Free Video Editing Programs for Journalists

With more and more news outlets incorporating video onto their websites, learning how to shoot and edit digital video news reports is a must. But while a digital video can now be shot with something as simple and inexpensive as a cellphone, professional video editings software programs like Adobe Premiere Pro or Apples Final Cut can still be daunting for beginners, both in cost and complexity. The good news is that there are plenty of free alternatives. Some, like Windows Movie Maker, are probably already on your computer. Others can be downloaded from the web. And many of these free video editing programs are pretty easy to use. So if you want to add digital video news reports to your blog or website, here are some options that will allow you to do basic video editing quickly and cheaply. (The caveat here is that if you eventually want to produce professional-looking news videos, youre probably going to want to master Premiere Pro or Final Cut at some point. Those are the programs used by professional videographers at news websites, and are well worth learning.) Windows Movie Maker Windows Movie Maker is free, easy-to-use software that will let you do basic video editing, including the ability to add titles, music, and transitions. But beware: Many users say the program crashes frequently, so when youre editing a video save your work frequently. Otherwise, you may lose everything youve done and have to start again. YouTube Video Editor YouTube is the worlds most popular video upload site, so it makes sense that it offers a basic video editing program. But the emphasis here is on BASIC. You can trim your clips and add simple transitions and music, but thats about it. And you can only edit videos that youve already uploaded to YouTube. IMovie iMovie is Apples equivalent of Windows Movie Maker. It comes installed free on Macs. Users say its a good basic editing program, but if you dont have a Mac, youre out of luck. Wax Wax is free video editing software thats a bit more sophisticated than the other programs mentioned here. Its strength is in the array of special effects options offered. But its greater sophistication means a steeper learning curve. Some users say it can be tricky to learn. Lightworks This is a feature-rich editing program that comes in both free and paid versions, but people who have used it say even the free version offers lots of sophisticated features. Of course, as with any of the more versatile editing programs, Lightworks takes time to learn and may be intimidating for neophytes. WeVideo WeVideo is a cloud-based editing program that comes in both free and paid versions. Its both PC and Mac-compatible and offers users the ability to work on their videos anywhere or to share and collaborate on video editing projects.

I. Introduction. Schindler’S List Begins In Kraków, Poland

I. Introduction Schindler’s List begins in Krakà ³w, Poland during World War II. At this time, the Nazi Party was trying to cleanse the world of â€Å"impure† people including Jews and rounded up all of the Jewish to make them work. In the movie, Oskar Schindler used Jews from the Krakà ³w ghetto to staff his factory instead of sending them to concentration camps. At first, he uses them only to make money, using bribery in order to get workers. Eventually, he realizes he is saving them from harsh treatment elsewhere and continues to make sure they don’t get sent to Plaszà ³w. At the end of the movie, Schindler creates a list of all the Jews he can afford to buy, around 1,100, and starts a munitions factory. The munitions they made did not work, so†¦show more content†¦In the movie, Amon Goeth, the commandant of the Plaszà ³w camp, sits on his balcony and shoots Jews with no reason to. During one of the early scenes, a young girl yells, â€Å"Bye Jew s, bye Jews!† as the Jewish are rounded up into the Krakà ³w ghetto, showing that the hatred of the Jewish is learned and accepted by both young and old. One person can convince many others that their way is the right way and the only way. Another important point is that one person can change the world. It is really important to the film because Schindler was just one man and he alone, with some help from Stern, saved so many lives. He could have saved one life and still made a difference, but he gave over one thousand people another chance to live. Each life he saved is a life not lost to the horrors of the Holocaust. He did all he could possibly do and still didn’t think it was enough. During one scene in the movie, a young Nazi boy finds a girl he knows and her mother. He tells them to come with him and he’ll put them in the ‘good’ line. Even though he had to follow orders, he still tried to help them. Sometimes it only takes one person to change another’s life for the better. III. Importance of the Film Schindler’s List is based on the true story of Oskar Schindler. It is brutally honest and gives viewers an important insight on what actually occurred during the Holocaust. Every time I watch a movie or video about the Holocaust, I

Business Process Management - Architecture - and Modeling

Question: Discuss about the Business Process Management, Architecture, and Modeling. Answer: Business Process Architecture This article reflects on business process architecture and design that is generally used by different organizations (Barros 2007). The article is based on certain business model architectures which can be implemented by various organizations in order to improve their business strategies in the competitive marketplace. It illustrated two real life cases of business process management. The first proposal for the architecture was developed in the year of 1988 and the proposed frameworks are used to design the organizational business architectures. In the business architecture it is also mentioned that, business processes that is relevant to the organizational development is an integrated process, consists of customer satisfaction, supply chain management system, support in the resource management etc. The paper depicts general BP architecture, which is business process ontology its execution management types of different macro processes and their process flow is also mentioned in this report. Apart from this, Barros (2007) stated that, the operating macro processes followed by Hp and APQC serves the same purpose but the process and information flowing techniques are different. According to Barros (2007) there are major four grouping macro processes such as Macro1, Macro2, Macro3 and Macro4, these are used to build business architectures. It has been also mentioned that the proposed business process pattern described are adopted by Hp and APQC. The sales management models, TV channel value chain model, operational risk management model and evaluation of new capabilities within the organization are also mentioned in this article (Barros 2007). However, to improve the process management system several data development procedures and analysis of those data are made with the help of th e developed operational risk management model. The overall discussion provides a long term and improved business process architecture that is helpful to develop the architecture supported by some of the well known organizations. However, the methodologies provide a secure connection between the architecture to the business logic approaches but certain limitations are defined. The article does not describe the factor integration that might support the designed business application. It highlighted executable business design models to avoid mapping. The major limitation of the article is this it provides applicable design model but when the business logic become complex the BPMN and BPEN model is unable to execute it. Therefore, in order to overcome the entire challenges al the required implementations are needed to be incorporated with it. Business Process Management The article reflects on a particular case which is strictly focused on the outcome of business process management experienced from a survey report of Swiss bank. According to Peter Kng andClaus Hagen (2007), it defines that how information technology is implemented in Swiss bank and how it helps to reduce risks within the organization. The objective of the article is to describe process reengineering in terms of information technology. Swiss bank has chosen Process oriented organizational design as a source for competitive design that explores the relationship between the process orientation and firm performance (Peter Kung andClaus Hagen 2007). The bank is considering multi dimensional construct, to examine the impact of management process in organizational performance. The application of IT and process restricting collaboration improve the financial structure of the company. According to Peter Kng andClaus Hagen (2007), the level of competition is increasing rapidly in the financia l industry and many of the organizations are suffering from this. A crucial limitation of this article which was admitted by Kung and Hagen also is that increased importance and demands of financial packaged software are not available always and may not be to provide cost effective integration for BPM systems. Another limitation of the process is that, the time estimated for the financial transaction is reduced in this modern approach whereas in traditional approaches the time utilization is very high. According to (Kung and Hagen 2007) every BPM system has reporting and performance measurement approaches some of them are broad but some of them are very basic. The authors have identified the risks present in implementation of BPM system in banking sector but do not provide any possible solutions or recommendations against the problems leads to unsuccessful completion of the research work. The lessons which are learnt from this article are that business process management in banking sector organization can provide better and unique quality of services to the customers. It is very crucial for banking organizations to retail global competitive advantages. However, the solutions to mitigate problems of BPM model related to financial packages, performance measurement report are not properly addressed in this article. Business Process Modeling This article reflects on standard business process model, the use of which is rapidly increasing in the business organizations namely as Business Process Modelling Notations (BPMN). It concentrates on who where, how and why the BPMN process modeling are using. According to Recker (2008) the article firmly focuses on BPMN process modelers and the risks associated to it during the modeling ad designing of BPMN. It is also mentioned that BPMN is an enough rich language that, defines multiple attitudes of the business processes including the initial process up to inter organizational process. Additionally, how the Queensland University of Technology served a worldwide survey on the real life application of BPMN in the business organizations are defined. From the survey it is also determined that the practices are adopted by different vendors such as education providers, consultants throughout world. Advertisements arranged by different companies also circulated the survey. Recker (2008), stated that BPMN is one of the most popular tools used by both IT and business communities. BPMN is used for business documentation, analysis and process simulation Major limitation is though lots of users are using BPMN process but they are not familiar to the language. Due to the vastness the process is still undergoing simultaneous revisions and extensions (Recker 2008). The author has collected data from the respondents who are using BPMN but have no practical knowledge about its developments, required tools and techniques. This kind of biased information has not the capacity to measure completeness and precision. In addition, problems and improvement areas of BPM model have been addressed but its real impacts on the users or business owners are not properly evaluated in this article. The article is found to be very helpful as it described all the lectures covered in class. It described the articulation process structures and decomposition of BPMN properly. However, the development of BPMN model, intention to fix inconsistencies or errors is not addressed properly in the article. In addition, poor development of BPMN model and its impacts on the business organization are not highlighted in this article. Reference Recker, J., (2008). BPMN Modeling Who, Where, How and Why. [online] https://www.sparxsystems.com.au. Available at: https://www.sparxsystems.com.au/press/articles/pdf/bpmn_survey.pdf [Accessed 9 Aug. 2016]. Barros, O., (2007). Business processes architecture and design.Business Process Trend,1. [online] https://www.bptrends.com/publicationfiles/05-07-ART-Business%20Processes%20and%20Design-Barros.pdf Kung, P. and Hagen, C., (2007). The fruits of Business Process Management: an experience report from a Swiss bank. [online] https://information-management-uni-fribourg.ch/. Available at: https://information-management-uni-fribourg.ch/Kueng_Hagen_2007.pdf [Accessed 9 Aug. 2016].

The Protagonists Growth an Example of the Topic Literature Essays by

The Protagonists Growth Introduction Need essay sample on "The Protagonists Growth" topic? We will write a custom essay sample specifically for you Proceed Huck in Huckleberry Finn written by Mark Twain came from a poor family and has grown independently. He is frequently homeless but despite this kind of environment he is under, he remained an intelligent boy. He may have his own unique way of thinking, but he remained steadfast on his beliefs and was able to learn from his independent ways. His self-reliance and perseverance turned him into a mature boy. Emma on the other hand as written by Jane Austen, is a girl who was born from a rich family. She may be well off but has insecurities in her life. Emma was deprived of attention and so she keeps on involving herself on other peoples lives. She was always jealous of other people. Her matchmaking tactics lead her life to a complicated one. Lastly, Asher in Asher Lev by Chaim Potok, is an interesting inpidual with conflicting personalities. Being raised a Jew; he was taught to be religious and was filled with inculcation as he grows up. He was trained to be closely attached and dependent to his family. However, as such, Asher remained a normal boy. He was gifted with a talent in art and this became his way of expressing himself. The powerful influence of his gift led his life into opposing directions, and confused his thoughts of which path to choose. Body The theme of Huck Finn is more of perseverance. The setting as the society itself, is Hucks home. His every adventure is a new learning experience for him. At an early age, he was able to inflict good, though sometimes unusual, thoughts of how to survive. He said that people get down on a thing when they dont know anything about it (Twain, 2004). However, this became his guide to survival. No one was there to teach him about anything so he was compelled to get down on these things to learn. Moreover, he struggled with different problems that adults face, but still take things positively. If Emma was in Hucks place, she would be rather helpless. It would be so difficult for her to survive in this kind of setting, but maybe she would be mature when this happens. As for Asher, it would be somewhat similar because he was almost independent when he chose his dream over his family, this only shows he has a mind of his own and old enough to decide for himself. The Emmas theme is more on jealousy. She has grown immature despite her good start. She was fortunate to have been raised in a wealthy family, but unfortunately remained childish as she gets older. She always gets other peoples attention; further became selfish and self-centered. Jealousy became more evident here. Matchmaking is her greatest amusement in the world (Austen, 2005). She finds it as an amusement an entertainment, rather than being concerned to help others. Unlike Asher, that thought about her parents dream despite his urge of becoming an artist. As compared to Huck, growing by himself gave him a mature mind even if his family wasnt there support him, while Emma with all the luck in her life, this didnt seem to help in her sense of maturity. She didnt have genuine good intentions when dealing with other peoples problem. The theme of My Name is Asher Lev is more on ambition. Asher was born with a gift (Potok, 2004), his love of art. He was raised well by his parents but things shifted when his gift became much evident as he matured. He was torn between this gift and being a server of the church. He thought of his life as he was living with his family and how was it like without them. Asher chose the world of art at the end of the story. Compared to Huck, he has grown to think for his own future, they are both independent at this aspect. However, Hucks really with the complete independence. Contrastingly with Emma that has grown immature despite all the good things in her life, the wealthy life and all the love in the world. Conclusion All the protagonists in the novels were of moral thought. They have grown in different ways but arrived in good morals. The novels want its readers to reflect. Maturity is just a matter of self-reliance and be able to decide and think by myself. Bibliography: Austen, J. (2005). Emma. New York: Cambridge University Press. p. 13. Potok, C. (2004). My name is Asher Lev. New York: Rosetta Books. Twain, M. (2004). The Adventures of Huckleberry Finn. London: Collector's Library. p. 5.

Free Essays on Johannes Kepler

Johannes Kepler Johannes Kepler was born on December 27, 1571, a premature child. He was born in Weil, in Swabia, a wine region in Southwest Germany not far from France. Kepler waent to the University of Tuebingen, a Protestant institution, where he studied mainly theology and philosophy, but also mathematics and astronomy. After Kepler graduated from Tuebingen, he was offered a professorship of astronomy in faraway Graz, Styria where he went in 1954. One of the duties of this Professorship was to make astrological predictions. While lecturing to his math class in Graz, contemplating some geometric figure involving Concentric Circles and triangles on the backboard, Kepler suddenly realized that figures of the type shown here determine a definite fixed ratio between the sizes of the two circles, provided the triangle has all sides equal, and a different ratio between the sizes will occur for a square between the two cirtcles, another for a regular pentagon. He really believed in the Copernicah Sy stem, so he saw the planetary orbits as six concentric circles. He felt the universe would somehow show mathematical beauty of symmetry. He suggested that the orbits might be arranged so that regular polygons would just fit between adjacent ones, and maybe somehow this reflected some invisible underlying structure holding it all together. Disappointingly, he found it just didn’t work the ratio’s where wrong. Then he had another inspiration. The universe was three-dimensional, and instead of thinking about circles, he should be thinking about spheres, with the planetary orbits along the equators. The anologue would be two concentric spheres with a tetrahedron between them, so that the outer sphere passes through the verticles of the tetrahedron, and the inner sphere touches all its sides, but is completely contained in the tetrahedron. There were just six planets, so five spaces between spheres, and there are just five regular solids... Free Essays on Johannes Kepler Free Essays on Johannes Kepler Johannes Kepler Johannes Kepler was born on December 27, 1571, a premature child. He was born in Weil, in Swabia, a wine region in Southwest Germany not far from France. Kepler waent to the University of Tuebingen, a Protestant institution, where he studied mainly theology and philosophy, but also mathematics and astronomy. After Kepler graduated from Tuebingen, he was offered a professorship of astronomy in faraway Graz, Styria where he went in 1954. One of the duties of this Professorship was to make astrological predictions. While lecturing to his math class in Graz, contemplating some geometric figure involving Concentric Circles and triangles on the backboard, Kepler suddenly realized that figures of the type shown here determine a definite fixed ratio between the sizes of the two circles, provided the triangle has all sides equal, and a different ratio between the sizes will occur for a square between the two cirtcles, another for a regular pentagon. He really believed in the Copernicah Sy stem, so he saw the planetary orbits as six concentric circles. He felt the universe would somehow show mathematical beauty of symmetry. He suggested that the orbits might be arranged so that regular polygons would just fit between adjacent ones, and maybe somehow this reflected some invisible underlying structure holding it all together. Disappointingly, he found it just didn’t work the ratio’s where wrong. Then he had another inspiration. The universe was three-dimensional, and instead of thinking about circles, he should be thinking about spheres, with the planetary orbits along the equators. The anologue would be two concentric spheres with a tetrahedron between them, so that the outer sphere passes through the verticles of the tetrahedron, and the inner sphere touches all its sides, but is completely contained in the tetrahedron. There were just six planets, so five spaces between spheres, and there are just five regular solids...

Welcome Emails How to Build Trust With New Subscribers - CoSchedule

Welcome Emails How to Build Trust With New Subscribers Pop quiz: A visitor comes across your website and decides to subscribe to your email list so they don’t miss out on any special offers, sales, or product launches. What do you do? If you’re an email marketer, your answer should be: Send a welcome email. Seventy-five percent of marketers think welcome emails are effective. Plus, 53% are already using them. How to Craft the Best Welcome Email to Build Trust With New SubscribersGet Your Free Welcome Email Template + Bonus Resources This post is packed full of great advice. But, you could probably use some tools to help pen perfect welcome emails. Enter these four templates: Welcome Email Copy Template: Craft creative email copy that gets your new subscribers excited. Email Subject Line Templates: Write better subject lines to make sure those emails get opened. Email Marketing Calendar Template: Plan out your email marketing workflows all on one calendar. Email Subject Line A/B Test Template: Track opens on subject lines, and refine them over time. Download them now, and then lets get down to work. Write better welcome emails with these templates from @What Makes a Welcome Email So Effective (and Important)? Three reasons: 1 ) The Attention Bonus Your new subscribers are still in engagement mode and very likely are still online and probably your website, too. In fact, the read rate for welcome emails is 34% as compared to 24% for normal commercial emails. 2 ) The Expectation Frankly, new subscribers sign up fully expecting an email to come to their inbox quickly. This is particularly true if you’re offering a sign-up discount, whitepaper, or other incentive. If you have an audience looking for your message, that’s reason alone to follow through. 3) The Opportunity to Get More Data With so many eyes on your message, why not leverage the opportunity to get more data? Ask your new subscribers for preferences in terms of products and services, message frequency, demographics, etc. The more data you collect, the better you can segment your list and target your future email marketing campaigns. Here is how marketers are currently using their welcome emails: Source: Return Path Here are three reasons why welcome emails are so important for marketers.Planning and Executing Your Welcome Email When putting together your welcome email, keep these 5 steps in mind: 1 ) Set Expectations and Keep Them To build trust amongst your new email subscribers, you need to deliver what you promised at sign-up. Did you promise a discount? A whitepaper? A free trial? Deliver it with your welcome email. Ultimately, your welcome email needs to be the foundation of your email experience with your subscribers. Therefore, setting expectations is important throughout every piece of your welcome email including: The From Name The Subject Line Email Copy As you’ll notice from the example inbox below, From Names and subject lines are critical to welcome emails: Allowing the user to know exactly WHO the email is from is key. After all, you’re much more likely to open an email from someone you know than someone you don’t. Subject lines are also important. They can be welcoming, thankful, and back up any sort of discounts or promotions you offered at sign-up. Exclusivity, â€Å"special† mentions, etc., can play key roles in subject line effectiveness as well. Do This With : Use our free Email Subject Line Tester to optimize every subject line you write, before you hit send. Your email content should back up what you promised as well. Whether it’s a plain-text approach or a more â€Å"traditional† HTML/image-based email is up to you. Generally, welcome email copy is clear and concise, but word count alone doesn’t determine whether a welcome email is successful (at least at a universal, all-industries level). This plain-text approach to a welcome email comes from Groove. This email, meant to establish a relationship between subscribers and the CEO, garnered a 41% response rate: This welcome email from Blurb  uses concise text and imagery to give a clear idea to the subscriber about what to expect. 2 ) Use What Data You Have to Personalize Your Welcome Email Make use of whatever information you have or collect sign-up to personalize your welcome message. For example, if you have first name, use it. Hope For Justice  is a non-profit organization that has used ‘first name personalization’ in their welcome email subject line, thereby enhancing the open rates. See how Freedom  includes the first name of the subscriber in their welcome email. Office  asks for the subscriber’s birthday in the last email of their welcome email series with an enticing copy and CTA â€Å"I WANT A BIRTHDAY GIFT†. Provide information and content that’s relevant to how they signed up or what they signed up for. For example: If they signed up directly:  Provide brand and product/service information. For new customers:  You can cross-sell similar or â€Å"next logical† products. For someone who requested a whitepaper or similar document:  Provide the link to download. For someone who requested a demo on your website:  Use this space for content that is aimed at getting the demo started. As mentioned before, you can also use this time to ask for more information. To make the email entertaining, you can use a rich media element  like high-resolution images, GIF, or a cinemagraph. 3 ) Design Compelling and Prominent CTAs The marketer’s reason behind a welcome email (and email marketing in general) is converting subscribers into customers. Your call to action (CTA) should be first and foremost in your mind in terms of how to design your welcome email. Simply put, it should be obvious what you want your customers to do. Your copy (and buttons) should be concise and easy to find. Hollister includes two distinct CTAs targeted to ‘guys’ and ‘girls’. The readers know exactly what the CTA is intended to do. Eddie Bauer includes one primary CTA that allows the subscribers to meet their team, with additional supporting CTAs that urge readers to involve themselves more into the brand on their social channels and blog. If you want to draw more attention to your CTA, you can use an interactive element  like an animated gif or even a countdown clock to generate urgency around a special offer. Recommended Reading: How to Write a Call to Action in a Template With 6 Examples 4 ) Use Color Effectively Colors can influence perception with your customers. Want proof? 60% of emails distinctly use the color blue. It represents trust, integrity, and efficiency, all virtues that are very important to consumers. Recommended Reading: The Know It All Guide to Color Psychology In Marketing 5 ) Introduce New Subscribers to Your Social Channels The time when someone subscribes to your emails is when they are most interested in your brand. This is a great time to tell them about other ways to connect with you- namely your social media pages. Give them a reason to do so- for example, tell them that it is on social media that you disclose your offers first. They are more likely to follow you on social media now than any other time because they are curious about your brand. McDonald’s  launches the third email of their welcome series with the subject line â€Å"We’ve got a real connection† to promote their social media channels and acquire more subscriber information. Below, see how Office  highlights their social media channels under the heading â€Å"Let’s hang†. Note: Also notice the request to get whitelisted at the outset of the email. 6 ) Send Immediately Ideally, a welcome email is sent immediately after someone signs up for your mailing list. As mentioned previously, these new subscribers are most engaged and likely still on your website. Make sure your automation is set right to deliver your welcome message as soon as possible. Multiple Welcome Emails Can Be Better than 1 You may have a lot that you want to share with your new subscriber. But conveying it all in one email could simply be too much. Sending a series of welcome emails can help you build trust in your brand as you gradually provide all the information new subscribers may be looking for. How many emails you include in your series is up to you. I usually recommend starting with a 3-email series. Your First Email Sent immediately after you’ve received the subscriber’s email address. You should include: A sign-up confirmation message Some sort of ‘Thank You for signing up’ or ‘Welcome onboard’ messaging Language that sets subscriber expectations. Tell them what to expect and when to expect it. The Bath and Body Works  example below is a great example of a simple and informative first welcome email. Your Second Email Sent 24 hours after the first email is sent. Some elements you can include: Social media links to connect with them on other platforms. Your bestselling products (or product categories) Below is the second welcome email from Bath and Body Works. You’ll see that they introduce their categories of products. Your Third Email Sent 2 days after the second email is delivered. Some elements you can include: Local store information Product information A request to collect additional subscriber data Below is the third message from the Bath and Body Works  welcome series. Examples of Welcome Emails You Will Love Welcome emails are crucial for creating a good first impression. I’ve rounded up some quality B2C and B2B welcome email examples that I think do just that. 1 ) BBC They begin by setting the stage for what the subscribers can expect in the days to come and when they will be receiving emails. They suggest videos that the subscriber may like to check out- adding that the suggestions may not be spot on. The BBC uses this opportunity to ask for further engagement so they can collect more data and deliver better suggestions. Nice work! 2 ) Boden Boden welcomes the new subscriber by telling the subscriber about the benefits they will be enjoying by joining the brand’s email list. They also offer a 15% welcome discount and free shipping. They complete the package by providing links to social platforms in the footer. 3 ) Best Buy A warm welcome with solid, prominent CTAs, links to important categories, and social buttons in the footer. 4 ) Cotton On This email begins by introducing the subscriber to the Cotton On family of brands. They personalize the email by adding the subscriber’s first name. A coupon code to redeem a 20% welcome discount makes the email even more engaging. They also prominently display the link to the preference center where the subscriber can set their email preferences. 5 ) J. Crew J. Crew keeps it simple. They nudge the subscriber to explore their website through two links (they could test CTA buttons). Through a secondary offer, the subscriber can also sign up for the style guide. Social buttons are included in the footer but are not prominent. 6 ) GoDaddy This is a nice approach from GoDaddy. They provide help to businesses in making the right domain name choice through 10 tips. They also highlight the first purchase discount at the top along with a prominent CTA. Let’s Recap Here are some common best practices to follow. Do: Send your welcome email or the first in the series immediately after sign-up. Any delay can affect campaign performance and subscriber engagement moving forward. Keep your welcome email simple. A straightforward, scannable design, a warm welcome, and a brief description of what they can expect in your future emails should do the trick. Personalize your email with the help of whatever data you have- subscriber name, first interaction point, etc. A personal touch can go a long way. Use imagery and colors that are consistent with your brand. There should be no disconnect between the look and feel of one channel to another. Use automation to make your life easier. Set rules for welcome emails to be triggered on completion of signup forms, document download requests, free trial requests, and even new purchases. Get your subscribers to whitelist your sender email address so that your future email campaigns don’t end up in the spam folder. And here are some common pitfalls to avoid. Don't: Set the wrong expectations. Deliver what you promise. Nothing can harm your reputation more than not fulfilling a promise. Showcase links to social channels on which you are not active or are not relevant. Brag (too much) about your brand or product/services. Take an inbound approach to your content and let subscribers know how you or your product/service can help them solve a problem. Email marketing can build trust between your brand and your subscribers. Your welcome email lays that foundation. Make sure your welcome email (or series) lays a strong, positive foundation. Have you tried anything innovative in your welcome emails that gave you great results? Share in the comments below.

History of Mathematics High School Essay Example | Topics and Well Written Essays - 500 words

History of Mathematics High School - Essay Example The rods are placed in columns with the rightmost column representing the units, the next column representing the tens, then the nest representing the hundreds, and so on. Red rods represent the positive numbers while black rods represent the negative numbers. For example, the number 25 will have a representation using the rods where 5 will be placed in the rightmost column and 2 will be placed in the next column. An empty column represents zero (Chinese Rod Numerals (Counting Rods)). The rods were carried in a pouch and placed on a counting board which had compartments corresponding to the ones, tens, hundreds place and so on. Each compartment was split into two parts. The right part is for the heng (1 to 9) rods and the left part was for the tsangs (10 to 90) rods. Whole numbers are represented by combining these two types of rods. After the rods were placed in their rightful compartments, they were then manipulated by repositioning and reforming them as required by the arithmetic operation. The first evidence of the existence of zero is from the Sumerian culture in Mesopotomia some 5,000 years ago (Wallin). This was in the form of cuneiform symbol for numbers where a slanted double wedge between two cuneiform symbols indicates an absence of a number or zero. Over time it became a positional notation form in the Babylonian Empire.

Health Care PublicPolicy Assignment Example | Topics and Well Written Essays - 1000 words

Health Care PublicPolicy - Assignment Example During the mid-2000s, the American Hospital Association (AHA) predicts that the United States would experience a shortage of employees serving the healthcare department. These workers include physicians, nurses, dentists, and medical interns. The healthcare workers shortages observed is due to the increased growth seen in the population, the high number of aging patients such as the baby boomers and the rise in the number and occurrence of chronic diseases. This essay will explore the causes, which are responsible for the shortage of healthcare workers in the US, and remedies that have been put in place to help alleviate the shortage. It is important for the government to understand and identify the causes of healthcare workers shortages. Identifications of such shortages enable for effective planning and coming up with solutions to curb the rise in healthcare workers shortages effectively. The following are some of the causes that were determined to contribute to the scarcity of healthcare workers in the US. The increase in the demand for healthcare in the US is a great contributor to healthcare workers shortages. The demand increase is due to the rising population numbers (putting more pressure on the strained healthcare services), a large number of the US population growing old, and a large number of chronic diseases recurring often. For instance, the U.S. Census Bureau projected that the population growth of the U.S. will increase by 13 percent while the aging population will compromise 20 percent of the population by 2030. On the other hand, 50 percent of the population will be suffering from chronic diseases (U.S. Department of Commerce, 2010). These statistics show the massive demand for the healthcare givers that will be required in a few years. The current shortage being experienced will thus be magnified in a few years time. There is an inadequate growth

The impact of the internet Essay Example for Free

The impact of the internet Essay 1. INTRODUCTION The Internet has taken the business community by storm since the early 1990s. When the community realised the potentiality of the Internet they hailed it as the most transforming invention in history. It has the ability to completely change the way business is being done. And, it is doing so at a feverish pace, turning business upside down and inside out (The Economist 1999). Information Technology (IT) experts went on to use the Internet technology to spin off the Intranet and Extranet to enhance business competition. Together with the Internet, their innovative implementations were able to provide competitive advantage for a company. The Internet, Intranet and Extranet collectively have dramatically affected business. A growing number of corporations believe in the technologys potential to lower cost, add value, improve productivity and create new business opportunities (The Economist Intelligence Unit 2001). So much has been written about the Internet, Intranet and Extranet. What exactly are they? What are their impacts on current business practices and activities? This report seeks to address these questions in the Trading Process Network, a business tool that integrates the Internet, Intranet and Extranet technologies. First, the report introduces the Internet, Intranet and Extranet. Then, it goes on to provide a brief description of the Trading Process Network. Subsequently, the study proceeds to critically review the positive and negative impacts of the Trading Process Network on current business practices and activities. It concludes with some key findings resulting from the positive impact and then provides some suggestions to overcome the negative impacts. 2. INTERNET, INTRANET AND EXTRANET. The Internet technology has risen so fast in the last ten years that it is now considered a business necessity. The Star (2004), a local newspaper, published the figure below summarising the history of the Internet. (source: Star 2004) Figure 1: History of the Internet. Presently, business corporations all over the world are scrambling to implement this technology to take advantage of its impact on their business practices and activities. The Internet The Internet is a dynamic group of computer networks that interconnect computers around the globe (Comer 1997). It is a network of networks thus a powerful form of information and communication technology. Figure 2 illustrates the Internet setup. (source: GE Lighting, www.gelighting.com) Figure 2: The Internet network Computers linking to the Internet communicate by using a common Internet protocol to disseminate information across computers (Kambil 1995). Users of the Internet can communicate electronically, retrieve information and interact with other computers. Therefore, Kambil (1995) said that the Internet is basically used for: * Electronic mail and news services * File transfer to and from remote computers * World Wide Web * Telnet the ability to use remote computers The World Wide Web is the information space for storing and retrieving hypertext documents on the Internet through a unique addressing scheme (Schaper Volery 2002). Often, the Internet is known as the World Wide Web or Information Superhighway because of its superior information reservoir. Any information placed on public web servers can be viewed by anyone with Web access using a browser such as Netscape Navigator or Microsoft Internet Explorer (Bullock et al. 1997). The Intranet. The Intranet is an internal corporate communication networks riding on the transmission control protocol / internet protocol (TCP/IP) (Szuprowicz 1997). (source: GE Lighting, www.gelighting.com) Figure 3: The Intranet network It is designed for staff use only and does not to allow outsiders access. The intranet hooks into corporate databases giving the individual users access to all this data through the standard Web browsers that access Web pages on the Internet (Competia n.d. in Knowlegdepoint 2002). Although the Intranet still allows company employees access to the Internet, outsiders are prevented from entering the internal corporate sites by security features (see Figure 3). The Extranet. An extranet is an extension of the Intranet that is partially accessible to authorised distributors, suppliers, customers and business partners (Long and Long 2005). Simply, an extranet is set up on the same TCP/IP network as the Intranet which allows outsiders access to that same internal corporate information (Bullock et al. 1997). Refer to Figure 4. (source: GE Lighting, www.gelighting.com) Figure 4: The Extranet network Like a private business club, the extranet centralises business transaction by using the same user-friendly technology that has made the Internet a global network. Its members can include companies of all sizes located in virtually every corner of the world (GE Information Services 1999). The Hierarchy. The Internet is the conceptual incubator of both intranets and extranets, and universal connectivity has liberated corporate communications practices (Franklin Jr. 1997). Though they are all Internet and Web based technologies, there are differences between them such as: * The type of information each are designed to disseminate * The targeted group of people allow to access the information * Security Table 1 below compares some of the common differences: Information Type Targeted Group Security Internet general general public lacking Intranet corporate employee moderate Extranet specific to business selected outsiders good Table 1: Common differences between Internet and Web based technologies Wailgum (1998, p. 1) appropriately summed up the differences with this statement: First there was the Internet, which is available for everyone to use. Then businesses got smart and started developing their own intranets that used the same friendly Web interface but put up firewalls so that only employees could see the information on the site. Finally, the extranet was created. It finds itself somewhere in between. Theres still a firewall, but you allow only selected outsiders, such as business partners and customers, inside. Following the differences, the structural hierarchy can actually be illustrated as shown in Figure 5 below: (source: Bullock et al. 1997) Figure 5: The Internet hierarchy The Internet, the World Wide Web and Internet-based technologies such as intranets and extranets provide global links to a businesss customers and suppliers. This allows electronic commerce (e-commerce) applications (Schaper Volery 2002). Phil Gibson, director of interactive marketing at National Semiconductor, is blunt about the importance of the Internet, Intranet and Extranet to the applications when he said, Without all the nets, you just cant do that. (Franklin Jr. 1997). 3. THE TRADING PROCESS NETWORK. The Trading Process Network (TPN) is a technology that integrates the Internet, Intranet and Extranet into a package to revolutionise the way  business is done. It is pioneered by General Electric (GE), a well diversified company with business in technology (aircraft engine, plastics, power generators and consumer electronics) and services (financial services, television broadcasting and medical and science services) (General Electric 2004). (source: General Electric, www.ge.com) GEs leadership in management has long been recognised and progressive. Many of its successful business portfolio management, strategic planning, quality initiatives, employee empowerment and business process reengineering are business models for companies worldwide ( 1997). Jack Welch, GE former chief executive officer, anticipated the potential threat of the Internet. He told the MRO Today magazine (Arnold 2001, p. 1) that: Its like any big change. You can look at it in one of two ways: as an opportunity or as something to fear. You have to have a certain amount of fear to see the opportunities. The Internet is all about getting information from its source to the user without intermediaries. The new measurement is how fast information gets from its origin to users and how much unproductive data gathering, expediting, tracking orders and the like can be eliminated. Seeing reality today means accepting the fact that e-business is here. Its not coming. Its not the thing of the future. Its here. The challenge is to resolve issues in the context of the new Internet reality. Tentativeness in action can mean being cut out of markets, perhaps not by traditional competitors but by companies never heard of 24 months ago. GEs challenge is to leverage the Internet technology as a strategic weapon at a corporate level to change its business practices and activities. It started developing the TPN in 1995 as just an internal GE Intranet using an Oracle7.2 database server with a Netscape Communications commerce server and custom software developed by GE. One year later, it developed to include the Extranet. Full integration with the Internet occurred in 1998 when GE, Thomas Publishing Company and Oracle together created a data registry accessible via the web to search out suppliers of such goods or services. The database lists over 60,000 products from about 6,000 vendors and it took six IT people three months to create ( 1997; 1998; Linthicum 1996; 1997; n.d.). Figure 6 shows a typical TPN concept. (source: Bullock et al 1997) Figure 6: A typical Trading Process Network model. Basically, the TPN allows GE to call for tenders and manages bids from suppliers around the world via the web. Using the TPN Intranet software and other standard office applications, GE creates a set of tender documents with a response form. GE then searched the TPN Internet database for suppliers and decides whom it would like to receive a quotation. The tender documentation is forwarded to the list of prospective suppliers through the TPN Extranet. Suppliers who are interested in bidding began to download the call for tender and passed back to the TPN upon completion. GE may then access and evaluate them anytime ( n.d.). The TPN is so successful that many corporations wasted no time in emulating GEs initiative by creating their own version of the TPN. Today, many corporations have implemented the TPN system in one form or another. For example, Tesco developed the Tesco Information Exchange that linked the retailer with all its suppliers to increase product availability and reduce wastage (GE Information Services 1999). Presently, GE is also commercially offering its TPN technology comprehensively to companies around the world ( n.d.). Its global implementation has impacted business practices and activities which shall be discussed shortly. 4. POSITIVE IMPACT OF THE TPN ON BUSINESS. Since the TPN is a collaboration of the three web-based technologies, it is essential to critically review the positive impact of the three technologies on current business practices and activities separately. Many of the evidences presented here are taken from the impact on GEs business practices and activities. This is because as the world most admired company (General Electric 2004), GEs business practices and activities has been acknowledged and adopted globally as role models. The TPN Internet Impact. As an Internet solution to conduct business electronically and simplify business processes like purchasing, selling and marketing, the TPN impacts business practices and activities in many ways (http://www.mngt.waikato.ac.nz/depts/mnss/courses/ 456/cases/geis.htm n.d.). Some of these impacts are listed on the Computing Insights website (, n.d.): * Instantaneous Communication. The Internet establishes immediate communication between companies and their prospects, customers, and employees without waiting and down time. It is a very fast and efficient method of communication, with messages arriving anywhere in the world in a matter of seconds (Schapel Volery 2002). By taking advantage of this the TPN enables GE to evaluate suppliers bids and award within the same day and orders may start arriving to the supplier within 24 hours ( 1997). Speed in despatching specialised information enhances service relationship thus providing superior service (Khambil 1995). * Global Access. The worldwide reach of the Internet opens the door to unlimited business opportunities by instantly placing it in any office or any home. Business  websites are doors to businesses that never close. Information about products and services are accessible anytime. The web is ideal for providing whole year round self-services ( 1998). GE Lightings 46 plants around the world procure materials and parts from more than 25,000 suppliers globally. By utilising the TPN, GE Lighting has electronic access to this list. With only a set of catalogues and documents GE Lighting obtained multiple feedbacks instantaneously ( 1997). Furthermore, the TPN provides global access to Gary Reiner, CIO of GE to monitor GEs mission operations once every 15 minutes across the companys 13 different businesses around the globe with different time zones (Lindorff 2002). * Instantaneous Customisation The Internet keeps businesses in the fast lane by offering goods and services in real time thus providing individual company the ability to tailor to the needs of customers. According to Barua et al. (n.d.), Dell Computer implemented an online supply chain management application which is somewhat similar to the TPN to help its component suppliers increase the accuracy of their forecasts by providing them access to direct customer order information. This way Dells suppliers can customised their products to Dell customers needs. Frantz (2000, p. 2) provided another example from GE Aircraft Engines: GE Aircraft Engines maintenance and overhaul market frequently requires decision on retention, rebuilding or discarding a worn part. Previously, the worn part was sent to the customer to be evaluated or the repairs had to wait until a customers representative could inspect it at GE, often taking many days. Today, a new customised part can be graphically transmitted over the TPN and quickly evaluated by the customer before installation. * New Distribution Channels. The Internet can rapidly reduce the time to market for new products because direct distribution shortens the path to markets. Electronic commerce can be used to find the best deal from distributors in terms of time and cost (Schapel Volery 2002). The TPN is a secure electronic commerce environment that supports the business-to- business buying and selling of goods and services. It provides GE the ability to find new distributors based upon the database records ( n.d.). Home Depot is one such distributor when it set up a TPN form of Internet application that enables GE appliances purchased at Home Depot to be delivered directly to consumers homes from the nearest GE warehouse (Barua et al. n.d.). * E-Shopping The Internet enables many companies to create an electronic shopping environment that enables users to browse, review, select and purchase products instantly. It is a revolutionary business tool, guaranteed to attract new, web-knowledgeable customers who buy everything online (Schapel Volery 2002). This is the TPNs primary solution where the TPN Marketplace provides purchasing professionals access to a searchable catalogue of GE goods and services including pricing and contract terms in a standardised format (Mark 2001). The TPN Intranet Impact. By allowing company staff exclusive access to corporate information electronically, the TPN Intranet positively impacts current business practices and activities. Some of these impacts are mentioned in the  Vialogix website (Vialogix n.d.): * Increase productivity. The Intranet has the ability to increase staff productivity. According to the Vialogix website, many companies have invested in intranets to boost productivity and encourage knowledge sharing. Its to have tools aimed at productivity, at letting employees do their jobs better and more efficiently, says Pam Wickham, e-business public relations manager and manager of GE (USA Today (Tech Report) 2001). Bill Snook, a sales manager at GE Energy Services in Canada said his TPN Intranet sales portal home page is the gateway to all the applications that he has. Anthes (2003, p. 2) reported Snook as saying: Before I used to go from one application to another to search for things randomly and each required a separate sign-on and password. The new portal has made multitasking much more efficient and has increased face time with customers. In May 2001, IBM launched its TPN offshoot known as the WorldJam where its 52,600 employees worldwide convened online to swap ideas on how to work faster without undermining quality (Fast Company 2001 in Vialogix n.d.). * Reduced paperwork. When employees communicate through the Intranet they effectively reduce the amount of paperwork required such as internal memos, invoices and printed company newsletters. Forbes (2001 in Vialogix n.d.) reported that GE processed 3.1 million paper invoices in 2000. Today, half of those invoices are processed digitally. John Rice, the chief executive of GE Transportation system, confirmed this fact when he said that the 1 million pieces of paper GE faxes to suppliers  each year are going to go away (GE Transportation System 2000). * More informed/empowered employees. There are many types of competitive or business intelligence information that can be included on an Intranet. Users can easily navigate and locate this information using the point-and-click hyperlinking technology (Linthicum 1996) to be informed and empowered. General Electric uses the TPN to manage its business intelligence by keeping its globally dispersed workforce informed. In a survey by the Society for Human Resource Management, more than 85% said the intranet is useful for disseminating information (USA Today (Tech Report) 2001) Szuprowicz (1997, p. 7) found out that the information available in the TPN are: Annual report of the company, financial data and business information designed to allow employees to manage their own investments. In addition, GE provides employees direct access to the GE travel centre which allows them to schedule their own business trips. * Savings in expenditure. Companies exploit the inexpensive Intranet web technology for in-house applications. Since the web applications use only a single browser, training is less. Moreover, implementation costs are considerably low due to a single interface, protocol and middleware architecture (Linthicum 1996). In a 1997 survey, American Express discovered the magnitude of the savings (Fast Company 2001 in Vialogix n.d.): It was found that at a typical company where paper still predominated, the average cost of handling a single expense account was #36 or more. After switching to a similar TPN approach the cost reduced to as little as $8 per  account. * Connects users across disparate platforms. The TPN Intranet is a new dynamic client/server application development platform for corporate applications that uses open standards such as TCP/IP, HTTP, HTML, CGI, ODBC and Java to connect heterogeneous database (Linthicum 1996). Venki Rao, an IT leader in GE Power Systems, said that the TPN sales portal software has an open architecture and is flexible, making it especially easy to connect all the different platforms (Anthes 2003). USA Today (Tech Report) (2001, p. 1) reported that after GE revamped its Intranet last year, 10 million visitors a week used it: By connecting all its disparate platforms through the TPN, GE employees can now create personalised pages, read industry-specific news or check the weather. They also can download tax forms and review benefits information. An online marketplace offers discounts on GE appliances, Dell computers and other products.

Essay on Camus’ The Stranger (The Outsider): Reader Response Criticism

Reader Response Criticism to Camus’ The Stranger (The Outsider)  Ã‚        Ã‚  Ã‚   In The Stranger (The Outsider), Albert Camus anticipates an active reader that will react to his text. He wants the reader to form a changing, dynamic opinion of Meursault. The reader can create a consciousness for Meursault from the facts that Meursault reports. By using vague and ambiguous language, Camus stimulates the reader to explore all possibilities of meaning. Camus also intends to shock the reader into rereading passages. Through discussion of narrative structure, the opening lines, the role of pity, resentment toward Meursault’s judges, and the relationship between murder and innocence, I will prove that Camus’ purpose is to bring the reader to introspect on their own relationship with society. Through narrative structure, Camus invites the reader to create and become the consciousness of Meursault. Utah Sate University Professor David Anderson notices that â€Å"Meursault takes the stance of simply reporting these impressions, without attempting to create a coherent story from them.† Indeed, in Part One, what Meursault reports are exclusively facts. Micheline Tisson-Braun comments that Meursault â€Å"registers facts, but not their meanings; ... is purely instantaneous; he lacks the principle of unity and continuity that characterizes man† (49). Through generalization, the reader links the details of Meursault’s life. The reader thereby creates their own meaning for Meursault’s actions. Meursault, without a memory or an imagination, refuses to spend time connecting events and contemplating essences. The reader does this for Meursault. Thus, the reader creates a consciousness for Meursault that is uniquely the reader’s. It exactly represen ts Meursau... ...der to experience the trial in the place of Meursault. Perhaps Camus wrote all of Part One to set up the reader in a situation where they must reassess their relationship with society. Whatever the reader’s emotional response, Camus places the reader in position to experience the trial, l’absurde. Through anticipation of a responsive reader, Camus communicates the essence of l’absurde. Works Cited Camus, Albert. L’à ©tranger. France: Éditions Gallimond, 1942. Camus, Albert. The Stranger, trans. Mathew Ward. New York: Random House, Inc., 1988. Girard, Renà ©. â€Å"Camus’ Stranger Retried.† â€Å"to double business bound† Essays on Literature, Mimesis, and Anthropology. Baltimore: Johns Hopkins U P, 1978. Tisson-Braun, Micheline. â€Å"Silence and the Desert: The Flickering Vision.† Critical Essays on Albert Camus, ed. Bettina L. Knapp. Boston: G. K. Hall & Co., 1988.   

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