MOBILE COMMUNICATIONS
Mobile communication is the application of wireless technology in the access network. It offers many useful features,
&bullEasy installation for rapid roll out
&bullProven platform with scalability
&bullFuture proof
&bullReliable and secure
&bullMobility
It is a very rapidly growing and popular service which was revolutionised telecommunications. It has become a backbone for business success and efficiency. It connects subscribers to the public switched telephone network(PSTN) using radio signals as a substitute for copper.it allows any body to communicate with any one while on the move.
Different technologies emerged for different types of requirements-coverage, capacity, mobility, bandwidth.
GSM
CDMA
CORDECT
PHS
AMPS,DAMPS
EVOLUTIONS OF MOBILE COMMUNICATIONS:-
FIRST GENERATION(1G):ANALOG CELLULAR:-
The introduction to cellular systems in the late 1970s and early 1980s represented a quantum leap in mobile communication(especially in capacity and mobility). Semiconductor technology and microprocessors made smaller and lighter weight , and more sophisticated mobile systems a practical reality for many more users. These 1G cellular systems still transmit only analog voice information. The most prominent 1G systems are ANALOG MOBILE PHONE SYSTEM(AMPS), NORDIC MOBILE TELEPHONE(NMT) and TOTAL ACCESS COMMUNICATION SYSTEMS(TACS). With the 1G mobile introduction, the mobile market showed annual growth rates of 30 to 50 percent, rising to nearly 20 million subscribers by 1990.
SECOND GENERATION(2G):MOBILE DIGITAL SYSTEMS:-
The development of 2G cellular systems was driven by the need to improve transmission quality, system capacity and coverage. Further advances in semiconductor technology and microwave devices brought digital transmission to mobile communications.sppech transmission still dominates the airways,but the demands for fax,short message and data transmissions are growing rapidly. Supplementary services such as fraud prevention and encrypting of user data have become standard features that are compatible to those in fixed networks. 2G cellular systems include GSM, DIGITAL AMPS(D-AMPS),CDMA and PERSONAL DIGITAL COMMUNICATION. Today multiple 1G and 2G standards are used in world wide mobile communications. Different standards serve different applications with different levels of mobility, capability and service area standards are used only in one country or region and most are in compatible.
2G TO 3G GSM: EVOLUTION:-
Phase 1 of the standardization of GSM 900mhz band was completed by the EUROPEAN TELECOMMUNICATION STANDARD INSTITUTE (ETSI) in 1990 and included all necessary definitions for the GSM network operations. Several tele services and bearer services have been defined (including data transmission upto 9.6kbps), but only some very basic supplementary services offered. As a result, GSM standards were enhanced in phase 2 (1995) to incorporate a large variety of supplementary services that were compatible to digital fixed network integrated services digital network(ISDN) standards. In 1996, ETSI decided to further enhance gsm in annual phase 2 + releases that incorporate 3G capabilities.
LIMITATIONS IN 1G AND 2G SYSTEMS:-
&bullNo global standards
&bullNo common frequency band
&bullLow information bit rates
&bullLow voice quality
&bullNo support of video
&bullVarious categories of systems to meet specific requirements
figure shows the architecture of GSM.
INTERNATIONAL MOBILE TELECOMMUNICATIONS 2000:-
IMT:-A future standard in which a single inexpensive mobile terminal can truly provide communications any time and any where. The main characteristics of 3G systems, known collectively as IMT-2000 are a single family of compatible standards that have following characteristics
&bullUsed world wide
&bullUsed for all mobile applications
&bullSupport both packet witched(PS) and circuit switched(CS) data transmission
&bullOffer high data transfer rates 2MBPS.
&bullOffer high spectrum efficiency
IMT standards has made 17 proposals to meet the requirements of 2G systems.The most important IMT-2000 proposals are the UMTS (W-CDMA) as the successor to GSM,CDMA as the interim standard 95(IS 95) successor and time division synchronous(TD-SCDMA), UNIVERSAL WIRELESS COMMUNICATIONS-136(UWC 136/EDGE) as TDMA based enhancements to DAMPS/GSM all of which are leading previous standards toward the
ultimate goal of IMT 2000. The goals of the services to be provided in 3G systems by IMT 200 is shown in figure The Global System for Mobile Communications (GSM) is now the world's most successful wireless standard. Recent figures indicate that GSM has more than 100 million subscribers in 120 countries and attracts more than five million new users every month. There are nearly 300 GSM system operators worldwide. Current wireless or mobile systems, despite their evolution, are still constrained in terms of the data rate they can offer and their flexibility to manipulate complex, yet user-friendly multimedia services. This need presents the opportunity to the mobile radio, IT, and consumer electronics communities to offer users a mobile system capable of managing and delivering a much wider range of information services to the mass market. Elements of this opportunity include:
&bull An industry-wide and government commitment across the world;
&bull A coordinated program including spectrum, standards, and technology; and
&bull Synergy of communications, IT, and media workings to bring about global opportunities for businesses and consumers, while creating new ways of doing business, entertaining and informing.
A new mobile system for worldwide use is now being developed to enhance and supersede current systems. The Universal Mobile Telecommunications System (UMTS) will be an enhanced digital communications system that will provide universal communications to anyone, regardless of their whereabouts. UMTS will allow for wireless Internet access, video-conferencing, and other bandwidth intensive applications. Benefits from this new system of wireless communications are expected to be:
&bull Support to existing mobile services and fixed telecommunications services up to 2Mb/s;
&bull Support to unique mobile services such as navigation, vehicle location, and road traffic information services, which will become increasingly important in world market;
&bull The ability to enable the use of the system terminal from multiple environments - in the home, the office, and in the public environments -in both rural areas and city centers; and
&bull Provision of a range of mobile terminals - from a low cost pocket telephone to sophisticated terminals to provide advanced video and data services .
UNIVERSAL MOBILE TELECOMMUNICATION SYSTEMS(UMTS):-
INTRODUCTION:-
In January1998, the European Telecommunications Standards Institute (ETSI) decided on a single air interface standard for the proposed Universal Mobile Telecommunications System (UMTS). The system is one of the major new third-generation mobile systems being developed within the framework that has been defined by the International Telecommunications Union (ITU) and is known as IMT-2000. UMTS has been the subject of intense worldwide efforts on research and development throughout the past decade. The system has the support of many major telecommunications operators and manufacturers because it represents a unique opportunity to create a mass market for highly personalized and user-friendly mobile access to today's information society. The system seeks to build on and extend the capability of today's mobile, cordless, and satellite technologies by providing increased capacity and data capability as well as a far greater range of services using an innovative radio access scheme and an enhanced, evolving core network.The system will be a member of a new family of mobile telecommunications systems being developed by the ITU for deployment across the world. While using different radio frequencies in different countries, every system will offer the same set of features to users. This will allow handsets to be developed that can be carried from country to country as the user travels.
The key difference between this system and previous mobile (wireless) systems, such as GSM, is that the earlier systems were conceptually separate from the fixed (wire line) telephone network. The goal of this system is to integrate wire line and wireless systems to provide a universal communications service, such that a user can move from place to place while maintaining access to the sum set of services .
The system is intended to allow users to send and receive data at much higher bandwidths than supported by today's GSM system. While on the move, users will be able to access remote systems at up to 144Kbps. When stationary, connections of up to 2Mbp/s will be supported through wireless access to networks, with much higher performance being possible by plugging the handset into a network socket .
ETSI has chosen aggressive timescales for the introduction of UMTS in order to meet the demands of customers. The target date for its introduction has been set as the year 2002. figure shows the architecture of UMTS.
To meet the deadline, the ETSI is following a phased approach in hopes of allowing capabilities to improve over time following the initial system introduction. At launch, terrestrial UMTS will have the capability for data rates up to 2Mb/s. However, UMTS is designed as an open system that should allow for evolution to incorporate new technologies as they become standardized.
UMTS CRITICAL TECHNOLOGIES:- Some of the critical technologies essential for the successful introduction of UMTS are described below:
1)UMTS Terrestrial Radio Access (UTRA):-
The ETSI decision in January 1998 on the radio access technique for UMTS combined two technologies. The W-CDMA for paired-spectrum bands and TD-CDMA for unpaired band?. The idea was to develop a common standard to ensure an optimum solution for all the different operating environments and service needs .
The transmission rate capability of UTRA will provide at least 144 Kbit/s for full mobility applications in all environments, 384 Kb/s for limited mobility applications in the macro- and micro-cellular environments, and 2.048 Mb/s for low mobility applications particularly in micro-cellular environments. The 2.048 Mb/s rate may also be available for short range or packet applications in the macro-cellular environment, depending on deployment strategies, radio network planning, and spectrum availability.
2)Multi-mode Second Generation/UMTS Terminals:-
UMTS terminals will exist in a world of multiple standards that will enable operators to offer maximum capacity and coverage to their user base by combining UTRA with second- or third-generation standards. Therefore, operators will need terminals that are able to interwork with legacy infrastructures such as GSM/DCS2800 and DECT, as well as other second-generation, worldwide standards (such as those based on the US AMPS standard) because these may initially have more complete coverage than UMTS. Many UMTS terminals will therefore be multi-band and multi-mode. Building such terminals at a cost which is comparable to contemporary single-mode, second-generation terminals will become possible because of technological advances in semiconductor integration, radio architectures, and software radio.
3)Satellite Systems:-
At initial service launch in 2002, the satellite component of UMTS will be able to provide a global coverage capability. Implementation plans call for utilization of the S-band Mobile Satellite Service (MSS) frequency allocations identified for satellite IMT2000 and will provide services compatible with the terrestrial UMTS system .
4)SIM Cards/Smart cards:-
GSM introduced the Subscriber Identity Module (SIM) or Smart Card. SIM technology incorporates enhanced security and a degree of user customization to the mobile terminal. SIM requirements, security algorithms, card and silicon IC technology will continue to evolve up to and during the period of UMTS deployment . The smart card industry anticipates being able to offer cards with greater memory capacity, faster CPU performance, contactless operation, and greater capability for encryption. These advances will allow the UMTS Subscriber Identity Module (USIM) to add to the UMTS service package by providing portable high security data storage and transmission for users. In addition, the users will be able to store, down or upload images, signatures, personal files, fingerprint or other biometrics data through the card. Contactless cards will allow the users to perform business transactions such as electronic commerce or electronic ticketing without having to be removed from a wallet or phone .Electronic commerce and banking activities, utilizing smart cards, is expected to become widespread. Users will expect and be able to use their cards on any terminal over any network. New memory technologies can be expected to increase card memory sizes making larger programs and more data storage feasible. Several applications and service providers could be accommodated on one card. In theory, the users could decide which applications/services they want on their cards, much as they do for their desktop computers' hard disks .
5)Internet Protocol (IP) Compatibility:-
UMTS is a modular concept that takes advantage of the trend towards convergence of fixed and mobile networks and services, enabling a host of new applications. For example, a laptop with an integrated UMTS communications module becomes a general-purpose communications and computing device for broadband Internet access, voice, video telephony, and conferencing for either mobile, office, or residential use.UMTS may well become the most flexible broadband access technology available, as it allows for mobile, office and residential use in a wide range of public and non-public networks. The system can support both IP and non-IP traffic in a variety of modes including packet circuit switched and virtual circuit?. UMTS will be able to benefit from parallel work by the Internet Engineering Task Force (IETF) who is further extending its basic set of IP standards for mobile communication . New developments like IP version 6 allows parameters such as quality of service, bit rate, and bit error rate (BER), vital for mobile operation, to be set by the operator or service provider. Developments on new domain name structures are also taking place. These new structures will increase the usability and flexibility of the system, providing unique addressing for each user, independent of terminal application or location .
6)Cross platform interoperability:-
The need for the ability to transport multimedia content over various types of networks requires industry to develop cross-platform interoperability because the properties of the networks may have an effect on the content of the transmission. In many cases several different kind of networks will be cascaded (i.e. Ethernet, ATM, X.25 and UMTS) .
7)API and Development toolbox:-
It is expected that rapid development and deployment of new and innovative services will drive the UMTS market. A key enabler in this area will be the standardization of the UMTS application-programming interface (API). API allows for abstraction of both the terminal and the network. It will also provide a generic way for applications to access terminals and networks. The API will allow the same application to be used on a wide variety of terminals and will also provide a common method of interfacing applications to UMTS networks. The API will support security, billing, subscriber information, service management, call management, SIM management user interaction and content translation. It is expected that the API will build upon and extend today's technologies (i.e. Java, Wireless Application Protocol (WAP), GSM SIM Toolkit and Internet technologies) that exploit convergence with other emerging technologies for consumer products (such as digital televisions).
8)Client server architecture:-
One of the primary drivers for UMTS is service differentiation. UMTS allows network operators to market products based on more than just coverage and
capacity issues. The key to this benefit is the ability to develop and offer new products and features in short timescales, without requiring modifications from infrastructure suppliers.
figure shows client server architecture of UMTS.
Many new developments in the IT industry are based on a client/server technology, which allows intelligence to be downloaded transparently from a server into the user's terminal. The technology provides direct and immediate high performance user interaction and interpretation. On the other hand, tasks that must remain centralized, such as database residence, are held on central servers waiting to rapidly and efficiently respond to queries from the clients. However, in the mobile industry, intelligent terminals and USIM card will allow personalization of the user interface and provision of features not possible with basic terminals in today's client/server networks. As roaming traffic continues to increase, the ability to provide such features independently of the serving network will become increasingly important. Existing and evolving GSM standards, such as SIM Toolkit and Mobile Execution Environment, together with other initiatives such as WAP, provide the framework for delivering this enhanced client/server approach. The user of an object-oriented language such as Java is attractive because it is platform and operating system independent, and optimizes the download .
9)Customer Care and Billing Systems:-
UMTS will operate in a very different environment than today's mobile systems. Customer care and billing are inextricably linked. These systems must be able to effectively operate with all UMTS users and providers in a customer-friendly manner. For UMTS, a bill will no longer be just a dun but, instead, a key part of a highly sophisticated approach to customer care across all provider services. Convergence will not only require the interoperation of fixed, mobile, satellite, private and public systems but also the integration of players from non-telecommunications fields such as finance, entertainment, and the news media. This will require a harmonized solution to customer care and billing systems despite very different legacy practices.
The competitive services market will demand multiple flexible interconnections between players and roles. Seamless delivery will require a unification of management and a means to provide interworking without a prior relationship. Significantly higher levels of automation and timeliness will be required to support the billing and customer care operations. In addition, fraud management will need to be applied across the whole value chain. Charging and billing will need to mature as concepts and practices.
BENEFITS OF UMTS: what it offers?:-
Corporate use of UMTS (including global mobile access to Intranets) will be a key driver for UMTS. Businesses will demand greater flexibility for customization and more devolved service control to optimize productivity and operational efficiencies within corporate networks. UMTS subscriber and network management capabilities will offer enhanced capabilities to meet these new and evolving requirements .
The body of literature on UMTS indicates that it offers the promise of being a significant advancement in mobile communications technology. UMTS is being designed to ensure flexibility is presented to users, network operators and service developers. UMTS will offer significant benefits in communication abilities including:
&bullEase of use and low cost;
&bullNew and better services;
&bullPacket transmission and data rates on demand; and
&bullImproved mobility and coverage.
1)Ease of use and low costs:- Wireless customers want useful services, easy-to-use terminals and good value for money, UMTS is envisioned to offer services that are easy to use and customizable in order to address individual user needs and preferences. Terminals and other customized equipment will be available to allow easy access to these services. A wide array of inexpensive, available terminals and other periphery will be available. Costs for the actual UMTS service are projected to be low enough to ensure a mass market and provider competition.
2)New and better services:- Market studies show that voice will remain the dominant service for existing fixed and mobile telephone networks, including GSM, through 2005. Users will demand low-cost, high-quality voice service from UMTS. However, the opportunity for increased revenues through UMTS comes from offering advanced data and information services. Long term, industry forecasts for UMTS show a strongly growing multimedia subscriber base by the year 2010.
3)Fast access:- One factor, which clearly sets UMTS above the second-generation mobile systems, is its potential to support 2Mb/s data rates for users from the outset. This capability, together with inherent Internet Protocol (IP) support of UMTS, is a powerful combination to deliver interactive multimedia services as well as other new wideband applications such as video telephony and video conferencing.
As the demand for user data rates increases in the long term, UMTS will be developed to support even higher data rates, perhaps one or two orders of magnitude greater. In later phases of UMTS development, there will be a convergence with even higher data rate systems using mobile wireless Local Area Network (LAN) technologies (microwave or infrared) providing data rates of for example 155 Mb/s in indoor environments .
4)Packet transmission and data rate on demand.:-Most cellular systems in use today use circuit-switched technology for wireless data transmission. However, UMTS integrates packet and circuit data transmission. Packet data over the airwaves provides the user several benefits:
&bullVirtual connectivity to the network at all times;
&bullAlternative ways of billing. For example, pay-per-bit, per session or flat rate per month; and
&bullAsymmetric bandwidth in the uplink and downlink. As demanded by many emerging data services where one link direction carries simple commands and the other carries and content rich, bandwidth intensive traffic (for example Web browsing or video transmission).
UMTS is also being designed to offer data rate on demand, where the network reacts flexibly to a user's demands based upon his or her profile and the current status of the network. The use of packet-oriented transport protocols such as Internet Protocol (IP) for UMTS is being studied now. The combination of packet data and data rate on demand will remove technical barriers for the user and make operation of the system much cheaper. Simply put, there should be no worries about how and when to connect to the network.
UMTS services are based on standardized service capabilities, which are common throughout all UMTS user and radio environments. This means that a user will experience a consistent set of services even when he or she roams from his or her home network to other UMTS operators. Users will find the same interface, whether they are in their home network or roaming. The Virtual Home Environment (VHE) will ensure the delivery of the service provider's total environment, including for example, a corporate user's virtual work environment, independent of the user's location or mode of access (satellite or terrestrial).
VHE will also enable terminals to negotiate functionality with the visited network, possibly even downloading software so that it will provide "home- like" service. The ultimate goal is that all networks, signaling, connection, registration and any other technology should be transparent to the user so that mobile multimedia services are simple, user friendly and effective.
Mobility and Coverage:- UMTS has been designed from the outset to be a global system, comprising both national terrestrial and global satellite components. Through multi-mode, multi-band terminals it can use 2nd generation systems to extend its coverage for basic services. The overall goal of the system offering is to achieve truly personal communications using terminals that are able to roam from a private cordless or fixed network (Figure 1). A second goal is to achieve this with a consistent delivery of the services via VHE.
Figure 1. UMTS Coverage is Universal (Leino, 1999).
The UMTS radio access system UTRA will support operation with high spectral efficiency and service quality in all the physical environments in which wireless and mobile communication take place. Today's users live in a multi-dimensional world, moving between indoor, outdoor urban and outdoor rural environments with a degree of mobility ranging from stationary through pedestrian up to very high vehicular speeds. There are also different user density environments, including three-dimensional situations in high-rise buildings. UTRA has been specified for all these environments.
Limitations of UMTS:-
In practical implementations of UMTS, some users may be unable to access the highest data rates at all times. For example, the physical constraints of radio propagation and the economics of operating a network will mean that the system services might only support lower data rates in remote or heavily congested areas. Therefore, in order to ensure that the subscriber is always able to use their terminal, services will be adaptive to different data rate availability and other Quality of Service parameters.
In the early stages of UMTS deployment, traffic will probably be generated predominantly in locations such as airports and railway stations which operators will cover immediately following network launch. However, users will want full coverage so that they can access their services wherever they are . To offer this, UMTS technology is being defined to enable roaming with other networks. For example a GSM system operated by the same operator or alternatively by roaming agreements with other networks such as other GSM based systems or other third generation systems including UMTS compatible satellite networks, which will effectively be able to offer global coverage.
The limitations are,
1)Risk of further regulation:- There is a certain anxiety that an attempt to achieve circulation by means of administrative measures may lead to heavier regulation of UMTS (e.g. in the form of complicated procedures or excessive marking). Therefore, current efforts are intended to take care to aim to simplify regulation in all circulation measures.
2)Standardization:- Standardization will remain a key factor in providing quality services at an affordable cost and enabling roaming between systems. The success of UMTS depends upon the flexibility of interfaces and the capacity to evolve in parallel with technological development. Continued close co-operation between operators, manufacturers and regulators in the standardization of UMTS/IMT 2000 is crucial for successful harmonization of standardization proposals.
UMTS in the Long Term:-
In order to ensure that UMTS flourishes in the long term, its capabilities must be progressively increased by the addition of new technologies. These technologies are discussed below.
1)Re-configurable Terminals:- UMTS terminals will have to exist in a world of multiple standards, both second-generation standards and other members of the IMT-2000 family. In order to provide universal coverage, seamless roaming and non standardized services will no longer have fixed parameters, rather they will be in the form of a "toolbox" whereby the key parameters can be selected or negotiated to match the requirements of the local radio channel.
In addition to the capability to adapt to different standards as described above, terminals will enable network operators to distribute new communications software via download over the air in order to improve the terminals' performance in the network or to fix minor problems (e.g. an improved handover algorithm). This aspect of software downloads will generally be invisible to the user.
2)Application and Service Download:- When using today's multimedia terminals (e.g. PCs), users have accepted the idea that the capabilities of the terminal can be modified over time through a software download. It is now commonplace for a user to download a new "plug in" (for example a video or audio code) to access new types of content. The introduction of multimedia services on UMTS will take this concept into the mobile domain. UMTS "plug ins" will come from a variety of sources, for example:
&bullPre-installed on the users' terminal by the network operator or service provider;
&bullDownloaded over the air, at the user's request or automatically by the network - much as today, where many Internet service providers upgrade one's software or databases during a session; and
&bullSupplied on media such as DVD or CD-ROM.
Smart Antennas:- Smart antennas react intelligently to the received radio signal, continually modifying their parameters to optimize the transmitted and received signal. This allows them to:
&bullIncrease coverage and capacity by reducing interference between adjacent mobiles;
&bullOffer space division multiple access, where frequencies are assigned on a per-mobile rather than a per-cell basis allowing vastly increased capacity; and
&bullEnable user location in space, allowing the introduction of advanced location based services.
Broadband Satellite Systems:- Several broadband satellite systems are also planned for deployment in the post-2002 timeframe to offer data rates beyond 2Mb/s and into the Gigabits domain. Some of these systems may offer compatibility with UMTS service concepts using satellite frequency allocations in the 20-30 GHz range. The requirements of the terminal equipment and higher power consumption will necessitate larger size transportable or fixed terminals or smaller electronic components.
CONCLUSIONS:-
UMTS appears to offer significant benefits to personal and commercial endeavors. Technologies are being put in place to bring it into the mobile community. A phased introduction of UMTS hardware and services with coverage, capability and number of operators growing over time. This phased introduction ensures early availability of services to users while reducing risks for UMTS operators and manufacturers.
UMTS must be capable of co-existing and working with existing second-generation mobile communications technologies so that operators can choose to reuse their existing infrastructure assets and expertise. Global availability of UMTS servers will be ensured by providing for roaming between members of the IMT-2000 family and handover between GSM and UMTS. A number of technologies are required, in addition to the radio interface on which so much focus has been placed recently. Although most current attention is focused on the early years of deployment, UMTS is being defined with a view to the long term.
UMTS is a significant opportunity for manufacturers, operators, and content providers as a communications system and as a part of the greater information society. The vision of UMTS is as a customer-focused system, where customers include both network operators and end users. The challenge to the communications industry is to integrate the technologies needed for UMTS in a way which supports this goal and thereby transforms the vision for UMTS into reality.
