4g

OPPORTUNITIES & THREATS FOR IMPLEMENTATION OF 4G CELLULAR NETWORKS.

ABSTRACT The emerging technologies today have opened a lot of issues in the user oriented service developments. Customers support technologies with cost effectiveness and easy to handle at the end of service provider are the major issues developing any system. Consequently similar effects can be seen in recent developments in cellular networks. Initially started with simply analog voice service (known as 1G), the cellular service today are expected to provide high quality smooth video interaction (known as 4G).Besides this , the high speed data transfer is also a major requirement for the same. And all these must be fulfilled anywhere, anytime whenever the user wants to access. Thus, as the demands increase, the technologies have to find a commercial way to implement the user demands with an adequate quality of service. Such requirements put a Challenge to develop the network fulfilling the requirements of 4G cellular networks. This paper concentrates on the requirements of 4G cellular networks and what are the opportunities and threats if such networks are implemented. Introduction The concept of cellular communication is not new in the sense that wireless technology was already in operation for TV broadcast, terrestrial microwave link, F.M.Radio, satellite communications, etc. But here the idea is new to renovate the old wireless technology in the form of small service areas (Zones) known as cells, thus the system is called cellular system. The concept of cellular was implemented initially to provide simple voice services only in analog domain. Then the technology moved towards the development of digital technology. Hence the older systems were analog while nowadays they are digital cellular systems. The technology evolved in steps of 1G, 2G, 2.5G, 3G and now 4G. As the user density and various demands for services like high speed data, audio ,video, seamless connectivity, service at any time, anywhere increases, it becomes much complex to implement in real time systems which can be treated as key problems to 4G cellular technology. People often say that it will be realized successfully but it is not so simple. We hope the reader will realize the opportunities and threats for making 4G systems operational worldwide soon after reading this paper.

Brief History of Past & Present Cellular Technologies: 1G (First Generation) Cellular Systems: Initially the cellular services were started with simple analog voice based services. The development of cellular technologies were started around 1970 and implemented in around 1984. All these systems use two separate frequency bands for (from base station to mobile) and reverse (from mobile to base station) links. Such a system is referred to as Frequency Division Duplex (FDD) scheme. The typical allocated overall bandwidth in each direction is 25MHz. The widely used spectrum for these systems is 800-900MHz bands. The system uses analog frequency modulation scheme. There are different standards adopted in different countries are simply due to lack of vision for a common universal service and opinion difference of various bodies responsible for deciding the standards for their own countries ,which led the major issues in realization and implementation of 4G networks today. Basic features of 1G cellular system are Voice Oriented Analog Cellular Service, Limited Local and Regional Coverage, Circuits Switched Network and Core Network was PSTN. 2G (Second Generation) Cellular Systems: The drawbacks in 1G and growing demands for seamless connectivity led the cellular industry to design the second generation cellular systems. Further the quality of service also improved by using digital cellular technology instead of analog. The development of 2G was started in 1980 and implemented in around 1991. Like 1G, the 2G networks still use FDD scheme. The widely used spectrum for these systems is 800-900MHz bands. Global System for Mobile (GSM), IS-95, Japanese Digital Cellular (JDC) and IS-54 are the major standards in this category. The Table 1 indicates the important properties of 2G cellular systems. Basic features of 2G Cellular System are voice and basic data service at low data speeds (14.4 kbps), circuit switched network for voice application, packet switched network for basic data applications, enhancement towards packet switching networks and high data rates, etc. 2G Cellular System offered international roaming facility. Core network was PSTN

Table 1: Properties of 2G cellular systems System Region Access

GSM Europe/Asia TDMA/FDD

IS-95 US/Asia CDMA/FDD

JDC Japan TDMA/GDD

IS-54 US TDMA/FDD

method Modulation

GMSK

SQPSK/OPSK

p/4-DQPSK

p/4-DQPSK

scheme Frequency

935-960

869-894

810-826

869-894

bands(MH

890-915

824-849

940-956

824-849

z) Carrier

200

1250

25

30

Spacing(K Hz) 2G+/3G (Third Generation) Cellular System 2G+ Cellular System: Present Cellular Technologies are some where around 2.5G also known as 2G+. The additional features of mixed services, increased capacity, flexible billing and personalization are implemented in the 2G+ system. The development was started in around 1985 and implemented in around 1999.Increased data rates (384kbps) allow users to communicate faster than the 2G Systems. Further the mobility is now worldwide instead of limited regions. Still there are different standard in different countries as discussed above, which led to restrict the user access to become worldwide. General Packet Radio Systems(GPRS) and Enhanced Data For Global Evolution(EDGE) are the technologies added in the 2G Systems to enhance the services provided and also to enhance data rate which is known 2G+. The Basic access technologies are (TDMA & FDMA), CDMA in these types of systems. GSM Standards apply combined TDMA + FDMA technology to increase the capacity of the system while IS-95 system uses WCDMA technology for the same purpose. Basic features of 2G+ cellular system are digital voice and data applications, packet & Circuit switched network, EDGE-GPRS in GSM and 1xRTT in CDMA technologies to provide data rates upto 384kbps, increased capacity and higher data rates compared to 2G systems. Core networks of PSTN and packet network User oriented services are introduced in 2G+ like flexible billing and personalization.

3G Cellular System: Development of 3G was started in 1990 and implemented in some countries in around 2002. The purpose of migration to 3G networks was to develop an international standard that combines and gradually replaces 2G, 2G+ digital cellular networks, PCS and cellular data services. At the same time, 3G is expected to have improved quality of voice, capacity of the network and data rates. Inter network communication either voice or data should be possible. The technology is now data oriented rather than voice as enormous data applications are in demand from the users. 3G also provides multimedia services to the users everywhere WCDMA, CDMA2000 are the technologies as options to use. Though yet not completely implemented in India, 3G is expected to have features like digital voice, data, multimedia applications. Expected data rates are upto 2Mbps packet switched networks, global coverage and global roaming. Why 4G is required? At the first, we might have a question that why we even require 4G if 3G systems are working well. It is because of basically two reasons that one is substantial growth in overall number of subscribers and other is massive demand of new data services which can be either data , audio, image or video (interactive or noninteractive). These two factors are enough to cause a substantial bottle neck in cellular communication services. Though the projected data rate is around 2Mbps in 3G, the actual data rates are slower, especially in crowded areas or when network is congested. Further the data rates also depends on the users activity (moving or steady state) and location (indoor/outdoor) as expected , the data services like multimedia are going to play modest role and will dominate the cellular traffic instead of voice in future. In such scenario the present 1G & 2G systems will saturate and will have no room to survive. Also the demand for increasing data rates leads to higher band width requirement. These factors cause the cellular industry to develop a common standard for a system that can work to overcome almost all the limitations imposed by the previous cellular technologies. The expected features of 4G systems are much higher data rates around 100Mbps, higher bandwidth requirements of an order of hundreds of MHz, plenty of services like data, audio, video etc. Seamless connectivity and improved quality of service

keeping in mind the all existing networks can be merged or interconnected i.e. all in one. What is 4G? The figure1 (4G Cellular Network) shows the concept of 4G cellular network. The future 4G infrastructure will consist of a set of various networks using internet protocol. As a common protocol so that the users are in control as they will be able to choose every application and environment. Accessing information anywhere, anytime with seamless connection to a wide range of information, obtaining services, receiving a large volume of information, data, pictures, video and so on are the key of 4G infrastructure.

Legends: DAB LAN PAN WLAN DVB MAN WAN UMTS

: Digital Audio Broadcasting : Local Area Network : Personal Area Network : Wireless Local Area Network : Digital Video Broadcasting : Metropolitan Area N/w : Wide Area Network : Universal Cellular Telecommunications Systems

One of the terms popularly used to describe 4G is MAGIC stands for  M

: Mobile Multimedia

 A

: Anytime anywhere

 G

: Global mobility support

 I

: Integrated wireless solutions

 C

: Customized personal service

Main features of 4G cellular services are application, adaptability and dynamisms. In this full motion video, home entertainment systems, advance location systems and many different services are expected with enhanced response time and quality of service. The expected data rates are 2Mbps for vehicular applications, 10\20Mbps for pedestrian applications and 100Mbps for indoor applications. Such high data rates obviously require much high bandwidth in terms of several hundred MHz. Concentrating on access technology, ultra WCDMA and Orthogonal Frequency Division Multiplexing (OFDM) being spectral efficient are the two major options that can help to realize the expected features of 4G cellular networks. OFDM\COFDM allows many users to transmit in an allocate band, by subdividing the available bandwidth into many narrow bandwidth carriers. Each user is allocated several carriers to transmit their data. The transmission is generated in such a way that the carriers used are orthogonal to each other, thus allowing them to be packed together much closer than standard Frequency Division Multiplexing (FDM). Hence this leads to have high spectral efficiency in OFDM\COFDM technology. Seamless connectivity requires fast HAND OFFs between different networks as the user moves from one to another. This can be satisfied as the core network is IP based. While Maintaining the connectivity, the emphasis is also on quality of service, security and providing services at the cheapest rate. Although most service providers are still expanding and improving their existing 2G+ network, research towards 4G systems is making significant progress. This research has been launched worldwide in major companies such as Motorola, Qualcomm, AT&T, Nokia, Ericsson, Sun, HP, Nippon Telephone and Telegraph DoCoMo and other infrastructure vendors as well as academic Institutes. NTT, DoCoMo, Japan leads the research work of 4G and has announced that

They have already made up an indoor experiment of 100Mbps data rate, though the exact Specifications of the experiment are not yet announced. Within a matter of years, the demand for cellular data services will outgrow the 3G’s advances It’s commonly accepted that 4G will be a super-enhanced version of 3G. Other 4G points are that 4G systems will be deployed with software defined radios, allowing the equipment upgrades for new protocols and services via software upgrades. In addition, 4G holds the promise of worldwide roaming using a single handheld device. 4G outlook is embodied in five key elements of fully converged services, ubiquitous cellular access, diverse user devices, autonomous networks and software dependency. The aim of 3G was to provide multimedia, multi rate, cellular communications any time and anywhere. It is uneconomical to meet this requirement with only cellular radio. 4G systems will extend the scenario to an IP Network that integrates broadcasts, cellular, cordless, WLAN/PAN and fixed wire.4G is the “network of networks “with which users are in control. They will be able to decide the right system and even the right terminal for each applications and for each environment (mobility, coverage) providing personalized service irrespective of the underlying network. As a result, this makes the most efficient use of the available spectrum by directing users to the most appropriate network. Opportunities for implementing the 4G Network: As the matter is clear now that to meet the 4G requirements of high data rate, seamless connectivity, cost effective services, the core network for 4G must be an IP (Internet Protocol) based network. The vision to merge all networks in one core network requires to have an intermediate layer that provides the interface between the existing network protocols and required protocols. Hence the opportunities are open if all the networks are going to update their present network architecture and allow the desired change or upgradation in the existing network. If we examine the present status in India, GSM is dominating presently and CDMA is now competing with GSM in cellular market. EDGE and GPRS are just introduced and will take sometime to work fine according to the expectation. While complete 3G services are yet not introduced. It may happen that the cellular network waiting for 3G and upgrading themselves with 2G+ may switch over directly to 4G by completely

bypassing 3G as it seems a better option regarding cost effectiveness in the network upgradation and replacement. Since the expected technology for 4G is ultra WCDMA and /or OFDM, the present GSM networks must upgrade or replace the whole network to CDMA or OFDM networks, which is a big critical issue for the present GSM networks to survive. Migration of all networks like LAN, MAN, WLAN, HIPERLAN, DVB, DAB also requires transparent protocols and smart HAND OFFs which should be able to work for maintaining the quality of service and offering such services at the lowest cost. The path to the final 4G may be plotted in 4 steps:  Internet working of 2G+, 3G and internet (Circuit Switched Voice /Data)  Integration of all networks (Circuit Switched Voice & Packet Data)  IP based harmonization (Packet based Voice/Data) and  Full convergence of the networks (All IP based Voice /Data /Multimedia /End to End quality of service /Better Security /Seamless Connectivity /Entertainment and so on) Figure 2 (4G an integration of major growing fields) illustrates the advantages of 4G cellular if the integration of all networks is possible according to the projected path. It indicates the integration of media, information technology and communication fields which are the majoe growing fields in the user applications. Merging all the services in one hand-set like Voice, non Voice, Internet, e-Commerce, Multimedia, entertainment like News, Sports, Video on demand, Audio and so on are the attractive features for the future customer of 4G cellular industry if implemented with reliable end to end quality of service and faster data rates.

Threats for implementing the 4G Network Because deployment of 4G wireless technology is not expected until 2006 or even later, developers will hopefully have time to resolve issues involving multiple heterogeneous networks such as  Access,  Handoff,  Location coordination,  Resource coordination to add new users,  Support for multicasting,  Support for quality of service,  Wireless security and authentication,  Network failure and backup, and  Pricing and billing.  Network architectures will play a key role in implementing the features required to address these issues.

One of the most challenging problems facing deployment of 4G technology is how to access several different mobile and wireless networks. Figure3 shows three possible architectures: using a multimode device, an overlay network, or a common access protocol. (The figure 3 is given in the next page)

(a) A multimode device lets the user, Device or network initiate handoff between networks without the need for network modification or interworking devices

(b) An overlay network—consisting of several universal access points (UAPs) that store user, network, and device information—performs a handoff as the user moves from one UAP to another

(c) A device capable of automatically switching between networks is possible if wireless networks can support a common protocol to access a satellite-based network and another protocol for terrestrial networks.

Multimode devices One configuration uses a single physical terminal with multiple interfaces to access services on different wireless networks. Early examples of this architecture include the existing Advanced Mobile Phone System/Code Division Multiple Access dualfunction cell phone, Iridium’s dual function satellite-cell phone, and the emerging Global System for Mobile telecommunications/Digital Enhanced Cordless Terminal dual-mode cordless phone. The multimode device architecture may improve call completion and expand effective coverage area. It should also provide reliable wireless coverage in case of network, link, or switch failure. The user, device, or network can initiate handoff between networks. The device itself incorporates most of the additional complexity without requiring wireless network modification or employing interworking devices. Each network can deploy a database that keeps track of user location, device capabilities, network conditions, and user preferences. The handling of quality-of-service (QoS) issues remains an open research question.

Overlay network In this architecture, a user accesses an overlay network consisting of several universal access points. These UAPs in turn select a wireless network based on availability, QoS specifications, and user defined choices. A UAP performs protocol and frequency translation, content adaptation, and QoS negotiationrenegotiation on behalf of users. The overlay network, rather than the user or device, performs handoffs as the user moves from one UAP to another. A UAP stores user, network, and device information, capabilities, and preferences. Because UAPs can keep track of the various resources a caller uses, this architecture supports single billing and subscription. Conclusion Thus from the above discussion we can see that by implementing 4G accessing information anywhere, anytime with seamless connection to a wide range of information, obtaining services, receiving a large volume of information, data, pictures, video and so on can be achieved in no time with a single handheld Device. But 4G also faces some following threats as mentioned below. 

Connecting all networks in one common platform



Seamless connectivity and smart Hand Offs



Acquiring the required Data rates and Bandwidth

Reference 1. Kaveh Pahalvan & Prashant Krishnamurthy: “Principles of Wireless Networks” 2. Dr.Vijay K.Garg: “Wireless Network Revolution: 2G to 3G” 3. http://www.scirus.com, a technical search Engine which shows all technical content on the web.