7 Reasons to Enroll a Child in an Online Elementary School

Every year, hundreds of parents pull their kids out of traditional schools and enroll them in virtual programs. How do online elementary schools benefit children and their families? Why are parents so eager to remove their kids from the system that has worked for decades? Here are some of the most common reasons: 1. An online school gives kids the freedom to work on developing their passions. Two decades ago, primary school children were given little no homework. Now, students often return from school with hours of worksheets, drills, and assignments to complete. Many parents complain that students aren’t given the opportunity to focus on their own talents: learning an instrument, experimenting with science, or mastering a sport. Parents of online students often find that students are able to complete their assignments faster when they don’t have the distraction of peers to hold them back. Many online students are able to finish their coursework in the early afternoon, leaving many hours for kids to develop their own passions.​ 2. Online schools allow kids to get away from bad situations. Difficult situations with bullying, bad teaching, or a questionable curriculum may make school a struggle. Parents certainly don’t want to teach their kids to run away from a bad situation. However, some parents find that enrolling their child in an online school can be good for both their learning and their emotional health. 3. Families are able to spend more time together after enrolling their kids in online school. Hours of class, after-school tutoring, and extracurricular activities are leaving many families with no time to spend together (aside from homework tantrums). Online schooling lets kids complete their studies and still spend quality time with their loved ones. 4. Many online schools help kids work at their own pace. One of the drawbacks of traditional classrooms is that teachers must design their instruction to meet the needs of the students in the center. If your child is struggling to understand a concept, he may be left behind. Likewise, if your child is unchallenged, he may have to sit bored and uninspired for hours while the rest of the class catches up. Not all online schools let students work at their own pace, but a growing number provide students with the flexibility to get extra help when they need it or move ahead when they don’t. 5. Online schools help students to develop independence. By their nature, online schools require students to develop the independence to work on their own and the responsibility to complete assignments by the deadline. Not all students are up for the challenge, but kids that develop these skills will be better prepared for completing further education and joining the workforce. 6. Online schools help students develop technology skills. Technology skills are essential in almost every field and there’s no way for students to learn online without developing at least some of these essential abilities. Online learners tend to become proficient with internet communication, learning management programs, word processors, and online conferencing. 7. Families have a greater educational choice when they are able to consider online schools. Many families feel like they are stuck with few educational options. There may be only a handful of public and private schools within driving distance (or, for rural families, there may only be a single school). Online schools open up an entirely new set of choices for concerned parents. Families can choose from state-run online schools, more independent virtual charter schools, and online private schools. There are schools designed for young actors, gifted learners, struggling students, and more. Not all schools will break the bank, either. Publicly-funded online schools allow students to learn without charge. They may even provide resources like laptop computers, learning supplies, and internet access.

A Culture of Corruption Everyday Deception and Popular...

Daniel Jordan Smith presents an outstanding work full of insight and appreciation of Nigerian culture. The content is enriched by his years spent working there, his marriage to a Nigerian woman and his obvious affinity for the Nigerian people. Smith’s primary aim is to reflect upon popular Nigerian sentiment toward corruption but also to explore just how entrenched corrupt practices have become in society. The book focuses on two main elements; how Nigeria is as much a ‘culture of corruption’ as it is ‘against corruption’ (p. 6). The standard discourse that exists between Nigerians themselves as well as the rest of the world is that Nigeria has a history of debilitating corruption. Smith’s work is therefore appealing to a variety of†¦show more content†¦This is centred round the ‘moral economy’ of corruption (Olivier de Sardan, 1999). This concept refers to the practice of corruption justified by its perpetrators for reasons relating to cultural values; in ways that are not stigmatised or even deemed corrupt (Olivier de Sardan, 1999). An interesting term he utilises is the ‘idiom of accountability’ that explains the rise of popular discontent suggested by the title (p. 19). Smith regularly emphasises how traditional ideals of patron-clientism are considered the most important idiom of accountability left in a society spiralling out of control. ‘String pulling’ by patrons to assist friends and relatives is considered legitimate, to act otherwise would be c onsidered immoral (p. 17). While this is undoubtedly true, Smith overemphasises this point to the extent that the reader is left wondering if this is too simple an explanation for ambivalence. If this behaviour is the general consensus for both regular Nigerians as well as the political elite, the next section of the book unpacks how the public are becoming increasingly critical of their politicians. As Smith suggests patron-clientism is embedded in Nigerian society and so it appears nobody is spared from participating in it. The author himself used his connections to get his niece into a good school. Discontent is aggravated when modern bureaucracy meets traditional patron-clientism for the sole purposes of increasing one’s personal wealth. No longer operatingShow MoreRelatedStephen P. Robbins Timothy A. Judge (2011) Organizational Behaviour 15th Edition New Jersey: Prentice Hall393164 Words   |  1573 PagesBehavior 271 Understanding Work Teams 307 Communication 335 Leadership 367 Power and Politics 411 Conflict and Negotiation 445 Foundations of Organization Structure 479 v vi BRIEF CONTENTS 4 The Organization System 16 Organizational Culture 511 17 Human Resource Policies and Practices 543 18 Organizational Change and Stress Management 577 Appendix A Research in Organizational Behavior Comprehensive Cases Indexes Glindex 637 663 616 623 Contents Preface xxii 1 1 Read MoreOne Significant Change That Has Occurred in the World Between 1900 and 2005. Explain the Impact This Change Has Made on Our Lives and Why It Is an Important Change.163893 Words   |  656 PagesPublic Memories Tiffany Ruby Patterson, Zora Neale Hurston and a History of Southern Life Lisa M. Fine, The Story of Reo Joe: Work, Kin, and Community in Autotown, U.S.A. Van Gosse and Richard Moser, eds., The World the Sixties Made: Politics and Culture in Recent America Joanne Meyerowitz, ed., History and September 11th John McMillian and Paul Buhle, eds., The New Left Revisited David M. Scobey, Empire City: The Making and Meaning of the New York City Landscape Gerda Lerner, Fireweed: A Political

Byte Products free essay sample

In this case study, the situation Byte is facing is that their production facilities are operating at 100% capacity. Byte has three facilities in the United States and they are all running three 8 hr. shifts, 24 hours a day. Since demand for the products is so high, Byte has an immediate need to increase production but lacks the physical space to do so. This is a serious problem because other companies, both domestic and international, have been entering the market due to the high profit margin and consumer demand. Lack of available products from Byte will leave their loyal buyers no other choice but to entertain these new manufacturers. The C. E. O. and Chairman of the Board of Byte Products, James Elliot has addressed this problem by proposing the construction of a new production plant in the Southwest United States which once in operation will bill able to produce enough to keep up with the current demand. Unfortunately the new plant will take three years to build and if Byte is unable to supply enough product they will lose their hold on the market and other companies will step in to satisfy demand. Mr. Elliot has heard various suggestions from staff specialists on how to address this shortage of product. Byte could license production of their products to another company in the U. S. but premium charged to them to cover the overhead costs would increase the price of the product and they would lose customers. Another option would be to license their products overseas where manufacturing and overhead costs are much cheaper, When the company was was established, the founding members agreed to keep manufacturing in the United States and the shareholders believe this policy has been an asset. Licensing production overseas would enable others companies to reproduce there efficient production methods as well as leave them vulnerable to patent infringement. Any licensing of Byte’s production would not guarantee quality control and adherence to their standards. The only other option favorable to Mr. Elliot was the temporary leasing of another facility until the construction of the new plant is finished. The empty facility, located in the northeast U. S. could be inexpensively leased but would need three months for renovation. Unfortunately it has been determined that this facility will never be profitable due to inefficient production, high union labor costs and warehousing and transportation issues. Temporarily though using it for additional production would alleviate the supply shortage. Mr. Elliot feels this is their best option and will present it to the Board at the next meeting. Things do not go as well as he expected when outside director on the board opposes his solution on the premise that it is unethical to set up a temporary plant and disrupt a community. His arguments surprise and sway members of the board and he tells Mr. Elliot he feel there is no compromising using this temporary facility. Based on the facts of this case study, I feel that Byte management was lacking strategic planning for the future. If sales have consistently increased for the last six years, there should have been a plan put into place at least five years ago to address increased supply demands. Obviously the board and the shareholders were happy that the company was profitable but they did not plan for what was necessary to support future sales. The C. E. O. who was also on the board is doubly at fault for not doing the same. He should have presented a strategic plan to the board and they should have reviewed it. Corporate governance is one main issue in this case because a board of directors has a responsibility to the shareholders to oversee the activities of the corporation and to insure they are protected as well as to maximize profits. There is a conflict of interest when the C. E. O. is also the chairman of the board because the board may feel pressured to always go along with what the C. E. O. says. In this case it seems that neither the C. E. O. nor the board had a plan to deal with increased production needs. I think that Byte’s situation should have been addressed initially at the Evaluation and Control step of the strategic management model. They were obviously tracking their increased sales but where was the evaluation of how those numbers affected their production. They should have seen their limitations and planned for their increased product demands. This would have returned them to the first part of the strategic management mode, environmental scanning. Internally, their strengths did lie in the fact that that had a very efficient production system and they were a leader in the industry but they did not plan for increased production needs and this was a weakness in the structure of the organization and their chain of command. They should have analyzed the capabilities of the three plants they had and set up a pro forma based on increased sales to predict is they would be able to fulfill future orders. Eternally, they did not seem to anticipate that other companies might want to step into the market since there was demand, high profit margins and not a lot of competition. They should have known that a technology such as theirs would be increasing over time and that in order to stay the industry leader they would have to stay on top of their game and constantly watch out for any competition. I think that the board member who opposed the temporary solution should have expressed his feelings sooner or at least foreseen this situation. It is irresponsible for him to reject the proposal without having some idea of another solution. I think they can come to a compromise. If they do use the empty plant in the northeast U. S. they can try and bargain with the union to set up a plan that benefits the employees. By letting the community know in advance that the plant will only be open for three years, the company and the unions can work together to come up with a solution that benefits both parties. They could also offer job transfers to their employees. The company cannot realistically expect to make a profit at this plant but must recognize that it exists to offset shortages in production. That is where strategy formulation comes in to play. If the mission of the company is to supply their products and continue to be the industry leader they need to increase production and plan a schedule for sales fulfillment. There is also the other option of finding a plant closer to where they are building the new facility. Even if they might pay more to lease the building and set it up, the savings from labor costs and transportation costs might offset those factors. Corporate governance and the social responsibility of a company to the community could be addressed at Byte in the future by creating an nterprise strategy which explains the companies ethical values and social responsibilities and analyzes how they relate to the concerns of their various stakeholders. Stakeholder analysis would identify the primary and secondary stakeholders and the effects of ant strategic decisions on each group. Based on Carroll’s four responsibilities of a business organization, the economic and legal concerns of the primary stakeholders come first. Once these concerns are satisfied the social responsibilities which affect the secondary stakeholders should be addressed. Ethical responsibilities are standards of behavior not required by law but ignoring them could have serious consequences. Many people are expecting companies to act ethically and will not do business with those who do not act in a socially responsible manner. Even though it might be profitable for a company to operate this way in the long run they will suffer financially. The role of the board of directors of a company has changed significantly over the last decade due in part to ethical breaches made by top management of big companies. It is now legally required for boards to oversee management and boards themselves are now regulated by government. Management for companies as well as their boards have a responsibility to the shareholders who invest in them and to the stakeholders who enable them to operate. In this case, the profitability of Byte products is at risk as well as their corporate reputation. Proper and thorough strategic planning could have anticipated both situations and would have created strategies to address them both before they became major problems.

Vertical Handoff in Wireless Cellular Networks Essay Example

Vertical Handoff in Wireless Cellular Networks Essay Communication is always necessary in building relations to mankind, when two persons meet they need some medium to interchange their views but due to distance barriers some tools are required to communicate each other. At the end of 19th century, reckoned scientist Graham Bell laid the first stone in the field of communication using different tools regardless of distance. He invented first wired base telephony equipment. It was the solution for the voice communication for the people how far apart they are. After this radio based communication systems Era started. It was an extension of wired based networks. In the beginning it was developed for some special purposes like military and police usage. With the passage of time these systems emerged to allow common peoples to communicate with each other, rather then using wired based network. After this the age of faster communication and capabilities of voice get started and evolved into new telecommunication system. 1. 1 Evolution of Cellular Communication: During the 1980s mobile cellular network’s age started, because the wireless communication has under gone different changes during the past 10 years, So its experienced enormous growth. The Figure 1. shows the evolution of the cellular networks. In this figure we have categorized the Cellular networks into five different parts. The first four are existing parts and the last one is the future part. Figure 1. 1: Evolution of Cellular Network 1. 2. 1 First Generation (1G) First Generation mobiles networks utilize analogue transmissions. In 1979 Nippun Telephone and Telegraph (NTT) in Japan introduces the first operational cellular networks. In North America ATamp;T introduces the First Generation mobile systems for the customer in 1980s. This system was named as Advanced Mobile Phone Service (AMPS). We will write a custom essay sample on Vertical Handoff in Wireless Cellular Networks specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Vertical Handoff in Wireless Cellular Networks specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Vertical Handoff in Wireless Cellular Networks specifically for you FOR ONLY $16.38 $13.9/page Hire Writer In First Generation the basic structure of Cellular communication is characterized and many problems were resolved regarding accomplishment of cellular network. In First generation mobile networks the primary ambition was the voice chat. The above stated system was operational at 40 MHz bandwidth and 800 to 900 MHz Frequency. In 1988 this range was expended up to 10 MHz called expended spectrum in AMPS. 1. 2. 2 Second Generation (2G) At the end of 1980s Second Generation (2G) mobile network system was launched. In this system the traditional voice services and low rate data service was provided. The foremost change in this system regarding the First Generation was the switching from analogue to digital transmission, so due to digital transmission better data services and spectrum efficiency was provided. During Second Generation (2G) era the Global System for mobile communication (GSM) was developed in Europe. Using this system International roaming and seamless services was offered in Europe. In the beginning GSM operates at 900 MHz Frequency band with bandwidth of 50 MHz. Many more advancement was made in GSM during last two decades of previous century, due to these improvements GSM became 2. G cellular networks. GSM cellular network was implemented over 190 countries and have approximately 800 million subscribers. In 1996 a new digital cellular system with additional services and supporting more data rate, called TDMA was put into practice. At the end of 20th century Second Generation (2G) cellular system was dominated, whoever it was evolving into a new generation called 3G due to increasing rate of mobile traffic. The enhancement of GPRS in GSM enabled it to support relatively high data rate and sharing capacity between the different users. Theoretically General Packet Radio Services (GPRS) support 160 Kbps but practically it provides only 40 Kbps. 1. 2. 3 Third Generation (3G) The unexpected success of Second Generation (2G) networks persuaded the Telecom Companies to explore more to fulfil the upcoming user requirement of larger data rate and Quality of Services (QoS). This strong driving force enabled the vendors as well as Telecom Companies to launch the new applications such as wireless internet and video telephony. The Figure 2. 2 expresses the upcoming demands of users and services provided by the Telecom Companies. The International Telecommunication Union (ITU) was already working to develop 3G networks. In 2000 International Mobile Telephony (IMT) was developed by ITU with the target of 3G in Europe with the following upcoming targets. 1. The mobile system should propose the same voice quality as PSTN. 2. The mobile system should sustain the high data rate in moving vehicles. 3. The mobile system should bear up to 2 Mb data rate in indoor location. 4. The mobile system should maintain the symmetrical and asymmetrical data transmission. 5. The mobile system should keep up the packet switched and circuit switched data. 1. 2. 4 Fourth Generation (4G) The current standards of Telecommunication are driven to replace with 3G in upcoming years. This future cellular network is named as 4G. the objectives of 4G includes seamless communication with broad range connection with internet at any time anywhere and support of data, pictures and videos on internet. The 4G network will consist of internet protocols such as to facilitate the subscribers by enabling the selection of every application and any environment. In 4G cellular networks a high bandwidth with high data rate is required, also in 4G a quicker and optimized strategy of handover is required to make the clear and reliable communication. The 4G network system will run with the cooperation of 2G and 3G and also will impart IP based wireless communication. The main target in 4G will be video streaming on IP based protocol, such as IP TV. 1. 2 Emerging Technologies In cellular mobile networks, there are two major issues data rate and mobility, bandwidth and coverage according to these two issues we can divide network technologies into two different technologies. . The technologies with low data rate and mobility. 2. Technologies with high data rate and bandwidth with small coverage. According to these specifications in current age the technologies, WIMAX, WLAN, WIBRO, HSDPA and HSPA are offering high data rate mobility and coverage to both circuit switched networks and packet switched networks. 1. 3. 5 Wireless LAN The Wireless Local A rea Network (WLAN) is an unlicensed band of 802. 11 ISM frequency band. 802. 11 is one of the recent communication technologies of IEEE standard. It specifies medium access control (MAC) and physical layer that is why it is called Wireless LAN. It has three widely used types which operates on different frequency bands. These three types are 802. 11a, 802. 11b and 802. 11g. 802. 11a operates on 5 GHz frequency band and it gives the maximum data rate speed of 54 Mbps, which is higher than 802. 11b because 802. 11b operates on 2. 4 GHz frequency band and give the maximum data rate speed of 11Mbps. 802. 11b operates. 802. 11g is recently developed standards of Wireless LAN. It also operates on 2. GHz frequency band and give the maximum data rate speed of 54 Mbps. In 802. 11 Wireless LAN standards, the two types of MAC protocols Distributed Coordination Function (DCF) and Point Coordination Function (PCF) are used. Nowadays the most applications available in the markets are uses DCF because it is simple, robust and easy to implement. DCF is the basic MAC layer function in Wireless LANs, Which used Carrier Sense Multiple Access tech nique (CSMA) also with an addition of Collision Avoidance of (CA). It resolves the CA problems of the packets transmitted at the same time. 1. 3. 6 WIMAX The fiber optic transport services providing the high bandwidth and data rates is replaced by WIMAX wireless technology all across the world. WIMAX is emerging technology to fulfil the high data rate and QoS requirements of the customers, also it is the cheap deployment of voice services with no need of line of sight wireless channel. WIMAX signals have the property to adopt the atmospheric conditions everywhere. WIMAX electromagnetic waves also offer the support of adoptive coding and different operation modes, so voice and data services can easily be transported by WIMAX network platform. 1. 3. 7 Wireless Broadband (WiBro) The Wireless Broadband is recently developed wireless technology offering high speed data service over internet. Actually it is newest technology developed by Korean research group often referred as (Next G) communication system. WiBro is capable to provide high data rate communication with diversity of QoS according to the demands of users over wireless channels. In WiBro Orthogonal Frequency Division Multiple Access (OFDMA) is used according to IEEE 802. 16a standard, to provide the services in Heterogeneous network system. Since different broadband services offer different amount of data rates according to different priorities (e. . video streaming requires the high bandwidth, whereas voice services require higher priority). Orthogonal Frequency Division Multiple Access (OFDMA) operates under the different conditions (e. g. as the requirements of users data rate are given when the sub carrier assignment and transmit power allocation occur), this problem is solved by non linear pro gramming techniques in WiBro. 1. 3. 8 High Speed Downlink Packet Access (HSDPA) High Speed Downlink Packet Access (HSDPA) is introduced in (3G) wireless network obtain high speed data rates. By implementing HSDPA some problems arisen to address the major business topics, one of these problems is radio. The transmission scheme designed for GPRS is upgraded by EDGE is also has limited features. The optimization of only radio is not enough; also transmission strategy should be designed to overcome these problems in every day growing traffic. HSDPA is modified interface version of UMTS in 3GPP. It provides not only down link packet access but also it can be used for uplink data up to 14 Mbps per user. 1. 3. 9 High Speed Packet Access (HSPA) It is revised the version of HSDPA. It also offers the high data rate for downlink as well as uplink 14 Mbps. 2. WIRELESS LAN 3. 1 Introduction In Wireless Local Area Network (Wireless LAN) the user is facilitate with high bit rate connection because of wireless (Radio) connection. The range of wireless LAN is fairly short but it support high bit rate. In Wireless LAN, IEEE standards enumerate its different types and these IEEE standards also include the encryption algorithm (e. g. WEP) to make Wireless LAN more secure as compare to regular LAN. Figure 2. 1: WLAN Access Points The Figure 2. 1 demonstrates the simple physical architecture of Wireless LAN. In Wireless LAN the wired network is connected to Access Point (AP) that grants wireless access through Network Interface Card (NIC) to clients. 3. 2 Architecture of Wireless LAN Wireless Local Area Network instigate as an overlay to the Wired Local Area Network. Lightweight and Autonomous are two discrete architectures used in WLAN environment. Each of the architectures has wide impact on wired LAN architecture. The selection of WLAN architecture is based on the consideration of building, future proof, integrated wired and Wireless LAN to accomplish high return on investment. Both architectures are popular but Lightweight architecture has plus advantages over the WLAN market. 3. 3. 1 Lightweight Model Lightweight is the part of WLAN architecture. With most of wireless intelligence which residing at central controlling device, lightweight Wireless Access Point architecture have narrow functionality. Figure 2. 2: Lightweight Architecture Model Lightweight model is simple. The devices that provide the communication to the end user as Access Layer are identified by lightweight. Distribution layer provide the inter communication and the top layer (Core Layer) of Lightweight model is responsible fast and consistent data between networks. Wireless Access Point (WAP) resides at the interface of access layer and provides the communication interface to end user. In lightweight architecture model, the management of operation is easy because it give the permission to WAP from single device, because the lightweight WAP have the knowledge of visibility and attentiveness of the neighbours WAPs. They can observe and if any one of their neighbours becomes the victim of fault it notifies the wireless controller. Lightweight WAP may be Self-healing because to pay compensation for unsuccessful counterpart, controller commands the neighbouring WAP to regulate their power level, where as in autonomous there is no concept of the visibility of its WAP neighbouring and in this case to perform self healing it cannot adjust the power level. If single WAP is busy or overloaded then in this situation wireless controller can relieve the wireless client to neighbouring WAP. In critical applications such as VoIP, self-healing and load balancing are important issues. 3. 3. 2 Autonomous Model In Autonomous Model WAP is not mandatory as shown in Figure 2. Figure 2. 3: Autonomous Architecture Model Autonomous Wireless Access Point sustains the switching and strong security as well as networking function that are indispensable to route the wireless traffic. As in autonomous system there is no concept of the visibility of WAP so it cannot make the load balancing. Autonomous model cannot differentiate whether ne arest WAP is part of WLAN infrastructure or illegal rouge WAP. The difference between the autonomous and lightweight is negligible. The difference is only this that lightweight have one extra component (WLAN controller). 3. 3 Wireless LAN Protocol Stack In OSI Layer Model IEE 802. 11 instigate on Data Link Layer and Physical Layer. The Figure 2. 4 illustrates the IEEE 802. 11 Protocol Stack. Figure 2. 4: IEEE 802. 11 Protocol Stack * Logical Link Control (LLC) * Medium Access Control (MAC) Logical Link Control sub layer ensure that during interfacing with network layer 802. 11 protocol use the standard format, it is also responsible to make transparent the underlying hardware and protocol with upper layer. 802. 11 standards describe two types of operation for MAC sub layer i. e. Distributed Coordination Function (DFC) and Point Coordination Function (PCF). This layer is also makes sure the flaxen and systematic access to the wireless medium. In Distributed Coordination Function (DCF) mode asynchronous data is transferred. To control access to the shared medium, DCF mode employs the Carrie Sense Multiple Access (CSMA) with Collision Avoidance (CA). Point Coordination Function is proposed for time bound services. In PCF mode access point behave as Point Coordinator and Polls connected to terminals. In this way to sustain time bound services and certain level of Quality of Services (QoS), the bandwidth can be allocated scientifically. The IEEE 802. 1 standard also breaks the Physical Layer in to two sub layers. To offer the common physical interface for MAC layer which is self-determining of transmission technology, the Physical Layer Convergence Protocol (PLCP) was intended. On the basis of infrared and radio transmission (FHSS and DSSS) only three transmission technologies were instigated, when first time IEEE 802. 11 standard was intro duced. Afterward IEEE 802. 11a and 802. 11b initiated supplementary transmission technologies, such as HR-DSSS and OFDM respectively. 3. 4 Wireless LAN Components The components of Wireless LAN are * Basic Service Set (BSS) Extended Service Set (ESS) * Distribution Service (DS) * Mobile Node (MN) * Access Point (AP) 3. 5. 3 Basic Service Set In Basic Service Set (BSS) multiple stations can communicate with one another, because of electromagnetic waves circulation BSS does not refers to specific region. In BSS when there is no wired network and all the stations are mobile then BSS will become Independent Basic Service Set (IBSS). When AP enters in BSS then BSS will call Infrastructure BSS. In BSS when mobile stations communicate with each other than their communication will always held via AP. In this way double bandwidth will utilize as contrast to IBSS. . 5. 4 Extended Service Set (ESS) Extended Service Set (ESS) is set of IBSS. In ESS the traffic is forwarding from one BSS to anot her when Access Points communicate among themselves. In ESS Access point perform communication through physical means, called Distribution System (DS). All the Mobile Stations in ESS are happen to be a MAC Layer network, where all the stations are fixed. 3. 5. 5 Distribution System (DS) The Distributed System is physical medium through which Access points in their BSS communicate to exchange the frame for stations. These frames exchanged through physical mean. 3. 5. 6 Mobile Node (MN) In Wireless LAN Mobile Node is the most essential component. Through wireless medium the MN communicate with other MN and to AP which is associated with wired network. MN may be PC or Note book that is equipped with wireless Network Interface Card (NIC). 3. 5. 7 Access Point (AP) In Wireless and wired network the AP is a transceiver that can transmit, store and receive the data. AP also works as bridge between wired and wireless networks. In the wired network the AP is connected with the server that offers the service to MN. In wireless networks the AP acts as Base Station (BS), that combines the wireless network with wired network. . 5 Network Topologies of Wireless LAN 3. 6. 8 Ad-Hoc Model Ad-Hoc mode also refers to as peer-to-peer communication between the mobile nodes (MN). This mode is suitable where data is needed to be exchange. The range of ad-mode is inadequate to the Mobile Node only. Ad-hoc mode has the low precedence than infrastructure mode Figure 2. 5: Ad-Hoc Mode 3. 6. 9 Infrastructure Model In Infrastructure mode Mobile Node and Access Point are two basic components. In Infrastructure mode Mobile Nodes connected to an Access Point, and AP can communicate with Mobile Node and server linked to wired network. In the same zone more than one AP can sustain the Mobile Node. In Infrastructure mode when one Mobile Node move across one AP to other AP then the roaming function must be awake for better QoS. Figure 2. 6: Infrastructure Mode In case of roaming the, all AP desires the same authentication, key function as Extended Service set ID (ESSID) and Wired Encryption Protocol (WEP) while they operate on the equivalent channel. 3. 6 Wireless LAN Standards The standards of Wireless Local Area Network (WLAN) are developing gradually to get faster connection, and trying to get by with security and conflicting problems. The first standard of WLAN was introduced in 1997 and after this many other standards have been organized. Table 2. 1: WLAN Standards Protocol| Author| Frequency| Modulation| Data Rate| Comments| 802. 11| IEEE| 9mm MHz| FHSS| Upto 300 Kbps| Obsolescent| 802. 11b| IEEE| 2. 4 GHz, 900 MHz| DSSSFHSS legacy| 1-11 Mbps| Most Popular| 802. 11a| IEEE| 5 GHz UNII| OFDM| Upto 54 Mbps| Emerging| 802. 111h| IEEE| 5 GHz UNII| OFDM| Upto 54 Mbps| Adds Transient Power Control frequency selection to 802. 11a| HiperLAN| ETSI| 5. 15-5. 30 GHz or 17. 1 – 17. 2 GHz| GMSK| 23. 29 Mbps| European community Backed Standards| HiperLAN/2| ETSI| 5. 15-5. 30 GHz or 17. 1 – 17. 3 GHz| GMSK| 54 Mbps| European community Backed Standards| Bluetooth| Bluetooth Consortium| 2. 4 GHz| FHSS| 1 Mbps| Cable Replacement| 3. 7. 10 IEEE 802. 11 The development of WLAN began with the implementation of first IEEE 802. 11 WLAN standards. The 802. 11 standard have the utmost throughput up to 1 to 2 Mbits per secon d and operate in 2. 4 GHz frequency. The 802. 11 standard is based on radio technologies. WLAN intention was just to provide the wireless network infrastructure analogous to wired Ethernet network. . 7. 11 IEEE 802. 11b IEEE 802. 11b is most popular and organize standard as compare to 802. 11, which was launched in 1999. IEEE 802. 11b standard also operate in the same frequency 2. 4MHz like 802. 11 but the throughput rate was 11Mbits per second. The term WiFi (Wireless Fidelity) was first introduce in this standard 802. 11b, however later this term was changed to mean any type 802. 11 network together with 802. 11a, 802. 11b dual band. The WiFi term was used to ease the uncertainty issues of WLAN interoperability. 3. 7. 12 IEEE 802. 11a and HiperLAN This standard was bring out late in 1999 but in 2000 this standard was revised as an adjunct to 802. 11. 802. 11a standard operates in 5MHz frequency band instead of conventional 2. 4 MHz. To supporting data rate up to 54 Mbps, this standard was used in ODFM (Orthogonal Frequency Division Multiplexing). The emergence of 802. 11a and 802. 11b is quite slow because these two standards are not companionable with each other. Proxim and Envara, Inc manufactures emerge the dual mode products that support 802. 11a and 802. 11b standards. The 802. 11a standard is still quite sparse technology although 802. 11b emerge round about two year ago. The use of this standard was limited because in Europe 5MHz range permitted for use by reason of the overlapping of frequencies with the military channels. Once again 5GHz technologies may become more common as 2. 4 GHz technologies develop more common. One day 5 GHz can work much better than 2. 4 GHz because it may be possible that 2. 4 GHz frequency band become so congested by 4G and Bluetooth devices. 3. 7. 13 HiperLAN In August 2001, European Telecommunication Standard Institute (ETSI) standard for 5 GHz range was permitted, because in 2001 the use of 5 GHz technology has been scattering in Europe. HiperLAN (High Performance Radio Local Area Network) is IEEE 802. 11 standards. HiperLAN has already grown into two different standards, HiperLAN/1 and HiperLAN/2 respectively. HiperLAN/1 throughput is 20Mbps where as HiperLAN/2 throughput is 54 Mbps. Both standards work on 5 GHz frequency band and cannot be replaceable with 802. 11b standards because this standard requires total renovation of WLAN hardware. 3. 7. 14 IEEE 802. 11g This standard was scheduled for endorsement in the summer of 2003, this standard also operate on 2. 4 GHz technology, that is compatible with wide spread WLAN-technology, 802. 11b. The IEEE 802. 11g standard promise for better security than its precursor. If the network has to be slow down in sequence of 802. 11b client to understand the traffic, it will take long time before purchasing the expensive 802. 11g. 3. 7 IEEE 802. 11 Physical MAC Frame Format In IEEE802. 11 MAC frame format, each frame consists of following three components. †¢ MAC header * A variable length frame body * A frame check sequence (FCS) MAC header involves the sequence control information, duration, address and frame control. Variable length frame body contains the precise information about the type of frame. Frame sequence check enclose 32 bit Cyclic Redundancy Check (CRC). General frame format is shown below Figure 2. 7: MAC Frame Format The MAC frame format includes a set of field that arise in frame in fixed order. Figure 2. 4 illustrate the general MAC frame format. The fields address 2, address 3, address 4, frame body and sequence control are present in certain frame type. The length of â€Å"Duration ID† field is 2 bytes or 16 bits. The length of duration in this field is range from 0 to 32667. The Network Allocation Vector (NAV) is update using the duration values. In MAC Frame format there are four â€Å"Address† fields. These four address fields designate the transmitting and receiving address, source and destination address. The length of â€Å"Sequence Control† field is 16 bits. The sequence number and fragment number is also sub field of â€Å"Sequence Control† field. The length of â€Å"Frame Body† field is variable. This frame encloses the information explicit to individual frame type and subtype. The length of last â€Å"FCS† field is 32 bit. The calculation of FCS field is done above all the fields of MAC header and the fields of Frame Body. 3. 8. 15 Frame Control Field The frame control consists of further sub fields as shown in Figure 2. 5. Figure 2. : Frame Control Field The length of protocol version field is 2 bit. This field is constant in size. The protocol version for this standard is 0. All other values are reversed. Fundamental inappropriateness stays alive between the prior edition and new version when only the revision level will be implemented. Both â €Å"type† and â€Å"subtype† field identify the frame function. The type field is 2 bit and sub type is 4 bit in length. The length of â€Å"To DS† field is 1 bit. This field is set 0 in all other frames. This comprises the frames of all data type sent by STAs, which is connected with an AP. The next field â€Å"from DS† is 1 bit in length. It is also set 0 in all other fields. The length of next â€Å"More Fragment† is 1 bit. It set to 1 in all management type frames but set 0 in all other frames. The length of â€Å"Retry field† is 1 bit. It also set to 1 in any management type frame. To eliminate the duplication of frame the Receiving Station uses this as aid indicator. The length of â€Å"More Data† field is 1 bit. This field is valid in management type frame, which is transmitted by an AP to STA in save mode. The length of â€Å"WEP† field is 1. if the information processed by WEP algorithm is present in frame body field then WEP field is set to 1. The length of last field â€Å"Order† is 1 bit. This field also set 0 in all other frames. 3. 8 Security Issues in Wireless LAN Above discussed Wireless LAN standards have numerous security drawbacks which have not been preset yet. The main reason of these drawbacks is the nature of communication which is diverse in Wireless LAN when it contrasts with customary physical medium. Regrettably many Network Administrators (NA) are still unaware about these drawbacks although these drawbacks have been under conversation for long time. In future standards many of these security flaws are optimistically going to repair. . 9. 16 Security Issues between Wireless/Wired Networks Wireless LAN technology is more vulnerable to attacks as compared to traditional network because of its wireless communication. In Wireless ALN to tape somebody’s phone is much easier than conventional Ethernet network, because in Ethernet network, to gain access to traffic, the office has to be broken wher eas in wireless LAN anyone can get by simply to get into the range of WLAN. To eliminate this problem, the building should be isolated to stop Wireless LAN microwaves seeping out, but this process will be much pricey and tough. As in Wireless LAN, to tape somebody’s phone is easy so for this purposes numerous applications such as Airopeek (commercial wireless network traffic and protocol analyser)have been developed. Through Airopeek, even a new user, who don’t have experience about this can easily monitor and confine the traffic on unencrypted network. 3. 9. 17 The War of Driving and Chalking A new tool Netstumbler is used to monitor the WLAN to handle the new hacker culture evolved due to flaws mentioned above . The information about newly discovered WLAN is sent on the mapping system on the netstumbler by the users. The WLAN data and location can be found easily by a laptop NIC or GPS of a car during driving by the netstumbler. This new type of hacking is named as war driving and is more effective. Approximately 70 WLAN access points were found during the war driving at Helsinki in Finland last year. 3. 9. 18 Wired Equivalent Privacy Protocol Flaws This protocol is unsecured because it uses the RC4 encryption algorithms which already have the security faults. For getting the password to access the network, different types of free software are available on internet to hack the WEP; so many parties prove this hack able protocol. This hacking based on RC4 encryption algorithms which have weak initiation vectors. When there will be enough packets because of traffic load then initiation vectors disclose the WEP encryption key characters, so in this way by accessing the encryption key hackers get access to the network. In our discussion of security issues we assume that it is very rigid to install hacking program because these programs are not consistent in performance. 3. 9. 19 Counter Measures to WLAN Security Flaws In most of the cases it is a good approach to assume that all WLAN traffic is learnt by hackers. It makes users of WLAN technology to implement their own security solutions otherwise they may lose data confidentiality. There are some 802. 11b compatible equipments that use WEP but they avoid using weak initiation vectors that produce week packets on the network to make it vulnerable. It is a very easy way to enhance the security, but still there are flaws. The network is secure only if all the participants of the network don’t produce weak initiation vectors, moreover it is not possible to stop a device from initiating weak packets. So this solution becomes a serious vulnerability. On the other hand if a tunnel of VPN or SSH is used to encapsulate the WLAN traffic, the network becomes much secure. Tunnelled traffic doesn’t provide any chance for man-in-middle attacks. It is very easy to implement this approach, a VPN server is installed right behind WLAN access point so that only the encrypted traffic is allowed to enter into the network. Some problems in this solution are lack of awareness on the administrative level, cost and the installation of encryption servers. In addition denial of service problem may arise, and change of frequencies to avoid denial of service attacks is very hard. . UMTS 4. 9 Introduction UMTS (Universal Mobile Telecommunication System) is third generation (3G) mobile communications system being developed within the framework defined by ITU. In order to provide high quality mobile communication at low cost, UMTS is used to accelerate convergence and integration between Telecommunication, Information Technology and service provid er. UMTS support 2 Mbit data transfer rate per subscriber, facilitating, the deployment of mobile multimedia services such as downloading of MP3 audio and video streaming. UMTS is continuously bringing the development of new techniques and wireless technologies around the world. These common developments need the common agreement towards the standardization. The main objective of this standardization is to confirm identical specification for different parts. The UMTS was specified to ensure equipment compatibility based on UTRAN standardization. 3GPP specifications are generally based on GSM specifications and generally known as UMTS system. In this chapter we describe the UMTS technology. This chapter starts with small description of UMTS Technology such as its general architecture, protocol architecture, security architecture, future prospects, problems, services it provides and feasibility in the upcoming years in the vision of vertical handover. The chapter will be finalized with the brief introduction to overlay network and vertical handover which is main problem to solve the convergence scenario. 4. 10 UMTS Architecture UMTS system use radio interface and core network as GPRS. In UMTS new radio network is called UTRAN (UMTS Terrestrial Radio Access Network. and connected through Iu interface to core network of GPRS. In UMTS system mobile terminal is called User Equipment. The User Equipment is directly connected to Node B interface. In GSM system the Node B is similar to BTS and normally works as cell. Other Node Bs are controlled by RNC through Iub interface. The circuit switch data is transferred via Iu-CS and packet base data is transferred via Iu-PS interface respectively. In UTRAN Iur is new interface which connects two Radio Network Controllers but not same in GSM system. The Iur interface eliminates the Core Network burden and 100% facilitates the handling of Radio Resource management. Figure 3. 1: Fundamental Architecture of UMTS 4. 11 UMTS Protocol Stack In OSI model the UMTS is put into operation on three layers. * Physical Layer * Data Link Layer * Network Layer The UMTS protocol stack can be divided into * Control Plane In control plane the control information’s are exchanged. * User Plane Actual data is broadcasted between the users in user plane. * Management Plane In management plane the individual layers configuration is done. The UMTS protocol stack is illustrated in figure given below Figure 3. 2: Protocol Stack of UMTS Radio data transmission interrelated tasks are switch at physical layer of UMTS protocol stack. The Medium Access Control (MAC) Sublayer launch the logical channels which are multiplexed to form transport channel through which data is transmit. The Radio link Control (RLC) uses the diverse modes of operation to handle d