ITU Centres of Excellence for Europe

Mobile Broadband: LTE/LTE-Advanced, WiMAX and WLAN

Module 1: 3GPP mobile broadband: LTE/LTE-Advanced

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Table of contents 1.1. 3GPP evolution towards mobile broadband Internet......................................2

1.2. IMT-Advanced: the ITU standard for 4G ........................................................9

1.3. LTE/LTE-Advanced standardization (3GPP Rel-8 to 3GPP Release 12) ...15

1.4. Evolved Packet System (EPS), E-UTRAN...................................................25

1.5. Self Organizing Networks (SON) for LTE/LTE-Advanced ............................32

1.6. LTE/LTE-Advanced Radio Resource Management .....................................37

1.7. Radio network deployment and frequency planning ....................................44

1.8. Spectrum management (ITU WRC 2012) ....................................................48

1.9. Business models and forecasts for LTE/LTE-Advanced ..............................53

References .........................................................................................................57

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1.1. 3GPP evolution towards mobile broadband Internet

“We firmly believe that mobile

broadband data is becoming the largest opportunity … (for) mobile operators.

Mobile data services are contributing an increasing portion of carrier revenue …

as (they) move from low-bandwidth-intensive messaging applications to bandwidth-hogging

multimedia applications.” Wedbush Securities quoted on Barron’s website,

March 22, 2010 Global demand for mobile data services is exactly exploding. Nearly

everyone who uses a mobile phone or device anywhere in the world is demanding faster access to more multimedia data. More specifically, they’re demanding that all the applications they love on their tethered computers be available on their mobile devices. From an operator’s perspective, that demands bandwidth. Moreover, the network capacity overload and the potential crisis for mobile communications are guided by two primary factors: limited spectrum and growing data demands. Numerous forecasts indicate exponential data traffic growth as mobile data usage has more than doubled each of the last five years.

Major developments this past year include not only 3rd Generation (3G) ubiquity, but rapid deployment of 4th Generation (4G) networks; deepening smartphone capability; mobile broadband access; the availability of hundreds of thousands of mobile multimedia applications across multiple device ecosystems; the maturing of new form factors such as tablets; and a better understanding of what the industry needs to do to address data demands, which are growing exponentially. Over this past year, the need for additional spectrum has become particularly urgent, resulting in a number of new initiatives by industry and government.

This is, consequently, driving the need for continued innovations in wireless and mobile data technologies towards mobile broadband internet, in order to provide more capacity and higher Quality of Service (QoS). When it comes a word for the 3GPP technologies, they evolved from GSM-EDGE, to UMTS-HSPA-HSPA+, to now initial LTE/LTE-Advanced deployments, to provide increased broadband capacity and user experience. Furthermore, is overviewed the 3GPP evolutionary approach towards mobile broadband in more details.

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Generally, 3GPP standards development falls into three principal areas: radio interfaces, core networks, and services.

With respect to radio interfaces, rather than emphasizing any one wireless and mobile approach, 3GPP’s evolutionary plan is to recognize the strengths and weaknesses of every technology and to exploit the unique capabilities of each one accordingly. GSM, based on a Time Division Multiple Access (TDMA) approach, is mature and broadly deployed. Already extremely efficient, there are nevertheless opportunities for additional optimizations and enhancements. Standards bodies have already defined “Evolved EDGE,” which became available for deployment in 2011. Evolved EDGE more than doubles throughput over current EDGE systems, halves latency, and increases spectral efficiency, and for sure has open the road towards mobile broadband Internet.

Meanwhile, CDMA was chosen as the basis of 3G technologies including WCDMA for the frequency division duplex (FDD) mode of UMTS and Time Division CDMA (TD-CDMA) for the time division duplex (TDD) mode of UMTS. The evolved data systems for UMTS, such as HSPA and HSPA+, introduce enhancements and optimizations that help CDMA-based systems largely match the capabilities of competing systems, especially in 5 MHz spectrum allocations.

HSPA innovations such as dual-carrier HSPA, explained in detail in the appendix section “Evolution of HSPA (HSPA+),” coordinate the operation of HSPA on two 5 MHz carriers for higher throughput rates. In combination with MIMO, dual-carrier HSPA will achieve peak network speeds of 84 Mbps and quad-carrier HSPA will achieve peak rates of 168 Mbps. Release 11 capabilities such as 8-carrier downlink operation will double maximum theoretical throughput rates to 336 Mbps, which will ensure the transfer of mobile broadband Internet services with high level of QoS support.

Given some of the advantages of an Orthogonal Frequency Division Multiplexing (OFDM) approach, 3GPP specified OFDMA as the basis of its LTE effort. LTE incorporates best-of-breed radio techniques to achieve performance levels beyond what may be practical with some CDMA approaches, particularly in larger channel bandwidths. In the same way that 3G coexists with 2G systems in integrated networks, LTE systems will coexist with both 3G systems and 2G systems. Multimode devices will function across LTE/3G and LTE/3G/2G. Beyond radio technology, EPC provides a new core architecture that enables both flatter architectures and integration of LTE with both legacy GSM-HSPA networks, as well as other wireless technologies. The combination of EPC and LTE is referred to as the Evolved Packet System (EPS), which will be discussed latter in section 1.4.

HSPA+ and LTE are important to operators since these technologies provide the efficiency and capability being demanded by the quickly growing mobile broadband internet market. The cost for operators to deliver data (e.g., cost per GBit) is almost directly proportional to the spectral efficiency of the technologies. LTE has the highest spectral efficiency of any specified technology to date, making it one of the essential technologies as the market matures.

As market demands increase, HSPA+ is attractive to some operators since it maximizes the efficiencies in existing deployments and provides high

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performance with the use of new advanced techniques both in spectrum that is already being utilized and also in new spectrum. Specifically:

� Large Spectrum Utilization. HSPA+ can now be deployed in wider bandwidths such as 10Mhz and 20Mhz. This functionality both increases peak data rates and also improves spectral efficiency.

� Advanced MIMO. The introduction of MIMO enhancements and the addition of more transmit and receive antennas provides improved spectral efficiency in existing spectrum.

� Good Coverage Performance. Soft handover and other techniques provide improved coverage, especially at the edge of the cell.

As competitive pressures in the mobile broadband market intensify and as demand for more capacity continues unabated, LTE is developing deployment momentum for the reason that it offers an extremely efficient and effective way of delivering high performance, especially in new spectrum. Specifically:

� Wider Radio Channels. LTE can be deployed in wide radio channels (e.g., 10 MHz or 20 MHz). This increases peak data rates and also provides for more efficient spectrum utilization.

� Easiest MIMO Deployment. By using new radios and antennas, LTE facilitates MIMO deployment compared to the logistical challenges of adding antennas for MIMO to existing deployments of legacy technologies. Furthermore, MIMO gains are maximized because all user equipment supports it from the beginning.

� Best Latency Performance. For some mobile broadband applications, low latency (packet traversal delay) is as important as high throughput. With a low transmission-time interval (TTI) of 1 msec and flat architecture (fewer nodes in the core network), LTE has the lowest latency of any cellular technology.

LTE is available in both FDD and TDD modes. Many deployments will be based on FDD in paired spectrum. The TDD mode, however, will be important in enabling deployments where paired spectrum is unavailable. LTE TDD will be deployed in China, will be available for Europe at 2.6 GHz, and will operate in the U.S. Broadband Radio Service (BRS) 2.6 GHz band.

To address ITU’s IMT-Advanced requirements, 3GPP is developing LTE-Advanced, a technology that will have peak theoretical rates of more than 1 Gbps. See the following two sections for a detailed explanation.

However, LTE is one of the most promising wireless-technology platforms for the future. The version being deployed today is just the beginning of a series of innovations that will increase performance, efficiency, and capabilities, as depicted in Figure 1.1. The enhancements shown in the 2013 to 2016 period are the ones expected from 3GPP Releases 10 and 11 and are commonly referred to as LTE-Advanced. Subsequent releases such as Release 12 and 13, however, will continue this innovation through the end of this decade.

Although later sections (in this module) quantify performance and presents functional details of the LTE/LTE-Advanced technologies, here we will give a summary intended to provide a frame of reference for the subsequent discussion

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for 3GPP oriented mobile broadband Internet technologies. Table 1.1 summarizes the key 3GPP technologies and their characteristics.

Figure 1.1. LTE as a Wireless Technology Platform for the Future.

Table 1.1: Characteristics of 3GPP Technologies.

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Furthermore, Figure 1.2 shows the evolution of the different wireless and

mobile technologies and their peak network performance capabilities towards mobile broadband Internet. The development of GSM and UMTS-HSPA happens in stages referred to as 3GPP releases, and equipment vendors produce hardware that supports particular versions of each specification. It is important to realize that the 3GPP releases address multiple technologies. For example, Release 7 optimized VoIP (Voice over Internet Protocol) for HSPA, but also significantly enhanced GSM data functionality with Evolved EDGE. A summary of the different 3GPP releases is as follows:

� Release 99: Completed. First deployable version of UMTS. Enhancements to GSM data (EDGE). Majority of deployments today are based on Release 99. Provides support for GSM/EDGE/GPRS/WCDMA radio-access networks.

� Release 4: Completed. Multimedia messaging support. First steps toward using IP transport in the core network.

� Release 5: Completed. HSDPA. First phase of Internet Protocol Multimedia Subsystem (IMS). Full ability to use IP-based transport instead of just Asynchronous Transfer Mode (ATM) in the core network.

� Release 6: Completed. HSUPA. Enhanced multimedia support through Multimedia Broadcast/Multicast Services (MBMS). Performance

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specifications for advanced receivers. Wireless Local Area Network (WLAN) integration option. IMS enhancements. Initial VoIP capability.

� Release 7: Completed. Provides enhanced GSM data functionality with Evolved EDGE. Specifies HSPA+, which includes higher order modulation and MIMO. Performance enhancements, improved spectral efficiency, increased capacity, and better resistance to interference. Continuous Packet Connectivity (CPC) enables efficient “always-on” service and enhanced uplink UL VoIP capacity, as well as reductions in call set-up delay for Push-to-Talk Over Cellular (PoC). Radio enhancements to HSPA include 64 Quadrature Amplitude Modulation (QAM) in the downlink and 16 QAM in the uplink. Also includes optimization of MBMS capabilities through the multicast/broadcast, single-frequency network (MBSFN) function.

Figure 1.2: Evolution of TDMA, CDMA, and OFDMA Systems.

� Release 8: Completed. Comprises further HSPA Evolution features such

as simultaneous use of MIMO and 64 QAM. Includes dual-carrier HSDPA (DC-HSDPA) wherein two downlink carriers can be combined for a

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doubling of throughput performance. Specifies OFDMA-based 3GPP LTE. Defines EPC and EPS.

� Release 9: Completed. HSPA and LTE enhancements including HSPA dual-carrier downlink operation in combination with MIMO, HSDPA dual-band operation, HSPA dual-carrier uplink operation, EPC enhancements, femtocell support, support for regulatory features such as emergency user-equipment positioning and Commercial Mobile Alert System (CMAS), and evolution of IMS architecture.

� Release 10: Completed. Specifies LTE-Advanced that meets the requirements set by ITU’s IMT-Advanced project. Key features include carrier aggregation, multi-antenna enhancements such as enhanced downlink MIMO and uplink MIMO, relays, enhanced LTE Self Optimizing Network (SON) capability, eMBMS, Het-net enhancements that include enhanced Inter-Cell Interference Coordination (eICIC), Local IP Packet Access, and new frequency bands. For HSPA, includes quad-carrier operation and additional MIMO options. Also includes femtocell enhancements, optimizations for M2M communications, and local IP traffic offload.

� Release 11: In development, targeted for completion end of 2012. For LTE, emphasis is on Co-ordinated Multi-Point (CoMP), carrier-aggregation enhancements, and further enhanced eICIC including devices with interference cancellation. The release includes further DL and UL MIMO enhancements for LTE. For HSPA, provides 8-carrier on the downlink, uplink enhancements to improve latency, dual-antenna beamforming and MIMO, DLCELL_Forward Access Channel (FACH) state enhancement for smart phone-type traffic, four-branch MIMO enhancements and transmissions for HSDPA, 64 QAM in the uplink, downlink multi-point transmission, and non-contiguous HSDPA carrier aggregation.

� Release 12: In initial planning and discussion stages. Potential enhancements include enhanced small cells/Het-nets for LTE; LTE multi-antenna/site technologies such as 3D MIMO/beamforming and further CoMP/MIMO enhancements; new procedures and functionalities for LTE to support diverse traffic types; enhancements for interworking with Wi-Fi; enhancements for Machine Type Communications (MTC), SON, Minimization of Test Drives (MDT), and advanced receivers; device-to-device communication; energy efficiency; more flexible carrier aggregation; and further enhancements for HSPA+ including further DL and UL improvements and interworking with LTE.

Whereas operators and vendors actively involved in the development of wireless technology are heavily focused on 3GPP release versions, most users of the technology are more interested in particular features and capabilities such as whether a device supports HSDPA. For this reason, the detailed discussion of the 3GPP evolution will continue in the section 1.3, where the 3GPP Release 8 up to 3GPP Release 12 are presented in more details.

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1.2. IMT-Advanced: the ITU standard for 4G

The International Mobile Telecommunications-Advanced (IMT-Advanced) systems are mobile systems that include the new capabilities of IMT that go beyond those of well known IMT-2000. Such systems provide access to a wide range of telecommunication services including advanced mobile services, supported by mobile and fixed networks, which are increasingly packet-based and moves the broadband Internet to be truly mobile.

IMT-Advanced systems support low to high mobility applications and a wide range of data rates in accordance with user and service demands in multiple user environments. IMT Advanced also has capabilities for high-quality multimedia applications within a wide range of services and platforms, providing a significant improvement in performance and Quality of Service (QoS). Moreover, the consumer demands will shape the future development of IMT-2000 and IMT Advanced. Recommendation ITU-R M.1645 describes these trends in detail, some of which include the growing demand for mobile services, increasing user expectations, and the evolving nature of the services and applications that may become available. Also, Report ITU-R M.2072 details the market analysis and forecast of the evolution of the mobile market and services for the future development of IMT-2000, IMT-Advanced and other systems. This Report provides forecasts for the year 2010, 2015, and 2020 timeframes.

If we go back to IMT-2000 systems, they are providing access to a wide range of telecommunication services, supported by the fixed telecommunication networks (e.g. PSTN/ISDN/IP), and to other services which are specific to mobile users. To meet the ever increasing demand for wireless communication (e.g. increased no. of users, higher data rates, video or gaming services which require increased quality of service, etc.), IMT-2000 has been, and continues to be, enhanced.

The Figure 1.3 is taken directly from Recommendation ITU-R M.1645 and reflects the terminology in use at the time of its adoption. Resolution ITU-R 56 defines the relationship between “IMT-2000”, the future development of IMT-2000 and “systems beyond IMT-2000” for which it also provides a new name: IMT-Advanced. Resolution ITU-R 56 resolves that the term IMT 2000 encompasses also its enhancements and future developments. The term “IMT Advanced” should be applied to those systems, system components, and related aspects that include new radio interface(s) that support the new capabilities of systems beyond IMT-2000. The term “IMT” is the root name that encompasses both IMT-2000 and IMT-Advanced collectively. In October 2010, only two technologies are accepted within the IMT-Advanced umbrella: LTE-Advanced (LTE Release 10 & beyond) and Mobile WiMAX 2.0 (802.16m, also known as WirelessMAN-Advanced). Moreover, ITU IMT-Advanced defines the 4G mobile networks.

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denotes interconnection between systems via networks or the like, which allows

flexible use in any environments without making users aware of constituent systems.

Dark gray color indicates existing capabilities, medium gray color indicates enhancements to IMT-2000,

and the lighter gray color indicates new capabilities of Systems Beyond IMT-2000.

The degree of mobility as used in this figure is described as follows: Low mobility covers pedestrian speed, and high

mobility covers high speed on highways or fast trains (60 km/h to ~250 km/h, or more).

IMT-2000

Mobility

Low

High

1 10 100 1000

New CapabilitiesOf Systems Beyond

IMT-2000

Peak Useful Data Rate (Mb/s)

NewMobileAccess

New Nomadic / LocalArea Wireless Access

EnhancedIMT-2000

Enhancement

Systems Beyond IMT-2000 will

encompass the capabilities of

previous systems

Dashed line indicatesthat the exact data

rates associated with

Systems Beyond are

not yet determined.

KEY:

Digital Broadcast SystemsNomadic / Local Area Access Systems

Figure 1.3. Relationship between IMT-2000 (3G LTE) and IMT-Advanced (4G).

For the last 20 years, ITU has been coordinating efforts of government and industry and private sector in the development of a global broadband multimedia international mobile telecommunication system, known as IMT. Since 2000, the world has seen the introduction of the first family of standards derived from the IMT concept. ITU estimates that worldwide mobile cellular subscribers are likely to reach the 4 billion mark before the end of this year of which IMT systems technology will constitute a substantial part considering that already in 2007 (during the ITU World Radiocommunication Conference (WRC-07) in Geneva), there were more than 1 billion IMT-2000 subscribers in the world. It is realised that by the year 2010 there are 1 700 million terrestrial mobile subscribers worldwide. And moreover, it is envisaged that, by the year 2020, potentially the whole population of the world could have access to advanced mobile communications devices, subject to, amongst other considerations, favourable cost structures being achieved. There are already more portable handsets than either fixed line telephones or fixed line equipment such as PCs that can access the Internet, and the number of mobile devices is expected to continue to grow more rapidly than fixed line devices. Mobile terminals will be the most commonly used devices for accessing and exchanging information. User

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expectations are continually increasing with regard to the variety of services and applications. In particular, users will expect a dynamic, continuing stream of new applications, capabilities and services that are ubiquitous and available across a range of devices using a single subscription and a single identity (number or address). Versatile communication systems offering customized and ubiquitous services based on diverse individual needs will require flexibility in the technology in order to satisfy multiple demands simultaneously.

However, in planning process for the future development of IMT-Advanced, it is important to consider the timelines associated with their realization, which depend on a number of factors:

– user trends, requirements and user demand; – technical capabilities and technology developments; – standards development; – spectrum availability, including allowing sufficient time to re-locate

systems that may be using proposed bands; – regulatory considerations; – system (mobile and infrastructure) development and deployment. All of these factors are interrelated. The first five have been and will

continue to be addressed within ITU. System development and deployment relates to the practical aspects of deploying new networks, taking into account the need to minimize additional infrastructure investment and to allow time for customer adoption of the services of a major new mobile broadband system, such as IMT-Advanced.

The timeline associated with these different factors are depicted in Figure 1.4. When discussing the time phases for systems beyond IMT-2000 (IMT-Advanced), it is important to specify the time at which the standards are completed, when spectrum must be available, and when deployment may start. Exactly the progression towards IMT-Advanced is given in Figure 1.4.

The IMT-Advanced can be considered from multiple perspectives, including the users, manufacturers, application developers, network operators, and service and content providers as it is summarized in Table 1.2. Therefore, it is recognized that the technologies for IMT-Advanced can be applied in a variety of deployment scenarios and can support a range of environments, different service capabilities, and technology options. Consideration of every variation to encompass all situations is therefore not possible; nonetheless the work of the ITU-R has been to determine a representative view of IMT-Advanced consistent with the process defined in Resolution ITU-R 57 – Principles for the process of development of IMT-Advanced.

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Figure 1.4. Progression towards IMT-Advanced. Table 1.2. Objectives from multiple perspectives in IMT-Advanced.

Perspective Objectives

END USER

Ubiquitous mobile access

Easy access to applications and services

Appropriate quality at reasonable cost

Easily understandable user interface

Long equipment and battery life

Large choice of terminals

Enhanced service capabilities

User-friendly billing capabilities

CONTENT PROVIDER

Flexible billing capabilities

Ability to adapt content to user requirements depending on terminal, location and user preferences

Access to a very large marketplace through a high similarity of application programming interfaces

SERVICE PROVIDER

Fast, open service creation, validation and provisioning

Quality of service (QoS) and security management

Automatic service adaptation as a function of available data rate and type of terminal

Flexible billing capabilities

NETWORK OPERATOR

Optimization of resources (spectrum and equipment)

QoS and security management

Ability to provide differentiated services

Flexible network configuration

Reduced cost of terminals and network equipment based on global economies of scale

Smooth transition from IMT-2000 to systems beyond IMT-2000 (IMT-Advanced)

Maximization of sharing capabilities between IMT-2000 and 4G IMT-Advanced systems (sharing of mobile, UMTS subscriber identity module (USIM), network elements, radio

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sites)

Single authentication (independent of the access network)

Flexible billing capabilities

Access type selection optimizing service delivery

MANUFACTURER / APPLICATION DEVELOPER

Reduced cost of terminals and network equipment based on global economies of scale

Access to a global marketplace

Open physical and logical interfaces between modular and integrated subsystems

Programmable platforms that enable fast and low-cost development

The services that users will want in mobile broadband Internet, and the

rising number of users, will place increasing demands on radio access networks. These demands aren’t met by the enhancement of IMT-2000 radio access systems (in terms of peak bit rate to a user, aggregate throughput, and greater flexibility to support many different types of service simultaneously). It is therefore anticipated that there will be a requirement for a new radio access technology, as IMT-Advanced, or technologies at some point in the future to satisfy the anticipated demands for user mobility and higher bandwidth services.

Nowadays and further ITU-R Recommendations will develop these concepts in more detail. Other new Recommendations will address spectrum requirements for IMT-Advanced systems, which frequency bands might be suitable, and in what time-frame such spectrum would be needed, with a view to accommodating emerging broadband services and applications. It is expected that new spectrum requirements documented in these Recommendations will be addressed at a future World Radiocommunication Conference.

IMT-Advanced 4G systems will support a wide range of symmetrical, asymmetrical, and unidirectional services. They will also provide management of different QoS levels to realize the underlying objective of efficient transport of packet based services. In parallel, there will be an increased penetration of nomadic and mobile wireless access multimedia services over Internet.

The technologies, applications and services associated with IMT-Advanced 4G systems could well be radically different from the present, challenging the perceptions of what may be considered viable by today’s standards and going beyond what can be achieved by the future enhancement of other radio systems. The new radio access interface(s) are envisaged to handle a wide range of supported data rates according to economic and service demands in multi-user broadband environments with target peak data rates of up to approximately 100 Mbit/s for high mobility such as mobile access and up to approximately 1 Gbit/s for low mobility such as nomadic/local wireless access. These data rates are targets for research and investigation. They should not be taken as the definitive requirements for 4G systems.

Moreover, these data rates will be shared between active users. The achievable (peak or sustained) throughput for any individual user depends on many parameters, including the number of active users, traffic characteristics,

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service parameters, deployment scenarios, spectrum availability, and propagation and interference conditions. These data rates are the maximum value of the sum of the data rate for all of the active users on a radio resource; it is possible that the peak data rate needed in the upstream direction will be different from the downstream direction. The transport data rates may need to be higher due to overheads, such as signalling and coding. Depending on the services for which the technology (or technologies, such: LTE, LTE-Advanced, 802.11n, 802.16m) will be used, continuous radio coverage may not be needed in order to meet the service requirements.

Finally, here are summarized the key features (which cover the 4G requirements) of IMT-Advanced systems:

� a high degree of commonality of functionality worldwide while retaining the flexibility to support a wide range of services and applications in a cost efficient manner;

� compatibility of services within IMT and with fixed networks; � capability of interworking with other radio access systems; � high-quality mobile services; � user equipment suitable for worldwide use; � user-friendly applications, services and equipment; � worldwide roaming capability; � enhanced peak data rates to support advanced services and

applications (100 Mbit/s for high and 1 Gbit/s for low mobility were established as targets for research).

These features enable IMT-Advanced to improve the user experience of current and future mobile data and multimedia services and will make the broadband Internet truly mobile with high level of QoS provisioning. Moreover, the capabilities of IMT-Advanced systems are being continuously enhanced in line with user trends and technology developments.

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1.3. LTE/LTE-Advanced standardization (3GPP Release 8 to 3GPP Release 12)

The pursuit for higher data rate, higher capacity, higher throughput, lower delay, better spectrum efficiency and flexibility, high level of QoS provisioning, diversified mobile speed and greater coverage over cellular, resulted in GPRS/EDGE (2.5/2.75G) evolving to UMTS (3G) to HSPA (3.5G) to HSPA+ (3.75G). In one word, all is evolving towards mobile broadband internet access. Compared to a data rate of 180 kbps in EDGE, HSPA+ promises data rates of 42 Mbps downlink and 22 Mbps uplink. Clearly the trend indicates that the mobile phone will soon support broadband speeds. Now, with the advent of LTE (3.9G or Super 3G) and LTE Advanced (4G), mobile broadband just got broader.

Moreover, starting with 3GPP Rel-8, it had provided significant new capabilities, not only through enhancements to the WCDMA technology, but the addition of OFDM technology through the introduction of LTE as well. On the WCDMA side, Rel-8 provided the capability to perform 64 QAM modulation with 2X2 MIMO on HSPA+, as well as the capability to perform dual carrier operation for HSPA+ (i.e. carrier aggregation across two 5 MHz HSPA-HSPA+ carriers). Both of these enhancements enabled the HSPA+ technology to reach peak rates of 42 Mbps. Rel-8 also introduced E-DCH enhancements to the common states (URA_PCH, CELL_PCH and CELL_FACH) in order to improve data rates and latency and introduced discontinuous reception (DRX) to significantly reduce battery consumption.

In addition to enhancing HSPA-HSPA+, Rel-8 also introduced Evolved Packet System (EPS) consisting of a new flat-IP core network called the Evolved Packet Core (EPC) coupled with a new air interface based on OFDM called Long Term Evolution (LTE) or Evolved UTRAN (E-UTRAN). In its most basic form, the EPS consists of only two nodes in the user plane: a base station and a core network Gateway (GW). The node that performs control-plane functionality (MME) is separated from the node that performs bearer-plane functionality (Gateway). The basic EPS architecture is illustrated in Figure 1.5 with improved policy control and charging, a wider range of QoS capabilities, advanced security/authentication mechanisms and flexible roaming. The EPS architecture was designed to not only provide a smooth evolution from the 2G/3G packet architectures consisting of NodeBs, RNCs, SGSNs and GGSNs, but also provide support for non-3GPP accesses (e.g. WLAN, WiMAX and etc.) with help of the packet-optimized packet core system (Evolved Packet Core) that supports multiple access technologies, including 3GPP Internet Protocol Connectivity Access Network (IP CANs) like GSM EDGE Radio Access Network (GERAN), UTRAN and Evolved UTRAN (E-UTRAN) and also the mentioned non-3GPP IP CANs (WLAN, WiMAX and etc.) and even wired technologies. For more details about EPS see the following section (section 1.4).

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Figure 1.5. Basic EPS Architecture (based on 3GPP TS 23.401).

This access independent evolution of the packet core system architecture is the first major step towards the realization of an All-IP Network and reaching the point where LTE-Advanced meeting IMT-Advanced. The timeline of LTE releases and LTE-Advanced development is shown in Figure 1.6.

3GPP has not only evolved beyond addressing the Universal Terrestrial Radio Access Network (UTRAN) requirements to providing bandwidth intensive services. It has also put in a significant effort to evolve and simplify the packet core network. Branded as System Architecture Evolution (SAE), 3GPP has proposed a framework to evolve the 3GPP system to a higher data rate, lower latency.

Figure 1.6. 3GPP LTE releases timeline.

In Rel-8, LTE defined new physical layer specifications consisting of an OFDMA based downlink and SCFDMA99 based uplink that supports carrier bandwidths from 1.4 MHz up to 20 MHz. Rel-8 defined options for both FDD and TDD LTE carriers. Rel-8 also defined a suite of MIMO capabilities supporting open and closed loop techniques, Spatial Multiplexing (SM), Multi-User MIMO

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(MU-MIMO) schemes and Beamforming (BF). Because OFDMA and SC-FDMA are narrowband based technologies, LTE supports various forms of interference avoidance or coordination techniques called Inter-Cell Interference Coordination (ICIC). Finally, Rel-8 provided several other enhancements related to Common IMS, Multimedia Priority Service, support for packet cable access and service brokering, VCC enhancements, IMS Centralized Services (ICS), Service Continuity (SC) voice call continuity between LTE-HSPA VoIP and CS domain (called Single Radio VCC or SRVCC) and User Interface Control Channel (UICC) enhancements.

Although there are major step changes between LTE and its 3G predecessors, it is nevertheless looked upon as an evolution of the UMTS/3GPP 3G standards. Despite it uses a different form of radio interface, using OFDMA/SC-FDMA instead of CDMA, there are many similarities with the earlier forms of 3G architecture and there is scope for much re-use. Moreover, 3GPP LTE can be seen for provide a further evolution of functionality, increased speeds and general improved performance. In addition to this, LTE is an all IP based network, supporting both IPv4 and IPv6. There is also no basic provision for voice, although this can be carried as VoIP.

Let we summarise which new technologies has LTE introduced, when compared to the previous cellular systems. They enable LTE to be able to operate more efficiently with respect to the use of spectrum, and also to provide the much higher data rates that are being required.

� OFDM (Orthogonal Frequency Division Multiplex): 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; while 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 (Multiple Input Multiple Output): One of the main problems that previous telecommunications systems has encountered is that of multiple signals arising from the many reflections that are encountered. By using MIMO, these additional signal paths can be used to advantage and are able to be used to increase the throughput. When using MIMO, it is necessary to use multiple antennas to enable the different paths to be distinguished. Accordingly schemes using 2 x 2, 4 x 2, or 4 x 4 antenna matrices can be used. While it is relatively easy to add further antennas to a base station, the same is not true of mobile handsets, where the dimensions of the user equipment limit the number of antennas which should be place at least a half wavelength apart.

� SAE (System Architecture Evolution): as a part of the Evolved Packet Core (EPC). With the very high data rate and low latency requirements

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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.

Moreover, in Figure 1.7 we can see the functional decomposition of the Evolved Packet Core for 3GPP and non-3GPP IP Core Access Network. The EPC architecture is guided by the principle of logical separation of the signalling and data transport networks. The fact that some EPC functions reside in the same equipment as some transport functions, does not make the transport functions a part of the EPC. It is also possible that one physical network element in the EPC implements multiple logical nodes.

Figure 1.7. 3GPP Evolved Packet Core System Architecture

Also, in Table 1.3 the 3GPP LTE highlight specifications are summarized. Those specifications give an overall view of the performance that 3G LTE (Rel-8) is offering. It meets the requirements of industry for high data download speeds as well as reduced latency - a factor important for many applications from VoIP to gaming and interactive use of data. It also provides significant improvements in the use of the available spectrum.

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Table 1.3. 3GPP LTE highlight specifications

Parameter Details

Peak downlink speed 64QAM (Mbps)

100 (SISO), 172 (2x2 MIMO), 326 (4x4 MIMO)

Peak uplink speeds (Mbps)

50 (QPSK), 57 (16QAM), 86 (64QAM)

Data type All packet switched data (voice and data). No circuit switched.

Channel bandwidths (MHz)

1.4, 3, 5, 10, 15, 20

Duplex schemes FDD and TDD Mobility 0 - 15 km/h (optimised),

15 - 120 km/h (high performance) Latency Idle to active less than 100ms

Small packets ~10 ms Spectral efficiency Downlink: 3 - 4 times Rel 6 HSDPA

Uplink: 2 -3 x Rel 6 HSUPA Access schemes OFDMA (Downlink)

SC-FDMA (Uplink) Modulation types supported QPSK, 16QAM, 64QAM (Uplink and downlink)

With the standards definitions now available for LTE, the Long Term

Evolution of the 3G services, eyes are now turning towards the next development, that of the truly 4G technology named IMT-Advanced. The new technology being developed under the auspices of 3GPP to meet these requirements is often termed LTE-Advanced (LTE Release 10 & beyond).

While 3GPP Rel-9 focuses on enhancements to HSPA+ and LTE the Rel-10 focuses on the next generation of LTE for the ITU’s IMT-Advanced requirements and both were developed nearly simultaneously by 3GPP standards working groups. Several milestones have been achieved by vendors in recent years for both Rel-9 and Rel-10. Most significant was the final ratification by the ITU of LTE-Advanced (Rel-10) as 4G IMT-Advanced in November 2010.

HSPA+ was further enhanced in Rel-9 and was demonstrated at 56 Mbps featuring multi-carrier and MIMO technologies in Beijing at P&T/Wireless & Networks Comm China in 2009. Vendors anticipate that the steps in progress for HSPA+ will lead up to 168 Mbps peak theoretical downlink throughput speeds and more than 20 Mbps uplink speeds in Rel-10 in coming years. At Mobile World Congress 2010, the world’s first HSPA+ data call with a peak throughput of 112 Mbps was demonstrated by a leading vendor. M2M Identity Modules (MIM) with Rel-9 M2M Form Factors (MFF) are being shipped around the world for devices now embarking wireless in vehicles and harsh environments where humidity and vibration would not allow the traditional 2FF and 3FF to perform to the requirements. These MFF MIM also include additional software features to enable the expected life expectancy for such devices.

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Vendors are already progressing beyond LTE with the next generation of technologies in Rel-10 for IMT-Advanced, the LTE-Advanced, demonstrating that the evolution of LTE is secure and future-proof. In October 2009, 3GPP submitted LTE-Advanced to the ITU as a proposed candidate IMT-Advanced technology for which specifications could become available in 2011 through Rel-10. Milestones have already been achieved in the commercialization of Rel-10 and beyond. As early as December 2008, researchers conducted the world’s first demonstration of Rel-10 LTE-Advanced technology, breaking new ground with mobile broadband communications beyond LTE. A leading infrastructure company’s researchers successfully demonstrated Relaying technology proposed for LTE-Advanced in Germany. The demonstration illustrated how advances to Relaying technology could further improve the quality and coverage consistency of a network at the cell edge – where users were furthest from the mobile broadband base station. Relaying technology – which can also be integrated in normal base station platforms – is cost-efficient and easy to deploy as it does not require additional backhaul.

The demonstration of LTE-Advanced indicated how operators could plan their LTE network investments knowing that the already best-in-class LTE radio performance, including cell edge data rates, could be further improved and that the technological development path for the next stage of LTE is secure and future-proof.

Additionally, performance enhancements were achieved in the demonstration by combining an LTE system supporting a 2X2 MIMO antenna system and a Relay station. The Relaying was operated inband, which meant that the relay stations inserted in the network did not need an external data backhaul; they were connected to the nearest base stations by using radio resources within the operating frequency band of the base station itself. The improved cell coverage and system fairness, which means offering higher user data rates for and fair treatment of users distant from the base station, will allow operators to utilize existing LTE network infrastructure and still meet growing bandwidth demands. The LTE-Advanced demonstration used an intelligent demo Relay node embedded in a test network forming a FDD in-band self-backhauling solution for coverage enhancements. With this demonstration, the performance at the cell edge could be increased up to 50 percent of the peak throughput.

The performance and capabilities of 4G LTE (Rel-10) will be unmatched in the marketplace, allowing customers to do things never before possible in a wireless and mobile environment. Although not fixed yet in the specifications, there are many high level aims for the new LTE Advanced specification. These will need to be verified and much work remains to be undertaken in the specifications before these are all fixed. Currently some of the main features that wireless and mobile implementation of LTE-Advanced will provide are the following:

� Peak data rates: downlink - 1 Gbps; uplink - 500 Mbps. � Spectrum efficiency: 3 times greater than LTE. LTE-Advanced shall

operate in spectrum allocations of different sizes including wider

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spectrum allocations than those of LTE Release 8. The main focus for bandwidth solutions wider than 20MHz should be on consecutive spectrum. However, aggregation of the spectrum for LTE-Advanced should take into account reasonable user equipment (UE) complexity. Frequency division duplex (FDD) and time division duplex (TDD) should be supported for existing paired and unpaired frequency bands, respectively.

� Peak spectrum efficiency: downlink - 30 bps/Hz; uplink - 15 bps/Hz. � Spectrum use: the ability to support scalable bandwidth use and

spectrum aggregation where non-contiguous spectrum needs to be used.

� Latency: from Idle to Connected in less than 50 ms and then shorter than 5 ms one way for individual packet transmission.

� Cell edge user throughput to be twice that of LTE. � Average user throughput to be 3 times that of LTE. � Simultaneous user support: LTE provides the ability to perform two-

dimensional resource scheduling (in time and frequency), allowing support of multiple users in a time slot, resulting in a much better always-on experience while enabling the proliferation of embedded wireless applications/systems (in contrast, existing 3G technology performs one-dimensional scheduling, which limits service to one user for each timeslot).

� Mobility: Same as that in LTE: System shall support mobility across the cellular network for various mobile speeds up to 350km/h (or even up to 500km/h depending on the frequency band). In comparison to LTE Release 8, the system performance shall be enhanced for 0 up to 10 km/h.

� Compatibility: LTE Advanced shall be capable of interworking with LTE and 3GPP legacy systems.

� Security: LTE provides enhanced security through the implementation of Universal Integrated Circuit Card (UICC) Subscriber Identity Module (SIM) and the associated robust and non-invasive key storage and symmetric key authentication using 128-bit private keys. LTE additionally incorporates strong mutual authentication, user identity confidentiality, integrity protection of all signaling messages between UE and Mobility Management Entity (MME) and optional multi-level bearer data encryption.

� Simplified Worldwide Roaming: the widely adopted next-generation 3GPP standard, will provide the greatest opportunities for seamless international roaming.

� Mass Deployment: LTE’s inherent support for Internet Protocol version 6 (IPV6) addressing and International Mobile Subscriber Identity (IMSI)-based identifiers makes mass deployments of machine-to-machine applications over LTE-Advanced possible.

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These are many of the development aims for LTE Advanced. Their actual figures and the actual implementation of them will need to be worked out during the specification stage of the LTE Advanced system (beyond Rel-10).

On the other hand, as it was mention in the section 1.1, Release 11, is not scheduled to be finished until the very end of 2012. For LTE, emphasis is on Co-ordinated Multi-Point (CoMP), carrier-aggregation enhancements, and further enhanced eICIC including devices with interference cancellation. The release includes further DL and UL MIMO enhancements for LTE. For HSPA, provides 8-carrier on the downlink, uplink enhancements to improve latency, dual-antenna beamforming and MIMO, DLCELL_Forward Access Channel (FACH) state enhancement for smart phone-type traffic, four-branch MIMO enhancements and transmissions for HSDPA, 64 QAM in the uplink, downlink multi-point transmission, and non-contiguous HSDPA carrier aggregation. Table 1.4. Study items for Rel-11.

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In Rel-11, for example, a mechanism for accommodation, authentication and QoS control requested from the fixed access networks in EPS and Interworking with QoS-resource-allocation and authentication functions triggered by 3-th part applications have been added as new requirements in the specifications. Moreover, in Table 1.4 are summarized the Rel-11 requirements.

Furthermore, in the area of charging, the requirement that the network shall be able to reduce the user's data transmission speed once the user has exceeded a data-usage limit set by the telecommunications operator before hand was added.

Finally, the LTE Rel-12 and beyond will provide the initial enablers of meeting these challenging demands as well as a smooth way into the Beyond 4G era. Rel-12 enhancements focus on the four areas of Capacity, Coverage, Coordination (between cells), and Cost. Improvements in these areas are based on using several technology enablers: small cell enhancements, macro cell enhancements, New Carrier Type (NCT) and Machine-Type Communications (MTC). Small cell enhancements are also known as enhanced local access. NCT helps achieve the required changes in the physical layer and initially provides base station energy savings, flexibility in deployment and ways to reduce interference in heterogeneous networks (HetNets).Improvements in capacity and a more robust network performance are achieved by 3D Beamforming/MIMO (Multiple Input Multiple Output), advanced user equipment (UE) receivers and evolved Coordinated Multipoint (CoMP) techniques, as well as through Self-Organizing Networks for small cell deployments. Finally, new spectrum footprint and new business will be opened up by optimizing the system for Machine-Type Communications, as well as by, for example, using LTE for public safety.

LTE evolution continues strongly in Rel-12 and beyond by enhancing LTE and LTE-Advanced operation. In Figure 1.8 we present one possible radio evolution in the present decade. Rel-12 features aim at boosting performance and at entering new areas and spectrum. In the end, the tables 1.5 and 1.6 summarize the most promising Rel-12 features.

Figure 1.8. Illustration of the radio evolution in the present decade.

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Table 1.5. Benefits from 3GPP Release 12 – Boost performance.

Table 1.6. Benefits from 3GPP Release 12 – Expand to new areas and new spectrum.

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1.4. Evolved Packet System (EPS), E-UTRAN 3GPP Rel-8 specified the elements and requirements of the Evolved

Packet System (EPS) architecture that will serve as a basis for the next-generation networks. The specifications contain two major work items, namely LTE and System Architecture Evolution (SAE) that led to the specification of the Evolved Packet Core (EPC), Evolved Universal Terrestrial Radio Access Network (E-UTRAN), and Evolved Universal Terrestrial Radio Access (E-UTRA), each of which corresponds to the core network, radio access network, and air interface of the whole system, respectively. The EPS provides IP connectivity between a User Equipment (UE) and an external packet data network using E-UTRAN. In Figure 1.9, we provide an overview of the EPS, other legacy Packet and Circuit Switched elements and 3GPP RANs, along with the most important interfaces. In the services network, only the Policy and Charging Rules Function (PCRF) and the Home Subscriber Server (HSS) are included, for simplicity. In the context of 4G systems, both the air interface and the radio access network are being enhanced or redefined, but so far the core network architecture, i.e. the EPC, is not undergoing major changes from the already standardized SAE architecture.

Figure. 1.9. Illustration of the EPS for 3GPP accesses.

As we mentioned in the previous sections, 3GPP has proposed a

framework to evolve the 3GPP system to a higher data rate, lower latency, packet-optimized packet core system (EPC) that supports multiple access technologies, including 3GPP Internet Protocol Connectivity Access Network (IP CANs) like GSM EDGE Radio Access Network (GERAN), UTRAN and Evolved UTRAN (E-UTRAN) and non-3GPP IP CANs like WLAN, WiMAX and even wired

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technologies. This access independent evolution of the packet core system architecture is the first major step towards the realization of an All-IP Network and also it is fully compatible with LTE-Advanced, the new 4G technology.

The new SAE network is based upon the GSM / WCDMA core networks to enable simplified operations and easy deployment. Despite this, the SAE network brings in some major changes, and allows far more efficient and effect transfer of data. Moreover, there are several common principles used in the development of the LTE SAE network:

� a common gateway node and anchor point for all technologies. � an optimised architecture for the user plane with only two node

types. � an all IP based system with IP based protocols used on all

interfaces. � a split in the control / user plane between the MME, mobility

management entity and the gateway. � a radio access network / core network functional split similar to

that used on WCDMA / HSPA. � integration of non-3GPP access technologies (e.g. cdma2000,

WiMAX, etc) using client as well as network based mobile-IP.

The main element of the LTE SAE network is what is termed the Evolved Packet Core. This connects to the eNodeBs. Before, in the Figure 1.7 and 1.9 was illustrated the functional decomposition of the Evolved Packet Core for 3GPP and non-3GPP IP CAN. It is also possible that one physical network element in the EPC implements multiple logical nodes. Also, in Figure 1.10 is given a detail illustration of EPC/SAE architecture.

Figure. 1.10. EPC/SAE architecture: baseline.

As seen within the above figure, the LTE SAE Evolved Packet Core, consists of four main elements as listed below:

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� Mobility Management Entity, MME: The MME is the main control node

for the LTE SAE access network, handling a number of features: � Idle mode UE tracking � Bearer activation / de-activation � Choice of SGW for a UE � Intra-LTE handover involving core network node location � Interacting with HSS to authenticate user on attachment and

implements roaming restrictions � It acts as a termination for the Non-Access Stratum (NAS) � Provides temporary identities for UEs � The SAE MME acts the termination point for ciphering protection for

NAS signaling. As part of this it also handles the security key management. Accordingly the MME is the point at which lawful interception of signalling may be made.

� Paging procedure � The S3 interface terminates in the MME thereby providing the control

plane function for mobility between LTE and 2G/3G access networks. The SAE MME also terminates the S6a interface for the home HSS for roaming UEs. It can therefore be seen that the SAE MME provides a considerable level of overall control functionality.

� Serving Gateway, SGW: The Serving Gateway, SGW, is a data plane element within the LTE SAE. Its main purpose is to manage the user plane mobility and it also acts as the main border between the Radio Access Network, RAN and the core network. The SGW also maintains the data paths between the eNodeBs and the PDN Gateways. In this way the SGW forms a interface for the data packet network at the E-UTRAN. Also when UEs move across areas served by different eNodeBs, the SGW serves as a mobility anchor ensuring that the data path is maintained.

� PDN Gateway, PGW: The LTE SAE PDN gateway provides connectivity for the UE to external packet data networks, fulfilling the function of entry and exit point for UE data. The UE may have connectivity with more than one PGW for accessing multiple PDNs.

� Policy and Charging Rules Function, PCRF: This is the generic name for the entity within the LTE SAE EPC which detects the service flow, enforces charging policy. For applications that require dynamic policy or charging control, a network element entitled the Applications Function, AF is used.

In order that requirements for increased data capacity and reduced latency can be met, along with the move to an all-IP network, it is necessary to adopt a new approach to the network structure. For 3G UMTS / WCDMA the UTRAN (UMTS Terrestrial Radio Access Network, comprising the Node B's or basestations and Radio Network Controllers) employed low levels of autonomy. The Node Bs were connected in a star formation to the Radio Network Controllers (RNCs) which carried out the majority of the management of the radio

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resource. In turn the RNCs connected to the core network and connect in turn to the Core Network.

To provide the required functionality within LTE SAE, the basic system architecture sees the removal of a layer of management. The RNC is removed and the radio resource management is devolved to the base-stations. The new style base-stations are called eNodeBs or eNBs.

The eNBs are connected directly to the core network gateway via a newly defined "S1 interface". In addition to this the new eNBs also connect to adjacent eNBs in a mesh via an "X2 interface". This provides a much greater level of direct interconnectivity. It also enables many calls to be routed very directly as a large number of calls and connections are to other mobiles in the same or adjacent cells. The new structure allows many calls to be routed far more directly and with only minimum interaction with the core network.

Moreover, from a user-plane perspective there are only the eNBs and the gateways, which is why the system is considered ‘‘flat’’. The result is a reduced complexity compared to previous architectures.

Figure. 1.11. LTE-Advanced E-UTRAN architecture.

In Figure 1.11, the architecture of E-UTRAN for LTE-Advanced is presented. The core part in the E-UTRAN architecture, as we said before is the enhanced Node B (eNodeB or eNB), which provides the air interface with user plane and control plane protocol terminations towards the UE. Each of the eNBs is a logical component that serves one or several E-UTRAN cells, and the interface interconnecting the eNBs via X2 interface. Additionally, Home eNBs (HeNBs, also called femtocells), which are eNBs of lower cost for indoor coverage improvement, can be connected to the EPC directly or via a gateway that provides additional support for a large number of HeNBs. Further, 3GPP is considering relay nodes and sophisticated relaying strategies for network performance enhancement. The targets of this new technology are increased

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coverage, higher data rates, and better QoS performance and fairness for different users. In addition to the new Layer 1 and Layer 2 functionality, eNBs handle several other functions. This includes the radio resource control including admission control, load balancing and radio mobility control including handover decisions for the mobile or user equipment (UE). The additional levels of flexibility and functionality given to the new eNBs mean that they are more complex than the UMTS and previous generations of base-station. However the new 3G LTE SAE network structure enables far higher levels of performance. In addition to this their flexibility enables them to be updated to handle new upgrades to the system including the transition from 3G LTE to 4G LTE-Advanced.

Moreover, The EPC specifies two types of IP-IP Gateway logical functions for the user plane – the Serving Gateway (S-GW) and the PDN Gateway (P-GW). The S-GW and P-GW are core network functions of the E-UTRAN based access. They may be implemented in one physical node or in separate physical nodes. Early deployments are likely to see a single node implementation of S-GW and P-GW functions with future proof design to decouple these functions such that S-GWs in visited networks can connect to P-GWs of home networks for home PLMN routed IP services.

Figure. 1.12. SAE Gateway (S-GW) and PDN Gateway (P-GW) Architecture.

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As shown in Figure 1.12, both the S-GW and P-GW are built on core

datacom routing and switching technologies supporting the Layer 2 and Layer 3 suite of an All IP Network. Therefore, it is anticipated that the S-GW and P-GW are logical migration and evolution paths for the traditional IP-IP Gateway product lines. Each IP-IP Gateway vendor will have their own hardware and platform USP that supports line-rate switching and packet forwarding with very low latency of high volume IP traffic. There exists a striking similarity between the S-GW and P-GW functions. Other than the commonality at the core datacom layer, they both act as the Policy Enforcement Points (PEP) for dynamic QoS policies. While the S-GW is dedicated to policy and QoS enforcement at packet level, the P-GW functions as the PEP at the service level. On the charging front, both the S-GW and P-GW have a role to play. While the S-GW is involved in generating charging records at packet level, the P-GW takes up the responsibility for producing charging records at service level. Deep Packet Inspection and Legal Intercept are dedicated functions of the P-GW, but nothing prevents the S-GW from implementing these functions as well. Given that the S-GW is the direct interface point for E-UTRAN eNodeB (S1-U interface), functions such as inter-E-UTRAN mobility anchoring for the user plane (coordinating with the MME) and eNodeB packet reordering are exclusively meant for S-GW implementation. Since the S-GW directly interfaces with the GERAN and UTRAN networks (S4 and S12 interfaces), it also acts as the anchor point for inter-3GPP RAT mobility.

The P-GW on the other hand is primarily responsible for the IP address allocation of the UE in the AIPN and acts as the anchor point for mobility across the non-3GPP IP-CANs (for both trusted and non-trusted). For network based mobility, the P-GW acts as the Gateway Local Mobility Anchor (LMA) terminating Proxy Mobile IPv6 (PMIPv6) for the control signaling and IPv4/IPv6 tunneling for the user plane. This corresponds to the S2a and S2b interfaces for the trusted and non-trusted non-3GPP IP-CAN respectively, where the non-3GPP IP-CANs directly terminate into the P-GW, bypassing the S-GW (as in the case of the non roaming architecture for EPS or home routed architecture or the case of local breakout within the visited PLMN). The trusted or non-trusted non-3GPP IP-CAN typically emulates the MAG function of the network based mobility architecture. For deployment architectures where the S-GW is in the path of the chained home routed solution, the S-GW additionally plays the role of a back-to-back Gateway LMA and MAG function. In such scenarios, the S2a and S2b interfaces from the trusted and non-trusted non-3GPP IP-CAN respectively, are routed to the P-GW via the S-GW.

There are two deployment models to address host-based mobility. In the first deployment model, the S2a and S2b interfaces are based on MIPv4 technology. The P-GW acts as a MIPv4 Home Agent and the trusted and non-trusted non-3GPP IP-CAN provide the Foreign Agent function for the Mobile Node (the UE). The user plane is based on the tunneling of end-to-end IPv4 over transport IPv4. The second deployment model assumes that the UE is capable of acting as a DSMIPv6 client and the P-GW is the DSMIPv6 Home Agent. All other nodes in the network are IP Access router systems. This deployment model

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applies to both 3GPP and non-3GPP IP-CANs (the S2c interface between the UE and the P-GW). The formal interface between the S-GW and the P-GW is called S5 (where S-GW and P-GW are within the same PLMN) and S8 (where S-GW belongs to visited PLMN and the P-GW to the home PLMN). The S5 and S8 interfaces are otherwise functionally similar. There are two protocol options for these interfaces. The first option is to support GTP tunnels between S-GW and P-GW, GTP-C for control signaling and IP tunneling over GTP-U for the user plane. This typically applies to 3GPP access deployments, where the S-GW acts as a GTP-U relay between the 3GPP access network and the P-GW. If the UE over the 3GPP access network supports DSMIPv6, then it is possible to run the S2c interface over GTP over the P-GW and S-GW connection.

The second deployment model allows PMIPv6 to run as the control signaling protocol on the S5 and S8 interfaces. For 3GPP access, this implies that the S-GW terminates the GTP-U tunnels and tunnels user IP over transport IP towards P-GW. Initial deployments will possibly start with non-roaming architectures, with the S-GW and P-GW interface being initially S5 focused. Additionally, equipment vendors will be looking into collapsed S-GW and P-GW functions within a single physical node. Hence, vendors are likely to start implementing the S5 interface as proprietary lightweight implementations. However, the interface design must be future proof to make a way for the more formal S5 interface and to evolve to the S8 interface for decoupled S-GW and P-GW solutions, as operators start insisting on roaming architectures and home PLMN routed IP services.

Both the S-GW and P-GW will have Diameter interfaces towards network hosted Policy and Charging Rules Functions (PCRFs) and Service-based Policy Decision Functions (SPDFs)/Radio Access Control Functions (RACFs). The Diameter based Gxc and S7 interfaces control the Policy and Charging Enforcement Function (PCEF) within the S-GW and P-GW functions. It is also likely that the operator network may not have a centralized Policy Decision Point – in this case the S-GW and P-GW must be in a position to accept dynamic policy and QoS decisions from distributed PDPs in the network after implementing a local PDP within the Gateway for resolving policy conflicts. The Gateways must also realize the Diameter interfaces (S6b and S6c) towards external AAA functions for non-3GPP accesses.

As a conclusion we can clearly say that the new SAE/EPC architecture together with E-UTRAN for LTE/LTE-Advanced provides a new approach for the core and access networks, enabling far higher levels of data to be transported to enable it to support the much higher data rates that will be possible with those 3GPP technologies. In addition to this, other features that enable the CAPEX and OPEX to be reduced when compared to existing systems, thereby enabling higher levels of efficiency to be achieved.

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1.5. Self Organizing Networks (SON) for LTE/LTE-Advanced As every mobile network, LTE/LTE-Advanced systems also need to be

managed. Since LTE is an evolvement of UMTS, the management should also evolve from UMTS. There is a trend to simplify the management by auto-configuration and auto-optimization. However, the complexity of LTE system also place new demands on the Operations and Maintenances of the network. Self-Organizing Networks (SON) is seen as one of the promising area for an operator to save operational expenditures. The SON, aims to leapfrog to a higher level of automated operation in mobile networks. Therefore SON is currently discussed in 3GPP standardisation.

But, in the same beginning, let we see which are the main drivers for SON:

� The number and structure of network parameters have become large and complex;

� Quick evolution of wireless networks has led to parallel operation of 2G, 3G, EPC infrastructures;

� The rapidly expanding number of Base Stations (especially Home eNB) needs to be configured and managed with the least possible human interaction. Moreover, SON aims to configure and optimize the network automatically,

so that the interaction of human can be reduced and the capacity of the network can be increased. An intelligent network with the ability to quickly and autonomously optimize itself could sustain both network quality and a satisfying user experience. SON offers tremendous potential and many ways of improving operating efficiency. In Figure 1.13 illustrates the functional overview of SON for LTE/LTE-Advanced, i.e. the three classes of key functions prominently in SON are given.

Figure. 1.13. Functional overview of SON.

Self-configuration comprises all tasks necessary to automate the deployment and commissioning of networks and the configuration of parameters. Network elements operate autonomously, running setup routines, authenticating

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and connecting to the OSS, as well as linking up and swapping parameters with need-to-know neighbours. More precisely said, the self-configuration process is defined as the process where newly deployed nodes (eNBs) are configured by automatic installation procedures to get the necessary basic configuration for system operation. Self-configuration process works in preoperational state, which starts from when the eNB is powered up and has backbone connectivity until the RF transmitter is switched on.

Figure. 1.14. Framework for SON.

As shown in Figure 1.14 (where the SON framework is shown), self-configuration includes two stages: basic setup and initial radio configuration. The whole procedure is shown in Figure 1.15:

1. An IP address is allocated to the new eNB and the information of the Selfconfiguration Subsystem of OAM (Operation and Management) is given to the eNB.

2. A GW is configured for the new eNB so that the eNB can exchange IP packets with other internet nodes.

3. The new eNB provides its information, including type, hardware and etc., to the Self-configuration Subsystem for authentication. Necessary software and configuration data are downloaded from the Self-configuration Subsystem.

4. The new eNB is configured based on the transport and radio configuration data.

5.The new eNB connects to the normal OAM subsystems for other management functions.

6. S1 and necessary X2 interfaces are established.

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Figure. 1.15. Self-configuration procedure.

Self-optimization serves to improve or recoup network quality by tuning network parameters on the fly. Key tasks involve brokering handovers and balancing loads among neighbouring cells. Contributing to a greener network environment, SON offers advanced energy-saving features. Self-optimization process more precisely is defined as the process where UE & eNB measurements and performance measurements are used to autotune the network. This process works in operational state, which starts when the RF interface is switched on. The self-optimization process collects measurement information from UE and eNB and then with the help of external optimization tool, it auto-tune the configuration data to optimize the network. A typical example is neighbour list optimization.

Finally, the self-healing encompasses a set of key functions designed to cope with major service outages, including detection, root cause analysis, and outage mitigation mechanisms. Auto-restart and other automatic alarm features afford the network operator even more quick-response options. Self-planning combines configuration and optimization capabilities to dynamically re-compute parts of the network, the aim being to improve parameters affecting service quality.

Another issue is the allocation of SON’s functions and algorithms. A self-configuration Subsystem will be created in OAM to be responsible for the self-configuration of eNB. For self-optimisation functions, they can be located in OAM or eNB or both of them. So according to the location of optimisation algorithms, SON can be divided into three classes: Centralised SON, Distributed SON and Hybrid SON.

In Centralized SON, optimisation algorithms are executed in the OAM System. In such solutions SON functionality resides in a small number of

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locations, at a high level in the architecture. Figure 1.16 shows an example of Centralized SON.

Figure 1.16. Centralized SON.

In Centralized SON, all SON functions are located in OAM systems, so it is easy to deploy them. But since different vendors have their own OAM systems, there is low support for optimization cases among different vendors. And it also does not support those simple and quick optimization cases. To implement Centralized SON, existing Itf-N interface needs to be extended.

In Distributed SON, optimization algorithms are executed in eNB. In such solutions SON functionality resides in many locations at a relatively low level in the architecture. Figure 1.17 shows an example of Distributed SON. In Distributed SON, all SON functions are located in eNB, so it causes a lot of deployment work. And it is also difficult to support complex optimization schemes, which require the coordination of lots of eNBs. But in Distributed SON it is easy to support those cases, which only concern one or two eNBs and require quick optimization responses. For Distributed SON, X2 interface needs to be extended.

In Hybrid SON, part of the optimization algorithms are executed in the OAM system, while others are executed in eNB. Figure 1.18 shows an example of Hybrid SON. In Hybrid SON, simple and quick optimization schemes are implemented in eNB and complex optimization schemes are implemented in OAM. So it is very flexible to support different kinds of optimization cases. And it also supports the optimization between different vendors through X2 interface. But on the other hand, it costs lots of deployment effort and interface extension work.

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Figure 1.17. Distributed SON.

Figure 1.18. Hybrid SON.

Overall we can conclude that SON for LTE/LTE-Advanced is designed to leapfrog to the next level of automated operation with the twin aims of improving network quality and driving down OPEX. Various self-configuration, optimization, and healing functions cater to specified SON use cases, bringing big benefits to a wide range of operating scenarios. While 3GPP standardization efforts will assure the necessary interoperability, the real power behind SON performance is architecture and algorithms. This challenges vendors to turn up viable implementations and efficient, robust SON LTE/LTE-Advanced functions – and it affords them many opportunities to differentiate their offerings. Indeed, the lack of a clear-cut implementation compels vendors to persist with rigorous research.

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1.6. LTE/LTE-Advanced Radio Resource Management An intelligent radio resource management (RRM) is the core system of

LTE/LTE-Advanced networks in order to provide the broadband mobility needs of upcoming years. RRM system will schedule the available radio resources in a best way, so all the users will be served by enough transmission capability and required level of QoS and mobility, and also RRM system will assure that the assigned resources would not interfere with any previous assigned resources. Using aggressive frequency reuse (factor of 1) in LTE/LTE-Advanced network means that the whole frequency spectrum will be available in single eNodeB which creates large effect of inter cell interference (ICI) especially at the edge of the cell. Moreover, the development of Self Organizing Network (given in the previous section) techniques, algorithms and eventually standards is a critical step in LTE/LTE-Advanced femtocell deployments and a great confirmation about the importance of RRM.

The LTE system requires optimized signaling as well as optimized radio transmission and radio access network. The radio access network of the LTE system, Evolved UMTS Radio Access Network (E-UTRAN) is agreed to have only one type of node – eNodeB. LTE system prefers UEs to be less intelligent, and allows network to have all control over services and resources. These system features should be considered sufficiently in designing the optimized LTE signaling protocols and radio resources management algorithms. The E-UTRAN is discussed in more details in section 1.4.

Furthermore, as we mentioned, the LTE-Advanced should be real mobile broadband wireless network that provides peak data rates equal to or greater than those for wired networks, i.e., FTTH (Fiber To The Home), while providing better QoS. The major high-level requirements of LTE-Advanced are reduced network cost (cost per bit), better service provisioning and compatibility with 3GPP systems. Just to mention that LTE-Advanced being an evolution from LTE is backward compatible. Here will be summarized some of the major technology proposals of LTE-Advanced are:

� Asymmetric transmission bandwidth � Layered OFDMA � Advanced Multi-cell Transmission/Reception Techniques � Enhanced Multi-antenna Transmission Techniques � Enhanced Techniques to Extend Coverage Area � Support of Larger Bandwidth in LTE-Advanced

Access such as Frequency Division Duplex (FDD) and Time Division Duplex (TDD) are the two most prevalent duplexing schemes used in fixed broadband wireless networks. FDD uses two distinct radio channels and supports two-way radio communication and TDD uses a single frequency to transmit signals in both the downstream and upstream directions. Symmetric transmission results when the data in down-link and in the up-link are transmitted at the same data rate. This is one of the cases in voice transmission which

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transmits the same amount of data in both directions. However, for internet connections or broadcast data (for example, streaming video), it is likely that more data will be sent from the server to the UE (the down-ink).

Based on the current and future traffic demands in cellular networks the required bandwidth in up-link will be narrower than that in down-link. So asymmetric transmission bandwidth will be a better solution for efficient utilization of the bandwidth (see Figure 1.19).

Figure 1.19. Support of Asymmetric Bandwidths for LTE Advanced.

In layered OFDMA structure, the entire system bandwidth comprises multiple basic frequency blocks. The bandwidth of basic frequency block is, 15–20 MHz. Layered OFDMA radio access scheme in LTE-Advanced will have layered transmission bandwidth, support of layered environments and control signal formats. The support of layered environments helps in achieving high data rate (user throughput), QoS, or widest coverage according to respective radio environments such as macro, micro, indoor, and hotspot cells.

The control signal formats are straightforward extensions of L1/L2 control signal formats of LTE to LTE-Advanced. Independent control channel structure is used for each component carrier. Control channel supports only shared channel belonging to the same component carrier.

In a multi-user multi-cell environment employing multi-transmission/reception antenna devices for each cell have multiple first units and second units in wireless communication. The first units consists of a predetermined antenna and the second unit consists of the following sub-units:

� Estimation unit: Estimates channel information on signals from the individual first units and estimates information of noise and interference signals from adjacent cells.

� Calculation unit: Calculates the sum of transfer rates for each user group having at least one first unit using the information estimated by the estimation unit.

� Determination unit: Determines one user group by comparing the sum of the transfer rates of each user group calculated by the calculation unit.

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� Feedback unit: Information on the user group determined by the determination unit is fed back to the first units of the corresponding cell.

In LTE-Advanced, the advanced multi-cell transmission/reception processes (also called as coordinated multipoint transmission/reception) helps in increasing frequency efficiency and cell edge user throughput. Faster handovers among different inter-cell sites are achieved by employing Inter-Cell Interference (ICI) management (that is, inter-cell interference coordination (ICIC) aiming at inter-cell orthogonalization).

Moreover, the mobile broadband traffic in wireless communications has been increasing multi folds over the years, which amplifies the requirement of higher-order MIMO channel transmissions and higher peak frequency efficiency than LTE. In LTE-Advanced, the MIMO scheme has to be further improved in the area of spectrum efficiency, average cell through put and cell edge performances (see Figure 1.20). With multipoint transmission/reception, where antennas of multiple cell sites are utilized in such a way that the transmitting/receiving antennas of the serving cell and the neighboring cells can improve quality of the received signal at the UE/eNodeB and reduces the co-channel interferences from neighboring cells. Peak spectrum efficiency is directly proportional to the number of antennas used. In LTE-Advanced the antenna configurations of 8x8 in DL and 4x4 in UL are planned.

Figure 1.20. MIMO Tx & Rx Schemes LTE-Advanced (8 X 4 MIMO).

Moreover, the Remote Radio Requirements (RREs) using optical fiber should be used in LTE-Advanced as effective technique to extend cell coverage (see Figure 1.21). Layer 1 relays with non-regenerative transmission, that is, repeaters can also be used for improving coverage in existing cell areas. Layer 2 and Layer 3 relays can achieve wide coverage extension through an increase in Signal to Noise Ratio (SNR).

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Figure 1.21. RRE using optical fibers.

Finally, peak data rates up to 1Gbps are expected from bandwidths of 100MHz. OFDM adds additional sub-carrier to increase bandwidth. The available bandwidth may not be continuous as a result of fragmented spectrum. To ensure backward compatibility to the current LTE, the control channels such as synchronization, broadcast, or PDCCH/PUCCH might be needed for every 20 MHz.

Furthermore, are discussed the two fundamental types of RRM; the first type is general RRM schemes and the second type is with the consideration of SON requirements. As already in LTE Rel-8 and also in LTE-Advanced robust general minimum RRM requirements ensure good mobility performance across the cellular network for various mobile speeds and different network deployments. The minimum RRM requirements are defined both in idle mode and in active mode. In Active mode the requirements are defined both without DRX and with DRX in order to ensure that good mobility performance in all cases while still minimising UE battery consumption especially with long DRX cycles. Different network controlled parameter values for cell reselection in idle mode and for handover in active mode can be utilized for optimizing mobility performance in different scenarios, which also include low mobility and high mobility scenarios.

The General resources scheduling algorithms are the following:

• Proportional fairness resource allocation algorithm: the priority for each user at each resource block should be calculated first and then the user how has the maximum priority the RB (resource block) will be assigned to him and the algorithm continues to assign the RBs to the next maximum priorities between the users until all RBs are assigned or all users have been served. This priority of k-th user to be assigned with j-th resource block at time (t) is given by: Pkj(t)=RDRkj(t) /Rk(t)

Where RDRkj (t) is the requested data rate for the k-th user over j-th RB in time (t) and Rk (t) is the low-pass filtered averaged data rate of the k-th user. The value of RDR is estimated by using AMC (Adaptive Modulation and Coding) selection which is depends on current transmission channel condition. In case of retransmission RDR is different from the one for new

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resource user request in order to guarantee the successful transmission, so the RDR estimated form is:

RDRkj=RMCS(SNRAC) Here RMCS is the rate estimation function and SNRAC is the accumulated

signal to noise ratio over the transmission channel. In any time interval of scheduling is updated as follows: Rk(t+1)=(1−a)Rk(t)+aDRDk(t) Where (a) is the average rate window size and DRDk (t) is the aggregate data rate for user k at time t.

• Softer frequency reuse based resource scheduling algorithm: By the aim of reduction of frequency selective scheduling gain loss and to increase the data rate at the cell edge, this scheme is proposed. By this algorithm the frequency reuse factor is 1 at the center and the edge of the cell. The frequency scheduler is working in a way that the cell edge’s users have higher probability of using the frequency band with higher power and the cell center’s users have the higher probability of using frequency band with lower power. Here the priority is calculated by: Pkj(t)=RDRkj(t) / Rk(t)Fkj. This formula is modifications form of the previous algorithm where Fkj is the priority factor and can take value between 0 and 1 among the following cases:

User k at cell center, RB j is low power User k at cell center, RB j is high power User k at cell edge, RB j is low power User k at cell edge, RB j is high power Giving different values to Fkj is the way of controlling the resources

assignment to users in the edge and center of the cell.

• Round robin scheduling algorithm: this method is used to allocate the radio resources to users, the first user will be served with the whole frequency spectrum for a specific period of time and then serve the next user for another time period. The previously server user will placed at the end of the waiting queue till to be served again in the next round. All the new resources request also will be placed at the end of waiting queue. This scheme offers great fairness in radio resource assignment among the users but with lowering the whole system throughput.

• Resource scheduling scheme based on maximum interference: this algorithm all the users in the cell are ranked according to the experienced interference so the user with the worst CQI (Channel quality indicator) will be in the top of ranking and scheduled to assign RBs for him and the turn goes for the user with the next worst CQI to have his RBs. The ranking K can be presented as:

K=argmax( Yk(t)) Where Y is the vector of experienced interference by the users in the cell in time (t).

• Resource scheduling algorithm based on dynamic allocation: this allocation algorithm is using a kind of signaling process by a small chunks of class traffic smaller than the packet of streaming class traffic are transmitted in the network, this algorithm gives equal allocation of the radio resources but not with the capacity of traffic which can be handled by these physical resource blocks (PRB). This algorithm depends on three main parameters:

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M=total number of available PRBs U=total users to multiplex on a PRB

RB=resource blocks which are assigned to k user. Thus the k user select best PRB from N based on the channel condition.

Furthermore, the Radio Resource Management for SON in LTE/LTE-

Advanced can be as following:

• Joint radio resource management: All operators have to deal with coexistence RATs and the integration between LTE/LTE-Advanced networks and other wireless networks, so the exploitation of the complementarities between technologies through JRRM will be needed. This scheme is based on Reinforcement Learning (RL). The RRM through smart mechanisms that take jointly into account the resources available in all the RATs to make the appropriate allocations, these are referred to as Joint RRM (JRRM) or Common RRM (CRRM). The mechanism puts RL agent in each cell which works in Real time independently from the agents in other cells, and it is responsible for distributing the users among the technologies and the decision can be taken either at session initiation, or during session lifetime, which could lead to a vertical handover. For example, in this model if we assume that the reuse factor is 3 in the LTE, so that only 8 out of 24 frequency chunks (resource blocks) are assigned to one cell as active. The remaining 16 chunks would be used by neighboring cells.

• Multi radio resource management: incorporates a multi-radio resource and mobility management, allowing for intelligent network-centric access selection, seamless handovers and optimized load balancing over a number of different kinds of access networks, including 3GPP and non-3GPP networks. This system consists of three parts; the first one MRM-TE is located on the user terminal and it has to provide intersystem measurement functions and an initial access selection algorithm that is used as long as the terminal has not yet established a connection with the access network. The second part MRM-NET is located in the access network and is associated with all active users within its service area. Last part (MRM-HAM) is the heterogeneous access management function and its main mission is to make access selection decisions based on various input parameters such as link performance, resource usage and availability measurements.

• Cognitive radio resource management: the concept idea is to enrich the LTE system with Cognitive features which can be used to provide the system with knowledge that derives from past interactions with the environment. The selfmanagement function of cognitive systems may be introduced in the terminal level, access point or network segment level. The system examines the current operated context has been treated in the past for better and suitable exploitation of experience and knowledge that can be used to produce wiser RRM decisions and actions. Next we must explain the concept of Intra Cell RRM: Intra-cell configuration includes sub-carrier assignment, power allocation and adaptive modulation. Each one of them is reflected by DSA (Dynamic Spectrum Access), APA (Adaptive Power Allocation) and AM

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(adaptive modulation) respectively. Multiple sub-carriers are allowed to be assigned to a single user. However, the same sub-carrier isn’t allowed to be assigned in more than one user, and the number of subcarriers that should be assigned to any user depends on many factors parameters like user location, the requested service, user profile and Network Operators (NOs) policies.

• Dynamic fractional frequency reuse scheme: In the system a mix of high and low reuse frequency resources (e.g., reuse 1 and 3, respectively) are allowed in each cell. The user’s distance from the cell center is the factor which means the reuse 1 is for the close users from the cell center while the lower reuse resources are assigned to interference-limited users at the cell edge. In the Down Link FRR: by the consideration of the distribution of mobile or traffic load the basic idea is the usage of a relative narrowband transmit power (RNTP) indicator, which is exchanged between BSs on the X2 interface. The RNTP is a per physical resource block (PRB) indicator which conveys a transmit power spectral density mask that will be used by each cell. This feature results in arbitrary soft reuse patterns being created across the system. Every cell would have a special subband for generating low interference with its reduced transmit spectral density. Based on the knowledge of which cell is causing the dominant interference in the DL, the scheduler can inquire the RNTP report in that cell to know which subband is being transmitted at reduced power and hence generating less interference, and can choose to schedule mobile in that subband so that it experiences higher SINR. For the Up Link FFR another indicator is used (high interference indicator HII), which is defined per PRB, can be exchanged between cells via the X2 interface to implement uplink FFR. When the HII bit is set to 1 for a particular PRB so it has high sensitivity to uplink interference for this cell; when the HII bit is set to 0 so it signifies that this PRB has low sensitivity to uplink interference and by The exchange of HII reports between cells allows the creation of fractional reuse patterns through uplink scheduling and power control.

Finally, in order to design an intelligent RRM for LTE/LTE-Advanced

networks many issues should be taken under our consideration, efficient frequency reuse; fairness; QoS; inter cell interference control (ICIC); optimum power allocation; SON requirements and vertical handover.

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1.7. Radio network deployment and frequency planning The upgrade to LTE/LTE-Advanced is relatively straightforward, with new

LTE infrastructure having the ability to reuse a significant amount of the UMTS-HSPA cell site and base station including using the same shelter, tower, antennas, power supply and climate control. Different vendors have different, so-called “zero-footprint” solutions, allowing operators to use empty space to enable re-use of existing sites without the need for any new floor space.

An operator can add LTE capability simply by adding an LTE baseband card. New multi-standard radio units (HSPA and LTE), as well as LTE-only baseband cards, are mechanically compatible with older building practices, so that operators can use empty space in an old base station for LTE baseband cards, thus enabling re-use of existing sites without the need for any new floor space, as mentioned previously.

Base station equipment is available for many bands including the 1.7/2.1 GHz AWS band and the 700 MHz bands in the U.S.A. (for more details about other frequency bands of LTE / LTE-Advanced and their spectrum management see the following section 1.8). On the device side, multi-mode chipsets will enable devices to easily operate across UMTS and LTE networks.

There are many different scenarios that operators will use to migrate from their current networks to future technologies such as LTE/LTE-Advanced. Figure 1.22 presents various scenarios including operators who today are using CDMA2000, UMTS, GSM and WiMAX. For example, as shown in the first bar, a CMDA2000 operator in scenario A could defer LTE deployment to the longer term. In scenario B, in the medium term, the operator could deploy a combination of 1xRTT, EV-DO Rev A/B and LTE and, in the long term, could migrate EV-DO data traffic to LTE. In scenario C, a CDMA2000 operator with just 1xRTT could introduce LTE as a broadband service and, in the long term, could migrate 1xRTT users to LTE including voice service.

3GPP and 3GPP2 both have specified detailed migration options to LTE. One option for GSM operators that have not yet committed to UMTS, and do not have an immediate pressing need to do so, is to migrate directly from GSM/EDGE or Evolved EDGE to LTE with networks and devices supporting dual-mode GSM-EDGE/LTE operation.

Moreover, in order to achieve effective performance and broadband mobility, a careful radio planning needs to be performed. Since LTE and LTE-Advanced are very flexible, i.e. they can be deployed in various frequency bands using a mixture do channel bandwidths, the actual planning decision is based on various factors, some of which are illustrated in the Figure 1.23.

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Figure 1.22. Different Deployment Scenarios for LTE.

Figure 1.23. Factors influencing LTE cell planning.

The typical deployment will be based on a three sector site. This is apparent due to historic frequency planning methods, vendor implementation and also the fact that allocation of the LTE PCI (Physical Cell Identifier) includes a CellID

1 (Cell Identity Group Number) and CellID2 (Cell Identity Number), the latter

is encoded as 0, 1, or 2 to reflect one of the three sectors. There are also various scenarios when a two sectored site or an omni directional site would be implemented.

In addition to standard frequency reuse, LTE/LTE-Advanced radio planning can also employ SFR (Soft Frequency reuse). To explain the concept of SFR, it is first best to describe FFR (Fractional Frequency Reuse) and PFR (Partial Frequency Reuse) schemes. In this two network technologies, OFDMA (Orthogonal Frequency Division Multiple Access) and SC-FDMA (Single Carrier - Frequency Division Multiple Access) are defined. These both utilize 15KHz subcarriers which are then grouped into PRB (Physical Resource Blocks), each containing 12 subcarriers equating to 180KHz of spectrum. The figure 1.24 presents this concept.

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Figure 1.24. The utilization of 15KHz subcarriers.

There are various options how these Physical Resource Blocks can be

allocated, as well as implemented for FFR, PFR and SFR. Fractional and partial frequency reuse schemes are both fundamentally based on allocating a number of these PRBs in a sector. The main issue with these is that they limit the maximum throughput available to a user - since they are not able to allocate the full bandwidth.

In comparison, the concept of Soft Frequency Reuse enables the system to maximize the capacity of the network by enabling each sector to utilize the full bandwidth. To do this, SFR adjusts the power allocated to certain PRB’s in order to mitigate ICI (Inter Cell Interference). It also enables the eNB to allocate the full bandwidth (all PRBs at a lower power) to users close to the cell, thereby achieving higher peak rates. This process is shown in Figure 1.25.

Figure 1.25. The Soft frequency reuse.

In addition, the LTE/LTE-Advanced system includes ICIC (Inter-cell

Interference Coordination) techniques which enable the eNB (Evolved Node B),

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via the X2 interface (eNB to eNB), to pass overload and high interference information. This in turn may be used by the eNB to dynamically adjust the number and power of PRBs allocated in a cell. In the following figure 1.26 the above techniques are illustrated.

Figure 1.26. Inter-cell Interference Coordination technique.

Another capability being planned for LTE-Advanced is relays as shown in Figure 1.27. The idea is to relay frames at an intermediate node, resulting in much better in-building penetration, and with better signal quality, user rates will be much improved. Relay nodes can also improve cell-edge performance by making it easier to add picocells at strategic locations. Relays provide a means for lowering deployment costs in initial deployments in which usage is relatively low. As usage increases and spectrum needs to be allocated to access only, operators can then employ alternate backhaul schemes.

Figure 1.27. LTE-Advanced Relay.

The final phase of the Radio Frequency planning and deployment process

involves continuous optimisation of the Radio Frequent plan to accommodate for changes in the environment or additional service requirements (e.g. additional coverage or capacity). This phase starts from initial network deployment and involves collecting measurement data on a regular basis that could be via drive testing or centralised collection. The data is then used to plan new sites or to optimize the parameter settings (e.g. antenna orientation, downtilting, frequency plan) of existing sites.

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1.8. Spectrum management (ITU WRC 2012) Spectrum continues to be one of the most important issues facing the

industry. There are two issues to consider. One is the limited amount of spectrum available to support this dynamic industry and the other is how the industry is responding to take advantage of available technology.

Given that spectrum is a limited resource, the industry is undertaking the following initiatives to leverage all available spectrum:

� Increasing the spectral efficiency of technologies to continually increase the bits per second of data bandwidth for every available Hertz.

� Adapting specifications to enable operation of UMTS-HSPA and LTE/LTE-Advanced in all available bands.

� Designing both FDD and TDD versions of technology to allow operation in both paired and unpaired bands.

� Designing carrier aggregation techniques in HSPA+ and LTE-Advanced that bonds together multiple radio channels (both intra- and inter-frequency bands) to improve both peak data rates and efficiency.

� Deploying as many new cells (large and small) as is feasible.

It might be thought that new technologies such as small cells and smart antennas would obviate the need for spectrum. These technologies, however, are already on the roadmap for 3GPP evolution and, by themselves, do not sufficiently increase capacity to meet growing demand.

ITU World Radiocommunication Conferences (WRC), held every three or four years, are mandated to review and revise the Radio Regulations, the international treaty governing the use of radio-frequency spectrum (spectrum management) and satellite orbit resources. The agenda of a world radio-communication conference may include any other question of a worldwide character within the competence of the conference.

The WRC for 2012 took place in Geneva, Switzerland, from 23 January up to 17 February 2012, and was triggering event for the radio communication world and the frequency management sphere. The unprecedented number of proposals (more than 1700) addressing the various items on the WRC-12 agenda cover almost all radio services and applications, and illustrated the importance of this conference to governments and businesses.

The scope and complexity of the WRC-12 agenda make it impossible to consider all the items in a section as brief as this. And in summarizing the main topics to be dealt with by the conference, the specific concerns and interests of some groups or entities will inevitably be neglected. With those caveats in mind, here shortly we can summarize WRC-12 (for more details see the references), and we can say that it focus on:

� the review and possible revision of the international regulatory framework for radiocommunications, in order to reflect in the Radio Regulations the increasing convergence of radio services arising from the rapid evolution of information and communication technologies (ICT), and to adapt to new and potentially disruptive technologies such as software-defined and cognitive radio systems or short-range devices;

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� the management of satellite orbits and associated spectrum resources, for which the increasing demand may soon exceed current availability;

� the allocation of scarce radio-frequency spectrum to provide new opportunities for radiocommunication services, including those for the safety and security of maritime and aeronautical transport, as well as those dedicated to scientific purposes related to the environment, and to disaster prediction, mitigation and relief;

� the introduction and development of mobile broadband and other advanced technologies, including the use of the digital dividend resulting from the switchover from analogue to digital terrestrial television broadcasting and the development of advanced digital satellite broadcasting applications.

Other topical subjects to be addressed include science, radiodetermination and radionavigation-satellite matters. The conference also has the task of identifying items for the agenda of the next conference, which is scheduled to take place in 2015.

Moreover, can the current international regulatory framework adequately meet the changing requirements for radio communication spectrum in a way that allows innovative technologies to be implemented in a timely manner? The conference is answering that question. The corresponding agenda item aims at addressing changes to the Radio Regulations that will make them more responsive to new technological developments and convergence. Discussions on this subject started in WRC-03, and of course they are concluded at WRC-12.

One of the most complex topics regarding satellite regulations that the conference is likely to encounter concerns a series of procedures, processes and provisions that no longer seem to be aligned with the principles on which they were based. This concerns, in particular, the principle of equitable access contained in Article 44 of the ITU Constitution. The procedures in the spotlight include those related to the processes for publication, coordination, notification, recording, bringing into use, suspension and due diligence applicable to satellite networks. Voluminous and intricate proposals are tabled, and each proposed change in the procedures could affect current and future satellite operations. This item is likely to occupy the conference throughout its duration, and the reports by the Radiocommunication Bureau and the Radio Regulations Board will help to move these discussions forward. The 22.0 GHz band is one of the most favourable frequency bands for advanced digital satellite broadcasting applications, which require larger bandwidth capacity than ever needed before. These applications include ultra-high definition television, three-dimensional television, digital multimedia video information systems, multi-channel high definition television, large screen digital imagery, and extremely high resolution imagery. These applications have been extensively studied in ITU–R to enhance the broadcasting service. Despite the complexity of this area, the conference is likely to make permanent arrangements for use of the 21.4–22 GHz band by the broadcasting-satellite service, to facilitate use of this band for advanced digital satellite broadcasting applications which require larger bandwidth capacity.

At WRC-07, the band 790–862 MHz was allocated to the mobile service in Region 1 (Africa and Europe), complementing previous allocations to that service in Regions 2 (Americas) and 3 (Asia and Australasia), and was identified for

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international mobile telecommunications (IMT) worldwide. At that time, concerns were raised about the protection of services (mainly broadcasting and aeronautical radionavigation services) that were already allocated in this frequency band in the event that neighbouring administrations would implement mobile service. WRC-12 will therefore consider the results of sharing studies in this band to ensure the adequate protection of the services involved, and take appropriate action. In an unprecedented effort to resolve this difficult problem, the administrations of CEPT and RCC have adopted a pragmatic approach by developing and concluding a series of bilateral frequency coordination agreements that are expected to smooth out the opposing views which had initially been expressed on the compatibility between the mobile and the aeronautical radionavigation services in this band.

The studies and discussions on this agenda item have also highlighted the need in a number of Region 1 countries to urgently review the WRC-07 allocation to the mobile service in the UHF band to face the growing demand for mobile broadband. Pressure is therefore likely to grow in favour of a worldwide mobile allocation of the 700 MHz band, which is being considered in Regions 2 and 3 for the digital dividend.

Furthermore, the aeronautical community is seeking to facilitate the introduction of new aeronautical mobile systems in the bands 112–117.975 MHz, 960–1 164 MHz and 5 000–5 030 MHz. These systems provide radio links that are critical for the safety and regularity of flights, and surface communications at airports. The ITU–R compatibility studies showed that sharing is generally possible. The use of the 1.5/1.6 GHz bands by the aeronautical mobile-satellite (route) service has priority with regard to other mobile-satellite service systems. This is required to ensure interference-free communications with aircraft, taking into account the safety of life aspects of such links. At present, this priority is established through multilateral or bilateral frequency coordination meetings between mobile-satellite service operators. Proposals to WRC-12 suggest additional procedures to resolve concerns that have been expressed about the ability of this practice to accommodate aeronautical requirements. Also, the WRC-12 will consider spectrum requirements and possible regulatory actions, including the identification of globally harmonized spectrum, in order to support the safe operation of unmanned aircraft systems in the non-segregated airspace used by civil aviation. Although unmanned aircraft systems have traditionally been used in segregated airspace where separation from other air traffic can be assured, administrations expect broad deployment of unmanned aircraft systems in non-segregated airspace alongside manned aircraft.

The development of unmanned aircraft systems is based on recent technological advances in aviation, electronics and structural materials, making the economics of unmanned aircraft system operations more favourable, particularly for repetitive, routine and long-haul and long-duration applications. The required spectrum will be used for command and control of unmanned aircraft, for relay of air-traffic control communications, and for relay of sense and avoid data. The unmanned aircraft systems will be composed of a terrestrial component (radio links between the unmanned aircraft and its control station)

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and a satellite component (radio links between satellite and unmanned aircraft control station, and between satellite and unmanned aircraft).

Moreover, the main topic to be discussed under the terrestrial component is possible new allocations to the aeronautical mobile (route) service in all or some portions of the bands 5 000–5 150 MHz and 15.4–15.5 GHz. The main topics relating to the satellite component are, first, the use of communication links within existing allocations to the aeronautical mobile-satellite (route) service, and second, the use of existing fixed-satellite service, mobile-satellite service and aeronautical mobile-satellite service allocations for communication links between the unmanned aircraft and satellite, and between the unmanned aircraft control station and satellite. There is a general understanding of the pressing need for allocations for unmanned aircraft systems, particularly for the terrestrial component, and the discussion may well centre on the exact band and amount of spectrum. Concerning maritime safety, WRC-12 is expected to adopt special measures to enhance maritime safety systems for ships and ports. Enhancements are proposed in three main areas to:

� provide satellite detection of signals from automatic identification systems on board ships (by adopting a new allocation to the mobile-satellite service around 156 MHz for satellite detection of automatic identification system signals, to provide global ship-tracking and enhance search and rescue);

� improve the broadcasting of safety and security information for ships and ports (by making a worldwide allocation to the maritime mobile service in the 495–505 kHz band as well as a regional allocation in 510–525 kHz band in Region 2 — which would enhance transmission of safety and security information in ports and coastal waters);

� improve VHF communications for port operations and ship movement (it is planned to revise Appendix 18 of the Radio Regulations in order to implement new digital technologies in the band 156–174 MHz and increase the number of simplex channels to make more channels available for the ports with heavy traffic where communications are congested).

Given the existing situation, the global maritime community has agreed on special measures to enhance maritime safety systems for ships and ports, recognizing that additional satellite channels may be required to enhance and accommodate global ship tracking capabilities. Everyone is keen to agree on the proposed methods and options.

On the other side, several WRC-12 agenda items are related to important environmental topics, in particular the use of ICT in combating climate change and mitigating its effects, and in predicting natural disasters and facilitating relief efforts. Since the 1970s, interest in and use of oceanographic radar operating in the 3 to 50 MHz range has increased significantly. Preparatory work has identified potential spectrum allocations in terms of both compatibility with other users and effectiveness of ocean measurements. The need for additional data to mitigate the effects of disasters, including tsunamis, to understand climate change, and to ensure safe maritime travel has led to the consideration of the operational use of oceanographic radar networks on a global basis. Increased reliance on the data from these systems for maritime safety and disaster response, as well as for oceanographic, climatological and meteorological

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operations, has driven the need to improve the regulatory status of the spectrum used by oceanographic radars while taking into account the protection of existing allocated services. The ITU membership seems to fully support making allocations for this application.

Long-range lightning detection using observations near 10 kHz has been performed since 1939, originally with a labour-intensive system for measuring the direction from which signals were received. Since 1987, there has been an automated system to derive strike locations: a distributed network of ground-based sensors can locate the origin of the lightning strike, using the time differences between the arrival of the lightning emission at the individual sensor sites. The maximum spectral emissions from lightning strikes are between 9 and 20 kHz. At these frequencies, the sky waves reflected off the ionosphere propagate for long distances with relatively little attenuation. It is thus possible to receive the emissions from a lightning strike at thousands of kilometres from the strike location. The conference will consider the possibility of an allocation in the frequency range below 20 kHz for passive systems for lightning detection in the meteorological aids service. Operational non-geostationary meteorological satellite (MetSat) systems now use the band 7 750–7 850 MHz to gather instrument data to dedicated earth stations with a bandwidth of up to 63 MHz. The measurements and observations performed by the MetSat systems provide the data used in operational meteorology, climate monitoring and detection of global climatic changes. The data have significantly improved operational meteorology, in particular with respect to numerical weather prediction. The next generation of non-geostationary MetSat systems will have to provide continuity of data, aligned to the measurements and observations performed by the current systems. These future systems will also perform additional and higher-resolution measurements and observations of meteorological and climate parameters, requiring much higher data rates and bandwidth as compared to current systems. The necessary bandwidth for future non-geostationary MetSat systems to fulfil those requirements would be up to 150 MHz. The conference is expected to support the corresponding extension of bandwidth.

Finally, the WRC-12 conference considers the need for regulatory action to foster the development of advanced wireless systems and applications, such as software-defined radio, cognitive radio systems, short-range devices, fixed wireless systems above 71 GHz, gateway links for high-altitude platform stations, and electronic news gathering. The Radio Regulations, in their current form, are generally considered to provide an appropriate framework for the development of these systems and applications. Specific requirements can be addressed through the standardization work of the ITU–R study groups.

Previous WRCs have successfully provided for timely enhancements to the Radio Regulations to cope with technical and regulatory developments, and to address the needs of the ITU membership for the allocation, management and use of the radio-frequency spectrum and orbit resources. In keeping with the tradition of goodwill and international cooperation which has always prevailed under these circumstances, the WRC-12 undoubtedly is another successful milestone in the history of the ITU.

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1.9. Business models and forecasts for LTE/LTE-Advanced The Telecom Market has seen tremendous changes and this trend will

certainly continue. New entrants and existing operators continue to adopt and integrate new Telecom technologies, reinventing and reinvigorating their business models. Today we are seeing the traditional Telecom boundaries blurring with traditional Mobile Operators moving into the fixed line broadband business and Fixed Operators looking to expand their reach outside of the home, towards mobile broadband internet. At the LTE World Summit in 2008, the whole telecom industry weighed the choice between LTE and WiMAX. At that time, LTE was only vaguely understood, and much was made of its fast 150Mbps downlink rate. But, at the LTE World Summit in 2009, the industry came to understand the importance of LTE and began discussing the challenges faced by LTE. Such challenges included the 2.6GHz band coverage and voice over LTE (VoLTE). As we said before, the radio technologies are moving from voice to data, from narrowband to mobile broadband, from single-mode to multimode, from multiple technologies to key technologies dominated by OFDM and MIMO. However, there is only one goal underlying these trends: to provide more wireless bandwidth. LTE and moreover, the LTE-Advanced are important stepping stones on this evolutionary path.

But, firstly let we see what has driven the rapid development of LTE/LTE-Advanced in recent years? One of the most important factors has been growing market demands for wireless data services. Users need fast and convenient data services through their terminals, and operators need all-IP networks for high-speed data connectivity. Competition between fixed-line and mobile operators has also driven the evolution of radio technologies. Moreover, the growth of wireless data traffic has brought in more revenue for operators which have, in turn, pushed forward radio technologies. Another driving force has been operators seeking higher benefits and lower costs.

First of all, one significant question is stepping before the telecom operators: When to deploy LTE/LTE-Advanced? The timing of LTE network deployment is affected by the progress of LTE/LTE-Advanced standardization and maturity of commercial LTE terminals and systems and also by the economic level, demands for wireless data services, user habits, and spectrum licenses issued by governments. This means the timing of LTE deployment may vary from country to country. Only deploying at the right time brings the best return on investment. This is fundamental to a profitable LTE business model. As evidenced by the premature deployment of 3G, there are risks related to unfinalized 3GPP specifications, poor interoperability (even between terminals and systems of the same manufacturer), mobility of 2G and 3G, poor coverage, and lack of terminals and services. These issues can well be regarded as a checklist for successful LTE deployment. So too, late deployment might mean that good market opportunities slip by. So if we want to answer of the question: How should an operator decide the proper time to deploy LTE? The answer is: This is a hard question. However, the following points should be considered:

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� 3G services have grown rapidly, wireless broadband data traffic is

surging, and user habits have been fully developed. Sales of 3G terminals and data cards have also grown rapidly.

� Wireless data revenues have risen substantially and now account for a larger portion of operators’ total income. Statistics collected by Qualcomm from Vodafone, Telstra, Verizon, and AT&T show that wireless data services increased by an average of 30% from 2008 to 2009. These tier-one mobile operators are all running LTE trials. Verizon announced its commercial LTE network in December 2010.

� Wireless data volume exceeds that of voice, and data revenue is now greater than voice revenue. CSL, Hong Kong’s largest mobile operator, has seen an explosive growth in data traffic since the launch of commercial HSPA+ in March 2009. CSL continued its LTE cooperation with ZTE, aiming at future mobile applications that can meet strong demands for high-speed broadband services.

� Trial and commercial LTE plans of competitors should be considered. Tier-one operators, multinationals, and the largest operator in a country are always leaders in LTE deployment. LTE trials are usually run to build a high-end brand image. The second largest operator in a country also usually develops LTE in order to catch up with or even surpass the leader.

An LTE network provides a data rate of up to 100Mbps in the downlink and 50Mbps in the uplink. On the other side, LTE-Advanced provides a data rate of up to 100 Mbit/s for high and 1 Gbit/s for low mobility were established as targets for research. These high data rates greatly enhance user experience. With greater spectrum efficiency, simpler architecture and the ability to re-use low frequency spectrum, LTE/LTE-Advanced will boast much improved capacity for both voice and data delivered at a significantly lower cost compared to legacy technologies. These improvements contribute to a lower cost per bit for both voice and data services. In fact, some simulations are showing voice services on UMTS to be several times more expensive than LTE. The relative total cost of ownership (TCO) for LTE by Subscribers GB/month also presents significant improvement opportunities over existing 3.5 G networks.

Moreover, the studies on LTE/LTE-Advanced business models are ongoing, and recent studies have focused on mobile broadband Internet. In the foreseeable future, LTE/LTE-Advanced business models may be found in high-speed and high-bandwidth Internet services, mobile Internet platforms, on-line wireless communities, and Machine-to-Machine (M2M) communications.

LTE/LTE-Advanced are supplying the users with a high-speed service experience. According to some surveys, those who subscribed to LTE/LTE-Advanced early had begun to like the technology. Over 90% of those surveyed were originally 3G users and 43% owned iPhones. 65% used LTE to supplement fixed bandwidth and 54% would not consider turning back to 3G. The new technology is shaping mobile Internet usage habits: 26% of those surveyed said they would use their mobile more for work, 23% downloaded larger files than

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before, 19% would watch on-line TV or streaming movies, and 16% were using Internet more often as a result of subscribing to LTE.

All this shows that users are demanding better mobile broadband experience whenever conditions allow. Once they have the improved experience, it is hard to turn back to the lower-rate service. As one old saying goes, “It is hard to become frugal after being accustomed to luxury.” The emergence of cloud computing is further boosting the prosperous development of Internet data services.

Moreover, from voice only mobile phones to multimedia phones and iPhone and Android terminals, mobiles have tended to develop into mobile broadband Internet platforms (see figure 1.28). This is also the developmental trend of computers. Terminals are evolving into Internet service platforms where all processing is completed via service plug-ins to the cloud and using a background high-speed mobile data network.

Figure 1.28. Computers and mobile devices evolving towards mobile broadband internet

platforms.

The ultimate goal of communications is to connect anything or anyone to anything or anyone from anywhere at any time at any place. New technologies such as network convergence, all-IP, and RFID have made this goal possible. LTE and LTE-Advanced are important stepping stones in the path toward this ultimate goal. Mobile Internet platforms have been introduced to provide users with fast and easy access to a variety of local and Internet applications. People will change from using fixed terminals to using mobile terminals and from point-to-point connections to online communities and games circles.

With the trend towards high-bandwidth all-IP networks, M2M technology—which allows the flow of data to be transferred in real time between machines or between people and machines using wireless networks and background server networks―has been commercially deployed in Europe, Korea, and Japan. M2M applications can be found in safety monitoring, mechanical and repair service, public transportation, fleet management, industrial automation, and citywide

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information networks. Operators currently providing M2M services include BT, Vodafone UK, T-Mobile, NTT-Docomo, and SK. The development of M2M services has just started in China.

Finally, the evolution in the telecommunications industry is unceasing. There will be challenges accompanied by opportunities. In the LTE/LTE-Advanced age, operators, regulators and equipment suppliers must understand the latest changes and quickly adapt by preparing for new business models and new sources of profit.

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[1] Mobile Broadband Explosion, Rysavy Research/4G Americas, August 2012

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[4] 3GPP LTE : http://www.radio-electronics.com/info/cellulartelecomms/lte-long-term-evolution/3g-lte-basics.php

[5] 3 GPP LTE-Advanced: http://www.radio-electronics.com/info/cellulartelecomms/lte-long-term-evolution/3gpp-4g-imt-lte-advanced-tutorial.php

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[9] ITU Paves the Way for Next-Generation 4G Mobile Broadband Technologies, ITU, 21 October 2010.

[10] 3GPP TR 23.882: ‘3GPP system architecture evolution, report on technical options and conclusions’.

[11] ETSI: ‘Long term evolution of the 3GPP radio technology’ and ‘System architecture evolution’.

[12] Sayan Kumar Ray, “Fourth Generation (4G) Networks: Roadmap- Migration to the Future”, IETE Technical Review Vol 23, No 4, pp 253-265, July-August 2006.

[13] Savo G Glisic, “Advanced Wireless Networks: 4G Technology”, John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England, 2006.

[14] Sujuan Feng and Eiko Seidel, Self-Organizing Networks (SON) in 3GPP Long Term Evolution, Nomor Research GmbH, Munich, Germany, May 2008.

[15] Self-Organizing Network (SON): Introducing the Nokia Siemens Networks SON Suite – an efficient, future-proof platform for SON, Nokia Siemens Networks, 2009.

[16] Modar Safir Shbat and Vyacheslav Tuzlukov, Combined Radio Resource Management for 3GPP LTE Networks, Advances in Mathematical and Computational Methods, ISSN: 2160-0643 Volume 1, Number 1, September, 2011.

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Redana, Roberto Rossi, Andreas Saul, Rainer Schoenen, Pawel Sroka, “D1.1 Initial Report on Advanced Radio Resource Management”, CELTIC / CP5-026, January 2009.

[18] LTE-Advanced: Future of Mobile Broadband, Tata Consultancy Services Limited, 2009.

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