LONG TERM EVOLUTION (LTE) Offers superior user experience and simplified technology for 4G mobile broadband A Seminar Report Submitted in Partial Fulfillment of the Requirements for the Award of Bachelor of Technology in Electronics and Communication Engineering of University of Kerala By REUBEN E. MBOJE Under the Guidance of Dr. S. SURESH BABU Mr. NISHANTH. N

JULY 2008 DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

THANGAL KUNJU MUSALIAR COLLEGE OF ENGINEERING KOLLAM – 691 005

THANGAL KUNJU MUSALIAR COLLEGE OF ENGINEERING KOLLAM – 691 005

CERTIFICATE This is to certify that the Seminar entitled “Long Term Evolution” is an authentic Report of the work done by REUBEN E. MBOJE in partial fulfillment of the requirements for the award of the degree Bachelor of Technology in Electronics and Communication Engineering of the University of Kerala during the period July-December 2008. Dr. S. SURESH BABU

Coordinator

Prof. HELEN MASCREEN

Head of the department

Long Term Evolution (LTE) Offers superior user experience and simplified technology for 4G mobile broadband A seminar Report by: 7940: REUBEN E. MBOJE, 7th Semester, Dept of Electronics & Communication Engineering, TKMCE.

Contents Executive Summary ________________________________________ 1 Foreword________________________________________________ 3 Acknowledgement_________________________________________ 4 Long Term Evolution (LTE) 1. Introduction__________________________ 5 2. Standardization Path___________________ 6 3. LTE Key Features_______________________7 4. System Architecture___________________ 9 5. Network Upgrading to LTE______________ 11 6. LTE Services__________________________ 13 7. LTE Vs WiMAX________________________ 15 8. Conclusion__________________________ 17 References_____________________________ 18

Long Term Evolution (LTE) Offers superior user experience and simplified technology for 4G mobile broadband

Executive Summery As the demand for high speed Internet is increasing with a rapid pace, the need for mobile broadband becomes a reality. People wish to get broadband wherever they go, and not just at home or office. It has been estimated that, 1.8 billion people who will have broadband by 2012, some two-thirds will be mobile broadband consumer and the majority of the these will access High Speed Packet Access (HSPA) and Long Term Evolution (LTE)[1]. People, particularly in Tanzania, has already started to browse the Net and e-mails using High Speed Downlink Packet Access (HSDPA)-enabled notebooks, making video calls, send and receive video or music using 3G cell phones. LTE shows greater promise such that the user experience will be even better [1]. LTE will further enhance bandwidth-hungry applications like interactive TV, mobile video blogging, advanced online games or professional services. LTE will also bring many technical benefits to GSM/UMTS based cellular networks [2]. LTE is the project within the Third Generation Partnership Project (3GPP) to improve Global System for Mobile communication (GSM) a 2G technology and Universal Mobile Telecommunication System (UMTS) a 3G technology. The main goals for this project/evolution concern increased data rates, improved spectrum efficiency, improved coverage, and reduced latency. Taken together, these will allow carriers to provide more data and voice services over a given bandwidth and reduced operator costs in a variety of traffic scenarios. Put simply LTE will offer three important benefits for consumers and operators: Performance and capacity: LTE promises to provide downlink peak rates of at least 100Mbit/s. In theory the technology allows the speeds over 200Mbit/s some vendors such Ericsson has already demonstrated the peak rate of about 150Mbit/s. In addition, Radio Access Network (RAN) round-trip times (latency) is expected to be less than 10ms [1]. Simplicity: First, an overarching characteristic of LTE technology is its deployment in scalable bandwidths ranging from 1.25 MHz to 20 MHz [2]. Furthermore it can operate in all 3GPP frequency bands in paired and unpaired spectrum allocations. LTE also supports both FDD (Frequency Division Duplex) and TDD (Time Division Duplex) [1]. Second, LTE deploys a “flat”, all-IP based core network with a simplified architecture,

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open interfaces and transport network that are easier to build, maintain and introduce services on [1][2]. Wide range of terminals: Since LTE supports hand-over and roaming to existing network many bandwidth-hungry devices such as mobile-computer-severs and consumer electronic devices, such as notebooks, ultra-portables, gaming devices, cameras and smart-phones, will incorporate LTE embedded modules [1].

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Foreword The fourth-generation is yet to be defined by International Telecommunication Union (ITU), the internationally recognized entity chartered to produce an official definition of the next generation of wireless technologies. However today the communications industry has witnessing significant posturing about wireless technologies and systems such as LET and WiMAX that claim to be 4G. Actually 4G networks as defined by ITU are not expected before the year 2010 as LTE, the prime candidate of the 4G network, is still on standardization state. The on-going standardization process is under the 3GPP. 3GPP is collaboration between groups of telecommunications associations, to make a globally applicable third generation (3G) mobile phone system specification within the scope of the International Mobile Telecommunications-2000 project of ITU. In its simplest form, LTE promises to deliver the mobile broadband Internet and other mobile services throughout the globe, connecting the “last mile” of communications services for both developed and emerging nations. In this seminar topic, REUBEN has done an excellent job covering the technical, business, and user details of LTE. The tutorials provided throughout the text are especially convenient for those new to LTE. Overall, I find this seminar topic extremely useful and personally believe that the author managed to successfully consolidate his mastery of LTE technology. I hope the reader finds the report useful in enhancing and understanding broadband wireless networks. - Aron Kaisi, Wireless Technical Editor & Project Manager, www.ictdocumentation.com.

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Acknowledgement I would like to thank my foundation KwetuBongo and my fellow staff at iCTDOCUMENTATION who encouraged me to write this seminar topic even when my better instincts told me the time and energy commitment would be overwhelming. I also thank Dr. S. SURESH BABU who accepted the abstract about this seminar topic during the first days of the class. I would be remiss if I fail to express my profound gratitude to my parents and my Government (Tanzania) for the continuous financial support they offer for my pursuit of Telecom engineering career here in Kerala, India. “Am missing you, Mom, and I can’t wait to see you on

July 2009”. Reuben E. Mboje, T₇, 7940: Dept Electronics & Communication Engineering, TKMCE. October 5, 2008.

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1. Introduction Long Term Evolution (LTE) describes the latest standardization work by 3G Partnership Project (3GPP) in the mobile network technology tree previously realized the GSM/EDGE and UMTS/HSxPA network technologies that now account for over 85% of all mobile subscribers [3]. In this latest standardization work which started in late 2004, the 3GPP (set out in December, 1998) defines a set of high level requirements (new high-speed Radio Access method) for mobile communications systems to compete with other latest cellular technologies particularly WiMAX. In preparation for further increasing user demands and tougher competition from new radio access technologies, LTE is enhanced with a new radio access technique called Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) [3]. Via this technology LTE is expected to improve end-user throughputs, sector capacity, reduce user plane latency and consequently offers superior user experience with full mobility. Unlike other latest deployed technologies such as HSPA, LTE is accommodated within a new Packet Core architecture called Enhanced Packet Core (EPC) network architecture. Technically, 3GPP specifies the EPC to support the E-UTRAN. EPC is designed to deploy TCP/IP protocols thus enabling LTE to support all IP-based services including voice, video, rich media and messaging with end-to-end Quality of Service (QoS). The EPC network architecture also enables improved connections and hand-over to other fixed-line and wireless access technologies while giving an operator the ability to deliver a seamless mobility experience [4]. To achieve all the targets mentioned herein, LTE Physical Layer (PHY) employs advanced technologies that are new to cellular applications. These include Orthogonal Frequency Division Multiple Access (OFDMA) and Multiple Input Multiple Output (MIMO) data transmission. Smart Antennas are also deployed to accomplish those targets. Furthermore, the LTE PHY deploys the OFDMA for the Downlink (DU) - that is from the Base Station (BS) to the User Equipment (UE) and Single Carrier Frequency Division Multiple Access (SC-FDMA) for the Uplink (UL). These technologies will further minimize the LTE system and UE complexities while allowing flexible spectrum deployment in existing or new frequency spectrum [4] [5]. LTE enjoys the support from a collaborative group of international standards organizations and mobile-technology companies that form 3GPP. However, a strong support comes from Ericsson and Qualcomm vendors that have decided not to support WiMAX, the competitor of LTE [7]. Motorola which also supports WiMAX claims to be the leading contributor in LTE standards Radio Access Network (RAN) 1 & 2 and a top three contributor to EPC 1 & 2 standards [3]. The standardization work on LTE is continuing, and Motorola claims to introduce LTE in ‘Q4 2009 [8]. However, LTE is assumed to dominate world’s mobile infrastructure markets after 2011 [2].

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2. Standardization Path The standardization of LTE started in November 2004, when a RAN Evolution Workshop in Toronto Canada accepted contributions from more than 40 operators, vendors and research institutes that included 3GPP members and nonmembers organizations. Contributions were merely a range of views and proposals on the UTRAN. Following those contributions, 3GPP started a feasibility study, in December 2004, so as to develop a new framework for evolution of the 3GPP Radio Access technology towards: Increased data rates Reduced cost per bit Increased service provisioning - that is more services with better user experience Flexibility in usage of both new and existing frequency bands High-data-rate Low-latency Simple architecture, open interface and packet-optimized RAN technology Needless to say, the study maps out specifications for RAN that are capable to support the wireless broadband internet scenario which is already enjoyed in today’s cable networks – adding full mobility to enable exciting new service possibilities [1][2]. Currently LTE specifications are described in 3GPP Release 8. The 3GPP Release 8 is the latest set of standards that describes the technical evolution of 3GPP mobile network systems [2]. It is the successor of 3GPP Release 7 that includes a set of specifications for HSPA+, the ‘missing bridge’ between HSPA and LTE. Actually HSPA+ is described in both, the 3GPP Release 7 and 8, allowing the designing of simpler ‘flat’, all-IP based network architecture and bypassing many of the legacy equipments required for UMTS/HSPA [2]. The specifications of the 3GPP Release 8 standard are assumed to complete at the end of 2008. Obviously the finalization of the 3GPP Release 8 will further progress the market interest in commercial deployment of LTE. The 3GPP Release 8 will compile the completion of 3GPP Release 7 HSPA+ features, Voice over HSPA and EPC specification and Common IP Multimedia Subsystem (IMS) [9].

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3. LTE Key Features As it has been discussed earlier, technically speaking, a fundamental objective of the 3GPP LTE project is to offer higher data speeds for both DL and UL transmissions. In addition to that, it is obviously LTE to be characterized by reduced packet latency while promising a superior experience in online gaming, Voice over IP (VoIP) videoconferencing and other real-time professional services. Now that based on the feasibility study under 3GPP, important feature of LTE are now discussed in detail:

3.1 OFDMA on the DL and SC-FDMA on the UL 3GPP Release 8 specifies an all-new RAN that combines OFDMA-based modulation and multiple access schemes for the downlink, as well as SC-FDMA for uplink. These new technologies (OFDM schemes) are deliberately deployed to split available spectrum into thousands of extremely narrowband carriers, such that each carrier is capable of carrying a part of signal. This is what is known as multiple carrier transmission [4][5]. To enhance the OFDM schemes, LTE also employs other higher order modulation schemes such as 64QAM and sophisticated Forward Error Correction (FEC) schemes such as tail biting, convolutional coding and turbo coding. Furthermore, complementary radio techniques such as MIMO and Beam Forming with up to four antennas per station are also deliberately deployed for further enhancement of innate spectral efficiency of OFDM schemes [2]. The results of these radio interface features are obvious, enabling LTE to have improved radio performance. As such they yield the spectral efficiency up to 3 to 4 times that of HSDPA Release 6 in the LTE DL and up to 2 to 3 times that of HSUPA Release 6 in UL [4][5]. Consequently, theoretically, the DL peak data rates extend up to 300Mbit/s per 20MHz of spectrum. Similarly, theoretical UL peak data rates can reach 75Mbit/s per 20MHz of spectrum as well as supporting at least 200 active users per cell in 5MHz [2].

3.2 All-IP Packet Optimized Network Architecture LTE has a ‘flat’, all-IP based core network with a simplified architecture, open interface and fewer system nodes. Indeed, the all-IP based network architecture together with the new RAN reduces network latency, improved system performance and provide interoperability with existing 3GPP and non-3GPP technologies [11]. Within 3GPP, all-IP based core network architecture is now known as Evolved Packet Core (EPC). EPC is the result of standardization work within 3GPP which targeted to convert the existing System Architecture Evolution (SAE) to an all-IP system [2].

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3.3 Advanced Antenna Techniques LTE is enhanced with MIMO, Spatial-Division Multiple Access (SDMA) and Beam Forming [14]. These are advanced radio antenna techniques which are complementary to each other. These techniques are deployed for better air interface via enhancing the innate spectral efficiency of OFDM schemes [2]. Furthermore, these techniques can be used to trade-off between higher sector capacity, higher user data rates, or higher cell-edge rates, and thus enable mobile operators to have finer control over the end-user experience [11].

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4. System Architecture The figure below shows the LTE architecture as of 2007.

E-UTRAN

Operators IP Services SGSN

HSS

MME

UE

PCRF

eNode B

SGW

PDN GW

Internet

ePDG

Trusted non 3GPP IP Access

Trusted /un-trusted non 3GPP IP Access

Un-trusted non 3GPP IP Access

UE Figure 1: LTE System Architecture

The architecture consists of the following functional elements:

4.1 Evolved Radio Access Network (RAN) The evolved RAN consists of the LTE base station (eNode B) that interfaces with the UE. The eNode B contains the PHY, Media Access Control (MAC), Radio Link Control (RLC), and Packet Data Control Protocol (PDCP) layers. Therefore the eNode B performs some tasks such as resource management, admission control, scheduling and enforcement of negotiated UL QoS [4].

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4.2 Serving Gateway (SGW) The SGW guides and forwards user data packets. Furthermore, during inter-eNode B handover SGW acts as the mobility anchor for the user plane. It can also act as an anchor for mobility between LTE technology and other 3GPP technologies. When the UE is in idle state, the SGW terminates the DL data path of the UE and triggers paging when DL data arrives for the UE [4].

4.3 Mobility Management Entity (MME) MME handles Control Signaling for mobility [1]. When the UE is in idle mode, the MME is responsible for UE tracking and paging procedure that includes retransmissions [4]. MME is also involved in the bearer activation/deactivation process. In addition MME can choose the SGW for a UE at the initial attach and at time of intra-LTE handover involving core Network (CN) node relocation. MME can interact with the Home Subscriber Server (HSS) so as to authenticate the user [4].

4.4 Packet Data Network Gateway (PDN GW) PDN GW is a point of exit and entry of traffic for the UE. PDN GW performs packet filtering and acts as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX and 3GPP2 [4].

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5. Networks Upgrading to LTE LTE is deemed to become a next generation mobile communications standard or 4G mobile communications standard that started with today’s 2G and 3G networks. Technically, the design of LTE is based on today’s 3GPP family of cellular networks that dominated by Global System for Mobile communication (GSM), General Packet Radio Service (GPRS) and Enhanced Data rate for GSM Evolution (EDGE) as well as Wideband Code Division Multiple Access (WCDMA) and High Speed Packet Access (HSPA). Therefore LTE ensures a smooth evolutionary path to higher speeds and reduced latency to these existing networks.

Figure 2: Networks upgrading flow chart

Contrary to today’s networks that deploy hybrid packet/circuit switched networks, LTE uses the advanced new radio interface. As such to harness the full potential of LTE it requires an evolution from the existing network architecture to a simplified, all-IP environment architecture. This evolution has advantages to operator’s point of view. These advantages include reduced costs for variety of services, blended applications combining voice, video and data services plus interworking with other fixed and wireless networks.

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Furthermore since the design of LTE is based on today’s UMTS/HSPA family of standards, it will obvious enhance the capabilities of the existing cellular network technologies to delivery broadband services which were accustomed to fixed broadband networks. In other words, LTE will unify the voice-oriented environment of today’s mobile networks with the data-centric service possibilities of the fixed Internet. To the operator’s point of view, the smooth upgrading of the existing networks to LTE will allow the introduction of LTE’s all-IP concept progressively. As such operator will be able to retain the value of its existing voice-based service platforms at the same time getting the benefit of high performance in data services delivered by LTE network [2].

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6. LTE Services LTE promises to delivery truly mobile broadband services through a combination of very high DL and UL transmission speeds and reduced packet latency [2]. LTE also ensures efficient use of spectrum and spectral flexibility which means wider deployment options while adding exciting new value-added services possibilities [2]. What is more, LTE technology is suitable for deployment in scalable bandwidths ranging from 1.25 MHz to 20 MHz [2]. All these features have a meaning in terms of operators point of view, user experience and business customers. To operator’s point of view, the actual performance achieved by LTE will depend on the bandwidth allocated for services, and not the choice of spectrum band itself. This gives the operator a considerable flexibility in their commercial and technical strategies. As such if the operator focuses on network capacity he will then deploys LTE at higher frequencies. On the other hand for cost effective coverage the operator should deploys LTE at lower frequencies [2]. In this way LTE stabilizing and reversing a stead declining of Average Revenue Per User (ARPU) which is the characteristic of many mobile markets [2]. For consumers, the high DL and UL transmission speeds promise the large-scale streaming, downloading and sharing of video, music and rich multimedia content. As such in future electronics consumer products such as notebooks, ultra-portables, gaming devices and video cameras are expected to operate over LTE via standardized PCI Express embedded module. The figure below shows examples of devices that could use LTE.

Figure 3: LTE User Equipments For business customers it will mean high-speed transfer of large files, high-quality videoconferencing and secure nomadic access to corporate networks. Similarly, LTE brings the characteristics of today’s ‘Web 2.0’ into the mobile space for the first time. Alongside secure ecommerce, this will span real-time peer-to-peer applications like multiplayer gaming and file sharing. The following table illustrates some of the services and applications that LTE will enable and enrich in the mobile space.

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Table 1: LTE Services

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7. LTE Vs WiMAX WiMAX and 3GPP LTE are the two wireless technologies that will eventually be used to deliver data at a very high speed (up to 100mbit/s for WiMAX and up to 300Mbit/s for LTE) beyond the 3G technologies. This high speed offered by the two technologies is fast enough to potentially replace cable broadband connections with wireless and enabled some existing services currently deemed to be too bandwidth-hungry to be delivered using existing mobile technologies.

Table 2: LTE Vs WiMAX Contrary to LTE which is still under standardization, WiMAX is already in the market with the first national fixed-WiMAX rollout in the 3.5GHz range was carried out by Wateen Teleco in Pakistan [7]. However, the world's first large scale mobile WiMAX deployment is due in the US. This is this a joint venture between Sprint Nextel Corp. and Clearwire Corp. and it is expected to

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reach 120 million to 140 million people in the U.S by the end of 2010. On the other hand, LTE is assumed to dominate world’s mobile infrastructure markets after 2011. As such, some wireless operators such as AT&T Inc. and Verizon have already stated plans to adopt LTE, with major rollouts planned for 2011 or 2012 [12]. As it has been discussed herein, LTE is the natural upgrade path for GSM/EDGE and UMTS/HSxPA network technologies that now account for over 85% of all mobile subscribers in the world. On upgrading to LTE, the existing GSM/EDGE and UMTS/HSxPA operators can use their current infrastructure (BT towers) integrating with new equipments making the whole process to be cost effective. When compared to WiMAX, an operator has to start from ground zero to setup a WiMAX network. Therefore LTE will have a significant global advantage over WiMAX in the long term [12].

7.1 Operators & Vendors Based on core network architectures of WiMAX and LTE, obviously, the two technologies will both be adopted, with LTE be the best upgrading option for GSM/EDGE and UMTS/HSxPA and WiMAX mostly appealing to cable operators [7]. This can be seen in the US where by Sprint and Clearwire are aligned behind WiMAX, while Verizon Wireless and AT&T are behind LTE [12]. WiMAX is under the WiMAX forum, comprises of more than 500 vendors and mobile operators such as Vodafone. The forum was established to promote solutions based on the IEEE 802.16 standards. As for equipment manufacturers, Intel has invested billions of dollars in WiMAX research and chip sets and showed off conceptual mobile Internet devices at the Consumer Electronics. Vodafone as a mobile operator and Motorola Corp they both support WiMAX and LTE. However LTE enjoys a strong support from Qualcomm and Ericsson who decided not to support WiMAX.

7.2 From Technical Point of View Both LTE and WiMAX use OFDMA in downlink and deploy MIMO technology, to improve reception in a single cell site [12]. However a WiMAX network process all the information in a wider channel so as to optimize optimizes channel usage to the maximum. LTE, on the other hand, organizes the available spectrum into smaller chunks [14]. Since WiMAX sticks with OFDMA in the downlink as well as in uplink, LTE uses SC-OFDMA in uplink. A major drawback of OFDMA-based system is its high Peak to Average Power Ratio (PAPR) [1]. As such a high PAPR requires expensive and inefficient power amplifiers which eventually increase the cost of the user equipment and drains the battery faster [1]. Therefore SC-FDMA is theoretically designed to work more efficiently with lower-power end-user devices than OFDM is by grouping together the resource blocks and hence reduce the need for power amplifiers [1].

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8. Conclusion LTE is an optimized mobile-OFDMA solution built from the ground up for mobility, which allows operators to offer advanced wireless services in new and wider bandwidths of up to 20MHz. LTE builds on HSPA’s success and will complement existing HSPA and HSPA+ networks with a capacity boost in high-demand areas. LTE’s high performance, integrated QoS support and low latency allow operators to efficiently target the entire range of IP services, from delaysensitive services such as telco-quality VoIP to HD-quality video streaming. LTE will support a full range of devices, including desktop modems, mobile phones, laptops and UMPCs, and will effectively meet the demand for connectivity from a new generation of consumer electronics. LTE allows operators to economically address all market segments and many types of innovative services, including the stringent needs of corporate clients with highbandwidth demands. LTE is based on a simplified, flattened IP-based network architecture that improves network latency and is designed to interoperate and ensure service continuity with existing 3GPP networks. LTE leverages the benefits of existing 3G technologies and enhances it further with additional antenna techniques, such as higher-order MIMO and SDMA. The 3G ecosystem of device manufacturers will leverage 3G knowledge and experience to ensure the availability of multimode devices that suit a variety of applications and end-user preferences in the years ahead

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References: [1] Long Term Evolution (LTE): an introduction http://www.ericsson.com/technology/whitepapers/lte_overview.pdf [2] Towards Global Mobile Broadband- White Paper from UMTS Forum February, 2008 www.umtsforum.org/component/option,com_docman/task,doc_download/gid,1904/Itemid,12/ [3] Long Term Evolution (LTE) - White Paper from Motorola http://www.motorola.com/staticfiles/Business/Solutions/Industry%20Solutions/Service%20Providers/W ireless%20Operators/LTE/_Document/Static%20Files/6833_MotDoc_New.pdf [4] Long Term Evolution (LTE): A Technical Overview by Motorola http://www.motorola.com/staticfiles/Business/Solutions/Industry%20Solutions/Service%20Providers/W ireless%20Operators/LTE/_Document/Static%20Files/6834_MotDoc_New.pdf [5]Overview of 3GPP LTE Physical Layer: White Paper by Dr. Wes McCoy, Technical Editor Freescale semiconductor http://www.freescale.com/files/wireless_comm/doc/white_paper/3GPPEVOLUTIONWP.pdf [6] LTE - Delivering the optimal upgrade path for 3G networks http://www.nokia.com/NOKIA_COM_1/Press/Press_Events/Nokia_Technology_Media_Briefing/LTE_Pre ss_Backgrounder.pdf

[7] WiMAX Guide: In association with Motorola, October 2007. http://www.motorola.com/staticfiles/Business/Products/Wireless%20Broadband%20Networks/WiMAX /_Documents/Static%20Files/Operator_Guide_to_WiMAX_October2007(2).pdf

[8] Motorola LTE Update: Interview with Darren McQueen http://www.motorola.com/staticfiles/Business/Solutions/Industry%20Solutions/Service%20Providers/W ireless%20Operators/LTE/_Document/Static%20Files/Darren%20McQueen_QA_FINAL.pdf [9] Updates to 3GPP Release 7 and Release 8 White Paper http://www.3g.co.uk/PR/July2008/6346.htm

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[10] Key Features of LTE Radio Interface: By Erik Dahlman, Anders Furuskär, Ylva Jading, Magnus Lindström and Stefan Parkvall http://www.ericsson.com/ericsson/corpinfo/publications/review/2008_02/files/6_LTE.pdf [11] 3GPP Long Term Evolution: Qualcomm Incorporated, January 2008. http://www.qualcomm.com/common/documents/white_papers/3GPP_LTE.pdf [12] WiMax vs. Long Term Evolution: Let the battle begin http://www.computerworld.com/action/article.do?articleId=9085202&command=viewArticleBasic [13] WIMAX AND LTE - Either or both? http://www.eurocomms.com/features/112044/WIMAX_AND_LTE_-_Either_or_both%3F.html

[14] The difference between WiMax and LTE from technical specifications http://blogger.xs4all.nl/jurjen1/archive/2008/07/06/400647.aspx

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