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ABSTRACT

Master's degree work: 159 pages, 58 figures, 8 tables, 20 references, 7 appendixes.In this thesis the 3GPP LTE (Long Term Evolution) was investigated. The LTE is the evolution of the UMTS system, which will make possible to deliver next generation high quality multimedia services according to the telecommunication system. This work contains the OFDM techniques of LTE, down link, up link and modulation of LTE. The present work also contains Equalization compensation of Inter symbol Interference (ISI) created by multipath signal prorogation within time dispersive channels.The results of all calculations showed that the investigation of the performance characteristics to OFDM techniques will increase the Communications quality that will be used as an input for a future LTE system level simulator.

LTE, 3GPP, IEEE 802.11, WiMAX, GSM,WCDMA,HSDP, OFDM, OFDMA, SC-FDMA, MIMO, CP, ISI, ICI, DL-LTE, UP-LTE, SU-SISO, SU-MIMO, MU-MIMO, Bit Error Rate, SNR, SIR, SINR and PAPR.

: 159 , 58 , 8 , 20 , 7 . 3GPP LTE (Long Term Evolution) . LTE UMTS, . OFDM LTE, , LTE. (ISI) . , , OFDM ', LTE.

LTE, 3GPP, IEEE 802.11, WiMAX, GSM,WCDMA,HSDP, OFDM, OFDMA, SC-FDMA, MIMO, CP, ISI, ICI, DL-LTE, UP-LTE, SU-SISO, SU-MIMO, MU-MIMO, Bit Error Rate, SNR, SIR, SINR and PAPR.

: 159 , 58 , 8 , 20 , 7 . 3GPP LTE (Long Term Evolution) .LTE UMTS, . OFDM LTE, , LTE. (ISI) . , , OFDM , LTE.

LTE, 3GPP, IEEE 802.11, WiMAX, GSM,WCDMA,HSDP, OFDM, OFDMA, SC-FDMA, MIMO, CP, ISI, ICI, DL-LTE, UP-LTE, SU-SISO, SU-MIMO, MU-MIMO, Bit Error Rate, SNR, SIR, SINR and PAPR.

ACKNOWLEDGMENTS

The work in this thesis (Master Degree) was the result of research carried out at the Department of Telecommunication Systems and Networks Engineering at Of KharkovNational University of Radio Electronic, Ukraine. In the first place, I am grateful to my supervisor Prof. Loshakov who encouraged me and believed in my success and for his significant contribution in making this thesis a reality. I would like to thank the staff of my university and my department for all the support that they gave me during my study until the end. Special thanks to my colleagues and friends, especially Haider Khudhair Al Zayadi how were been an amazing colleague that always supported me, and with whom I have learned a lot. My friends in Iraq how were help me and pray for me Zaid Saadoon Hassoon , Haider Abbas Zuoaid , Ahmmed Ali Majeed , Mr. Hassan Ali Oklah and my Director Mr. Talal Al Shara and his Aides Mr. Kamil Shunien and Mr. Salam Suaood.I would like to thank my family for their full support, patience, entertaining phone calls, and writing advice which made the completion of this thesis possible.I am thankful to the friends I have made during my stay at Kharkov; they are the support and kindness I needed for living far away from home. I will keep in my heart the new family we have imagined in the early days at Kharkov Finally.

I would like to Thanksgiving and Praise God for all the successes in my life, not letting me down at time of crises and showing me the silver lining in the dark clouds.

At last Dedicate this humble work to the Prophet of Mercy Muhammad (Pray God be upon him) the Muslim prophet.

CONTENT

ABSTRACT..LIST OF ABBREVIATIONS ..

INTRODUCTION

1 Generation of Mobile Communications..

1.1 Mobile Generations

1.1.1 Zero generation of Mobile phones...

1.1.2 Advanced Mobile Phone System (AMPS)/ 1G.1.1.3 Second Generation (1990)1.1.4 Second Generation 2G+ / (2.5G & 2.75G)..1.1.5 Third Generation (3G)..

1.2 3GPP Specifications.1.2.1 LTE in Mobile Radio.1.2.2 The Fourth Mobile Generation

Conclusion ...

2 Long Term Evolution principles and Effective Parameters

2.1 LTE History ..................2.1.1 Background2.1.2 Evolution from third generation cellular systems.

2.2 Evolved System Architecture overview ..

2.3 LTE Air interface concepts ...........

2.3.1 OFDMA as a downlink multiple access method .....

2.3.2 SC-FDMA as an uplink multiple access method .2.3.3 Multiple Input Multiple Outputs MIMO in LTE

2.4 LTE Goals ..2.4.1 LTE Features..2.4.2 LTE Services..2.4.3 Technologies Associated with LTE..2.4.4 Interoperability..

2.5 LTE Technical, Multiple Access Techniques...............................2.5.1 Downlink OFDMA.2.5.2 Peak to Average Power Ratio (PAPR)2.5.3 Frequency Offset 2.5.4 Uplink SC-FDMA..2.5.5 SC-FDMA Transmitter.2.5.6 SC-FDMA Receiver2.5.7 Frequency Bands for FDD and TDD2.6 WiMax2.6.1 WiMax and Broadband Wireless Access.2.6.2 WiMax Specifications2.7 Compare between LTE & WiMax.2.8 LTE as an Alternative Technology to WiMax..CONCLUSION..

3 Orthogonal Frequency Division Multiplexing OFDM in LTE Technology..

3.1 OFDM System Model ....

3.2 Orthogonal Frequency-Division Multiplexing System 3.2.1 Sub-channels Spacing and Frequency Orthogonal..3.2.2 Modulation Scheme3.2.3 Cyclic Prefix

3.3 OFDM Downlink LTE Setup ....

3.3.1 Parameters Specifications

3.3.2 Pilot Pattern

3.4 Multi-Cell Broadcast/Multicast Transmission and OFDM.........

3.5 Downlink and Uplink in LTE.3.5.1 OFDMA (Downlink) of LTE.3.5.2 SC-FDMA (Uplink) of LTE..

3.6 Ability of OFDMA and SC-FDMA systems to Increase the performance of LTE

3.6.1 The use OFDMA in downlink

3.6.2 SC-FDMA..

3.6.3 Simulation Results.................

3.7 Advantages and disadvantages of OFDMA...CONCLUSION..

4 Effective methods and parameters techniques for OFDM in 3GPP LTE

4.1 OFDM Basics......................................

4.1.1 OFDM Parameters and Characteristics ...

4.1.2 Orthogonal...

4.2 DESIGN and IMPLEMENTATION of OFDM.....

4.2.1 System Configurations and Parameters.

4.2.2 OFDM Transmitter (Frame Guards)..4.2.3 OFDM transmission4.2.4 OFDM reception..4.2.5 Frequency offset4.2.6 Effect of frequency offset in OFDM receiver..4.2.7 Cyclic prefix.4.2.8 Use of cyclic prefix in multipath channel.4.2.9 Choosing the cyclic prefix duration

4.3 3GPP LTE System Technical

4.3.1 Long Term Evolution..

4.3.2 Uplink Transmission....

4.3.3 Why OFDM is most favored for broadband systems4.3.4 SC-FDMA Modulation.4.3.5 OFDM..4.3.6 OFDM to SC-FDMA4.3.7 Frequency Spread OFDM4.3.8 Subcarrier Mapping.4.3.9 Single Carrier Modulation

4.4 Peak to Average Power Ratio (PAPR)........4.4.1 What is PAPR4.4.2 PAPR of a single sine tone4.4.3 PAPR of a complex sinusoidal..4.4.4 PAPR of a complex sinusoidal..4.4.5 Maximum expected PAPR from an OFDM waveform.4.4.6 PAPR analysis.CONCLUSION......

5 LABOUR PROTECTION SAFETY IN EMERGENCY SITUATIONS..

5.1 Analysis conditions .......

5.2 Accident Prevention ......

5.3 Productions Sanitary ......

5.4 Fire Safety .........

5.5 Safety in Emergency .....

CONCLUSIONS..........

References ....

APPENDIX ......

Appendix A .....

Appendix B .....

Appendix C .....

Appendix D .....

Appendix E .....

Appendix F .....Appendix G..

LIST OF ABBREVIATIONS

3GPP3rd Generation Partnership Project

ASAccess stratum

ARQAutomatic repeat request

CDDCyclic delay diversity

CDMACode division multiple access

Co-MIMOCo-operative MIMO

CNcore network

CoMPCo-operative Multi-point

CPCyclic prefix

CQIChannel quality indicator

CRCCyclic redundancy check

CWCodeword

DC-HSDPADual-Carrier HSDPA

DFTDiscrete Fourier transform

DLDownlink (base station to subscriber transmission)

E-DCHEnhanced dedicated channel

E-UTRANEvolved UMTS terrestrial radio access network

EDGEEnhanced Data rates for GSM Evolution

eMBMSEvolved multimedia broadcast multicast service

eNbEvolved Node B

EPCEvolved packet core

E-UTRAEvolved UTRA

E-UTRANEvolved UTRAN

FDDFrequency division duplex

FFTFast Fourier transform

GSMGlobal system for mobile communication

HARQHybrid automatic repeat request

HSPAHigh speed packet access

HSUPAHigh speed uplink packet access

ICIInter-Carrier Interference

IEEEInstitute of Electrical and Electronics Engineers

IFFTInverse FFT

IOTInteroperability test

IPInternet protocol

LTELong term evolution

MACMedium access control

MBMSMultimedia broadcast multicast service

MBSFNMulticast/broadcast over single-frequency network

McpsMegachips per Second

MCSModulation and Coding Scheme

MIMOMultiple input multiple output

MISOMultiple input single output

MMEMobility management entity

MMSEMinimum Mean Square Error

MSEMean Square Error

MU-MIMOMultiple user MIMO

NASNon-access stratum

OFDMOrthogonal frequency division multiplexing

OFDMAOrthogonal frequency division multiple access

PDNpacket data network

PHYPhysical layer

P-GWpacket gateway

PMIPrecoding matrix indicator

PRBPhysical Resource Blocks

QAMQuadrature amplitude modulation

QPSKQuadrature phase shift keying

RBResource block

RNCRadio network controller

RSReference signal

SAESystem architecture evolution

SFBCSpace-frequency block coding

SFNSingle-Frequency Network

S-GWServing gateway

SIMOSingle input multiple output

SINRSignal to Interference plus Noise Ratio

SIRSignal to Interference Ratio

SISOSingle input single output

SNRSignal-to-noise ratio

SU-MIMOSingle user MIMO

TBSTransport Block Size

TD-SCDMATime Domain Synchronous Code Division in Multiple Accesses

TDDTime division duplex

TRTechnical report

TrCHTransport channel

TTATelecommunications Technology Association

TTIThe Transmission Time Interval

UEUser equipment

ULUplink (subscriber to base station transmission)

UMBUltra-mobile broadband

UMTSUniversal mobile telecommunications system

UTRAUniversal terrestrial radio access

UTRANUniversal terrestrial radio access network

W-CDMAWideband code division multiple access

WiBroWirelessBroadband

INTRODUCTION

Mobile communication has become the most important requirements of global societies. In the last century, technology has evolved from being expensive to a small number of individuals available to and affordable for the vast majority of the population of the world. Of the first experiments with radio communications Guglielmo Marconi by the 1890s, where making to launch mobile wireless communications. To understand the complex mobile communication systems through the generations, it is important to understand where they came from and how it evolved cellular systems. I have changed the task of developing mobile phone technology as well, to become an increasingly complex task of interest to the international standards development organizations, such as the Third Generation Partnership Project (3GPP).Techniques are often divided into generations in mobile communications, with 1G being analog mobile radio systems of the 1980s, 2G mobile systems, the first digital, and 3G systems to deal with the first mobile broadband data. Is often called the long-term evolution (LTE) "4G", but many also claims that the LTE release of 10, also referred to as LTE, is the beginning of the evolution of 4G, with the first version of LTE (Release 8) and then being labeled as "3.9 G ". The contest runs for the preparation of new generations in the mobile system, which is really just a call, and what is important is the actual capacity of the system and how to increase the capacity of the channel carriers and purity.3GPP LTE is the future 4G standard and globally recognized as the natural evolution of for GSM/EDGE and UMTS/HSPA networks. Release 8 was frozen in December 2008 and this has been the basis for the first wave of LTE equipment. LTE specifications are very stable, with the added benefit of small enhancements having been introduced in 3GPP Release 9.

Figure 1.1- in 3GPP Standard Generations

This thesis include four topics first topic describe the Mobile Generations included 3GPP LTE telecommunication concepts is introduced, the history of technology system and brief overview.Second topic dealing with LTE system overview, system architecture, LTE goals and Comparison LTE with WiMax. Third topic , Using Orthogonal Frequency Division Multiplexing OFDM in LTE Technology, This topic focuses on OFDM system, OFDM Downlink and Uplink LTE Setup, and the LTE Transmitter and Receiver.In the last topic four describe Mathematical models and MATLAB simulations for increasing quality of (LTE) using (OFDM).

1 Generation of Mobile Communications

1.1 Mobile Generations

Public mobile telephone history begins in the 1940s after World War II. Although primitive mobile telephones existed before the War, these were specially converted two way radios used by government or industry, with calls patched manually into the landline telephone network. Many New York City fireboats and tugboats had such radiotelephones in the1930s.Mobile generations started from 0G to 4G are discussed in this topic.

Figure 1.2- Mobile Generations

1.1.1 Zero generation of Mobile phonesIn 1945, the zero generation (0G) of mobile telephones was introduced. 0G mobile telephones, such as Mobile Telephone Service, were not officially categorized as mobile phones, since they did not support the automatic change of channel frequency during calls, which allows the user to move from one cell (the base station coverage area) to another cell, a feature called "handover".

1.1.2 Advanced Mobile Phone System (AMPS)/ First Generation, (1972-1989)The standard was developed by Bell labs and officially introduced in America in 1983. It was the Analog mobile phone standard. Advanced Mobile Phone System AMPS was the first generation cellular technology that uses separate frequencies.AMPS pioneers fathered the term "cellular" because of its use of small hexagonal "cells" within a system. AMPS cellular service operates in the 800 MHz Cellular FM band. Since it is an analog standard, it is very susceptible to static and noise and has no protection from eavesdropping using a scanner.

1.1.3 Second Generation (1990)The second generation (2G) of the wireless mobile network was based on low-band digital data signaling. The most popular 2G wireless technology is known as Global Systems for Mobile Communications (GSM). GSM systems, first implemented in 1991, are now operating in about 140 countries and territories around the world.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.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 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.

1.1.4 Second Generation 2G+ / (2.5G & 2.75G) W.L. Networks (1990 - 2000)The effective data rate of 2G circuit-switched wireless systems is relatively slow. As a result, GSM, PDC and other TDMA-based mobile system providers and carriers have developed 2G+ technology that is packet-based and increases the data communication speeds to as high as 384kbps. The emerged technologies in 2.5G are:- High Speed Circuit Switched Data (HSCSD) is one step towards 3G wideband mobile data networks. This circuit-switched technology improves the data rates up to 57.6kbps by introducing 14.4 kbps data coding and by aggregating 4 radio channels timeslots of 14.4 kbps.- 2.5G: General Packet Radio Service (GPRS) is an intermediate step that is designed to allow the GSM world to implement a full range of internet services without waiting for the deployment of full-scale 3G wireless systems. The data is packetized and transported over Public Land Mobile Networks (PLMN) using an IP backbone so that mobile users can access services on the Internet, such as SMTP/POP-based e-mail, ftp and HTTP-based Web services.- 2.75G: Enhanced Data rate for Global Evolution (EDGE) technology is a standard that has been specified to enhance the throughput per timeslot for both HSCSD and GPRS.

1.1.5 Third Generation (3G) Wireless Networks (2000-2011 STILL)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 technologies is its ability to unify existing cellular standards, such as CDMA, GSM, and TDMA, less than one umbrella. The following three air interface modes accomplish this result: wideband CDMA, CDMA2000 and the Universal Wireless Communication (UWC-136) interfaces.3G wireless networks consist of a Radio Access Network (RAN) and a core network. The core network consists of a packet-switched domain. The access network provides a core network technology independent access for mobile terminals to different types of core networks and network services.Either core network domain can access any appropriate RAN service; e.g. it should be possible to access a speech radio access bearer from the packet switched domain.

1.1.5.1 3G Networks 3G networks are intended to provide a global cellular communications with wide range of services including telephony, paging, messaging, Internet and broadband data.The International Telecommunication Union (ITU) started the process of defining the standard for third generation systems, referred to as International Mobile Telecommunications 2000 (IMT-2000). 3G is the third-generation technology also known as UMTS (Universal Mobile Telecommunications System) in the context of mobile phone standards. The third generation, as its name suggests, follows the first generation (1G) and second generation (2G) in wireless communications. The services associated with 3G provide the ability to transfer simultaneously both voice data (a telephone call) and non-voice data (such as downloading information, exchanging email, and instant messaging). The first country that introduced 3G on a large commercial scale was Japan. 3G networks are wide-area cellular networks that evolved to incorporate high-speed internet access and video telephony. Handsets could vary from hand-held phones to wireless laptops used for high-speed Internet access [2].

1.1.5.2 Features of Mobile GenerationsIn this section a comparison between the 2G and 3G generations are discussed to be able to know what the fourth generation will support, you should know what the generations nowadays support. Table 1.1 shows the core network, data rates, applications and availability of roaming in each generation. While Table 1-2 shows the data rates in detail in each generation including the next generations, LTE and Wimax. In next section and next topic, then discuss what the 4G and how differs from 3G in next topic this research discuss in detail about the LTE system and its specifications.

Table 1.1- Mobile Generations

1.2 3GPP Specifications

The Third-Generation Partnership Project (3GPP) is the standards-developing body that specifies the 3G UTRA and GSM systems. 3GPP is a partnership project formed by the standards bodies ETSI, ARIB, TTC, TTA, CCSA and ATIS. 3GPP consists of several Technical Specifications Groups (TSGs).A parallel partnership project called 3GPP2 was formed in 1999. It also develops 3G specifications, but for cdma2000, which is the 3G technology developed from the 2G CDMA based standard IS-95. It is also a global project, and the organizational partners are ARIB, CCSA, TIA, TTA and TTC. 3GPP TSG RAN is the technical specification group that has developed WCDMA, its evolution HSPA, as well as LTE, and is in the forefront of the technology. TSG RAN consists of five working groups (WGs):1. RAN WG1 dealing with the physical layer specifications.2. RAN WG2 dealing with the layer 2 and layer 3 radio interface specifications.3. RAN WG3 dealing with the fixed RAN interfaces, for example interfaces between nodes in the RAN, but also the interface between the RAN and the core network.4. RAN WG4 dealing with the radio frequency (RF) and radio resource management (RRM) performance requirements.5. RAN WG 5 dealing with the terminal conformance testing.

Figure 1.3- the Third-Generation Partnership Project (3GPP)

The scope of 3GPP when it was formed in 1998 was to produce global specifications for a 3G mobile system based on an evolved GSM core network, including the WCDMA-based radio access of the UTRA FDD and the TD-CDMA-based radio access of the UTRA TDD mode, The task to maintain and develop the GSM/EDGE specifications was added to 3GPP at a later stage. The UTRA (and GSM/EDGE) specifications are developed, maintained and approved in 3GPP.

Figure 1.4- 3GPP LTE ReleasesThe specifications of all releases 1.3 and figure 1.4 can be updated after each set of TSG meetings, which occur 4 times a year. The 3GPP documents are divided into releases, where each release has a set of features added compared to the previous release. The features are defined in Work Items agreed and undertaken by the TSGs. The releases up to Release 8 and some main features of those are shown in Figure. The date shown for each release is the day the content of the release was frozen. For historical reasons, the first release is numbered by the year it was frozen (1999), while the following releases are numbered 4, 5, etc.

1.2.1 LTE in Mobile RadioIn contrast to transmission technologies using media such as copper lines and optical fibers, the radio spectrum is a medium shared between different, and potentially interfering, technologies. As a consequence, regulatory bodies in particular, ITU-R (International Telecommunication Union Radio communication Sector) [1], but also regional and national regulators play a key role in the evolution of radio technologies since they decide which parts of the spectrum and how much bandwidth may be used by particular types of service and technology. This role is facilitated by the standardization of families of radio technologies a process which not only provides specified interfaces to ensure interoperability between equipment from a multiplicity of vendors, but also aims to ensure that the allocated spectrum is used as efficiently as possible, so as to provide an attractive user experience and innovative services.The complementary functions of the regulatory authorities and the standardization organizations can be summarized broadly by the following relationship:

On a worldwide basis, ITU-R defines technology families and associates specific parts of the spectrum with these families. Facilitated by ITU-R, spectrum for mobile radio technologies is identified for the radio technologies which meet ITU-Rs requirements to be designated as members of the International Mobile Telecommunications (IMT) family.Effectively, the IMT family comprises systems known as Third Generation (for the first time providing data rates up to 2 Mbps) and beyond.From the technology and standards angle, three main organizations have recently been developing standards relevant to IMT requirements, and these organizations continue to shape the landscape of mobile radio systems as shown in Figure 1.5.

Figure 1.5- landscapes of mobile radio systems

The uppermost evolution track shown in Figure 1.5 is that developed in the 3rd Generation Partnership Project (3GPP), which is currently the dominant standards development group for mobile radio systems and is described in more detail below.Within the 3GPP evolution track, three multiple access technologies are evident: theSecond Generation GSM/GPRS/EDGE family was based on Time- and Frequency-Division Multiple Access (TDMA/FDMA); the Third Generation UMTS family marked the entry of Code Division Multiple Access (CDMA) into the 3GPP evolution track, becoming known as Wideband CDMA (owing to its 5 MHz carrier bandwidth) or simply WCDMA; finally LTE has adopted Orthogonal Frequency-Division Multiplexing (OFDM), which is the access technology dominating the latest evolutions of all mobile radio standards [5].In continuing the technology progression from the GSM and UMTS technology families within 3GPP, the LTE system can be seen as completing the trend of expansion of service provision beyond voice calls towards a multiservice air interface. This was already a key aim of UMTS and GPRS/EDGE, but LTE was designed from the start with the goal of evolving the radio access technology under the assumption that all services would be packet-switched, rather than following the circuit-switched model of earlier systems. Furthermore, LTE is accompanied by an evolution of the non-radio aspects of the complete system, under the term System Architecture Evolution (SAE) which includes the Evolved Packet Core (EPC) network. Together, LTE and SAE comprise the Evolved Packet System (EPS), where both the core network and the radio access are fully packet-switched.The standardization of LTE and SAE does not mean that further development of the other radio access technologies in 3GPP has ceased. In particular, the enhancement of UMTS with new releases of the specifications continues in 3GPP, to the greatest extent possible while ensuring backward compatibility with earlier releases: the original Release 99 specifications of UMTS have been extended with high-speed downlink and uplink enhancements (HSDPA2 and HSUPA3 in Releases 5 and 6 respectively), known collectively as HSPA (High-Speed Packet Access). HSPA has been further enhanced in Release 7 (becoming known as HSPA+) with higher-order modulation and, for the first time in a cellular communication system, multi stream MIMO4 operation, while Releases 8, 9 and 10 introduce support for multiple 5 MHz carriers operating together in downlink and uplink.These backward-compatible enhancements enable network operators who have invested heavily in the WCDMA technology of UMTS to generate new revenues from new features while still providing service to their existing subscribers using legacy terminals.The first version of LTE was made available in Release 8 of the 3GPP specification series.It was able to benefit from the latest understanding and technology developments from HSPA and HSPA+, especially in relation to optimizations of the protocol stack, while also being free to adopt radical new technology without the constraints of backward compatibility or a 5 MHz carrier bandwidth. However, LTE also has to satisfy new demands, for example in relation to spectrum flexibility for deployment. LTE can operate in Frequency-Division Duplex (FDD) and Time-Division Duplex (TDD) modes in a harmonized framework designed also to support the evolution of TD-SCDMA (Time-Division Synchronous Code Division Multiple Access), which was developed in 3GPP as an additional branch of the UMTS technology path, essentially for the Chinese market.A second version of LTE was developed in Release 9, and Release 10 continues the progression with the beginning of the next significant step known as LTE-Advanced.A second evolution track shown in Figure 1.5 is led by a partnership organization similar to 3GPP and known as 3GPP2. CDMA2000 was developed based on the American IS- 95 standard, which was the first mobile cellular communication system to use CDMA technology; it was deployed mainly in the USA, Korea and Japan. Standardization in 3GPP2 has continued with parallel evolution tracks towards data-oriented systems (EV-DO), to a certain extent taking a similar path to the evolutions in 3GPP. It is important to note that LTE will provide tight interworking with systems developed by 3GPP2, which allows a smooth migration to LTE for operators who previously followed the 3GPP2 track.The third path of evolution has emerged from the IEEE 802 LAN/MAN5 standards committee, which created the 802.16 family as a broadband wireless access standard. This family is also fully packet-oriented. It is often referred to as WiMAX, on the basis of a so called System Profile assembled from the 802.16 standard and promoted by the WiMAX Forum. The WiMAX Forum also ensures the corresponding product certification. While the first version, known as 802.16-2004, was restricted to fixed access, the following version 802.16e includes basic support of mobility and is therefore often referred to as mobile WiMAX. However, it can be noted that in general the WiMAX family has not been designed with the same emphasis on mobility and compatibility with operators core networks as the 3GPP technology family, which includes core network evolutions in addition to the radio access network evolution. Nevertheless, the latest generation developed by the IEEE, known as 802.16m, has similar targets to LTE-Advanced.The overall pattern is of an evolution of mobile radio towards flexible, packet-oriented, multiservice systems. The aim of all these systems is towards offering a mobile broadband user experience that can approach that of current fixed access networks such as Asymmetric Digital Subscriber Line (ADSL) and Fiber-To-The-Home (FTTH).

1.2.2 The Fourth Mobile GenerationThe fourth generation promise Support terminal and personal mobility, Flexible roaming and hand-over supported To other different systems and networks, Efficient support of various services Including symmetrical and asymmetrical services, (Broadcast and distribution services), Maintaining QoS (comparable with wire-line network).The Target mobility and information bit rates are 2 Mbps for (250 Km/h), 20 Mbps for (60 Km/h) and finally 100 Mbps for (3 Km/h).4G promises Economic deployment of systems with optimized radio interfaces among macro cells, micro cells, indoor, hot spots and broadcast networks, and promises to accommodate mixed-mode multi-standard services, and to employ any future services.

1.2.2.1 Fundamental requirements for LTE-Advanced- Complete fulfillment of all the requirements for IMT-Advanced defined by ITU - LTE-Advanced has to fulfill a set of basic backward compatibility requirements Spectrum coexistence, implying that it should be possible to deploy LTE-Advanced in spectrum already occupied by LTE with no impact on existing LTE terminals infrastructure, in practice implying that it should be possible to upgrade already installed LTE infrastructure equipment to LTE-Advanced capability terminal implementation - Support for peak-data up to 1 Gbps in the downlink and 500 Mbps in the uplink. - Substantial improvements in system performance such as cell and user throughput with target values significantly exceeding those of IMT-Advanced. - Possibility for low-cost infrastructure deployment and terminals. - High power efficiency, that is, low power consumption for both terminals and infrastructure. - Efficient spectrum utilization, including efficient utilization of fragmented spectrum technical components of LTE-Advanced.-Wider bandwidth and carrier aggregation. -Extended multi-antenna solutions. -Advanced repeaters and relaying functionality. -Coordinated multi-point transmission. The Wider bandwidth and carrier aggregation:-1. LTE-Advanced will be an increase of the maximum transmission bandwidth beyond 20 MHz, perhaps up to as high as 100 MHz or even beyond 2. In case of carrier aggregation, the extension to wider bandwidth is accomplished by the aggregation of basic component carriers of a narrower bandwidth shown on figure 1.6.

Figure 1.6 - Special features in LTE-A [Rel. 10] a) carrier aggregations

b) Repeat (Relaying) in LTE-A [Rel. 10]1.2.2.2 Comparison of 3G and 4G Networks Lets take a look at different specifications of both 3G and 4G mobile systemsThe main difference between 3G and 4G networks are data rates, services, transmission methods, access technology to the Internet, the compatibility to interface with wire-line backbone network, quality of service and security, Table 1.2. As networks evolve, more content choices will be available to satisfy customer needs. 3Gs high-speed communications (upwards of 2 Mbps) and broadband services such as enhanced multimedia (voice, data and video) will attract many more customers. Service providers and network operators have already started embracing 3G wireless standards to offer new services to their techno-savvy customers. Put simply, 3G wireless technologies represents a shift from voice-centric services to multimedia-oriented services like video, voice, data and fax. Further deployment of 3G will see an explosion of personal communication devices and systems that deliver freedom of communications through mobility as well as wide-band wireless access to the Internet and advanced multimedia services. The 3G handsets, though, will be slightly bigger because they will have more software inside. In fact, as handsets morph into Personal Digital Assessments PDAs, the appliance we carry around will become increasingly like a computer. LTE is the next step from 2G (GSM) and 3G (based upon UMTS). LTE provides significantly higher peak data rates (100 Mbps downstream/30 Mbps upstream) and is backward compatible with existing GSM and UMTS networks.

Table 1.2 Comparisons between 3G Network and 4G Network

Table 1.3- Comparisons between 2.5, 2.75, 3 and 4G

CONCLUSION

Mobile generations started from 0G to 4G techniques are often divided into generations in mobile communications, with 1G being analog mobile radio systems of the 1980s, 2G mobile systems, the first digital, and 3G systems to deal with the first mobile broadband data. Is often called the long-term evolution (LTE) "4G", but many also claims that the LTE release of 10, also referred to as LTE, is the beginning of the evolution of 4G, with the first version of LTE (Release 8) and then being labeled as "3.9 G ". The contest runs for the preparation of new generations in the mobile system, which is really just a call, and what is important is the actual capacity of the system and how to increase the capacity of the channel carriers and purity.LTE is the next step from 2G (GSM) and 3G (based upon UMTS). LTE provides significantly higher peak data rates (100 Mbps downstream/30 Mbps upstream) and is backward compatible with existing GSM and UMTS networks.3GPP LTE is also the future 4G standard and globally recognized as the natural evolution of for GSM/EDGE and UMTS/HSPA networks. Release 8 was frozen in December 2008 and this has been the basis for the first wave of LTE equipment.The main difference between 3G and 4G networks is data rates, services, transmission methods, access technology to the Internet, the compatibility to interface with wire-line backbone network, quality of service and security.4G promises Economic deployment of systems with optimized radio interfaces among macro cells, micro cells, indoor, hot spots and broadcast networks, and promises to accommodate mixed-mode multi-standard services, and to employ any future services.

2 Long Term Evolution principles and Effective Parameters

2.1 LTE HistoryThe 3GPP Long Term Evolution (LTE) standard represents a major advance in cellular technology. LTE is designed to meet carrier needs for high-speed data and media transport as well as high-capacity voice support well into the next decade. LTE is well positioned to meet the requirements of next-generation mobile networks. It will enable operators to offer high performance, mass-market mobile broadband services, through a combination of high bit-rates and system throughput in both the uplink and downlink with low latency. Long Term Evolution (LTE) is one of the choices for next generation broadband wireless networks and is defined by the 3GPP standards as an evolution to a variety of 3G wireless networks such as UMTS and EVDO. Its high data rates enable advanced multimedia applications. The LTE network architecture, network interfaces and protocols, air interface and mobility will provide advanced mobile broadband services for years to come; LTE is an evolution of the current family of 3G mobile wireless standards. A main objective of Long Term Evolution (LTE) is to support IP multimedia services, including VoIP and high-speed data applications, with an always-on end-user experience comparable to that of fixed internet access, and at a lower cost per bit. This is achieved by flatter network architecture, improved spectral efficiency, providing a more flexible spectrum deployment, lower operating costs and better integration with other open standards such as WLAN and WiMAX.

2.1.1 BackgroundThe work towards LTE standardization started in November 2004 in a 3GPP Radio Access Network (RAN) Evolution Workshop in Toronto, Canada. As a result a study item was created for developing a framework and defining the targets for evolution of 3GPP radio access technology. Feasibility study for LTE E-UTRAN is given in a 3GPP document TR 25.912 [10]. This study was done to ensure the long term competiveness of 3GPP technology, which was seen necessary even though HSDPA technology was not yet deployed at that time. The specification work was considered complete five years later in March 2009 as the specifications for the evolved core network called System Architecture Evolution (SAE), were included and backwards compatibility to existing radio access technology was ensured. Today there are several live commercial LTE networks e.g. in Sweden and Germany. New LTE networks can be expected since the operators have shown great interest towards LTE technology. [1], [11].The first LTE release in 3GPP standards and the one studied in this thesis is Release 8. Shown on figure 2.1 According to International Telecommunications Union (ITU), LTE did not originally satisfy the requirements set for a 4G technology. ITU considered that Release 10, namely LTE-Advanced, would be the first 3GPP release to satisfy the requirements for an IMT-Advanced or 4G technology. The operators however werent happy with pre-4G or 3.9G labels and were advertising their LTE networks as fourth generation mobile networks. In December 2010 as a result of pressure from the operators, ITU declared in a press release that LTE as well as WiMaX and HSPA+ can officially be called 4G technologies [12]. The roadmap for 3G evolution in 3GPP and the way towards 4G is illustrated in Figure 2.1.

Figure 2.1- The roadmap for 3G evolution in 3GPP and the way towards 4G2.1.2 Evolution from third generation cellular systems The main motivation for LTE deployment is based on rapid growth in mobile data usage. Increased demand for high user data rates, lower latencies and operator demand for more capacity and efficient usage of the scarce radio spectrum are the driving forces behind the technology development. Flat rate pricing models for broadband subscriptions also create pressure for operators to minimize their cost per bit expenses as well as their network maintenance costs [1]. These issues have been tackled on several levels in both the radio access part of LTE, E-UTRAN, and the core network, SAE. LTE network elements support the monitoring of user data traffic, which makes other pricing models available for the operators. Flat rate pricing models are however preferred at least in the beginning as they are critical for LTE mass market adoption. [14] LTE inherits the cellular concept and many of its features from legacy systems in 3G cellular technologies but it also introduces a whole set of new concepts and features. Code Division Multiple Access (CDMA) used in third generation systems has been replaced by Orthogonal Frequency Division Multiple Access (OFDMA) as the multiple access method in downlink due to its good spectral properties and bandwidth scalability. OFDMA is well compatible with Multiple Input Multiple Output (MIMO) multi-antenna transmission techniques used in LTE. The downside of OFDMA is that it introduces a high Peak-to-Average Power Ratio (PAPR) in the transmitter side. This increases transmitter complexity and power consumption, which is a critical factor in the mobile terminal side. Therefore a multiple access scheme that minimizes the terminal power consumption, namely Single Carrier Frequency Division Multiple Access (SC-FDMA), was chosen for uplink. These schemes will be explained in detail later in this topic. Some of the most important LTE features are summarized below. - OFDMA as downlink multiple access method provides orthogonal among users and along with multiple-antenna techniques a good spectral efficiency. - LTE provides frequency flexibility as it has been allocated 17 paired and 8 unpaired bands with scalable bandwidth allocations of 1.4MHz to 20MHz. - Enhanced air interface concepts as well as a flat All-IP core architecture provides higher data rates and lower latencies with cost efficient operation. - Seamless interoperability with legacy 3GPP systems. Peak data rates in LTE release 8 are around 100Mbps in downlink and 50Mbps in uplink per cell. Latency is reduced to approximately 10ms in round trip times. These figures are a significant improvement from those of High Speed Packet Access (HSPA) not to mention earlier 3G or 2G releases. The evolution from third generation to fourth generation systems in terms of performance indicators such as data rates and latency are summarized in Table 2.1 [1].Table 2.1 the evolution from third generation to fourth generation systems in terms of performance.

2.2 Evolved System Architecture overview

The design goal of LTE architecture is a simplified and more efficient all-IP system, optimized for packet traffic. For example Radio Network Controller (RNC) used in early 3G releases for Radio Resource Management (RRM) functions, is removed and its intelligence is moved to the Evolved Node B (eNodeB). Another considerable difference to legacy cellular systems is that there is no circuit switched domain in LTE architecture. The core network is solely all-IP, and therefore control data and user data as well as voice are all transferred on top of packet switched IP-protocol. LTE terminal supporting multimode operation is however specified to be capable of Circuit Switched Fall Back (CS FB), which means that the terminal is transferred to UTRAN or GERAN circuit networks if there is no VoIP support in the LTE network. Later on when VoIP support is added, Single Radio Voice Call Continuity (SR-VCC) can be used for handing over existing VoIP calls to GSM and WCDMA circuit switched networks. Packet switched I-RAT handover is naturally also supported and can also be used as an intermediate step in handovers from LTE packet domain to 3G or 2G circuit switched domain [1]. LTE network can be divided into two subsystems. Evolved UTRAN is the radio access network that manages the wireless access part providing an access point to the users. Evolved Packet Core (EPC) is then the core network part that manages user mobility and interconnects the radio access part to other networks and services. Network elements are connected to each other by specified interfaces that will also be explained briefly here. The architecture is based on open interfaces, which means that the interworking devices can be manufactured by different vendors to incite more competition. The high level architecture of 3GPP LTE is illustrated below in Figure 2.2. A more detailed overview of LTE system architecture, network elements and the interworking principles between the elements via interfaces is specified in 3GPP document TS 23.401 General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network [17].

Figure 2.2- The high level architecture of 3GPP LTE

2.3 LTE Air interface concepts

LTE provides an impressive set of new air interface concepts. This section introduces OFDMA and SC-FDMA as downlink and uplink multiple access methods respectively. Multiple antenna techniques, such as MIMO, are also explained at the end of this chapter. Some of the most important LTE air interface techniques are illustrated in Figure 2.3 below. Some of these air interface techniques such as higher order modulation, fast link adaptation and HARQ, have been introduced also in the latest HSPA releases.The air interface is likely to be the bottleneck link in the network. Therefore for the most part the user delay as well as handover delay is caused by the air interface. Handover failures and call drops are also likely to be caused by, e.g. radio link failures in the air interface.

Figure 2.3- OFDMA, SC-FDMA as DL &UL multiple access methods respectively.

2.3.1 OFDMA as a downlink multiple access method Orthogonal frequency-division multiplexing (OFDM) is a digital modulation method used in several wireless radio access and broadcast systems such as WiMAX, WLAN and DVB, as well as ADSL wire line systems. It provides good spectral properties and performance in frequency fading channels. OFDM is based on closely-spaced narrowband subcarriers that are mutually orthogonal. The creation of OFDM signal in transmitter receiver chain is illustrated in Figure 2.4.

Figure 2.4- The creation of OFDM signal in transmitter receiver chainThe orthogonal subcarriers are created with an IFFT transformation of signal from frequency domain to time domain. Subcarriers are set to be 15 kHz apart in LTE. Then a cyclic extension is added to the signal, which is then transmitted over the air interface. The receiver then performs the cyclic extension removal and FFT operations in the opposite direction to extract the sent bits correctly. [20] OFDMA is then a multiple access method that allocates OFDM channels to multiple users and separates the users in frequency and time. The minimum allocation for one user in LTE is one resource block, which corresponds to 12 subcarriers in frequency and one Transmit Time Interval (TTI), which equals 1ms in time. Ideally there should be no Inter Carrier Interference (ICI) between users due to orthogonal carriers. In practice frequency synchronization is required due to receiver imperfections and frequency offset of moving UEs caused by the Doppler shift. Inter Symbol Interference (ISI) in time domain caused by delayed multipath versions of transmitted signals, is then mitigated by adding a guard interval, a cyclic extension, to the symbols. RAKE sub-receivers used in 3G systems for combining multipath components are therefore not needed in LTE. Traditional methods such as interleaving for burst error prevention and coding to provide Forward Error Correction (FEC) are also utilized to improve reliability of the radio transmission. Interference from other cells remains a major issue since same subcarriers are used in neighboring cells as LTE is a reuse 1 system. Various methods for Inter Cell Interference Coordination (ICIC) have been proposed to mitigate the interference, e.g. cell edge frequency reuse. [20] Power control can be utilized in downlink control channels but for data channels, power control is not utilized in LTE downlink. Instead a method called Adaptive Modulation and Coding (AMC) is used that adapts the modulation scheme and coding rate according to varying radio conditions. UE measures the channel quality and gives feedback to the eNodeB in Channel Quality Indicator (CQI) reports and according to the CQI, the eNodeB chooses the optimal Modulation and Coding Scheme (MCS). The goal is to achieve a target Block Error Ratio (BLER) that maximizes the throughput in the given radio conditions according to Carrier to Interference plus Noise Ratio (CINR). Modulation types QPSK, 16QAM and 64QAM as well as a wide set of coding rates are supported in LTE downlink. The modulation scheme defines how many bits can be carried per symbol. The coding rate then defines the ratio of redundant bits per user bits. Therefore the chosen MCS value defines an absolute value for the user throughput in given radio conditions. In a mobility case this means that as the user traverses towards the edge of neighboring cells that interfere with each other, his or her throughput decreases in a stepwise manner. Then as the handover occurs, the throughput goes to zero for the duration of the handover break. In the new cell the user throughput then starts to increase as he or she continues to move away from the cell edge and towards the cell centre and better radio conditions. [20]

2.3.2 SC-FDMA as an uplink multiple access method Uplink transmission uses SC-FDMA as multiple access method. The difference to OFDMA is that the data symbols in SC-FDMA occupy a frequency range of M*15 kHz adjacent subcarriers with M times the rate, hence the name Single Carrier. OFDMA symbols then consist of only one subcarrier that is transmitted at constant power during the entire symbol period of 66.7s.

Figure 2.5- The modulation schemesThe transmitter receiver chain is similar to that of OFDMA. The difference is that after modulation, the symbols are converted to frequency domain and mapped to the desired bandwidth. After that an IFFT is performed as in OFDMA to convert the signal back to time domain for radio transmission shown on figure 2.5. LTE uplink utilizes only slow power control since there is no near-far problem like in WCDMA due to orthogonal resources. The point is to reduce terminal power consumption and avoid a large dynamic receiver range in eNodeB side rather than interference mitigation. Power control for LTE is standardized in [18]. Uplink supports modulation types up to 64QAM but the terminal side may be limited to only 16QAM. LTE release 8 does not support multiple antenna transmission in uplink and therefore data rates are significantly lower compared to downlink transmission. [1] More extensive descriptions for LTE multiple access methods including detailed mathematical principles can found in references [6] for OFDMA and [15] for SC-FDMA.Multiple access methods as well as MIMO techniques discussed next are some of the key LTE air interface concepts. These concepts however have little relevance to I-RAT handovers.

2.3.3 Multiple Input Multiple Output MIMO in LTEMIMO, Multiple Input Multiple Output is another of the LTE major technology innovations used to improve the performance of the system. This technology provides LTE with the ability to further improve its data throughput and spectral efficiency above that obtained by the use of OFDM.Although MIMO adds complexity to the system in terms of processing and the number of antennas required, it enables far high data rates to be achieved along with much improved spectral efficiency. As a result, MIMO has been included as an integral part of LTE.2.3.3.1 LTE MIMO basicsThe basic concept of MIMO utilizes the multipath signal propagation that is present in all terrestrial communications. Rather than providing interference, these paths can be used to advantage.Two major limitations in communications channels can be multipath interference, and the data throughput limitations as a result of Shannon's Law. MIMO provides a way of utilizing the multiple signal paths that exist between a transmitter and receiver to significantly improve the data throughput available on a given channel with its defined bandwidth. By using multiple antennas at the transmitter and receiver along with some complex digital signal processing, MIMO technology enables the system to set up multiple data streams on the same channel, thereby increasing the data capacity of a channel.MIMO is being used increasingly in many high data rate technologies including Wi-Fi and other wireless and cellular technologies to provide improved levels of efficiency. Essentially MIMO employs multiple antennas on the receiver and transmitter to utilize the multi-path effects that always exist to transmit additional data, rather than causing interference.The schemes employed in LTE again vary slightly between the uplink and downlink. The reason for this is to keep the terminal cost low as there are far more terminals than base stations and as a result terminal works cost price is far more sensitive.For the downlink, a configuration of two transmit antennas at the base station and two receive antennas on the mobile terminal is used as baseline, although configurations with four antennas are also being considered.For the uplink from the mobile terminal to the base station, a scheme called MU-MIMO (Multi-User MIMO) is to be employed. Using this, even though the base station requires multiple antennas, the mobiles only have one transmit antenna and this considerably reduces the cost of the mobile. In operation, multiple mobile terminals may transmit simultaneously on the same channel or channels, but they do not cause interference to each other because mutually orthogonal pilot patterns are used. This techniques is also referred to as spatial domain multiple access (SDMA).2.3.3.2 Multiple antenna techniques The basic antenna configuration is Single Input Single Output (SISO), which means that one antenna is used to transmit data and one antenna receives the data. The fundamental idea to adding multiple antennas is that it improves performance because the radiated signals take different propagation paths. LTE release 8 supports multiple antenna modes of up to 4 transmit and 4 receive antennas. Multiple antenna methods used in LTE including SISO, SIMO, MISO and MIMO are illustrated below in Figure 2.6.

Figure 2.6- Multiple antenna methods

Multiple Input Single Output (MISO) and Single Input Multiple Output (SIMO) are transmitting and receive diversity techniques. They provide path diversity in poor radio conditions since fading loss can be much higher for the other signal path. The receiver can thus select the signal with a better CINR. Data rates are however not increased in diversity techniques since the same data is transmitted in both signal paths. Multiple Input Multiple Output (MIMO) differs from transmit diversity techniques in such a way that different data streams are sent in different signal paths. Theoretically in case of orthogonal data streams, the downlink user data rate can be doubled in case of 2x2 Single-User MIMO. The data streams are separated by using a channel matrix that aims to provide orthogonal signals at the receiver. Stream pairing feedback can be used in case of Closed Loop MIMO operation. This operation is similar to channel quality feedback CQI reporting but a different metric, namely Precoding Matrix Indicator (PMI) is used for transmitter precoding matrix optimization. Precoding is done to minimize the coupling of the spatial streams.Release 8 defines also Multi-User MIMO, which can be used in uplink direction so that the same time-frequency resources are utilized by two UEs. The data rate for the UEs is not increased but more capacity is added on a cell level. MIMO works in general well only in good radio conditions and therefore link adaptation is used to switch the transmission mode to transmit diversity in poor radio conditions, i.e. at the cell edge. Handovers within intra-frequency LTE cells always occur in transmit diversity mode since the cells are interfering with each other and thus the radio conditions are expected to be poor at the cell edge. [20]2.3.3.3 Single input single output (SISO)The most basic radio channel access mode is single input single output (SISO), shown on figure 2.7 which only one transmit antenna and one receive antenna are used defends in [1]. This is the form of communications that has been the default since radio began and is the baseline against which all the multiple antenna techniques are compared.

Figure 2.7- Single channel transmissions.2.3.3.4 Single Input Multiple Output (SIMO)A second mode which uses one transmitter and two or more receivers SIMO is often referred to as receive diversity. This radio channel access mode is particularly well suited for low signal-to-noise (SNR) conditions in which a theoretical gain of 3 dB is possible when two receivers are used. There is no change in the data rate since only one data stream is transmitted, but coverage at the cell edge is improved due to the lowering of the usable SNR.2.3.3.5 Multiple input single output (MISO)Multiple input single outputs (MISO) mode uses two or more transmitters and one receive MISO is more commonly referred to as transmit diversity. The same data is sent on both transmitting antennas but coded such that the receiver can identify each transmitter. Transmit diversity increases the robustness of the signal to fading and can increase performance in low SNR conditions. MISO does not increase the data rates, but it supports the same data rates using less power. Transmit diversity can be enhanced with closed loop feedback from the receiver to indicate to the transmitter the optimum balance of phase and power used for each transmit antenna.2.3.3.6 Multiple input multiple output (MIMO)The final mode shown in Figure 2.8 is full MIMO, which requires two or more transmitters and two or more receivers. MIMO increases spectral capacity by transmitting multiple data streams simultaneously in the same frequency and time, taking full advantage of the different paths in the radio channel. For a system to be described as MIMO, it must have at least as many receivers as there are transmit streams. The number of transmit streams should not be confused with the number of transmit antennas. Consider the diversity (MISO) case in which two transmitters are present but only one data stream. Adding receive diversity (SIMO) does not turn this configuration into MIMO, even though there are now two and two antennas involved. In other words, SIMO + MISO MIMO. It is always possible to have more transmitters than data streams but not the other way around. If N data streams are transmitted from fewer than N antennas, the data cannot be fully descrambled by any number of receivers since overlapping streams without the addition of spatial diversity just creates interference. However, by spatially separating N streams across at least N antennas, N receivers will be able to fully reconstruct the original data streams provided the path correlation and noise in the radio channel are low enough.Another crucial factor for MIMO operation is that the transmissions from each antenna must be uniquely identifiable so that each receiver can determine what combination of transmissions has been received. This identification is usually done with pilot signals, which use orthogonal patterns for each antenna.The spatial diversity of the radio channel means that MIMO has the potential to increase the data rate. The most basic form of MIMO assigns one data stream to each antenna and is shown in Figure 2.8.

Figure 2.8- 2x2 MIMO, no precedingIn this form, one data stream is uniquely assigned to one antennaknown as direct mapping. The channel then mixes up the two transmissions such that at the receivers, each antenna sees a combination of each stream. Decoding the received signals is a clever process in which the receivers, by analyzing the patterns that uniquely identify each transmitter, determine what combination of each transmit stream is present. The application of an inverse filter and summing of the received streams recreates the original data.A more advanced form of MIMO includes special preceding to match the transmissions to the Eigen modes of the channel. This optimization results in each stream being spread across more than one transmit antenna defends in [1]. For this technique to work effectively the transmitter must have knowledge of the channel conditions and, in the case of FDD, these conditions must be provided in real time by feedback from the UE. Such optimization significantly complicates the system but can also provide higher performance. Precoding for TDD systems does not require receiver feedback because the transmitter independently determines the channel conditions by analyzing the received signals that are on the same frequency.The theoretical gains from MIMO are a function of the number of transmit and receive antennas, the radio propagation conditions, the ability of the transmitter to adapt to the changing conditions, and the SNR. The ideal case is one in which the paths in the radio channel are completely uncorrelated, almost as if separate, physically cabled connections with no crosstalk existed between the transmitters and receivers. Such conditions are almost impossible to achieve in free space, and with the potential for so many variables, it is neither helpful nor possible to quote MIMO gains without stating the conditions. The upper limit of MIMO gain in ideal conditions is more easily defined, and for a 2x2 system with two simultaneous data streams a doubling of capacity and data rate is possible.MIMO works best in high SNR conditions with minimal line of sight. Line of sight equates to high channel correlation and seriously diminishes the potential for gains. As a result, MIMO is particularly suited to indoor environments, which can exhibit a high degree of multi-path and limited line of sight.

2.5 LTE GoalsLTE benefitsThe internet generation is used to having broadband access whenever and wherevernot just at home or in the office. People already browse the internet or send e-mail using HSPA-enabled notebooks that replace their fixed DSL modems with HSPA modems or USB dongles. Likewise, they send and receive videos and music using 3G phones. With LTE, the user experience will be even betterit will enhance capacity-demanding applications such as interactive TV, mobile video blogging, advanced games and professional services.PerformanceLTE is specified by 3GPP to provide downlink peak rates above 100Mbps. The current standardization of LTE allows for speeds more than 300Mbps and we have already demonstrated corresponding peak rates. Radio access network (RAN) roundtrip times will be less than 10ms, meaning LTE, more than any other technology, already meets key 4G requirements.CapacityLTE supports flexible carrier bandwidths from 1.4MHz up to 20MHz. It is being deployed in new spectrum and will offer optimal capacity when the full 20MHz bandwidth is utilized. LTE also supports frequency-division duplex (FDD) and time-division duplex (TDD). Several paired and unpaired spectrum bands have been identified by 3GPP. Operators can thus introduce LTE in new bands where it is easiest to deploy 10MHz or 20MHz carriers and eventually deploy LTE in all bands.SimplicityLTE radio network products will have several features to help simplify and reduce the cost of building and managing next-generation networks. These features, which go under the name of self-organizing networks (SON), include self-configuration and self-optimization. LTE will be deployed in parallel with simplified, IP-based core and transport networks that are easier to build and maintain.LTE base stationsRAN performance and, in particular, base station performance have a large impact on capital and operating expenditures (CAPEX/OPEX) when deploying and operating a radio network. Our new RBS 6000 series features extremely powerful base station architecture. It includes the Digital Unit for LTE (DUL), with a multi-core architecture as well as the Multi-Standard Radio (MSR) that supports LTE as well as GSM and WCDMA in the same radio unit. RBS 6000 thus provides a future-proof investment that is equally valid when the modules are used in RBS 2000 and RBS 3000.2.5.1 LTE Features Long Term Evolution offers the following features: Up to 100 Mbps (Downlink) Up to 50 Mbps (Uplink) Simplified Architecture Advanced MIMO Spatial Antenna Technology Open Interfaces Flexible Frequency (FDD/TDD) All IP Backbone.2.5.2 LTE Services Long Term Evolution (LTE) will offer the following services: Mobile VoIP Data (High-Speed) Text (SMS)/Multi-Media (MMS) Video-on-Demand Social Networking Mobile Conferencing M-Commerce (Banking/Advertisement).2.5.3 Technologies Associated with LTE The development of Long Term Evolution is associated with the following technologies: WiMax-technology used for Wireless Metropolitan Networks (WMANs) OFDM (Orthogonal Frequency Division Multiplexing)- OFDM technology has been incorporated into LTE because it enables high-data bandwidths to be transmitted efficiently while still providing a high degree of resilience to reflections and interference. The access schemes differ between the uplink and downlink: OFDMA (Orthogonal Frequency Division Multiple Access) is used in the downlink. SC-FDMA (Single Carrier-Frequency Division Multiple Access)- SC-FDMA(Single Carrier - Frequency Division Multiple Access) is used in the uplink. SC-FDMA is used in view of the fact that its peak to average power ratio is small and the more constant power enables high RF power amplifier efficiency in the mobile handsets - an important factor for battery power equipment. MIMO (Multi-Input Multi-Output) one of the main problems with previous telecommunications systems concerned distortion from reflected waves. By using MIMO, these additional signal paths can be used to advantage and are able to be used to increase the throughput. SAE (System Architecture Evolution)- With the very high data rate and low latency requirements for 3G LTE, it is necessary to evolve the system architecture to enable the improved performance to be achieved. One change is that a number of the functions previously handled by the core network have been transferred out to the periphery. Essentially this provides a much "flatter" form of network architecture. In this way latency times can be reduced and data can be routed more directly to its destination.2.5.4 Interoperability LTE hardware from multiple vendors is currently being tested for compatibility with older technologies such as GSM and 3G networks. The availability of commercial LTE terminals from multiple vendors and proven interoperability with networks providers is a prerequisite for any operator to launch commercial LTE services. Interoperability between infrastructure and terminals are keys with every technology, and it is particularly fundamental in such a new technology like LTE. LTE is designed to work with legacy technologies such as: GSM, 3G Networks, WCDMA, CDMA-2000 and WiMax.

2.6 LTE Technical, Multiple Access Techniques3GPP LTE have selected different transmission schemes in uplink and downlink due to certain characteristics. OFDMA has been selected for downlink i.e. from eNodeB to UE and SC-FDMA has been selected for uplink i.e. for transmission from UE to eNodeB. 2.6.1 Downlink OFDMA Orthogonal Frequency Division Multiplexing (OFDM) is already employed by cellular and non-cellular wireless transmissions such as mobile WiMAX and WLAN and is selected as multiplexing scheme for 3GPP LTE. OFDM is a spectral efficient transmission scheme in such a way that it divides a high-bit-rate data stream into several parallel narrowband low-bit-rate data streams often called sub-carriers or tones. This division is made in such a way that sub-carriers are orthogonal to each other which eliminates the need of non-overlapping sub-carriers to avoid inter carrier interference.The first carrier is selected so that its frequency contains integer number of cycles in a symbol period. In order to make sub-carriers orthogonal to each other, adjacent sub-carriers are spaced by: BSC = B / LWhere B: nominal bandwidth of high-bit-rate data stream L: number of sub-carriersTransmission on orthogonal sub-carriers is fine but only for the ideal situation such as there is no multi-path delay spread, but usually this situation doesnt exist in real world. To make transmission completely ISI free we also need to place a time guard in between the sub-carriers and their spacing. Making this time guard enough, larger than the maximum expected delay spread, makes transmission completely ISI free. This time guard also cause the power and bandwidth wastage and of course decrease the spectrum efficiency but this is dependent on what the time guard fraction of symbol duration is. 2.6.2 Peak to Average Power Ratio (PAPR)PAPR is defined as the peak power within one OFDM symbol normalized by the average signal power. When several OFDM sub-carriers align themselves in phase there occur a large PAPR which is the most difficult concern in RF engineering of traditional OFDM. The value of PAPR is directly proportional to the number of sub-carriers, given by log (10) (N dB PAPR ) where N is the number of sub-carriers Signals with a large PAPR need highly linear power amplifiers to avoid excessive inter modulation distortion and to achieve this linearity, amplifiers have to operate with a large back off from their peak power which results in low power efficiency (measured by the ratio of transmitted power to the DC power dissipated).2.6.3 Frequency Offset Although OFDM is resistant against multi-path fading it requires high degree of synchronization to maintain its sub-carrier orthogonality. In OFDM, the uncertainty in carrier frequency, which is due to the difference in the frequencies of local oscillators in the transmitter and receiver, give rise to a shift in frequency domain which is also called frequency offset. This frequency offset can also because by the Doppler shift effect. The demodulation of a signal with frequency offset can cause large bit error rate and might degrade the symbol synchronization performance.2.6.4 Uplink SC-FDMA SC-FDMA (Single Carrier Frequency Division Multiple Access) has been selected as 3GPP LTE uplink transmission technique (MS to eNodeB). It is a modified form of OFDMA and has similar throughput performance and essentially shown on figure 2.9 the same overall complexity as OFDMA. Like OFDM, SC-FDMA also consists on subcarriers but it transmits on subcarriers in sequence not in parallel which is the case in OFDM , which prevents power fluctuations in SC-FDMA signals i.e. low PAPR. In a cellular system with severe multipath propagation environment, SC-FDMA signals might cause inter symbol interference when they reach at the base station. The base station uses the adaptive frequency domain equalization to cancel the inter symbol interference, As most mobile terminals are empowered with a battery, it is a good idea to perform some complex operations like frequency domain equalization at base station rather putting any burden like linear power amplification, on mobile terminal because more resources are available on base station. 2.6.5 SC-FDMA TransmitterAt the input of transmitter, the binary input is modulated using QPSK, 16QAM or optionally using 64QAM. Then this modulated input is divided into blocks of N-symbols using N-point DFT (Discrete Fourier Transform) to convert to frequency domain representation Xk. Then each of these N-Point DFT output is modulated on one of orthogonal subcarriers that can be transmitted which results in a set Xl of complex subcarrier amplitudes. Then M-Point inverse DFT is applied to convert Xl to a time domain signal Xm. Then each Xm symbol is modulated on a single carrier and transmitted sequentially after the adding CP (circular prefix) to prevent IBI (inter block interference), and pulse shaping to reduce out-of-band energy. 2.6.6 SC-FDMA ReceiverThe receiver shapes the received signal, removes CP, and then the signal are converted to frequency domain using M-Point DFT. Then frequency domain equalization is performed and then these equalized symbols are transformed to time domain using N-Point IDFT and then detection and decoding take place.

Figure 2.9- SC-FDMA & OFDMA2.6.7 Frequency Bands for FDD and TDD LTE operates with both Frequency Division Duplex (FDD) and Time Division Duplex (TDD). Both methods allow multiple users to share bandwidth. LTE can be used in both paired (FDD) and unpaired (TDD) spectrum .Leading suppliers first product releases will support both duplex schemes. In general, FDD is more efficient and represents higher device and infrastructure volumes, but TDD is a good complement, for example, in spectrum center gaps. Because LTE hardware is the same for FDD and TDD, except for the radio unit, TDD operators will for the first time be able to enjoy the economies of scale that come with broadly supported FDD products. Fifteen different FDD frequency bands and eight different TDD frequency bands have been defined in the 3GPP for LTE use, as shown in Table 2.2.

Table 2.2- FDD & TDD Spectrum Bands

2.7 WiMax WiMAX is a short name for Worldwide Interoperability of Microwave Access. WiMAX is described in IEEE 802.16 Wireless Metropolitan Area Network (WMAN) standard. It is expected that WiMAX compliant systems will provide fixed wireless alternative to conventional DSL and Cable Internet. WiMAX is an emerging technology that provides high-speed mobile data and telecommunication services. It is a Last Mile Broadband Internet Access technology. It is intended to replace cable and DSL in some areas shown on figure 2.10. Typically, a WiMAX system consists of two parts: A WiMAX Base Station: Base station consists of indoor electronics and a WiMAX tower. Typically, a base station can cover up to 10 km radius (Theoretically, a base station can cover up to 50 kilo meter radius or 30 miles, however practical considerations limit it to about 10 km or 6 miles). Any wireless node within the coverage area would be able to access the Internet. A WiMAX receiver- The receiver and antenna could be a stand-alone box or a PCMCIA card that sits in a laptop or computer. Access to WiMAX base station is similar to accessing a Wireless Access Point in a WiFi network, but the coverage is more.

Figure 2.10- WiMax Network2.7.1 WiMax and Broadband Wireless Access The desire for bandwidth-intensive Internet access and other voice/data services has never been greater across all geographies and market segments. The DSL market, based on a variety of wire line infrastructures, has succeeded in reaching millions of business and private subscribers, and continues on a rapid growth curve. However, to supply the quick rollout of infrastructure to the last mile has become a difficult and expensive challenge for carriers who cannot keep pace with the demand. This has brought about a situation where subscribers who live in developed areas with broadband-ready infrastructure can enjoy all the benefits of DSL services, while those who do not, require another technology solution to fill the void. The need for Broadband wireless technology and specifically the introduction of the new WiMAX standard fits this agenda perfectly. Typical point-to-multipoint Broadband Wireless Access (BWA) systems are composed of two key elements: a base station and subscriber equipment. The base station connects to the network backbone and uses an outdoor antenna to send and receive high-speed data and voice to subscriber equipment, eliminating the need for extensive and expensive wire line infrastructure and providing highly flexible and cost-effective last-mile solutions.

Figure 2.11- Broadband Wireless Accesses2.7.2 WiMax Specifications The following are major points of WiMax (Wireless MAN IEEE 802.16) functionality: Range - 30-mile (50-km) radius from base station Speed - Up to 70 megabits per second Non-Line-of-sight (NLoS) between the user and a base station (BSS) Frequency bands - 2 to 11 GHz and 10 to 66 GHz (licensed and unlicensed bands) Defines both the MAC and PHY layers and allows multiple PHY-layer specifications. There is no need for line of sight (LOS) connections between subscriber terminals and the base station in WiMAX technology and it can support hundreds if not thousands of subscribers from a single base station shown on figure 2.12. It is also specified in 802.16 standards that it will supports low latency applications such as voice, video, and Internet access at the same time.

Figure 2.12 WiMax Metropolitan Wireless Networks2.8 Compare between LTE & WiMaxWiMAX and Long-Term Evolution (LTE) are two different (but not necessarily competing) technologies that will eventually be used to achieve data speeds of up to 100 Mbps. Speeds that are fast enough to potentially replace wired broadband connections with wireless, and enable services such as HDTV on mobiles and TVs without the need for a fixed-line or dish in the home, as well as a host of other exciting services currently seen as too bandwidth-hungry to be delivered using existing mobile technologies. WiMAX and LTE are both in different stages of development. WiMAX is widely recognized as being the first that will be brought to market. The world's first large scale mobile WiMAX deployment is due in the United States in 2009. However, although LTE may on paper be some years off it will bring with it many advantages, not least the fact that operators will be able to evolve their existing infrastructure and base station real estate to deliver it. The upper layers of LTE are based upon TCP/IP, which will likely result in an all-IP network similar to the current state of wired communications. LTE will support mixed data, voice, video and messaging traffic. LTE uses OFDM (Orthogonal Frequency Division Multiplexing) and, in later releases, MIMO (Multiple Input Multiple Output) antenna technology similar to that used in the IEEE 802.11n wireless local area network (WLAN) standard. The higher Signal to Noise Ratio (SNR) at the receiver enabled by MIMO, along with OFDM, provides improved coverage and throughput, especially in dense urban areas.

2.9 LTE as an Alternative Technology to WiMax An alternative high-speed mobile technology that could be used instead of, or to run alongside, WiMAX is LTE. The crucial difference is that, unlike WiMAX, which requires a new network to be built, LTE runs on an evolution of the existing UMTS infrastructure already used by over 80 per cent of mobile subscribers globally. This means that even though development and deployment of the LTE standard may lag Mobile WiMAX, it has a crucial incumbent advantage. There is also no doubt that the advent of WiMAX has injected a new sense of urgency to the LTE standardization effort. This may help provide operators keen to control investment with the confidence to wait for LTE technology to reach maturity before upgrading their existing infrastructure, rather than invest in a brand new WiMAX network. Even prior to the arrival of LTE, speeds of up to 7.2 Mbps are currently being reached by existing HSPA technology, which is being used by more than five million subscribers worldwide.Similarities between WiMax and LTE:-LTE (Long Term Evolution) and WiMax have the following similarities: Both use Multiple Input Multiple Output (MIMO) antenna technology. Both use OFDM. Both expect speeds to be in the 100 Mbps range. For example, both technologies provide the same approach for downlinks, and both have Multiple Input Multiple Output (MIMO), which means that information, is sent over two or more antennas from a single cell site to improve reception. In tough transmission locations, such as a dense downtown area, MIMO could be a relatively inexpensive means of improving reception to users. The downlinks from the Base Station to the end user in both LTE and WiMax are enhanced with OFDM (Orthogonal Frequency Division Multiplexing), a technology that supports sustained video and multimedia transmissions and is already being deployed in some non-LTE and -WiMax networks. It works by splitting up signals among multiple narrow frequencies, with bits of data sent at once in parallel. Needless to say, it is complex technology that will require sophisticated base stations, an added expense even for those carriers that see LTE as an upgrade path to GSM. Many industry analysts feel that LTE is not a direct replacement for GSM technology since newer equipment will be required to deploy LTE networks. That means a substantial investment is in store for carriers wanting to deploy LTE. The cost of a national WiMax network will be billions of dollars. Uplinks from the user to the cell tower will probably be different in the two technologies. OFDM will be used in WiMax, but a technology called SC-FDMA (Single Carrier-Frequency Division Multiple Access) will be used in LTE. SC-FDMA is theoretically designed to work more efficiently with lower-power end-user devices than OFDM.

Table 2.3- Compare Between LTE & WiMax

CONCLUSION

LTE uses OFDMA on the downlink, which is well suited to achieve high peak data rates in high spectrum bandwidth. WCDMA radio technology is basically as efficient as OFDM for delivering peak data rates of about 10 Mbps in 5 MHz of bandwidth. However, achieving peak rates in the 100 Mbps range with wider radio channels would result in highly complex terminals, and it is not practical with current technology. This is where OFDM provides a practical implementation advantage. Scheduling approaches in the frequency domain can also minimize interference, thereby boosting spectral efficiency. The OFDMA approach is also highly flexible in channelization, and LTE will operate in various radio channel sizes ranging from 1.4 to 20 MHz. On the uplink, however, a pure OFDMA approach results in high Peak to Average Ratio (PAR) of the signal, which compromises power efficiency and, ultimately, battery life. Hence, LTE uses an approach called SC-FDMA, which is somewhat similar to OFDMA but has a 2 to 6 dB PAR advantage over the OFDMA method used by other technologies such as IEEE 802.16e.LTE capabilities include:1. Downlink peak data rates up to 326 Mbps with 20 MHz bandwidth.2. Uplink peak data rates up to 86.4 Mbps with 20 MHz bandwidth.3. Operation in both TDD and FDD modes.4. Scalable bandwidth up to 20 MHz, covering 1.4, 2.5, 5, 10, 15, and 20 MHz in the study phase. Channels that are 1.6 MHz wide are under consideration for the unpaired frequency band, where a TDD approach will be used.5. Increased spectral efficiency over Release 6 HSPA by a factor of two to four.6. Reduced latency, to 10 msec. round-trip times between user equipment and the base station, and to less than 100 m.sec transition times from inactive to active.The overall intent is to provide an extremely high-performance radio-access technology that offers full vehicular speed mobility and that can readily coexist with HSPA and earlier networks.3 Orthogonal Frequency Division Multiplexing OFDM in LTE Technology

INTRODUCTION

Digital communications systems require each channel to operate at a specific frequency and with a specific bandwidth. In fact, communication systems have evolved so that the largest amount of data can be communicated through a finite frequency range. In this topic will make focus on the recent evolution of communications systems into using various mechanisms for effectively using the frequency spectrum. More specifically, will make describe how frequency division multiplexing (FDM) and orthogonal frequency division multiplexing (OFDM) are able to effectively utilize the frequency spectrum. In addition, distinguish the function and describe why OFDM systems are currently being implemented in some of the newest and most advanced communications systems.The design of the LTE physical layer (PHY) is heavily influenced by the requirements for high peak transmission rate (100 Mbps DL/50 Mbps UL), spectral efficiency, and multiple channel bandwidths (1.25-20 MHz). To fulfill the requirements, orthogonal frequency division multiplex (OFDM) was selected as the basis for the PHY layer. OFDM is a technology that dates back to the 1960s. It was considered for 3G systems in the mid-1990s before being determined too immature. Developments in electronics and signal processing since that time has made OFDM amateur technology widely used in other access systems like 802.11 (Wi-Fi) and 802.16 (WiMAX) and broadcast systems (Digital Audio/Video Broadcast DAB/DVB).

Figure 3.1- OFDM SUBCARRIER SPACING

3.1 OFDM System Model

Its well known that the channel transfer function, i.e., roughly speaking the frequency relationship between the received and the transmitted signal defends in [6], can have a multitude of shapes that in general lead to different attenuations for different frequencies. When it occurs, the channel is said to be frequency-selective. Thus at the receiver, this fact has to be taken into account and somehow compensated (equalized) to reconstruct the original signal, with the further problem of the noise corruption. The only way to do it is to estimate the channel response from the received signal. Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique based on the idea of splitting the channel into a define amount N of narrowband shown on figure 3.1 and independent sub-channels that are supposed to have a flat frequency response (shown on figure 3.2), of course different for each sub-channel.

Figure 3.2: Channel transfer function for each sub-channel.

Looking at the equalization problem from this point of view, such set of independent flat channels is easier to treat. By transmitting a narrowband signal, known from either the transmitter or the receiver, it would be possible to obtain the channel response at the signal frequency, simply observing the ratio between received and the known transmitted signal. Considering a wideband signal and channel contrariwise, the same treatment is not that immediate.The frequency selectivity derives from that environment identified as delay-dispersive or multipath, i.e., when more than a copy of the transmitted signal, each with a different delay and attenuation factor, reaches the receiver, due to the reflections. This fact highly limits high-data-rate transmission systems, and is the reason why OFDM is proper for such environments: due to the channel splitting, the signal is transmitted indeed over parallel low-data-rate sub-channels. The bandwidth of each sub channel, and hence their number, depends on some parameters: the most significant one is the delay spread that for the moment will be considered as assort of indicator of the channel time distortion. Intuitively, due to the signal echoes, the pulse shape will suffer a spreading in time, interfering with the adjacent transmitted pulses. In this regard, the symbol duration (N times larger, after the S/P conversion) of the narrowband channels, i.e., the inverse of their band width, must be larger than this spreading, in order to mitigate the Inter-Symbol Interference (ISI). Furthermore, it will be shown how this issues can be removed using the OFDM scheme, by an artifice named cyclic prefix.After introducing the working principle, the real implemented digital setup will be derived, in order to introduce a linear algebraic signal model. The last section then, provides the LTE downlink configuration, comprising the time domain frame structure, the pilot pattern and the OFDM parameters specification.

3.2 Orthogonal Frequency-Division Multiplexing System

To understand how the system works its useful to consider the scheme proposed shown on figure 3.3: information bits, mapped onto symbols defends in [6], according to a certain digital modulation (e.g., DPSK