Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

4G Network


Published on

My First paper on 4G Network in SE. Watch out the genuineness of the document. Thats the macro view of selection criteria !

Published in: Education, Technology, Business
  • Be the first to comment

4G Network

  1. 1. WALCHAND INSTITUTE OF TECHNOLOGY A PAPER PRESENTATION ON: 4G NETWORK Theme: Mobile, Wireless Communication Technologies and Services By: ABBAS HASHMI ROSHAN AUTHANKAR S.E. (C.S.E) S.E. (C.S.E) ph. No.:9096265578 ph. No.:9096401214 At ’09 Under Guidance of: Prof.L.M.R.J.Lobo Abstract:- 4G is the acronym for fourth-generation wireless, the stage of broadband mobile communications that will supersede the 3G. It is not defined by one standard, but rather represents a collection of technologies and protocols enabling the highest throughput and lowest cost wireless network. 4G networks based on packet radio technology represent a major change for the mobile industry. It will be a fully IP core integrated system with wide area coverage and high throughput with high spectral efficiency. It uses the OFDM, UWB, and MIMO wireless technology. A 4G system is powered up with GSM services, GPRS, interactive medias-such as teleconferencing, internet access, Wi-Max, and many more, and will be able to provide a comprehensive IP solution where voice, data and streamed multimedia can be given to users on an “Anytime, Anywhere” basis, and at higher data rates than ever. Nevertheless, pioneer acknowledges that the future of 4G technology is by no means certain. 4G is a way for the ultra-broadband mobile experience, along with highly efficient and economical devices and technologies. Thus, we need to explorer our minds to understand it and make it more susceptible for commercial basis. This paper focuses on the vision of 4G, its architecture and the extending horizons of 4Gnetwork. Page 1 of 12
  2. 2. Introduction:- Since the first generation of so-called “analogue” mobile radio networks was created in 1980, the mobile telephone has seen many upheavals. In 1991, with the appearance of GSM, second-generation (or 2G) mobile telephony, it became a veritable phenomenon. Gradually, almost everyone started to have a mobile phone. 2002 saw the arrival of UMTS, and 3G was born. To define a new generation of mobile systems that would see the light of day by 2010, the notion of 4G was introduced in the early 2000s. The idea was to perpetuate the logic of replacing one mobile generation with another every 10 years. The study of 4G examines drivers for network upgrades and the technologies that will be used to improve network performance including MIMO, error correction, OFDMA, scheduling and modulation, among others. If a new technology has interesting features, R&D endeavors to define what is missing for it to be able to communicate with other wireless communication systems. An integrated network-of-networks (i.e. All-IP network) is the vision for 4G mobile wireless systems architecture. This envisages that users can benefit in several ways from this unified access platform. The advantages, however, cannot be seized if we do not consider the dynamics and complexity in future environments. For instance, we believe that a model based on mobility hints, cross-layer activity information, and application-specific data can contribute to an effective network usage; what we need is a policy-based solution that can effectively expose context knowledge without a huge overhead. Diversity and heterogeneity in wireless systems evolution have placed the integration of hybrid mobile data networks as an enormous barrier towards the success of seamless networking. Seamless roaming and connectivity to highly integrated and heterogeneous networks is the key idea that springs from the 4G vision. Rise of the 4G Network:- Mobile networks have always focused on voice as the primary application, and that was certainly the case for analog networks (first generation [1G]), Time Division Multiple Access (TDMA) networks (2G), and even Code Division Multiple Access (CDMA) networks (3G). Now with the introduction of 4G networks, multimedia applications will assume primary importance. One of the most interesting and compelling applications in this area is mobile TV. 1G:- The first generation of wireless mobile communications was based on analog signaling. Analog Systems, implemented in North America, were known as Analog Mobile Phone Systems (AMPS), while systems implemented in Europe and the rest of the world were typically identified as a variation of Total Access Communication Systems (TACS). Analog systems were primarily based on circuit-switched technology and designed for voice, not data. 2G:- Page 2 of 12
  3. 3. The second generation (2G) of the wireless mobile network was based on low-band digital data signaling and circuit switched technology. The most popular 2G wireless technology is known as Global Systems for Mobile Communications. GSM technology is a combination of Frequency Division Multiple Access (FDMA) And Time Division Multiple Access (TDMA). The first GSM systems used a 25MHz frequency Spectrum in the 900MHz band. Today, GSM systems operate in the 900MHz and 1.8 GHz bands throughout the. While GSM technology was developed in Europe, Code Division Multiple Access (CDMA) technology was developed in North America. CDMA uses spread spectrum technology to break up speech into Small, digitized segments and encodes them to identify each call. While GSM and other TDMA-based systems have become the dominant 2G wireless technologies, CDMA technology is recognized as providing clearer voice quality with less background ‘80s ‘90s 2000s Initial stage Growing stage Expansion stage Mature stage Analog Digital IMT-2000 AMPS, GSM, PDC, IS- 4th generation NMT,NTT…. 95…. (3rd generation) (1st generation) (2nd generation) Mobile <300 bps 9.6k - 64kbps(packet) 64kbps – 384kbps 2 Mbps 20 Mbps(best Data 2Mbps(indoor) effort) PSTN 28.8kbps 64kbps ~1 Mbps(flat rate) ~20Mbps? Data (Fig 1: Evolutions of Mobile Systems with respect to time) noise, fewer dropped calls, enhanced security, greater reliability and greater network capacity. 2G wireless technology can handle some data capabilities such as fax and short message service at the data rate of up to 9.6 kbps, but it is not suitable for web browsing and multimedia applications.2Gsystem fueled with General Packet Radio Services (GPRS) is identified as 2.5G, a stepping stone towards 3G. Page 3 of 12
  4. 4. 3G:- Third Generation (3G) mobile devices and services transform wireless communications into on-line, real- time connectivity. 3G wireless technology allows an individual to have immediate access to location-specific services that offer information on demand. The concept of 3G wireless technology represents a shift from voice- centric services to multimedia-oriented (voice, data, video, fax) services. 3G wireless technology represents the convergence of various 2G wireless telecommunications systems into a single global system that includes both terrestrial and satellite components. One of the most important aspects of 3G wireless technology is its ability to unify existing cellular standards, such as CDMA, GSM, and TDMA, under one umbrella. Subscribers are likely to access 3G wireless services initially via dual band terminal devices. W-CDMA networks will be used for high- capacity applications and 2G digital wireless systems will be used for voice calls. 3G wireless networks consist of a Radio Access Network (RAN) and a core network. The core network consists of a packet-switched domain, which provide the same functionality that they provide in a GPRS system, and a circuit-switched domain, which includes 3G MSC for switching of voice calls. The access network provides a core network technology independent access for mobile terminals to different types of core networks and network services. The implementation of 3G wireless systems raises several critical issues, such as the successful backward compatibility to air interfaces as well as to deployed infrastructures. Rise of the 4G Network: Enabling the Internet Everywhere Experience Mobile networks have always focused on voice as the primary application, and that was certainly the case for analog networks [1G], Time Division Multiple Access networks (2G), and even Code Division Multiple Access networks (3G). Now with the introduction of 4G networks, multimedia applications will assume primary importance. One of the most interesting and compelling applications in this area is mobile TV. Given the enormous success of mobile services and the popularity of TV, this combination is a natural one. Variations on this theme include broadcast, multicast, and unicast of both real-time and stored content. Enabling these types of services on a broad scale clearly introduces some significant challenges, including latency, throughput, and network capacity. Characteristics of 4G mobile networks:- The study examines drivers for network upgrades and the technologies that will be used to improve network performance including MIMO, error correction, OFDMA, scheduling and modulation, among others. They must be engineered from the beginning to be all-IP end-to-end-representing a major change from the circuit- switched architectures that have dominated in the past and an essential step toward enabling multimedia applications. We will see a move away from closed RAN architectures and toward open systems with interoperability. The Internet has always been based on the concept of open systems, and this concept is being introduced in the mobile world. Base stations will be built by RAN vendors and mobile gateways will be built by IP Page 4 of 12
  5. 5. vendors. Open interfaces will allow network integrators to bring these pieces together to build a robust mobile network. The advantages of 4G:- New radio technologies can be more easily introduced into the network. A spectrally efficient system (in bits/s/Hz and bits/s/Hz/site), High network capacity: more simultaneous users per cell,A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions as defined by the ITU-R, Smooth handoff across heterogeneous networks, Seamless connectivity and global roaming across multiple networks, High quality of service for next generation multimedia support (real time audio, high speed data, HDTV video content, mobile TV, audio, high speed data, HDTV video content, mobile TV, etc)Interoperability with existing wireless standards, and Support for interactive multimedia, voice, streaming video, Internet, and other broadband services Seamless switching, and a variety of Quality of Service driven services Better scheduling and call admission control techniques. In summary, the 4G system shares and utilizes network resources to meet the minimal requirements of all the 4G enabled users. ARCHITECTURE:- The overall 4G architecture discussed in this paper is IPv6-based, supporting seamless mobility between different access technologies. Mobility is a substantial problem in such environment, because inter-technology handovers have to be supported. In our case, we targeted Ethernet (802.3) for wired access; Wi-Fi (802.11b) for wireless LAN access; and W-CDMA - the radio interface of UMTS- for cellular access (Fig. 1). With this diversity, mobility cannot be simply handled by the lower layers, but needs to be implemented at the network layer. An "IPv6- based"mechanism has to be used for interworking, and no technology-internal mechanisms for handover, neither on the wireless LAN nor on other technology, can be used. So, in fact no mobility mechanisms are supported in the W- CDMA cells, but instead the same IP protocol supports the movement between cells. Similarly, the 802.11 nodes are only in BSS modes, and will not create an ESS: IPv6 mobility will handle handover between cells. Summarizing Fig 2, the key entities are: -A user - a person or company with a service level agreement (SLA) contracted with an operator for a specific set of services. Our architecture is concerned with user mobility, meaning that access is granted to users, not to specific terminals. -A MT (Mobile Terminal) - a terminal from where the user accesses services. Our network concept supports terminal portability, which means that a terminal may be shared among several users, although not at the same time. -AR (Access Router) - the point of attachment to the network, which takes the name of RG (Radio Gateway) - for wireless access (WCDMA or 802.11). Page 5 of 12
  6. 6. -PA (Paging Agent) - entity responsible for locating the MT when it is in "idle mode" while there are packets to be delivered to it . -QoS Broker - entity responsible of managing one or more ARs/AGs, controlling user access and access rights according to the information provided by the AAAC System. -NMS (Network Management System) - the entity responsible for managing and guaranteeing availability of resources in the Core Network, and overall network management and control. (Fig 2: General Network Architecture) This network is capable of supporting multiple functions: •Inter-operator information interchanges for multiple-operator scenarios; •Confidentiality both of user traffic and of the network control information; •Mobility of users across multiple terminals; •Mobility of terminals across multiple technologies; •QoS levels guaranties to traffic flows (aggregates); •Monitoring and measurement functions, to collect information about network and service usage; •Paging across multiple networks to ensure continuous accessibility of users. We presented an architecture for supporting end-to-end QoS. This QoS architecture is able to support multi-service, multi-operator environments, handling complex multimedia services, with per user and per service Page 6 of 12
  7. 7. differentiation, and integrating mobility and AAAC aspects. It seems to provide a simple, flexible, QoS architecture able to support multimedia service provision for future 4G networks. Security will be an essential part of a 4G network architecture. The Internet Everywhere Experience will allow the mobile subscriber to access a whole host of Internet related services, but with that flexibility comes the risk associated with Internet connectivity. Next generation solutions must have a carefully thought out security approach that protects both the network and the subscriber. The Technologies Hired For 4G:- OFDM: To exploit the frequency selective channel property Orthogonal Frequency Division Multiplexing (OFDM) and OFD Multiple Access (OFDMA). OFDM transmits data by splitting radio signals that are broadcast simultaneously over different frequencies. OFDMA, used in mobile WiMax, also provides signals that are immune to interference and can support high data rates. It is said to use power more efficiently than 3G systems while using smaller amplifiers and antennas. This all translates to expected lower equipment costs for wireless carriers. The beauty of OFDM lies in its simplicity. One trick of the trade that makes OFDM transmitters low cost is the ability to implement the mapping of bits to unique carriers via BW=2R BW=2R N=1 -R +R -R +R BW=2R N=2 BW=3R/2 SC BW=R -R +R -R -3R/4 -R/4 +R/4 3R/4 +R BW=2R N=2 BW=4R/2 SC BW=2R/3 -R -R/3 +R/3 +R -R -2R/3 -R/3 R/3 2R/3 +R (Fig 3: Spectrum Efficiency of OFDM Compared to Conventional FDM) the use of IFFT. Unlike CDMA, OFDM receiver collects signal energy in frequency domain, thus it is ableto protect energy loss at frequency domain. In a relatively slow time-varying channel, it is possible to significantly enhance the capacity by adapting the data rate per subcarrier according to SNR of that particular subcarrier. OFDM is more resistant to frequency selective fading than single carrier systems. The OFDM transmitter simplifies the channel effect, thus a simpler receiver structure is enough for recovering transmitted data. If we use Page 7 of 12
  8. 8. coherent modulation schemes, then very simple channel estimation (and/or equalization) is needed, on the other hand, we need no channel estimator if differential modulation schemes are used. The orthogonality preservation procedures in OFDM are much simpler compared to CDMA or TDMA techniques even in very severe multipath conditions. OFDM can be used for high-speed multimedia applications with lower service cost. OFDM can support dynamic packet access. Single frequency networks are possible in OFDM, which is especially attractive for broadcast applications. The increasing requirement of data rate and quality of service for wireless communications calls for new techniques to increase spectrum efficiency and to improve link quality. OFDM has proved to be very effective in mitigating adverse multipath effects of a broadband wireless channel. Multiple Input Multiple Output (MIMO) technique has proved its potential by increasing the link capacity significantly via spatial multiplexing and improving the link capacity via space-time coding. Numerous research works are being published on MIMO enhanced OFDM based wireless systems. It is obvious that MIMO technique will be effectively used with OFDM based systems for providing mobile multimedia in future with reasonable data rate and quality of service (in terms bit error rate, BER). Orthogonality and OFDM:- The use of orthogonal subcarriers would allow the subcarriers’ spectra to overlap, thus increasing the spectral efficiency. As long as orthogonality is maintained, it is still possible to recover the individual subcarriers’ signals despite their overlapping spectrums. If the dot product of two deterministic signals is equal to zero, these signals are said to be orthogonal to each other. Orthogonality can also be viewed from the standpoint of stochastic processes. If two random processes are uncorrelated, then they are orthogonal. Given the random nature of signals in a communications system, this probabilistic view of orthogonality provides an intuitive understanding of the implications of orthogonality in OFDM. If the input signal has some energy at a cer tain frequency, there will be a peak in the correlation of the input signal and the basis sinusoid that is at that corresponding frequency. This transform is used at the OFDM transmitter to map an input signal onto a set of orthogonal subcarriers, i.e., the orthogonal basis functions of the DFT. Similarly, the transform is used again at the OFDM receiver to process the received subcarriers. The signals from the subcarriers are then combined to form an estimate of the source signal from the transmitter. The orthogonal and uncorrelated nature of the subcarriers is exploited in OFDM with powerful results. Since the basis functions of the DFT are uncorrelated, the correlation performed in the DFT for a given subcarrier only sees energy for that corresponding subcarrier. The energy from other subcarriers does not contribute because it is uncorrelated. This separation of signal energy is the reason that the OFDM subcarriers’ spectrumscan overlap without causing interference. MIMO:- To attain ultra high spectral efficiency MIMO uses signal multiplexing between multiple transmitting antennas (spacemultiplex) and time or frequency. It is well suited to OFDM, as it is possible to process Independent time symbols as soon as the OFDM Page 8 of 12
  9. 9. waveform is correctly designed for the channel. This aspect of OFDM greatly simplifies processing. The signal transmitted by m antennas is received by n antennas. Processing of the received signals may deliver several performance improvements: range, quality of received signal and spectrum efficiency. In principle, MIMO is more efficient when many multiple path signals are received. The performance in cellular deployments is still subject to research and simulations. However, it is generally admitted that the gain in spectrum efficiency is directly related to the minimum number of antennas in the link. Spatial multiplexing involves deploying multiple antennas at the transmitter and at the receiver. Independent streams can then be transmitted simultaneously from all the antennas. This increases the data rate into multiple folds (Fig 4: A MOMO having transmitters and receivers antennas) with the number equal to minimum of the number of transmit and receive antennas. This is called MIMO (as a branch of intelligent antenna). Multiple-input multiple-output (MIMO) wireless LAN technology supports two or more radio signals in a single radio channel, increasing bandwidth. MIMO does this by using multiplexing. MIMO is expected to support data rates as high as 315Mbps in 36MHz of spectrum. WiMAX:- Fourth-generation network technology is not so much a new modulation technology as it is a way of architecting networks. These networks are using a variety of mobile packet radio technologies along with Wi-Fi to offer a ubiquitous broadband experience for the mobile subscriber, the all new WiMax. More recently, the topic of WiMAX, a particular 4G technology which promises to deliver 70 Mb/s data speeds over a 50 km radius has been the focus of much attention and hype. WiMAX has been at the forefront of the move to all-IP end-to-end networks based on open systems, and this technology is already being deployed in fixed wireless applications and OFDMA and MIMO are seen as critical ingredients. Mobile WiMAX is an IEEE specification also known as 802.16e and designed to support as high as 12Mbps data-transmission speeds. It uses OFDMA and is the next-generation technology. The technologies used in WiMAX such as Orthogonal Frequency Division Multiple Access (OFDMA) and Multiple-Input Multiple-Output (MIMO) allow higher transmission efficiency per available spectrum. These technologies also support more powerful and effective resource management. Sprint, a leading name in the field, took the wraps off its Xohm wireless network in Baltimore, which uses Samsung WiMAX technology on the 2.5 GHz spectrum, offers faster download speeds than current 3G wireless networks. For instance, while AT&T's fastest HSDPA network claims speeds up to 3.6Mbps, Xohm promises even more. Page 9 of 12
  10. 10. IEEE 802.11 standard: (Table 1: 802.11b) Release date October 1999 IEEE 802.11 is a set of standards implementing WLAN computer communication in the 2.4, 3.6 and 5 GHz spectrum Op. frequency 2.4 GHz bands. They are maintained by the IEEE LAN/MAN Standards Throughput (Typ) 4.5 Mbit/s Committee IEEE 802.2. Net bit rate 11 Mbit/s 802.11b: Known as Wi-Fi, 802.11b is currently the Range indoor ~38 m leading market standard for wireless local-area networking. This version transfers data at 11 Mbits/s at distances of up to 300 ft. It operates at 2.4 GHz, so it shares spectrum with cordless phones, Bluetooth products, and many other unlicensed devices. It uses the complementary-code-keying (CCK) modulation scheme. (Table 2: 802.11a) 802.11a: Also known as Wi-Fi, 802.11a has yet to be Release date October,1999 widely accepted in the industry. It operates in the 5-GHz range at Op. frequency 5 GHz a 54-Mbit/s data rate and uses orthogonal-frequency-division- Multiplexing (OFDM) modulation, which is a faster data- Throughput (Typ) 23 Mbit/s transmission scheme than CCK. But it's not backward-compatible Net bit rate 54 Mbit/s with 802.11b. Gross bit rate 72 Mbit/s Range indoor ~35 m 802.11g: Like 802.11b, this version uses OFDM. It runs at 2.4 GHz and is expected to operate at 54 Mbits/s when it becomes an official standard, which the IEEE expects by July. It is backward-compatible with 802.11b. The "g" standard is still in the draft stage, but judging by the products that appeared at the recent International Consumer Electronics (Table 3: 802.11g) Release date June 2003 Show, "g" will likely be the standard of choice for most wireless network manufacturers. Some vendors are covering their bets by Op. frequency 2.4 GHz using chips that combine 802.11a, b, and g for 54-Mbit/s data Throughput (Typ) 19 Mbit/s rates over the 2.4- and 5.2-GHz bands. At least one company has announced a combination Wi- Fi/Bluetooth chip. Motorola, Net bit rate 54 Mbit/s Nokia, and Samsung, among other manufacturers, plan to Gross bit rate 72 Mbit/s integrate Wi-Fi into their cell phones. Range indoor ~38 m 802.11n: It is a proposed amendment which improves upon the previous 802.11 standards by adding multiple-input multiple-output (MIMO) and many other newer features. The TGn workgroup is not expected to finalize the amendment until December 2009. Enterprises, however, have already begun migrating to 802.11n networks based on Draft 2 of the 802.11n proposal. Page 10 of 12
  11. 11. A common strategy for many businesses is to set up 802.11n networks to support existing 802.11b and 802.11g client devices and while gradually moving to 802.11n clients as Release date 2009 part of new equipment purchases. Op. frequency 5 GHz and/or 2.4 Applications:- GHz 4G will open the door to a variety of mobile apps- Throughput (Type) Unknown Net bit rate 600 Mbit/s(using 440 Some analysts agree there is no “killer app” for 4G MHz channels) today. But with the mobile speeds being proposed with 4G, customers could participate in live video conferences while on the Range indoor ~70 m go or access bandwidth-intensive applications. (Table 4: 802.11n) Forrester’s Pierce says the real jewel of 4G will be its ability to prioritize business traffic and offer customers classes of service that they have come to expect from other business-grade IP services. At the present rates of 15-30 Mbit/s, 4G is capable of providing users with streaming high-definition television, but the typical cellphone's or smartphone's 2" to 3" screen is a far cry from the big-screen televisions and video monitors that got high-definition resolutions first and which suffer from noticeable pixelation much more than the typical 2" to 3" screen. A cellphone may transmit video to a larger monitor, however. At rates of 100 Mbit/s, the content of a DVD-5 (for example a movie), can be downloaded within about 5 minutes for offline access. 4G is being developed to accommodate the quality of service (QoS) and rate requirements set by forthcoming applications like wireless broadband access, Multimedia Messaging Service (MMS), video chat, mobile TV, HDTV content, Digital Video Broadcasting (DVB), minimal service like voice and data, and other streaming services for "anytime-anywhere". Mobile TV is just one example of the Internet Everywhere experience. At the heart of this experience are all-IP end-to-end mobile networks based on open systems. These networks will emerge from several different sources. WiMAX has emerged out of the IEEE 802.16 committee, Universal Mobile Telecommunications Service (UMTS) SAE/LTE out of the Third-Generation Partnership Project (3GPP), and 3GPP2 is working on a Radio Access Network (RAN) evolution for CDMA. It is expected that all three of these technologies, along with. Limitations of 4G:- Although the concept of 4G communications shows much promise, there are still limitations that must be addressed. One major limitation is operating area. Although 2G networks are becoming more ubiquitous, there are still many areas not served. Rural areas and many buildings in metropolitan areas are not being served well by existing wireless networks. This limitation of today’s networks will carry over into future generations of wireless systems. Page 11 of 12
  12. 12. The hype that is being created by 3G networks is giving the general public unrealistic expectations of always on, always available, anywhere, anytime communications. The public must realize that although high-speed data communications will be delivered, it will not be equivalent to the wired Internet – at least not at first. If measures are not taken now to correct perception issues, when 3G and later 4G services are deployed, there may be a great deal of disappointment associated with the deployment of the technology, and perceptions could become negative. If this were to happen, neither 3G nor 4G may realize its full potential. Another limitation is cost. The equipment required to implement a next generation network is still very expensive. Carriers and providers have to plan carefully to make sure that expenses are kept realistic. Also, a 4G handset will be required to transmit on the appropriate band anywhere in the world. This implies five or more conventional power amplifiers for a broadband cellular RF interface seeking to cover all 10 LTE bands – adding several pounds to the bill of materials. A further issue is that 3G and 4G standards use complex modulation schemes that increase data throughput in the operators’ spectrum but have a dramatic impact on the power consumption of RF transmitters and hence handset battery life. Conclusions:- In this paper, we presented a heterogeneous IP-based wireless access network handoff architecture that supports uplink and downlink traffic services with different bandwidth. This IP-based network uses the Internet standard, hierarchical mobile IP to support mobility of mobile nodes. We also illustrated the issues in the integration of cellular networks with 802.11 such as WLAN, and a multipath handoff scheme. It provides two end-to-end mobility supports to utilize disparity of available bandwidths in wireless cells improving system capacity and getting transmission efficiency. For future work, the performance of the proposed architecture and algorithm will also be evaluated through simulations. 4G networks will eventually deliver on all the promises. At times, it seems that technological advances are being made on a daily basis. These advances will make high speed data/voice-over-Internet-protocol (VoIP) networks a reality. This evolution will give the general public as well as the public safety community amazing functionality from the convenience of a single handheld device. References: [1]Pei L, Zhifeng T, Zinan L, Erkip E, Panwar S. Cooperative Wireless Communications: a Cross-Layer Approach. IEEE Wireless Communications, vol. 13, no. 4, pp. 84-92, August, 2006. [3]Frattasi S, Fathi H, Fitzek FHP, Katz M, Prasad R. Defining 4G Technology from the User Perspective. IEEE Network Magazine, vol. 20, no. 1, pp. 35-41, January-February, 2006. [4]IEEE 802.16 Broadband Wireless Access Working Group. Tapped Delay Line Channel Model and Parameter Settings for Link-Level 802.16 Simulations. June, 2006. Page 12 of 12