RESEARCH PROPOSAL

LTE CORE NETWORK EVOLUTION

Introduction

Through the early researches the evolution has happened from analog mobile generation (1G) to the most recent implemented third generation (3G). The new mobile generation communication systems assure to provide improved voice communication experience but try to. The research is intended to provide users with a new set of services. It is now left to us to explore new demands and to find new ways to extend the mobile systems communication architecture. The first step taken towards this aspect is the 2.5G, which gave users access to a data network (e.g. Internet access, MMS - Multimedia Message Service). However, users and applications demanded more communication power. As a response to this demand a new generation with new standards and architecture has been developed - 3G.

1. The First Generations (1G) and Second Generation (2G)

The first operational cellular communication system was deployed in the Norway in 1981 and was followed by similar systems in the US and UK. These systems provided voice transmissions by using frequencies around 900 MHz and analogue modulation. The second generation (2G) of the wireless mobile network was based on low-band digital data signaling. The most popular 2G wireless technology is known as Global Systems for Mobile Communications (GSM). FDMA (Frequency Division Multiple Access), which is a standard that lets multiple users access a group of radio frequency bands and eliminates interference of message traffic, is used to split the available bandwidth into carrier frequencies. Each frequency is then divided using a TDMA (Time Division Multiple Access) scheme into eight timeslots and allows eight simultaneous calls on the same frequency. This protocol allows large numbers of users to access one radio frequency by allocating time slots to multiple voice or data calls. TDMA breaks down data transmission, such as a phone conversation, into fragments and transmits each fragment in a short burst, assigning each fragment a time slot. With a cell phone, the caller does not detect this fragmentation. Today, GSM systems operate in the 900MHz and 1.8 GHz bands throughout the world with the exception of the Americas where they operate in the 1.9 GHz band. Similarly CDMA is the technique used in GSM which uses spread spectrum technology to break up speech into small, digitized segments and encodes them to identify each call. CDMA distinguishes between multiple transmissions carried simultaneously on a single wireless signal. It carries the transmissions on that signal, freeing network room for the wireless carrier and providing interference-free calls for the user. Several versions of the standard are still under development. CDMA promises to open up network capacity for wireless carriers and improve the quality of wireless messages and users' access to the wireless airwaves. Whereas CDMA breaks down calls on a signal by codes, TDMA breaks them down by time. The result in both cases is an increased network capacity for the wireless carrier and a lack of interference for

2014-15 Prof.Deepa.T.P. AcITPage 1

RESEARCH PROPOSAL

the caller. While GSM and other TDMA-based systems have become the dominant 2G wirelesses technologies, CDMA technology are recognized as providing clearer voice quality with less background noise, fewer roped calls, enhanced security, greater reliability and greater network capacity.

The Second Generation (2G) wireless networks mentioned above are also mostly based on circuit switched technology, are digital and expand the range of applications to more advanced voice services. 2G wireless technologies can handle some data capabilities such as fax and short message service at the data rate of up to 9.6 kbps, but it is not suitable for web browsing and multimedia applications.

So-called ‘2.5G’ systems recently introduced enhance the data capacity of GSM and mitigate some of its limitations. These systems add packet data capability to GSM networks, and the most important technologies are GPRS (General Packet Radio Service) and WAP (Wireless Application Protocol). WAP defines how Web pages and similar data can be passed over limited bandwidth wireless channels to small screens being built into new mobile telephones. At the next lower layer, GPRS defines how to add IP support to the existing GSM infrastructure. GPRS provides both a means to aggregate radio channels for higher data bandwidth and the additional servers required to off-load packet traffic from existing GSM circuits. It supplements today's Circuit Switched Data and Short Message Service. GPRS is not related to GPS (the Global Positioning System), a similar acronym that is often used in mobile contexts. Theoretical maximum speeds of up to 171.2 kilobits per second (kbps) are achievable with GPRS using all eight timeslots at the same time. This is about ten times as fast as current Circuit Switched Data services on GSM networks. However, it should be noted that it is unlikely that a network operator will allow all timeslots to be used by a single GPRS user. Additionally, the initial GPRS terminals (phones or modems) are only supporting only one to four timeslots. The bandwidth available to a GPRS user will therefore be limited

2. Third generation networks (3G)

2G wireless systems are voice-based. GSM includes short message service (SMS), enabling text messages of up to 160 characters to be sent, received and viewed on the handset. Most 2G systems also support some data over their voice paths, but at painfully slow speeds usually 9.6 Kb/s or 14.4 Kb/s. So in 2G, voice remains king while data is already dominant in wire line communications. And, fixed or wireless, all are affected by the rapid growth of the Internet. Planning for 3G started in the 1980s. Initial plans focused on multimedia applications such as video-conferencing for mobile phones. Today's 3G specifications call for 144 Kb/s while the user is on the move in an automobile or train, 384 Kb/s for pedestrians, and ups to 2 Mb/s for stationary users. That is a big step up from 2G bandwidth using 8 to 13 Kb/s per channel to transport speech signals. The second key issue for 3G wireless is that users will want to roam

2014-15 Prof.Deepa.T.P. AcITPage 2

RESEARCH PROPOSAL

worldwide and stay connected. Today, GSM leads in global roaming. Because of the commonness of GSM, users can get comprehensive coverage in Europe, parts of Asia and some U.S. coverage. A key goal of 3G is to make this roaming capacity universal. A third issue for 3G systems is capacity. As wireless usage continues to expand, existing systems are reaching limits. Cells can be made smaller, permitting frequency reuse, but only to a point. The next step is new technology and new bandwidth. International Mobile Telecommunications-2000 (IMT-2000) is the official International Telecommunication Union name for 3G and is an initiative intended to provide wireless access to global telecommunication infrastructure through both satellite and terrestrial systems, serving fixed and mobile phone users via both public and private telephone networks. GSM proponents put forward the universal mobile telecommunications system (UMTS), an evolution of GSM, as the road to IMT-2000. Alternate schemes have come from the U.S., Japan and Korea. Each scheme typically involves multiple radio transmission techniques in order to handle evolution from 2G. Agreeing on frequency bands for IMT-2000 has been more difficult and the consensus included five different radio standards and three widely different frequency bands. They are now all part of IMT-2000. To roam anywhere in this "unified" 3G system, users will likely need a quintuple-mode phone able to operate in an 800/900 MHz band, a 1.7 to 1.9 GHz band and a 2.5 to 2.69 GHz band.

Third-generation wireless also requires new infrastructure. There are two mobility infrastructures in wide use. GSM has the mobile access protocol, GSM-MAP. The North American infrastructure uses the IS-41 mobility protocol. These protocol sets define the messages passed between home location registers and visitor location registers when locating a subscriber and the messages needed to deal with hand-offs as a subscriber moves from cell to cell. 3G proponents have agreed on an evolution path so that existing operators, running on either a GSM-MAP or an IS-41 infrastructure, can interoperate. But the rest of the landline infrastructure to support IMT-2000 will be in flux in the near future. The IMT-2000 family is illustrated in this figure.

2014-15 Prof.Deepa.T.P. AcITPage 3

RESEARCH PROPOSAL

UMTS use the radio technology called W-CDMA (Wideband Code Division Multiple Access). W-CDMA is characterized by the use of a wider band than CDMA. W-CDMA has additional advantages of high transfer rate, and increased system capacity and communication quality by statistical multiplexing. W-CDMA utilizes efficiently the radio spectrum to provide a maximum data rate of 2 Mbps. With the advent of mobile Internet access, suddenly the circuit-based backhaul network from the base station and back has to significantly change. 3G systems are IP-centric and will justify an all-IP infrastructure. There will be no flip to 3G, but rather an evolution and, because of the practical need to re-use the existing infrastructure and to take advantage of new frequency bands as they become available, that evolution will look a bit different depending on where you are. The very definition of 3G is now an umbrella, not a single standard, however, the industry is moving in the right direction towards a worldwide, converged, network. Meanwhile, ever-improving DSPs will allow multi-mode, multi-band telephones that solve the problem of diverse radio interfaces and numerous frequency bands. When one handset provides voice and data anywhere in the world, that will be 3G no matter what is running behind the scenes.

3. Fourth generation networks (4G)

The objective of the 3G was to develop a new protocol and new technologies to further enhance the mobile experience. In contrast, the new 4G framework to be established will try to accomplish new levels of user experience and multi-service capacity by also integrating all the mobile technologies that exist (e.g. GSM - Global System for Mobile Communications, GPRS -

2014-15 Prof.Deepa.T.P. AcITPage 4

RESEARCH PROPOSAL

General Packet Radio Service, IMT-2000 -International Mobile Communications, Wi-Fi - Wireless Fidelity, Bluetooth). NTT DoCoMo, that has already a wide base of 3G mobile users, estimates the number of mobile communication terminals to grow in Japan from the actual 82.2 million to more than 500 million units by 2010. A multi-service platform is an essential property of the new mobile generation, not only because it is the main reason for user transition, but also because it will give telecommunication operators access to new levels of traffic. Voice will lose its weight in the overall user bill with the raise of more and more data services. Low-bit cost is an essential requirement in a scenario where high volumes of data are being transmitted over the mobile network. With the actual price per bit, the market for the new high demanding applications, which transmit high volumes of data (e.g. video), is not possible to be established. Also necessary is a QoS framework that enables fair and efficient medium sharing among users with different QoS requirements, supporting the different priorities of the services to be deployed. The core of this network should be based in Internet Protocol version 6 – IPv6, the probable convergence platform of future services (IPv4 does not provide a suitable number of Internet addresses). The network should also offer sufficient reliability by implementing a fault-tolerant architecture and failure recovering protocols. Migrating to 4G

The fact that 4G mobile networks intend to integrate almost every wireless standard already in use, enabling its simultaneous use and interconnection poses many questions not yet answered. The research areas that present key challenges to migrate current systems to 4G are many but can be summarized in the following: Mobile Station, System and Service. To be able to use 4G mobile networks a new type of mobile terminals must be conceived. The terminals to be adopted must adapt seamless to multiple wireless networks, each with different protocols and technologies. Auto reconfiguration will also be needed so that terminals can adapt to the different services available. This adaptation may imply that it must download automatically configuration software from networks in range. Moreover terminals must be able to choose from all the available wireless networks the one to use with a specific service. To do this it must be aware of specifications of all the networks in terms of bandwidth, QoS supported, costs and respect to user preferences. Terminal mobility will be a key factor to the success of 4G networks. Terminals must be able to provide wireless services anytime, everywhere. This implies that roaming between different networks must be automatic and transparent to the user. There are two major issues in terminal mobility, location management and handoff management. Location management deals with tracking user mobility, and handling information about original, current and (if possible) future cells. Moreover it must deal with authentication issues and QoS assurances. Handoff management primary objective is to maintain the communications while the terminal crosses wireless network boundaries. In addition, 4G networks, in opposition to the other mobile generations, must deal with vertical and horizontal handoffs, i.e., a 4G mobile client may move between different types of wireless networks (e.g. GSM and Wi-Fi) and between cells

2014-15 Prof.Deepa.T.P. AcITPage 5

RESEARCH PROPOSAL

of the same wireless network (e.g. moving between adjacent GSM cells). Furthermore, many of the services available in this new mobile generation like videoconference have restrict time constraints and QoS needs that must not be perceptible affected by handoffs. To avoid these problems new algorithms must be researched and a prevision of user mobility will be necessary, so as to avoid broadcasting at the same time to all adjacent antennas what would waste unnecessary resources. Another major problem relates to security, since 4G pretends to join many different types of mobile technologies. As each standard has its own security scheme, the key to 4G systems is to be highly flexible. Services also pose many questions as 4G users may have different operators to different services and, even if they have the same operator, they can access data using different network technologies. Actual billing using flat rates, time or cost per bit fares, may not be suitable to the new range of services. At the same time it is necessary that the bill is well understood by operator and client. A broker system would be advisable to facilitate the interaction between the user and the different service providers. Another challenge is to know, at each time, where the user is and how he can be contacted. This is very important to mobility management. A user must be able to be reached wherever he is, no matter the kind of terminal that is being used. This can be achieved in various ways one of the most popular being the use of a mobile-agent infrastructure. In this framework, each user has a unique identifier served by personal mobile agents that make the link from users to Internet.

The fourth generation (4G) of wireless cellular systems has been a topic of interest for quite a long time, probably. Since the formal definition of third generation (3G)systems was officially completed by the International Telecommunications Union Radio communication Sector(ITU-R)in 1997. A set of requirements was specified by the ITU-R regarding minimum peak user data rates in different environments through what is known as the International Mobile Telecommunications 2000 project(IMT-2000).The requirements included 2048 kbps for an indoor office, 384kbps for outdoor to indoor pedestrian environments, 144kbps for vehicular connections and 9.6kbps for satellite connections. With the target of creating a collaboration entity among different telecommunications associations, the 3rdGeneration Partnership Project (3GPP) was established in 1998. It started working on the radio, core network, and service architecture of a globally applicable 3G technology specification. Even though 3G data rates were already real in theory, initial systems like Universal Mobile Telecommunications System (UMTS) did not immediately meet the IMT 2000 requirements in their practical deployments. Hence the standards needed to be improved to meet or even exceed them. The combination of High Speed Downlink Packet Access (HSDPA) and the subsequent addition of an Enhanced Dedicated Channel, also known as High Speed Uplink Packet Access (HSUPA),led to the development of the technology referred to as High Speed Packet Access (HSPA)or, moreinformally,3.5G. Motivated by the increasing demand for mobile broadband services with

2014-15 Prof.Deepa.T.P. AcITPage 6

RESEARCH PROPOSAL

higher data rates and Quality of Service (QoS), 3GPP started working on two parallel projects, Long Term Evolution (LTE) and System Architecture Evolution (SAE), which are intended to define both the radio access network (RAN) and the network core of the system, and are included in 3GPP Release8. LTE/SAE, also known as the Evolved Packet System (EPS), represents a radical step forward for the wireless industry that aims to provide a highly efficient, low-latency, packet optimized, and more secure service. The main radio access design parameters of this new system include OFDM (Orthogonal Frequency Division Multiplexing) waveforms in order to avoid the inter symbol interference that typically limits the performance of high-speed systems, and MIMO (Multiple-Input Multiple-Output) techniques to boost the data rates. At the network layer, an all-IP flat architecture supporting QoS has been defined. The world’s first publicly available LTE service was opened by Telia Sonerain the two Scandinavian capitals Stockholm and Oslo on December 14, 2009, and the first test measurements are currently being carried out.

OBJECTIVES

Need to ensure the continuity of competitiveness of the 3G system for the future User demand for higher data rates and quality of service Low complexity Avoid unnecessary fragmentation of technologies for paired and unpaired band operation Provide packet switching technology over wireless system by ensuring QoS parameters.

REVIEW OF LITERATURE

There are few past woks done on redesigning the 4G-LTE architecture wherein we have listed hew works that have supported to arrive at the present work. The first one being “The Evolution to 4G Cellular Systems: Architecture and Key Features of LTE-Advanced Networks” where the discussion is about the era of new wireless communications. Eventually it will penetrate into our daily life and change the way we live just like many technological innovations whose original research came from the life needs. To achieve these requirements, the society of 3rd Generation Partnership Project (3GPP) is presently evolving Long Term Evolution Advanced (LTE Advanced) as a development of the standard of LTE. The goal of this generation is to produce specifications for a new radio-access technology geared to higher data rates, low latency and greater spectral efficiency. LTE-Advanced is therefore not a new technology; it is an evolutionary step in the continuing development of LTE The description in this article is based on LTE release 10 and thus provides a complete description of the LTE-Advanced radio access from the bottom up. Also it provides a deeper insight into some of the technologies that are part of LTE and its evolution and introduces describing to the background for the development of the

2014-15 Prof.Deepa.T.P. AcITPage 7

RESEARCH PROPOSAL

LTE system, in terms of events, activities, organizations and other factors that have played an important role. This paper provides detailed coverage of the air-interface technologies and protocols that survived the analysis of the highly sophisticated technology evaluation process typically used in the LTE-Advanced networks.

The second paper referred was “4G LTE Technologies: System Concepts” where the discussion was about LTE (Long Term Evolution, or so called 4G) services from major US telcos, such as VERIZON, AT&T, T-Mobile, etc. These broadband wireless services claim to surpass current 3G cellular networks, paving the way to true wide area mobility, multimedia services while on-the-go and greater interactivity. In this white paper, the technical aspects of Long Term Evolution, its architecture, and its differences with earlier 3G systems.

METHODOLOGY

There are many architectures available to implement LTE out of which we have considered the Circuit-switched fallback (CSFB). So the feature of this will be enhanced to provide packet switching to voice calls with minimum latency.

LEARNING MODULE

Consider the present architectures for LTE wherein we find the three methods to implement it.

1. Voice over LTE (VoLTE)

This approach is based on the IP Multimedia Subsystem (IMS) network, with specific profiles for control and media planes of voice service on LTE defined by GSMA in PRD IR.92. This approach results in the voice service (control and media planes) being delivered as data flows within the LTE data bearer. This means that there is no dependency on (or ultimately, requirement for) the legacy Circuit Switch voice network to be maintained.

2. Circuit-switched fallback (CSFB)

In this approach, LTE just provides data services, and when a voice call is to be initiated or received, it will fall back to the circuit switched domain. When using this solution, operators just need to upgrade the MSC instead of deploying the IMS, and therefore, can provide services quickly. However, the disadvantage is longer call setup delay.

3. Simultaneous voice and LTE (SVLTE)

In this approach, the handset works simultaneously in the LTE and circuit switched modes, with the LTE mode providing data services and the circuit switched mode

2014-15 Prof.Deepa.T.P. AcITPage 8

RESEARCH PROPOSAL

providing the voice service. This is a solution solely based on the handset, which does not have special requirements on the network and does not require the deployment of IMS either. The disadvantage of this solution is that the phone can become expensive with high power consumption.

TESTING MODULE

The basic steps are as follows:

1. Test latency of CSFB LTE architecture.2. Convert the Circuit Switching mode to Packet Switching mode.3. Test the delay of conversion modes.4. Implement the packet switching mode over CSFB.5. Check the delay in the improved architecture.

EXPECTED OUTCOME

We can expect a new architecture that provides packet switching for voice calls with a very minimum latency.

References

[1] “Mobile cellular, subscribers per 100 people”, International Telecommunication Union Statistics, 2002 http://www.itu.int/ITU-D/ict/statistics/at_glance/cellular02.pdf

[2] Kim, Y., Jeong, B.J., Chung, J., Hwang, C., Ryu, J.S., Kim,K., Kim, Y.K., “Beyond 3G: Vision, Requirements, and Enabling Technologies”, IEEE Communications Magazine, March 2003, pp. 120-124

[3] ITU-R PDNR WP8F, “Vision, Framework and Overall Objectives of the Future Development of IMT-2000 and Systems beyond IMT-2000,” 2002.

[4] “2G – 3G Cellular Wireless data transport terminology”, Arc Electronics ww.arcelect.com/2G-3G_Cellular_Wireless.htm

[5] Schiller, J., “Mobile Communications”, slides http://www.jochenschiller.de/

[6] Tachikawa, Keiji, “A perspective on the Evolution of Mobile Communications”, IEEE Communications Magazine, October 2003, pp. 66-73

2014-15 Prof.Deepa.T.P. AcITPage 9

RESEARCH PROPOSAL

[7] Hui, Suk Yu, and Yeung, Kai Hau, “Challenges in the Migration to 4G Mobile Systems”, IEEE Communications Magazine, December 2003, pp. 54-59

[8]"An Introduction to LTE". 3GPP LTE Encyclopedia. Retrieved December 3, 2010.

[9]"Long Term Evolution (LTE): A Technical Overview". Motorola. Retrieved July 3, 2010.

[10] "Newsroom • Press Release". Itu.int. Retrieved 2012-10-28.

[11]"ITU-R Confers IMT-Advanced (4G) Status to 3GPP LTE" (Press release). 3GPP. 20 October 2010. Retrieved 18 May 2012.

[12] pressinfo (2009-10-21). "Press Release: IMT-Advanced (4G) Mobile wireless broadband on the anvil". Itu.int. Retrieved 2012-10-28.

[13] "Newsroom • Press Release". Itu.int. Retrieved 2012-10-28.

[14]"Work Plan 3GPP (Release 8)". 16 January 2012. Retrieved 1 March 2012.

2014-15 Prof.Deepa.T.P. AcITPage 10