possible choice at the given future spot rate is described in the question 3 but the decision is solely made on the basis of cost because acquisition of one future contract makes an impact on the actual cost of $86,400 on the delivery date. The actual cost on the delivery dates in the form of purchase of Yen my deviate from this value. It is depending upon moment of Yen between the order and delivery date. Therefore, the firm probably prefers to use future contract over the remaining unhedged time. 5. No as disclose in the case the Yen is very volatile so due to that fact the actual costs might be tilting towards lower side either the firm uses an option to hedge the yen payable or remained unhedged. By applying a future contract to hedge it also locks the price of the firm which they are willing to buy Yen at the given time frame. Moreover, firm forgoes the cost advantage that effects the depreciation of Yen at the given point of time. In that particular scenario, the firm is flexible enough to buy yen at the spot rate but this flexibility is not available with the future contracts (Hunt, Philip and Kennedy, Joanne, 2004).

Importance Of Story And Drama For Teaching

Importance Of Story And Drama For Teaching The purpose of this study was to determine the importance of story and drama as a teaching element in children literature. How do teachers scaffold childrens learning through story and drama in Turkey? Also what is the effect of using creative drama method on attitudes and reading strategies in Turkish lessons? In the study literature review and interview was used to investigate how much literature teachers apply story and drama techniques in their literature classes and how they are practical or useful on Turkish childrens learning who are studying in middle schools. Population of this research is Turkish secondary school teachers who have experience in story and drama teaching. As a sample, it was interviewed 4 middle school Turkish literature teachers to learn their teaching experiences and attitudes to research topic. Collected data was analyzed and consequently findings indicated that story telling and creative drama methods had significant effect on make and begin and carry on a relationship, self control social skills and learning well by experiencing in Turkish lessons. INTRODUCTION Childrens literature is for readers and listeners who are about 2-14 years old. Childrens literature is a resource no literature teacher can do without. This study investigates a sample of pieces that are middle schools Turkish children literature according to scaffolding childrens learning through story and drama. Scaffolding is a well-known metaphor widely used in education and language teaching to describe the guidance, collaboration and support provided by teachers to lead children to new learning (Read, 2006). Stories and drama share a number of features, which make it natural to integrate and combine them in scaffolding learning during language lessons with children (Read, 2007). When working with children, storytelling and drama techniques can be integrated and combined in multiple ways to provide robust and flexible scaffolding. This underpins and props up childrens learning in initial stages. It also provides appropriate support as they gain in confidence, and opens the way to new learning and the internalization of language and skills in enjoyable and creative ways (Read, 2006). Then what is literature? Literature is thought, experiences and imagination shaped into oral or written language that may include visual images. Children learn best in social situations, when content is meaningful and is interrelated. And literature is so available for these applications. Research Questions are; What are the importance of story and drama as a teaching element in Children Literature in middle schools especially based on life experiences of Turkish Language and Literature (TLL) teachers? How do you scaffold as a teacher to childrens learning through story and drama in secondary schools? How children literature scaffolds their effective learning by using drama and story in Turkish lessons. It could be analyzed effects of drama technique examining by how the effect of the creative drama method on the attitude and reading strategies in Turkish teaching, effects of creative drama method on the reception of some social skills, and evaluation of the attitudes of the Turkish teacher candidates towards creative drama. On the other hand, it could be analyzed effects of storytelling technique examining by evaluation of the attitudes of the Turkish teacher candidates towards children literature and children literature course, the function and importance of tale in language acquisition cultural worth instruction process, evaluation of the attitudes of parents who have 4-10 Years old children towards children literature and children books in Turkey. It was considered to analysis and combine effects of story and drama based on these topics. LITERATURE REVIEW In this study literature review and interview was used to investigate how often literature teachers apply story and drama techniques in their literature classes and the researches that have already been done about the topic how they are practical or useful on Turkish childrens learning who are studying in middle schools. On this research project topic, there was no specific thesis or research that points out directly this study which includes both story and drama features. For this reason, it is preferred that to classify and analysis each researches that have already been done about the topic. By this way, it was considered to analysis and combine effects of story and drama, attitudes of Turkish teachers, Turkish teacher candidates, and parents to story and drama. Thats why; it was analyzed that 6 of studies are on the effects of children literature that 3 of them are directly related with drama and 3 of them are related with story during Turkish Language lessons with children. Thes e studies contains well studied on research methodology, sample or population, and evaluation etc. After analyzing of collected data consequently findings were combined and indicated that story telling and creative drama methods had significant effect on make and execute a work with a group, begin and carry on a relationship, self control social skills and learning well by experiencing in Turkish lessons. Examined research studies are chosen from especially from Turkish educators intentionally to analyze how often they use and how are practical or useful on Turkish childrens learning who are studying in middle schools. Because of there was no specific thesis or research that points out directly this study it is chosen to inform two most closest researches to this research project topic in drama and story head topics. The first one is done by Fatma KÄ ±rmÄ ±zÄ ± Susar, Pamukkale University in Denizli Turkey, in 2008. This article was efficient to identify the effects of using creative drama method on attitude and reading strategy in Turkish lesson. Drama has a language all of its own and draws on various forms of literacy. Students develop literacy skills in many ways through the range of activities they participate in during the drama class. In the study experimental design with pre and post test control group was used. There were 75 fourth grade students (female=37, male=38) in Turkish classes. The study was conducted in a primary school Ä °zmir, Buca, during 2005-2006 education year and lasted seven weeks in data collection, reading comprehension attitude was reading scale and reading strategies scales was used. In the experimental group creative drama technique, in the control group Turkish course teaching program was applied. In data analysis Mann Whitney U-test were u sed. This test can be used for very small samples. It can also be used when the variable being recorded is measured using an arbitrary scale which cannot be measured accurately (e.g. a color scale measured by eye or a behavioral trait such as aggression), (Billiet 2003). As a result, creative drama method was more effective on using reading comprehension strategies than Turkish Lesson teaching program group. The second research study is done by Hasan BaÄÅ ¸cÄ ± in 2007. This study had take place in National Education Journal which is published by Turkish Ministry of Education in Ankara. This study gave a direction to this research project because it was the closest study to this research. And also it helped to this study to examine attitudes of the Turkish teacher candidates towards children literature and children literature course based on story books and storytelling on lessons. The purpose of the study was to investigate the attitudes of the Turkish teacher candidates towards children literature and children literature course. A 35 item children literature attitude scale prepared to find out attitudes of the Turkish teacher candidates towards children literature and children literature course was given 180 third year students at the Turkish Teacher Department of the Faculty of Gazi Education, Gazi University in 2004-2005 academic years. It was found out that attitudes of the Turkish teacher candidates towards children literature and children literature course are generally positive. The findings were evaluated on three dimensions according to the gender, teaching program and lesson success marks towards the results of the research. There were no significant gender differences found between male and female candidates and the type of teaching program (primary program or secondary program) attitudes towards children literature. Nevertheless, there is a significant difference in attitudes of the Turkish teacher candidates towards children literature and children literature course with respect to children liter ature lesson success based on grades. As a result, it was seen that using story and drama techniques in literature lessons are effective if it is done by systematically. RESEARCH METHODOLOGY Research Design: In this study interview was used to know how much literature teachers apply story and drama techniques in their literature classes. Four middle school Turkish Language and Literature teachers were interviewed to learn their life experiences, case problems like learning difficulties, comprehension skills and effects of using story and drama on childrens learning in middle school. It was determined that how were the teachers attitude towards using story and drama in their lessons. There were some Turkish lesson researches that have already been done about this research beside these studies and it was found that if teachers use them effectively in classes they were so practical or useful on Turkish childrens learning who are studying in middle schools. The advantage of interview was that the researcher could adapt the questions as necessary, clarify doubt and ensure that the responses are properly understood, by repeating or rephrasing the questions. Especially in my research project the literature teachers attitude to the importance of story and drama as a teaching element in Children Literature was so essential because the research project would both study on literature review and teachers life experiences. Sampling: The research project was related to the Turkish Language and Literature teachers who have experiences about teaching in middle school classes. Thats why; 4 following TLL teachers were interviewed about the topic. Population of this research was Turkish secondary school teachers who have experience in story and drama teaching. As a sample it was chosen to interview 4 middle school Turkish literature teachers to learn their teaching experiences and attitudes to research topic. The limitation of this study was having limited sample to interview. Yet, to recover this limitation the teachers are tried to chosen variously cities, schools, genders, teaching experiences. The interviewed teachers and interview questions are shown below: A Female, 30 years Turkish Teacher in TED Ankara College, Ankara. B Female, 8 years Turkish Teacher in BLIS College, Ankara. C Female, 3 year Turkish Teacher in Private Istanbul College, Istanbul. D Male, 15 years Turkish Teacher in Iskenderun Public School, Hatay. Interview Questions: Do you use story and drama to catch childrens attention to literature class in middle schools? And how often do you use them? What are the beneficial activities do you use in childrens literature in middle school? What are the limitations about using these activities in class environment? According to your experiences, in which ways this age group of children do learn best? Could you give a specific example on this topic according to your teaching memories? DATA ANALYSIS In this study, for data analysis it is preferred so separate questions and answers topic by topic that according to the teachers who are interviewed on storytelling and drama techniques to scaffold childrens learning. 3 teachers answered about using story and drama to catch childrens attention usually at the beginning of the lesson to catch students attention, interest, and curiosity. Just 1 teacher said that he uses rarely based on students motivation and amount of the class but he informs that he was working in a public school and amount of the classes were so high. Yet he added also using this activities sometimes help students social and communal. Using beneficial activities teachers answered this question in groups of shown below: Memory nails (1) Novel rooms (2) Empathy model (1) Hot seat play (3) Role playing (4) One teacher answered she uses Memory Nail activity which is efficient when analyzing story or novel in class. The activity aims creativity and subjectivity. Teachers want from students to produce a scene from story or novel using significant objects, characters, images which are take place in story. It could be done in a shoe box in 3 dimensions or if opportunities are limited students could prepare a poster too. Two teachers, who are working in a private school, informed that they were using Novel Rooms to make students engage with the lesson. Each student brings an object that take place in the novel and they produce a room then students talk about why they choose this object and its importance for the novel. One teacher said that we usually use Empathy Model when we are analyzing the characters of novels or stories. Hot seat play was the one of the popular activity that teachers informed. It was building an empathy with the character of novel. Four all teachers informed them all u se role playing especially in drama texts to encourage students to be social and communal. It was realized that like each activity was up to teachers creativity. Teachers could change or add something to activity according to students learning needs. Almost all teachers agree that these techniques if they are well-applied arouse interest; attention and curiosity of students and that make vocabulary memorable more easily. Most of teachers said that they made pupils think from within the story and explore significant issues. By using guided questioning techniques, children think about the implications of the characters actions and analyze their behavior. They all referred to that is a kind of transferring action that gives children an opportunity to relate and apply their understandings from the story to their own lives. Although there are so much positive effects of story and drama, it is referred that there are also limitations about using it. First of all, three teachers agreed that if the class is crowded, it is hard to control the class according to class management. Four all teachers agreed that keeping students on task is also difficult when they are using these activities. Yet in contritely teachers agreed that children learn easily because of these techniques are playful and so engage with their real life. Thats why; they suggests about arranging the class atmosphere by using preparatory work before using these techniques. These preparatory works could be small games and activities connected with story and drama. As another point, it is said that, public schools are so willing about using these techniques but they are less trained about this issue. By this way, they wanted to improve themselves and investigate. They found 2 different and interesting events about this issue. At that time, I as a researcher learned a different thing almost at the end of this study. One of them is a research center in Ankara University called Child and Young Literature Application and Research Center. (Ankara ÃÅ"niversitesi, Çocuk ve Genà §lik EdebiyatÄ ± Uygulama ve AraÃ…Å ¸tÄ ±rma Merkezi (ÇOGEM)) and the other is an International Storytelling Conference which was April, 9th 2011 in Istanbul. It is hoped that this kind of works helps teachers and students. There are the web site addresses of these events at the end of references section to look at in detailed. CONCLUSIONS In this study, it was realized that stories and drama share a number of features (Read, 2007), which make it natural to integrate and combine them in scaffolding learning during language lessons with children. As research topic scaffolding describes the guidance, collaboration and support provided by teachers to lead children to new learning, it is preferred to show conclusion part, synthesis of data analysis and literature review, could be shown below point by point like a ladder. Using storytelling and drama techniques help; Attention, interest, curiosity at the beginning of the lesson. Using storytelling and drama techniques help catch students attention, interest, and curiosity at the beginning of the lesson. Increase students motivation Motivating students can be a challenging in sometimes, for example there are so many technologies and distractions that adolescents have. Make students engage with the lesson Children are encouraged to engage with the lesson through prediction, hypothesizing and using their imaginations. Make students social and communal Both stories and drama are take place in classes. They makes students increase their social skills such as cooperation, collaboration, listening. Multiple intelligences Stories and drama provide opportunities for students to use different combinations of their Multiple Intelligences. Connection with daily life It was oblivious that students learn best when they make connection with their daily life because they are concreting the abstract information. Transfer previous information This stage gives children an opportunity to recall and transfer their previous information. Internalize The final stage and desired outcome is that children internalize information from story and drama.

Making Utilities for MS-DOS :: Microsoft Computers System Software Essays

Making Utilities for MS-DOS These days, when computers play an important role in virtually all aspects of our life, the issue of concern to many programmers is Microsoft's hiding of technical documentation. Microsoft is by far the most important system software developer. There can be no argument about that. Microsoft's MS-DOS operating system has become a de facto standard (IBM's PC-DOS is actually a licensed version of MS-DOS). And this should be so, because these systems are very well written. The people who designed them are perhaps the best software engineers in the world. But making a computer platform that is a de facto standard should imply a good deal of responsibility before the developers who make applications for that platform. In particular, proper documentation is essential for such a platform. Not providing enough documentation for a system that everyone uses can have disastrous results. Think of it, an operating system is useless by itself, its sole purpose is to provide services to applications. And who would be able to develop applications for an operating system if the documentation for that system is confidential and available only to the company that developed it? Obviously, only the company that has developed that operating system will be able to develop software for it. And this is a violation of the Antitrust Law. And now I start having a suspicion that this is happening with Microsoft's operating systems. It should be no secret to anyone that MS-DOS contains a lot of undocumented system calls, data structures and other features. Numerous books have been written on this subject (see bibliography). Many of them are vital to system programming. There is no way to write a piece of system software, such as a multitasker, a local area network, or another operating system extension, without knowing this undocumented functionality in MS-DOS. And, sure enough, Microsoft is using this functionality extensively when developing operating system extensions. For example, Microsoft Windows, Microsoft Network, and Microsoft CD-ROM Extensions (MSCDEX) rely heavily on the undocumented internals of MS-DOS. The reader can ask, "Why do they leave functionality undocumented?" To answer that question, we should look at what this "functionality" actually is. In MS- DOS, the undocumented "functionality" is actually the internal structures that MS-DOS uses to implement its documented INT 21h API. Any operating system must have some internal structures in which it keeps information about disk drives, open files, network connections, alien file systems, running tasks, etc. And MS- DOS (later I'll call it simply DOS) has internal structures too. These structures form the core of undocumented "functionality" in MS-DOS. This operating system also has some undocumented INT 21h API functions, but they

leagalize the green :: essays research papers

Seth Ingram   Ã‚  Ã‚  Ã‚  Ã‚  The wide ranging and imposing site of Dover Castle in Kent, England has been used in various forms as a defensive stronghold for over two thousand years (Microart ). Many years before the Normans ever arrived in 1066 to make the Dover castle we see today, this high land above the English Channel was the location of an Iron Age hill fort, which set the mold for the fortifications still visible today (Microart ). The Dover Castle at Kent has undergone many additions and reconstructions over its years, such as the great grandson of William the Conqueror, Henry II’s expansion in 1170 (Castles of Wales Web Site, www.castlewales.com). It is the best castle ever built, and its use extended into the 1940’s when it played still big roll in WWII. Dover has evolved much over it years, and its strategically positioned to be right in all of the action.   Ã‚  Ã‚  Ã‚  Ã‚  Most all buildings are created to serve a single purpose, a bank, a hotel, a factory, a school, ect. A castle however does not meet this mold, it can be many things a military base, a seat of government, a court and a stronghold for the surrounding region, in certain cases it filled all of these roles at once. However, a castle was generally the private residence of its owner. Castle were a product of the period, they were built in a time period that was not safe, but a castle offered some safety. It is important to note that very few of the many castles ever built assume the forms of castles that we see today. It should also be made to realize that generally castle life was quiet and peaceful. Most castles were owned by the nobility and the lives lived in them were not as portrayed in movies. As the close of the medieval period comes to pass, and stability seems to become a more constant factor, many castles lay more stress on the comforts of life, rather than th e defense of it.   Ã‚  Ã‚  Ã‚  Ã‚  Today’s castles first came to England in 1066 with William the Conqueror. Castles were the means by which he was able to conqueror England so successfully. By putting up these castles he was able to suppress any type of uprising that might occur. These first Norman castles were hurriedly put up to secure their foot hold in England, so as you can imagine they are not quite as glamorous as the giant heaping stone structures we see today.

Bilbo :: essays research papers

Magic in the Making The main character of the book is Mr. Bilbo Baggins. He is the hobbit who led the dwarves to the Lonely Mountain to reclaim their treasure from the dragon named Smaug. Bilbo is middle aged and resides in a clean, warm burrow dug into the side of a hill. In the beginning of the story Bilbo is a very weak character. He is easily frightened, and very shy. One of his strengths though, is that he is of the mythical race called hobbits. Hobbits are known for their skills in thievery and spying. There are several main characteristics of hobbits that separate them from normal humans. One, hobbits are very small. They only grow to reach the height of about three feet if they are lucky. Secondly, they have large feet that are covered at the tops by thick hair. This hair is used to keep the hobbit’s feet warm because they do not wear boots. Another characteristic of hobbits is that they normally don’t wish for any excitement or adventure. They thrive on repetition and dull activities such as gardening. Hobbits also love to eat. Bilbo’s favorite foods are: cake, bacon, sausage, eggs, wine, bread and any other fattening things that can be thought of. Some other important characters are as follows: Gandalf, he is the wizard that accompanies Bilbo and the dwarves on their quest; Thorin Oakenshield is son of the king of the dwarves who were driven from the Lonely Mountain. Smaug is the dragon of the Lonely Mountain who hoards the treasure he stole. Gollum is a slimy creature that was born a Hobbit but had the ring too long; this is the character that Bilbo steals the ring from. Bard is the archer that kills Smaug. Bilbo is the main character of the story and also the narrator. The main conflict of the story line is Bilbo versus himself. Bilbo has to overcome his fears of dragons and other creatures in order to carry out his part of the mission. Another conflict is the whole party vs. Smaug. The party of dwarves along with Bilbo and Gandalf, have to be able to destroy the dragon in order to claim their so deserved treasure. Bilbo completes this task by finding the dragon’s weak spot and relaying the location to an archer in Lake Town. Both of these conflicts are won by the end of the story.

Internet and Intranet Connectivity Through Wireless Local Area Network (Wlan)

CHAPTER 1 Introduction Chapter 1 Introduction 1. 1 What is WLAN? 1. 1. 1 WLAN Wireless Local Area Network (WLAN) is a kind of local area network which established using a wireless link between the service providers and the clients using some wireless equipment. This network development is based on the IEEE 802. 11 standard. 1. 1. 2 IEEE 802. 11 IEEE 802. 11 denotes a set of Wireless LAN/WLAN standards developed by working group 11 of the IEEE LAN/MAN Standards Committee (IEEE 802). The term 802. 11x is also used to denote this set of standards and is not to be mistaken for any one of its elements. There is no single 802. 1x standard. The term IEEE 802. 11 is also used to refer to the original 802. 11, which is now sometimes called â€Å"802. 11 legacy† [1]. The 802. 11 family currently includes six over-the-air modulation techniques that all use the same protocol. The most popular techniques are those defined by the b, a, and g amendments to the original standard; security was originally included and was later enhanced via the 802. 11i amendment. 802. 11n is another modulation technique that has recently been developed; the standard is still under development, although products designed based on draft versions of the standard are being sold. Other standards in the family (c–f, h, and j) are service enhancements and extensions or corrections to previous specifications. 802. 11b was the first widely accepted wireless networking standard, followed by 802. 11a and 802. 11g [1]. 802. 11b and 802. 11g standards use the 2. 40 GHz (gigahertz) band, operating (in the United States) under Part 15 of the FCC Rules and Regulations. Because of this choice of frequency band, 802. 11b and 802. 11g equipment can incur interference from microwave ovens, cordless telephones, Bluetooth devices, and other appliances using this same band. The 802. 1a standard uses the 5 GHz band, and is therefore not affected by products operating on the 2. 4 GHz band. Table 1. 1: Protocol Summary of IEEE 802. 11 Protocol Legacy 802. 11a 802. 11b 802. 11g 802. 11n Release Date 1997 1999 1999 2003 2006 Operating Frequency GHz 2. 4-2. 5 5 2. 4-2. 5 2. 4-2. 5 2. 4 and/or 5 Throughput (Typ) Mbps 0. 7 23 4 19 74 Data Rate (Max) Mbps 2 54 11 54 248 = 2Ãâ€" 2 ant Range (Indoor) meters ~25 ~30 ~35 ~35 ~70 Range (Outdoor) meters ~75 ~100 ~110 ~115 ~160 2 1. 2 Why it should be used? Bangladesh entered the Internet world in 1993 using offline E-mail services. Online Dial-up services started in 1996 through VSAT based data connectivity. But it is not possible to give a Dial-up connection to all because; it uses the BTTB’s telephone line. While Dial-up is active the phone line is busy and it is not possible to give a client more than 4/5 Kbps speed. Using an ADSL modem it can be increased to more than 2 Mbps. But it is not enough for a corporate user and also it is very costly and there are many other problems which has described below. The Ethernet connectivity can give a maximum of 100 Mbps. But its range is too small. Wireless LAN has vast benefits over wired network in some aspects. In our country especially in big cities like Dhaka, it is very hard job to establish a wired network all over the city. Because, it is over populated, buildings were made with out any proper plan and also the roads. Generally the wire lines are established over head, which is not so secured. Wire can be broken due to any kind of natural or man made problem. It may be theft. Or it can be misused by any one by taking a parallel line from it. It may create leak of data security. It is also very expensive to establish a copper wire network road by road and maintenance of it. Besides that there are many rivers, cannels in our county, and also hill tracks in some parts. It is not possible to give a wired network over those. For all those reasons it is not a wise decision to use a wired network in our country. A Wireless LAN can be more reliable, low cost, convenient network considering above aspects. There are a number of Internet Service Provider (ISP) companies in our country giving Wireless LAN support to the clients. Those are known as Wireless ISP. These ISPs give internet or intranet service to the clients as their requirements. Those networks are reliable and also secured. It is easy to establish a connection in the company’s coverage area using a wireless device at the client end. The Wireless ISP Company should have proper resources to give that coverage. A model of a Wireless ISP company’s wireless part for Bangladesh is given below. The nation wide link can be a optical fiber or microwave link. Here the main coverage is shown in Dhaka city and thus BSSs are shown at here is more than one. It can be expand the network in other areas by adding additional equipments required to establish a BSS. And also it can give coverage on other areas by establish same network on that area. Figure 1. 1: Model of a Wireless ISP 1. 3 Why one should be interested in WLAN field? The telecom industry is changing with breathtaking speed. There are a lot of telecommunication and Wireless ISP companies working in our country and there are a lot of companies to come. At present telecommunication is the most challenging and interesting field out of all other e ngineering fields. All the telecom company has some common structure. So, there are many similarities between a mobile or PSTN (Public Switched Telephone Network) operator and a Wireless ISP. The skills one gather from a Wireless ISP can use in the telecom companies. The man can be skilled on installing different devices, surveying a site, proposing a link budget. He can face the practical problems occur in installing radio networks and can be skilled in solving those problems and also troubleshoot the devices and the radio link. In the mobile operators, there are many restrictions. One can not work with all things. But as still Wireless ISP companies are smaller in our country one can get opportunity to work in different sections which will increase his experiences and skills. Lastly it can be say that, as it is a challenging field, the person likes facing challenges will enjoy working in this field 4 1. 4 Organization of this report This Internship report has seven chapters in total. The second chapter contains theory about the radio frequency properties and different modulation techniques In third chapter, different RF antennas and it accessories are described. Fourth chapter contains the Wireless LAN’s theory and architecture in brief. Chapter five analyzes to survey a site, and how to budget a link. The sixth chapter describes the device installation process for the APERTO and CANOPY devices. The seventh and final chapter is the concluding chapter where limitations of this works are reported and few suggestions of our work are provided along with the concluding remarks. 1. 5 Aims and objectives 5 RF Properties and Modulation Techniques CHAPTER 2 6 Chapter 2 RF Properties and Modulation Techniques 2. 1 Radio Frequency 2. 2. 1 Radio Frequency Radio frequencies are high frequency alternating current (AC) signals that are passed along a copper conductor and then radiated into the air via an antenna. An antenna converts/transforms a wired signal to a wireless signal and vice versa. When the high frequency AC signal is radiated into the air, it forms radio waves. These radio waves propagate (move) away from the source (the antenna) in a straight line in all directions at once. 2. 2. 2 RF Behaviors RF is sometimes referred to as â€Å"smoke and mirrors† because RF seems to act erratically and inconsistently under given circumstances. Things as small as a connector not being tight enough or a slight impedance mismatch on the line can cause erratic behavior and undesirable results. The following sections describe these types of behaviors and what can happen to radio waves as they are transmitted. Gain Gain, illustrated in Figure 2. 1, is the term used to describe an increase in an RF signal' amplitude [2]. Gain is usually an active process; meaning that an external s power source, such as an RF amplifier, is used to amplify the signal or a high-gain antenna is used to focus the beam width of a signal to increase its signal amplitude. Figure 2. 1: Power gain However, passive processes can also cause gain. For example, reflected RF signals combine with the main signal to increase the main signal' strength. Increasing the RF s signal' strength may have a positive or a negative result. Typically, more power is s better, but there are cases, such as when a transmitter is radiating power very close to legal power output limit, where added power would be a serious problem. 7 Loss Loss describes a decrease in signal strength (Figure 2. 2). Many things can cause RF signal loss, both while the signal is still in the cable as a high frequency AC electrical signal and when the signal is propagated as radio waves through the air by the antenna. Resistance of cables and connectors causes loss due to the converting of the AC signal to heat. Impedance mismatches in the cables and connectors can cause power to be reflected back toward the source, which can cause signal degradation. Objects directly in the propagated wave' transmission path can absorb, reflect, or s destroy RF signals. Loss can be intentionally injected into a circuit with an RF attenuator. RF attenuators are accurate resistors that convert high frequency AC to heat in order to reduce signal amplitude at that point in the circuit. [2] Figure 2. 2: Power loss Being able to measure and compensate for loss in an RF connection or circuit is important because radios have a receive sensitivity threshold. A sensitivity threshold defined as the point at which a radio can clearly distinguish a signal from background noise. Since a receiver’s sensitivity is finite, the transmitting station must transmit signal with enough amplitude to be recognizable at the receiver. If losses occur between the transmitter and receiver, the problem must be corrected either by removing the objects causing loss or by increasing the transmission power. Reflection Reflection, (as illustrated in Figure 2. 3) occurs when a propagating electromagnetic wave impinges upon an object that has very large dimensions when compared to the wavelength of the propagating wave [3]. Reflections occur from the surface of the earth, buildings, walls, and many other obstacles. If the surface is smooth, the reflected signal may remain intact, though there is some loss due to absorption and scattering of the signal. Figure 2. 3: Reflection 8 RF signal reflection can cause serious problems for wireless LANs. This reflecting main signal from many objects in the area of the transmission is referred to as multipath. Multipath can have severe adverse affects on a wireless LAN, such as degrading or canceling the main signal and causing oles or gaps in the RF coverage area. Surfaces such as lakes, metal roofs, metal blinds, metal doors, and others can cause severe reflection, and hence, multipath. Reflection of this magnitude is never desirable and typically requires special functionality (antenna diversity) within the wireless LAN hardware to compensate for it. Refraction Refraction describes the bending of a radio wave as it passes through a medium of different density. A s an RF wave passes into a denser medium (like a pool of cold air lying in a valley) the wave will be bent such that its direction changes. When passing through such a medium, some of the wave will be reflected away from the intended signal path, and some will be bent through the medium in another direction, as illustrated in Figure 2. 4. [3] Figure 2. 4: Refraction Refraction can become a problem for long distance RF links. As atmospheric conditions change, the RF waves may change direction, diverting the signal away from the intended Diffraction Diffraction occurs when the radio path between the transmitter and receiver is obstructed by a surface that has sharp irregularities or an otherwise rough surface [3]. At high frequencies, diffraction, like reflection, depends on the geometry of the obstructing object and the amplitude, phase, and polarization of the incident wave at the point of diffraction. Diffraction is commonly confused with and improperly used interchangeably with refraction. Care should be taken not to confuse these terms. Diffraction describes a wave bending around an obstacle (Figure 2. 5), whereas refraction describes a wave bending through a medium. Taking the rock in the pond example from above, now consider a small twig sticking up through the surface of the water near where the rock. As the ripples hit the stick, they would be blocked to a small degree, but to a larger degree, the ripples would bend around the twig. This illustration shows how diffraction acts with obstacles in its path, depending on the makeup of the obstacle. If Object was large or jagged enough, the wave might not bend, but rather might be blocked. 9 Figure 2. 5: Diffraction Diffraction is the slowing of the wave front at the point where the wave front strikes an obstacle, while the rest of the wave front maintains the same speed of propagation. Diffraction is the effect of waves turning, or bending, around the obstacle. As another example, consider a machine blowing a steady stream of smoke. The smoke would flow straight until an obstacle entered its path. Introducing a large wooden block into the smoke stream would cause the smoke to curl around the corners of the block causing a noticeable degradation in the smoke' velocity at that point and a significant s change in direction. Scattering Scattering occurs when the medium through which the wave travels consists of objects with dimensions that are small compared to the wavelength of the signal, and the number of obstacles per unit volume is large [3]. Scattered waves are produced by rough surfaces, small objects, or by other irregularities in the signal path, as can be seen in Figure 2. 6. Figure 2. 6: Scattering Some outdoor examples of objects that can cause scattering in a mobile communications system include foliage, street signs, and lampposts. Scattering can take place in two primary ways. First, scattering can occur when a wave strikes an uneven surface and is reflected in many directions simultaneously. Scattering of this type yields many small amplitude reflections and destroys the main RF signal. Dissipation of an RF signal may occur when an RF wave is reflected off sand, rocks, or other jagged surfaces. When scattered in this manner, RF signal degradation can be significant to the point of intermittently disrupting communications or causing complete signal loss. 10 Second, scattering can occur as a signal wave travels through particles in the medium such as heavy dust content. In this case, rather than being reflected off an uneven surface, the RF waves are individually reflected on a very small scale off tiny particles. Voltage Standing Wave Ratio (VSWR) VSWR occurs when there is mismatched impedance (resistance to current flow, measured in Ohms) between devices in an RF system. VSWR is caused by an RF signal reflected at a point of impedance mismatch in the signal path. VSWR causes return loss which is defined as the loss of forward energy through a system due to some of the power being reflected back towards the transmitter. If the impedances of the ends of a connection do not match, then the maximum amount of the transmitted power will not be received at the antenna. When part of the RF signal is reflected back toward the transmitter, the signal level on the line varies instead of being steady. This variance is an indicator of VSWR. [2] As an illustration of VSWR, imagine water flowing through two garden hoses. As long as the two hoses are the same diameter, water flows through them seamlessly. If the hose connected to the faucet were significantly larger than the next hose down the line, there would be backpressure on the faucet and even at the connection between the two hoses. This standing backpressure illustrates VSWR, as can be seen in Figure 2. . In this example, you can see that backpressure can have negative effects and not nearly as much water is transferred to the second hose as there would have been with matching hoses screwed together properly. Figure 2. 7: VSWR-like water through a hose VSWR Measurements VSWR is a ratio, so it is expressed as a relationship between two numbers. A typical VSWR value would be 1. 5:1. The two numbers re late the ratio of impedance mismatch against a perfect impedance match. The second number is always 1, representing the perfect match, where as the first number varies. The lower the first number (closer to 1), the better impedance matching your system has. For example, a VSWR of 1. 1:1 is better than 1. 4:1. A VSWR measurement of 1:1 would denote a perfect impedance match and no voltage standing wave would be present in the signal path. Effects of VSWR Excessive VSWR can cause serious problems in an RF circuit. Most of the time, the result is a marked decrease in the amplitude of the transmitted RF signal. However, 11 since some transmitters are not protected against power being applied (or returned) to the transmitter output circuit, the reflected power can burn ut the electronics of the transmitter. VSWR' effects are evident when transmitter circuits burn out, power s output levels are unstable, and the power observed is significantly different from the expected power. The methods of changing VSWR in a circuit include proper use of proper equipment. Tight connections between cables and connectors, use of impedance matched hardware throughout, and use of high-quality equipment with calibration reports where necessary are all good preventative measures against VSWR. VSWR can be measured with high-accuracy instrumentation such as SWR meters, but this measurement is beyond the scope of this text and the job tasks of a network administrator. 2. 2 Spread Spectrum 2. 2. 1 Spread Spectrum Spread spectrum is a communications technique characterized by wide bandwidth and low peak power. Spread spectrum communication uses various modulation techniques in wireless LANs and possesses many advantages over its precursor, narrow band communication [4]. Spread spectrum signals are noise-like, hard to detect, and even harder to intercept or demodulate without the proper equipment. Jamming and interference have a lesser affect on a spread spectrum communication than on narrow band communications. For these reasons, spread spectrum has long been a favorite of the military. 2. 2. 2 Narrow Band Transmission A narrowband transmission is a communications technology that uses only enough of the frequency spectrum to carry the data signal and no more, spread spectrum is in opposition to that mission since it uses much wider frequency bands than is necessary to transmit the information. This brings us to the first requirement for a signal to be considered spread spectrum. A signal is a spread spectrum signal when the bandwidth is much wider than what is required to send the information. [4] Figure 2. 8 illustrates the difference between narrowband and spread spectrum transmissions. One of the characteristics of narrow band is high peak power. More power is required to send a transmission when using a smaller frequency range. In order for narrow band signals to be received, they must stand out above the general level of noise, called the noise floor, by a significant amount. Because its band is so narrow, and high peak power ensures error-free reception of a narrow band signal. 12 Figure 2. 8: Narrow band verses Spread Spectrum on a frequency domain A compelling argument against narrowband transmission-other than the high peak power required to send it-is that narrow band signals can be jammed or experience interference very easily. Jamming is the intentional overpowering of a transmission using unwanted signals transmitted on the same band. Because its band is so narrow, other narrow band signals, including noise, can completely eliminate the information by overpowering a narrowband transmission; much like a passing train overpowers a quiet conversation. 2. 2. 3 Spread Spectrum Technology Spread spectrum technology allows taking the same amount of information than previously using a narrow band carrier signal and spreading it out over a much larger frequency range. For example, 1 MHz at 10 Watts with narrow band, but 20 MHz at 100 mW with spread spectrum. By using a wider frequency spectrum, we reduce the probability that the data will be corrupted or jammed. A narrow band jamming attempt on a spread spectrum signal would likely be thwarted by virtue of only a small part of the information falling into the narrow band signal' frequency range. s s Most of the digital data would be received error-free [4]. Today' spread spectrum RF radios can retransmit any small amount of data loss due to narrowband interference. While the spread spectrum band is relatively wide, the peak power of the signal is quite low. This is the second requirement for a signal to be considered spread spectrum. For a signal to be considered spread spectrum, it must use low power. These two characteristics of spread spectrum (use of a wide band of frequencies and very low power) make it look to most receivers as if it were a noise signal. Noise is a wide band, low power signal, but the difference is that noise is unwanted. Furthermore, since most radio receivers will view the spread spectrum signal as noise, these receivers will not attempt to demodulate or interpret it, creating a slightly more secure communication. 2. 2. 4 Frequency Hopping Spread Spectrum (FHSS) Frequency hopping spread spectrum is a spread spectrum technique that uses frequency agility to spread the data over more than 83 MHz. Frequency agility refers to the radio’s ability to change transmission frequency abruptly within the usable RF frequency band [4]. In the case of frequency hopping wireless LANs, the usable portion of the 2. GHz ISM band is 83. 5 MHz, per FCC regulation and the IEEE 802. 11 standard. 13 How FHSS Works In frequency hopping systems, the carrier changes frequency, or hops, according to a pseudorandom sequence. The pseudorandom sequence is a list of several frequencies to which the carrier will hop at specified time intervals before repeating the pattern. The transmitter uses this hop sequence to select it s transmission frequencies. The carrier will remain at a certain frequency for a specified time (known as the dwell time), and then use a small amount of time to hop to the next frequency (hop time). When the list of frequencies has been exhausted, the transmitter will repeat the sequence. Figure 2. 9 shows a frequency hopping system using a hop sequence of five frequencies over 5 MHz band. In this example, the sequence is: 1. 2. 449 GHz 2. 2. 452 GHz 3. 2. 448 GHz 4. 2. 450 GHz 5. 2. 451 GHz Figure 2. 9: Single frequency hopping system Once the radio has transmitted the information on the 2. 451 GHz carrier, the radio will repeat the hop sequence, starting again at 2. 449 GHz. The process of repeating the sequence will continue until the information is received completely. The receiver radio is synchronized to the transmitting radio' hop sequence in order to s receive on the proper frequency at the proper time. The signal is then demodulated and used by the receiving computer. Effects of Narrow Band Interference Frequency hopping is a method of sending data where the transmission and receiving systems hop along a repeatable pattern of frequencies together. As is the case with all spread spectrum technologies, frequency hopping systems are resistant-but not immune-to narrow band interference. In example in Figure 2. 9, if a signal were to interfere with our frequency hopping signal on, say, 2. 51 GHz, only that portion of the spread spectrum signal would be lost. The rest of the spread spectrum signal would remain intact, and the lost data would be retransmitted. 14 In reality, an interfering narrow band signal may occupy several megahertz of bandwidth. Since a frequency hopping band is over 83 MHz wide, even this interfering signal will cause little de gradation of the spread spectrum signal. Frequency Hopping Systems The IEEE and Open-Air standards regarding FHSS systems describe: 1. The frequency bands which may be used 2. Hop sequences 3. Dwell times 4. Data rates The IEEE 802. 1 standard specifies data rates of 1 Mbps and 2 Mbps and Open-Air (a standard created by the now defunct Wireless LAN Interoperability Forum) specifies data rates of 800 kbps and 1. 6 Mbps. In order for a frequency hopping system to be 802. 11 or Open-Air compliant, it must operate in the 2. 4 GHz ISM band (which is defined by the FCC as being from 2. 4000 GHz to 2. 5000 GHz). Both standards allow operation in the range of 2. 4000 GHz to 2. 4835 GHz. Channels A frequency hopping system will operate using a specified hop pattern called a channel. Frequency hopping systems typically use the FCC’s 26 standard hop patterns or a subset thereof. Some frequency hopping systems will allow custom hop patterns to be created, and others even allow synchronization between systems to completely eliminate collisions in a co-located environment. Figure 2. 10: Co-located frequency hopping system Though it is possible to have as many as 79 synchronized, co-located access points, with this many systems, each frequency hopping radio would require precise synchronization with all of the others in order not to interfere with (transmit on the same frequency as) another frequency hopping radio in the area. The cost of such a set of systems is prohibitive and is generally not considered an option. If synchronized radios are used, the expense tends to dictate 12 co-located systems as the maximum. 15 If non-synchronized radios are to be used, then 26 systems can be co-located in a wireless LAN; this number is considered to be the maximum in a medium-traffic wireless LAN. Increasing the traffic significantly or routinely transferring large files places the practical limit on the number of co-located systems at about 15. More than 15 co-located frequency-hopping systems in this environment will interfere to the extent that collisions will begin to reduce the aggregate throughput of the wireless LAN. Dwell Time In frequency hopping systems, it must transmit on a specified frequency for a time, and then hop to a different frequency to continue transmitting. When a frequency hopping system transmits on a frequency, it must do so for a specified amount of time. This time is called the dwell time. Once the dwell time has expired, the system will switch to a different frequency and begin to transmit again. Suppose a frequency hopping system transmits on only two frequencies, 2. 401 GHz and 2. 402 GHz. The system will transmit on the 2. 01 GHz frequency for the duration of the dwell time100 milliseconds (ms), for example. After 100ms the radio must change its transmitter frequency to 2. 402 GHz and send information at that frequency for 100ms. Hop Time When considering the hopping action of a frequency hopping radio, dwell time is only part of the story. When a frequency hopping radio jumps from frequency A to frequency B, it must change the transmit frequency in one of two ways. It ei ther must switch to a different circuit tuned to the new frequency, or it must change some element of the current circuit in order to tune to the new frequency. In either case, the process of changing to the new frequency must be complete before transmission can resume, and this change takes time due to electrical latencies inherent in the circuitry. There is a small amount of time during this frequency change in which the radio is not transmitting called the hop time. The hop time is measured in microseconds ( µs) and with relatively long dwell times of around 100-200 ms, the hop time is not significant. A typical 802. 11 FHSS system hops between channels in 200-300  µs. With very short dwell times of 500 – 600 µs, like those being used in some frequency hopping systems such as Bluetooth, hop ime can become very significant. If we look at the effect of hop time in terms of data throughput, we discover that the longer the hop time in relation to the dwell time, the slower the data rate of bits being transmitted. 2. 2. 5 Direct Sequence Spread Spectrum (DSSS) Direct sequence spread spectrum is very widely known and the most used of the spread spectrum types, owing most of its popularity to its ease of implementation and high data rates. The majority of wireless LAN equipment on the market today uses DSSS technology. DSSS is a method of sending data in which the transmitting and receiving systems are both on a 22 MHz-wide set of frequencies. The wide channel enables devices to transmit more information at a higher data rate than current FHSS systems. 16 How DSSS Works DSSS combines a data signal at the sending station with a higher data rate bit sequence, which is referred to as a chipping code or processing gain. A high processing gain increases the signal’s resistance to interference. The minimum linear processing gain that the FCC allows is 10, and most commercial products operate under 20. The IEEE 802. 11 working group has set their minimum processing gain requirements at 11. The process of direct sequence begins with a carrier being modulated with a code sequence. The number of–chips-in the code will determine how much spreading occurs, and the number of chips per bit and the speed of the code (in chips per second) will determine the data rate. Direct Sequence Spread Spectrum (DSSS) Direct sequence spread spectrum is very widely known and the most used of the spread spectrum types, owing most of its popularity to its ease of implementation and high data rates. The majority of wireless LAN equipment on the market today uses DSSS technology. DSSS is a method of sending data in which the transmitting and receiving systems are both on a 22 MHz-wide set of frequencies. The wide channel enables devices to transmit more information at a higher data rate than current FHSS systems. How DSSS Works DSSS combines a data signal at the sending station with a higher data rate bit sequence, which is referred to as a chipping code or processing gain. A high processing gain increases the signal’s resistance to interference. The minimum linear processing gain that the FCC allows is 10, and most commercial products operate under 20. The IEEE 802. 11 working group has set their minimum processing gain requirements at 11. The process of direct sequence begins with a carrier being modulated with a code sequence. The number of-chips-in the code will determine how much spreading occurs, and the number of chips per bit and the speed of the code (in chips per second) will determine the data rate. Channels Unlike frequency hopping systems that use hop sequences to define the channels, direct sequence systems use a more conventional definition of channels. Each channel is a contiguous band of frequencies 22 MHz wide and 1 MHz carrier frequencies are used just as with FHSS. Channel 1, for instance, operates from 2. 401 GHz to 2. 423 GHz (2. 412 GHz  ± 11 MHz); channel 2 operates from 2. 406 to 2. 429 GHz (2. 417  ± 11 MHz), and so forth. Figure 2. 11 illustrates this point. 17 Figure 2. 11: channel allocation and Spectral relationship The chart in Table 2. 1 has a complete list of channels used in the United States and Europe. The FCC specifies only 11 channels for non-licensed use in the United States. Each of the frequencies listed in this chart are considered center frequencies. From this center frequency, 11 MHz is added and subtracted to get the useable 22 MHz wide channel. Easy to see that adjacent channels (channels directly next to each other) would overlap significantly. Table 2. 1: DSSS channel frequency Assignment Channel ID 1 2 3 4 5 6 7 8 9 10 11 FCC Channel Frequencies GHz 2. 412 2. 417 2. 422 2. 427 2. 432 2. 437 2. 442 2. 447 2. 452 2. 457 2. 462 ETSI Channel Frequencies GHz N/A N/A 2. 422 2. 427 2. 432 2. 437 2. 442 2. 447 2. 452 2. 457 2. 462 To use DSSS systems with overlapping channels in the same physical space would cause interference between the systems. DSSS systems with overlapping channels should not be co-located because there will almost always be a drastic or complete reduction in throughput. Because the center frequencies are 5 MHz apart and the channels are 22 MHz wide, channels should be co-located only if the channel numbers are at least five apart: channels 1 and 6 do not overlap, channels 2 and 7 do not overlap, etc. There is a maximum of three co-located direct sequence systems possible because channels 1, 6 and 11 are the only theoretically non-overlapping channels. The 3 non-overlapping channels are illustrated in Figure 2. 2 18 Figure 2. 12: DSSS non-overlapping Channel 2. 2. 6 Comparing FHSS and DSSS Both FHSS and DSSS technologies have their advantages and disadvantages, and it incumbent on the wireless LAN administrator to give each its due weight when deciding how to implement a wireless LAN [4]. This section will cover some of the factors that should be discussed when determining which technology is appropriate f or your organization, including: 1. Narrowband interference 2. Co-location 3. Cost 4. Equipment compatibility 5. Data rate and throughput 6. Security 7. Standards support Narrowband Interference The advantages of FHSS include a greater resistance to narrow band interference. DSSS systems may be affected by narrow band interference more than FHSS because of the use of 22 MHz wide contiguous bands instead of the 79 MHz used by FHSS. This fact may be a serious consideration if the proposed wireless LAN site is in an environment that has such interference present. Co-location An advantage of FHSS over DSSS is the ability for many more frequency hopping systems to be co-located than direct sequence systems. Since frequency hopping systems are-frequency agile-and make use of 79 discrete channels, frequency hopping systems have a co-location advantage over direct sequence systems, which have a maximum co- location of 3 access points. 19 Figure 2. 13: Co-location Comparison However, when calculating the hardware costs of an FHSS system to get the same throughput as a DSSS system, the advantage quickly disappears. Because DSSS can have 3 co-located access points, the maximum throughput for this configuration would be: 3 access points ? 1 Mbps = 33 Mbps At roughly 50% of rated bandwidth, the DSSS system throughput would be approximately: 33 Mbps / 2 = 16. 5 Mbps To achieve roughly the same rated system bandwidth using an IEEE 802. 11 compliant FHSS system would require: 16 access points ? 2 Mbps = 32 Mbps At roughly 50% of rated bandwidth, the FHSS system throughput would be approximately: 32 Mbps / 2 = 16 Mbps In this configuration, an FHSS system would require 13 additional access points t o be purchased to get the same throughput as the DSSS system. Also, additional installation services for these units, cables, connectors, and antennas would all need to be purchased. Cost: When implementing a wireless LAN, the advantages of DSSS may be more compelling than those of FHSS systems, particularly when driven by a tight budget. The cost of implementing a direct sequence system is far less than that of a frequency hopping system. DSSS equipment is widely available in today’s marketplace, and its rapid adoption has helped in driving down the cost. Only a few short years ago, equipment was only affordable by enterprise customers. Today, very good quality 802. 11b compliant PC cards can be purchased for under $100. FHSS cards complying with either the 802. 11 or Open-Air standards typically run between $150 and $350 in today' market depending on the manufacturer and the standards to which the cards s adhere. 20 Equipment compatibility and availability The Wireless Ethernet Compatibility Alliance (WECA) provides testing of 802. 11b compliant DSSS wireless LAN equipment to ensure that such equipment will operate in the presence of and interoperate with other 802. 11b DSSS devices. The interoperability standard that WECA created and now uses is called Wireless Fidelity, or Wi-Fi, and hose devices that pass the tests for interoperability are-Wi-Fi compliant-devices. Devices so deemed are allowed to affix the Wi-Fi logo on the related marketing material and devices themselves showing that they have been tested and interoperate with other Wi-Fi compliant devices. There are no such compatibility tests for equipment that uses FHSS. There are standards such as 802. 11 and Open-Air, but no organization h as stepped forward to do the same kind of compatibility testing for FHSS as WECA does for DSSS. Due to the immense popularity of 802. 11b compliant radios, it is much easier to obtain these units. The demand seems only to be growing for the Wi-Fi compliant radios while the demand for FHSS radios has remained fairly steady, even decreasing to some degree over the past year. Data rate and throughput The latest frequency hopping systems are slower than the latest DSSS systems mostly because their data rate is only 2 Mbps. Though some FHSS systems operate at 3 Mbps or more, these systems are not 802. 11 compliant and may not interoperate with other FHSS systems. FHSS and DSSS systems have a throughput (data actually sent) of only about half of the data rate. When testing the throughput of a new wireless LAN installation, achieving 5-6 Mbps on the 11 Mbps setting for DSSS or 1 Mbps on the 2 Mbps setting common using DSSS. When wireless frames are transmitted, there are pauses between data frames for control signals and other overhead tasks. With frequency hopping systems, this interframe spacing is longer than that used by direct sequence systems, causing a slow-down in rate that data is actually sent (throughput). Additionally, when the frequency hopping system is in the process of changing the transmit frequency, no data is sent. This translates to more lost throughput, albeit only a minor amount. Some wireless LAN systems use proprietary physical layer protocols in order to increase throughput. These methods work, yielding throughputs as high as 80% of the data rate, but in so doing, sacrifice interoperability. Security: It is widely touted-and is a myth-that frequency hopping systems are inherently more secure than direct sequence systems. The first fact that disproves this myth is that FHSS radios are only produced by a minimal number of manufacturers. Of this small list of manufacturers, all of them adhere to standards such as 802. 1 or Open-Air in order to sell their products effectively. Second, each of these manufacturers uses a standard set of hop sequences, which generally comply with a pre-determined list, produced by the standards body (IEEE or WLIF). These 2 items together make breaking the code of hop sequences relatively simple. 21 Other reasons that make finding the hop sequence quite simple is that the channel number is broadcasted in the clear with each beacon. Also, the MAC address of the transmitting access point can be seen with each beacon (which indicates the manufacturer of the radio). Some manufacturers allow the administrator the flexibility of defining custom hopping patterns. However, even this custom capability is no level of security since fairly unsophisticated devices such as spectrum analyzers and a standard laptop computer can be used to track the hopping pattern of a FHSS radio in a matter of seconds. Standards Support: DSSS has gained wide acceptance due to low cost, high speed, WECA' Wi-Fi s interoperability standards, and many other factors. This market acceptance will only accelerate due to the industry moving toward newer, faster DSSS systems such as the new 802. 1g and 802. 11a compliant wireless LAN hardware. WECA' new Wi-Fi5 s interoperability standard for 5 GHz DSSS systems operating in the UNII bands will help move the industry along even faster in the same direction it is already headed. The new standards for FHSS systems include Home RF 2. 0 and 802. 15 (in support of WPANs such as Bluetooth), but none for advancing FHSS systems in the enterp rise. 2. 2. 7 BPSK In BPSK, the phase of the carrier is varied to represent binary 1 or 0 . Both peak amplitude and frequencies remain constant as the phase changes. For example, if a phase of 0 represents binary 0, then the phase 180 represents binary 1. the phase of the signal during each bit duration is constant. And its value depends on the bit (0 or 1). Figure 2. 14 shows a conceptual view of BPSK. BPSK is also known as 2-PSK. because two different phases (0 and 180) are used. The table below shows BPSK which makes the relationship of phase to bit value. Bit 0 1 Phase 0? 180? Figure 2. 14: BPSK. 2. 2. 8 QPSK The diagram for the signal is given in Figure 2. 15. A phase of 0 now represents 00; 90 represents 01; 180 represents10; and 270 represents 11. This technique is called QPSK. The pair of bits represented by each phase is called a dibit. 22 Bit 00 01 10 11 Figure 2. 15: QPSK. Phase 0? 90? 180? 270? 2. 2. 9 QAM QAM is a Combination of ASK and PSK so that a maximum contrast between each signal unit (bit, dibit, tribit, and so on) is achieved. QAM takes the advantages of the fact that it is possible to send two different signals simultaneously on the same carrier frequency . by using two copies of the carrier frequency. One shifted by 90 with respect to the other. For QAM, each carrier is ASK modulated. The two independent signals are simultaneously transmitted over the same medium. In QAM the number of amplitude shifts is fewer than the number of phase shifts. Because amplitude changes are susceptible to noise and require greater shift distances than do phase changes, the number of phase shifts used by a QAM system is always larger than the number of amplitude shifts. [5] Figure 2. 16: QAM. 23 2. 2. 10 Orthogonal Frequency division Multiplexing (OFDM) Orthogonal Frequency division Multiplexing offers the highest data rates and maximum resistance to interference and corruption of all the signal manipulation techniques in use in 802. 1 today [5]. Although it is not considered a spread spectrum technique by the FCC, OFDM shares many qualities with spread spectrum communicators, including using a low transmit power and wider-than-necessary bandwidth. OFDM is used to provide data rates up to 54 Mbps in 802. 11a and 802. 11g. How OFDM Works OFDM achieves high data rates by squeezing a large number of Communication Channels into a given frequency band. Normally, two c ommunication channels must be separated by a certain amount of bandwidth or they overlap and interfere. Specially, each Channel has harmonics that extend up and down the frequency space, decreasing in amplitude as they get farther from the channels fundamental signal. Even if two channels are non-overlapping, their harmonics may overlap and the signal can be corrupted. An OFDM communicator can place adjacent communication channels very precisely in the frequency space in such a way that the channels harmonics exactly cancel each other, effectively leaving only the fundamental signals. OFDM achieves high data rates by dividing a single communication channel into a large number of closely-spaced, small bandwidth sub-carriers. Each sub-carrier individually has a relatively low data rate, but by transmitting data in parallel on all sub-carriers simultaneously, high data rates can be achieved. Figure 2. 17: OFDM frequency plot. Figure 2. 17 shows an example of a frequency spectrum for an OFDM transmitter. Each of the peaks represents a single sub-carrier, and the sub-carriers together make up the communications channel. The sub-carriers are precisely aligned so that the zero-points of their harmonics overlapped exactly. The majority of the harmonic energy will cancel out, leaving just the sub-carriers. 4 CHAPTER 3 RF Antenna and Accessories 25 Chapter 3 RF Antenna and Accessories 3. 1 Introduction Antennas are most often used to increase the range of wireless LAN systems, but proper antenna selection can also enhance the security of your wireless LAN. A properly chosen and positioned antenna can reduce the signal leaking out of workspace, and make signal interception extremely difficult. 3. 2 RF Antennas An RF antenna is a device used to convert high frequency (RF) signals on a transmission line (a cable or waveguide) into propagated waves in the air [6]. The electrical fields emitted from antennas are called beams or lobes. Antenna convert electrical energy into RF waves in the case of a transmitting antenna, or RF waves into electrical energy in the case of a receiving antenna. The physical dimensions of an antenna, such as its length, are directly related to the frequency at which the antenna can propagate waves or receive propagated waves. The physical structure of an antenna is directly related to the Shape of the area in which it concentrates most of its related RF energy. There are three generic categories of RF antennas: 1. Omni-directional 2. Semi-directional 3. Highly-directional Each category has multiple types of antennas, each having different RF characteristics and appropriate uses. As the gain of an antenna goes up, the coverage area narrows so that high-gain antennas offer longer coverage areas than low-gain antennas at the same input power level. 3. 2. 1 Omni-directional (Dipole) Antennas The dipole is an omni- directional antenna, because it radiates its energy equally in all directions around its axis. Dipole antenna is Simple to design; dipole antenna is standard equipment on most access points. Directional antennas concentrate their energy into a cone, known as a â€Å"beam. † Figure 3. 1: Dipole doughnut 26 Figure 3. 1 shows that the dipole' radiant energy is concentrated into a region that s looks like a doughnut, with the dipole vertically through the â€Å"hole† of the â€Å"doughnut. † The signal from an omni-directional antenna radiates in a 360-degree horizontal beam. If an antenna radiates in all directions equally (forming a sphere), it is called an isotropic radiator, which is the theoretical reference for antennas, but rather, practical antennas all have some type of gain over that of an isotropic radiator. The dipole radiates equally in all directions around its axis, but does not radiate along the length of the wire itself – hence the doughnut pattern. The side view of a dipole radiator as it radiates waves in Figure 3. 2. Figure 3. 2: Dipole-side view If a dipole antenna is placed in the center of a single floor of a multistory building, most of its energy will be radiated along the length of that floor, with some significant fraction sent to the floors above and below the access point. Figure 3. 3 shows examples of some different types of omni-directional antennas. Figure 3. 3: Sample omni-directional antenna Figure 3. 4 shows a two-dimensional example of the top view and side view of a dipole antenna. Figure 3. 4: Coverage area of an omni-directional antenna High-gain omni-directional antennas offer more horizontal coverage area, but the vertical coverage area is reduced, as can be seen in Figure 3. 5. 27 Figure 3. 5: Coverage area of high gain omni-directional antennas This characteristic can be an important consideration when mounting a high-gain omni antenna indoors on the ceiling. If the ceiling is too high; the coverage area may not reach the floor, where the users are located. Usages Omni-directional antennas are used when coverage in all directions around the horizontal axis of the antenna is required. Omni-directional antennas are most effective where large coverage areas are needed around a central point. For example, placing an omni- directional antenna in the middle of a large, open room would provide good coverage. Omni-directional antennas are commonly used for point-tomultipoint designs with a hub-n-spoke topology. Used outdoors, an omni-directional antenna should be placed on top of a structure (such as a building) in the middle of the Figure 3. 6: Point to multipoint link coverage area. For example, on a college campus the antenna might be placed in the center of the campus for the greatest coverage area. When used indoors, the antenna should be placed at the middle of the building or desired coverage area, near the ceiling, for optimum coverage. Omni-directional antennas emit a large coverage area in a circular pattern and are suitable for warehouses or tradeshows where coverage is usually from one corner of the building to the other. 3. 2. 2 Semi directional Antenna Semi directional antennas direct the energy from the transmitter significantly more in one particular direction rather than the uniform circular pattern that is common with the omni- directional antenna; Semi-directional antennas come in many different styles and shapes. Some semi- directional antennas types frequently used with wireless LANs are Patch, Panel, and Yagi (pronounced â€Å"YAH-gee†) antennas. All of these antennas are generally flat and designed for wall mounting. Each type has different coverage characteristics. Figure 3. shows some examples of semidirectional antennas. 28 Figure 3. 7: Sample semi-directional antenna Semi-directional antennas often radiate in a hemispherical or cylindrical coverage pattern as can be seen in Figure 3. 8. Figure 3. 8: Coverage area of a semi-directional antenna Usages Semi-directional antennas are ideally suited for short and medium range bridging. For example, two office buildings that are across the street from one another and n eed to share a network connection would be a good scenario in which to implement semidirectional antennas. In a large indoor space, if the transmitter must be located in the corner or at the end of a building, a corridor, or a large room, a semi-directional antenna would be a good choice to provide the proper coverage. Figure 3. 9 illustrates a link between two buildings using semi-directional antennas. Figure 3. 9: Point to point link using semi-directional antenna In some cases, semi-directional antennas provide such long-range coverage that they may eliminate the need for multiple access points in a building. For example, in a long hallway, several access points with omni antennas may be used or perhaps only one or two access points with properly placed semi-directional antennas – saving the customer a significant amount of money. In some cases, semi- directional antennas have back and side lobes that, if used effectively, may further reduce the need for additional access points. 29 3. 2. 3 Highly directional antenna Highly-directional antennas emit the most narrow signal beam of any antenna type and have the greatest gain of these three groups of antennas. Highly-directional antennas are typically concave, dish-shaped devices, as can be seen Figures 3. 10 and 3. 11. These antennas are ideal for long distance, point-to-point wireless links. Some models are referred to as parabolic dishes because they resemble small satellite dishes. Others are called grid antennas due to their perforated design for resistance to wind loading. Figure 3. 10: sample of a highly directional antenna Figure 3. 11: sample of a highly directional grid antenna Figure 3. 12: Radiation pattern of a highly directional antenna Usages High-gain antennas do not have a coverage area that client devices can use. These antennas are used for point-to-point communication links, and can transmit at distances up to 25 miles. Potential uses of highly directional antennas might be to connect two buildings that are miles away from each other but have no obstructions in their path. Additionally, these antennas can be aimed directly at each other within a building in order to â€Å"blast† through an obstruction. This setup would be used in order to get network connectivity to places that cannot be wired and where normal wireless networks will not work. 0 3. 2. 4 Antenna Gain An antenna element without the amplifiers and filters typically associated with it is a passive device. There is no conditioning, amplifying, or manipulating of the signal by the antenna element itself. The antenna can create the effect of amplification by virtue of its physical shape. Antenna amplification is the result of focusing the RF ra diation into a tighter beam, just as the bulb of a flashlight can be focused into a tighter beam creating a seemingly brighter light source that sends the light further. The focusing of the radiation Measured by way of beam widths, which are measured in degrees horizontal and vertical. For example, an omni-directional antenna has a 360-degree horizontal beam width. By limiting the 360-degree beam width into a more focused beam of, say, 30 degrees, at the same power, the RF waves will be radiated further. This is how patch, panel, and Yagi antennas (all of which are semi-directional antennas) are designed. Highly directional antennas take this theory a step further by very tightly focusing both horizontal and vertical beam widths to maximize distance of the propagated wave at low power. . 2. 5 Intentional Radiator As defined by the Federal Communication Commission (FCC), an intentional radiator is an RF device that is specifically designed to generate and radiate RF signals. In terms of hardware, an intentional radiator will include the RF device and all cabling and connectors up to, but not including, the antenna, as illustrated in Figure 3. 13 below . Figure 3. 13: Intentional Radiator Any reference to â€Å"power output of the Intentional Radiator† refers to the power output at the end of the last cable or connector before the antenna. For example, consider a 30- milliwatt transmitter that loses 15 milliwatts of power in the cable and another 5 milliwatts from the connector at the antenna. The power at the intentional radiator would be 10 milliwatts. As an administrator, it is your responsibility to understand the FCC rules relating to Intentional Radiators and their power output. Understanding how power output is measured, how much power is allowed, and how to calculate these values are all covered in this book. FCC regulations concerning output power at the Intentional Radiator and EIRP are found in Part 47 CFR, 1 3. 2. 6 Equivalent Isotropically Radiated Power (EIRP) EIRP is the power actually radiated by the antenna element, as shown in Figure 3. 14. This concept is important because it is regulated by the FCC and because it is used in calculating whether or not a wireless link is viable. EIRP takes into account the gain of the antenna. Figure 3. 14: Equivalent Isotropically Radiated Power Suppose a transmittin g station uses a 10-dBi antenna (which amplifies the signal 10fold) and is fed by 100 mill watts from the intentional radiator. The EIRP is 1000 mW, or 1 Watt. The FCC has rules defining both the power output at the intentional radiator and the antenna element. 3. 3 RF Accessories When wireless LAN devices connect together, the appropriate cables and accessories need to purchase that will maximize throughput, minimize signal loss, and, most importantly, allow making connections correctly. Different types of accessories are needed in a wireless LAN design. [7] 1. RF Amplifiers 2. RF Attenuators 3. Lightning Arrestors 4. RF Connectors 5. RF Cables 3. 3. 1 RF Amplifiers An RF amplifier is used to amplify, or increase the amplitude of, RF signal, which is measured in +dB. An amplifier will be used when compensating the loss incurred by the RF signal, either due to the distance between antennas or the length of cable from a wireless infrastructure device to its antenna. Most RF amplifiers used with wireless LANs are powered using DC voltage fed onto the RF cable with an injector near the RF signal source (such as the access point or bridge). Sometimes this DC voltage used to power RF amplifiers is called â€Å"phantom voltage† because the RF amplifier seems to magically power up. This DC injector is powered using AC voltage from a wall outlet, so it might be located in a wiring closet. In this scenario, the RF cable carries 32 both the high frequency RF signal and the DC voltage necessary to power the in-line amplifier, which, in turn, boosts the RF signal amplitude. Figure 3. 15 shows an example of an RF amplifier (left), and how an RF amplifier is mounted on a pole (right) between the access point and its antenna. Figure 3. 15: A sample of a fixed gain Amplifier RF amplifiers come in two types: unidirectional and bi-directional. Unidirectional amplifiers compensate for the signal loss incurred over long RF cables by increasing the signal level before it is injected into the transmitting antenna. Bi-directional amplifiers boost the effective sensitivity of the receiving antenna by amplifying the received signal before it is fed into the access point, bridge, or client device. Configuration and Management RF amplifiers used with wireless LANs are installed in series with the main signal path seen below in Figure 3. 16. Amplifiers are typically mounted to a solid surface using screws through the amplifier’s flange plates. Configuration of RF amplifiers is not generally required unless the amplifier is a variable RF amplifier. If the amplifier is variable, the amplifier must be configured for the proper amount of amplification required, according to RF math calculations. The manufacturer' user manual will s explain how to program or configure the amplifier. Figure 3. 16: RF amplifier placement in the wireless LAN system 3. 3. 2 RF Attenuators An RF attenuator is a device that causes precisely measured loss (in dB) in an RF signal. While an amplifier will increase the RF signal, an attenuator will decrease it. Consider the case where an access point has a fixed output of 100mW, and the only antenna available is an omni-directional antenna with +20 dBi gain. Using this equipment together would violate FCC rules for power output, so an attenuator could be added to decrease the RF signal down to 30mW before it entered the antenna. This configuration would put the power output within FCC parameters. Figure 3. 17 shows examples of fixed-loss RF attenuators with BNC connectors (left) and SMA connectors (right). Figure 3. 18 shows an example of an RF step attenuator. 33 Figure 3. 7: Sample of a fixed loss Amplifier Figure 3. 18: A sample of a RF step attenuator (Variable loss) Configuration and Management Figure 3. 19 shows the proper placement in a wireless LAN for an RF attenuator, which is directly in series with the main signal path. Fixed, coaxial attenuators are connected directly between any two-connection points between the transmitter and the antenna. For example, a fixed, coaxial antenn a might be connected directly on the output of an access point, at the input to the antenna, or anywhere between these two points if multiple RF cables are used. Variable antennas are generally mounted to a surface with screws through their flange plates or simply placed in a wiring closet on a shelf. Configuration of RF attenuators is not required unless a variable attenuator is used, in which case, the amount of attenuation required is configured according to your RF calculations. Configuration instructions for any particular attenuator will be included in the manufacturer' user manual. s Figure 3. 19: RF attenuator placement in a wireless LAN 3. 3. 3 Lightning Arrestors A lightning arrestor is used to shunt transient current into the ground that is caused by lightning. Lightning arrestors are used for protecting wireless LAN hardware such as access points, bridges, and workgroup bridges that are attached to a coaxial transmission line. Coaxial transmission lines are susceptible to surges from nearby lightning strikes. Lightning arrestor are only needed for outdoor antennas that are 34 Susceptible to lighting sticks in the vicinity. They are not necessary for indoor antennas because of the existing building ground. A lightning arrestor can generally shunt surges up to 5000 Amperes at up to 50 volts. Lightning arrestor performs the following function 1. Lightning strikes a nearby object 2. Transient current are induced in the antenna or the RF transmission line 3. The lightning arrestor senses these currents and immediately ionizes the gases held internally to cause a short (a path of almost no resistance) directly to earth ground. Figure 3. 20: Lightning Arrestors installed in a network 3. 3. 4 RF Connectors RF connectors are specific types of connection devices used to connect cables to devices or devices to devices. Traditionally, N, F, SMA, BNC, and TNC connectors (or derivatives) have been used for RF connectors on wireless LANs. In 1994, the FCC and DOC (Canadian Department of Communications) ruled that connectors for use with wireless LAN devices should be proprietary between manufacturers [7]. For this reason, many variations on each connector type exist such as: 1. N-type 2. Reverse polarity N-type 3. Reverse threaded N-type Figure 3. 21: Sample N-type and SMA Connector 35 Choosing an RF Connector There are five things that should be considered when purchasing and installing any RF connector, and they are similar in nature to the criteria for choosing RF amplifiers and attenuators. . The RF connector should match the impedance of all other wireless LAN components (generally 50 ohms). 2. Know how much insertion loss each connector inserted into the signal path causes. The amount of loss caused will factor into your calculations for signal strength required and distance allowed. 3. Know the upper frequency limit (frequency response) specified for the particular connectors. This point will be very important as 5 GHz wireless LANs become more and more common. Some connectors are rated only as high as 3 GHz, which is fine for use with 2. GHz wireless LANs, but will not work for 5 GHz wireless LANs. Some connectors are rated only up to 1 GHz and will not work with wireless LANs at all, other than legacy 900 MHz wireless LANs. 4. Beware of bad quality connectors. First, always consider purchasing from a reputable company. Second, purchase only high-quality connectors made by name-brand manufacturers. This kind of purchasing particularity will help eliminate many problems with sporadic RF signals, VSWR, and bad connections. 5. Make sure you know both the type of connector (N, F, SMA, etc. ) that you need and the sex of the connector. Connectors come in male and female. Male connectors have a center pin, and female connectors have a center receptacle. 3. 3. 5 RF Cables Proper cables are needed for connecting an antenna to an access point or wireless bridge. Below are some criteria to be considered in choosing the proper cables for your wireless network. 1. Cables introduce loss into a wireless LAN, so make sure the shortest cable length necessary is used. 2. Plan to purchase pre-cut lengths of cable with pre-installed connectors. Doing minimizes the possibility of bad connections between the connector and the cable. Professional manufacturing practices are almost always superior to cables manufactured by untrained individuals. 3. Look for the lowest loss cable available at your particular price range (the lower the loss, the more expensive the cable). Cables are typically rated for loss in dB/100-feet. The table in Figure 5. 29 illustrates the loss that is introduced by adding cables to a wireless LAN. 4. Purchase cable that has the same impedance as all of your other wireless LAN components (generally 50 ohms). 5. The frequency response of the cable should be considered as a primary decision factor in your purchase. With 2. 4 GHz wireless LANs, a cable with a rating of at least 2. 5 GHz should be used. With 5 GHz wireless LANs, a cable with a rating of at least 6 GHz should be used. 36 Table 3. 1: Coaxial Cable attenuation ratings LMR Cable 100A 195 200 240 300 400 400UF 500 600 600UF 900 1200 1700 30 3. 9 2. 0 1. 8 1. 3 1. 1 0. 7 0. 8 0. 54 0. 42 0. 48 0. 29 0. 21 0. 15 50 5. 1 2. 6 2. 3 1. 7 1. 4 0. 9 1. 1 0. 70 0. 55 0. 63 0. 37 0. 27 0. 19 150 8. 9 4. 4 4. 0 3. 0 2. 4 1. 5 1. 7 1. 2 1. 0 1. 15 0. 66 0. 48 0. 35 220 10. 9 5. 4 4. 8 3. 7 2. 9 1. 9 2. 2 1. 5 1. 2 1. 0. 80 0. 59 0. 43 450 15. 8 7. 8 7. 0 5. 3 4. 2 2. 7 3. 1 2. 2 1. 7 2. 0 1. 17 0. 89 0. 63 900 22. 8 11. 1 9. 9 7. 6 6. 1 3. 9 4. 5 3. 1 2. 5 2. 9 1. 70 1. 3 0. 94 1500 30. 1 14. 5 12. 9 9. 9 7. 9 5. 1 5. 9 4. 1 3. 3 3. 8 2. 24 1. 7 1. 3 1800 33. 2 16. 0 14. 2 10. 9 8. 7 5. 7 6. 6 4. 6 3. 7 4. 3 2. 48 1. 9 1. 4 2000 35. 2 16. 9 15. 0 11. 5 9. 2 6. 0 6. 9 4. 8 3. 9 4. 5 2. 63 2. 0 1. 5 2500 39. 8 19. 0 16. 9 12. 9 10. 4 6. 8 7. 8 5. 5 4. 4 5. 1 2. 98 2. 3 1. 7 37 CHAPTER 4 Wireless LAN 38 Chapter 4 Wireless LAN 4. 1 Wireless LAN (WLAN) 4. 1. 1 Wireless LAN Linking of t