INTRODUCTION
Pick up any newspaper today and it is a safe bet that you will find an article somewhere relating to mobile communications. If it is not in the technology section it will almost certainly be in the business section and relate to the increasing share prices of operators or equipment manufacturers, or acquisitions and take-overs thereof. Such is the pervasiveness of mobile communications that it is affecting virtually everyone’s life and has become a major political topic and a significant contributor to national gross domestic product (GDP).
The major driver to change in the mobile area in the last ten years has been the massive enabling implications of digital technology, both in digital signal processing and in service provision. The equivalent driver now, and in the next five years, will be the all pervasiveness of software in both networks and terminals. The digital revolution is well underway and we stand at the doorway to the software revolution. Accompanying these changes are societal developments involving the extensions in the use of mobiles. Starting out from speech-dominated services we are now experiencing massive growth in applications involving SMS (Short Message Service) together with the start of Internet applications using WAP (Wireless Application Protocol) and i-mode. The mobile phone has not only followed the watch, the calculator and the organiser as an essential personal accessory but has subsumed all of them. With the new Internet extensions it will also lead to a convergence of the PC, hi-fl and television and provide mobility to facilities previously only available on one network.
The development from first generation analogue systems (1985) to second generation (2G) digital GSM (1992) was the heart of the digital revolution. But much more than this it was a huge success for standardisation emanating from Europe and gradually spreading globally.
However, world-wide roaming still presents some problems with pockets of US standards IS-95 (a code division multiple access [CDMA] rather than a time division multiple access [TDMA] digital system) and IS- 136 (a TDMA variant) still entrenched in some countries. Extensions to GSM (2G) via GPRS (General Packet Radio Service) and EDGE (Enhanced Data rates for GSM Evolution) (E-GPRS) as well as WAP and i-mode (so called 2.5G) will allow the transmission of higher data rates as well as speech prior to the introduction of 3G.
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| 4G WIRELESS TECHNOLOGY |
Mobile systems comprise a radio access together with a supporting core network. In GSM the latter is characterised by MAP (Mobile Applications Protocol), which provides the mobility management features of the system.
GSM was designed for digital speech services or for low bit rate data that could fit into a speech channel (e.g. 9.6kbit/s). It is a circuit rather than a packet oriented network and hence is inefficient for data communications. To address the rapid popularity increase of Internet services, GPRS is being added to GSM to allow packet (Internet Protocol [IP]) communications at up to about 100kbit/s.
Third generation (3G) systems were standardised in 1999. These include IMT-2000 (International Mobile Telecommunications 2000), which was standardised within ITU-R and includes the UMTS (Universal Mobile Telecommunications System) European standard from ETSI (European Telecommunications Standards Institute), the US derived CDMA 2000 and the Japanese NTT DoCoMo W-CDMA (Wideband Code Division Multiple Access) system. Such systems extend services to (multirate) high-quality multimedia and to convergent networks of fixed, cellular and satellite components. The radio air interface standards are based upon W-CDMA (UTRA FDD and UTRA TDD in UMTS, multicarrier CDMA 2000 and single carrier UWC-136 on derived US standards). The core network has not been standardised, but a group of three—evolved GSM (MAP), evolved ANSI-41 (from the American National Standards Institute) and IP-based— are all candidates. 3G is also about a diversity of terminal types, including many non-voice terminals, such as those embedded in all sorts of consumer products. Bluetooth (another standard not within the 3G orbit, but likely to be associated with it) is a short-range system that addresses such applications. Thus services from a few bits per second up to 2Mbit/s can be envisioned.
For broadband indoor wireless communications, standards such as HIPERLAN 2 (High Performance Local Area Network—ETSI’s broadband radio access network [BRAN]) and IEEE 802.lla have emerged to support IP based services and provide some QoS (quality of service) support. Such systems are based on orthogonal frequency division multiplexing (OFDM) rather than CDMA and are planned to operate in the 5GHz band.
Whereas 2G operates in 900 and 1800/1900MHz frequency bands, 3G is intended to operate in wider bandwidth allocations at 2GHz. These new frequency bands will provide wider bandwidths for some multimedia services and the first allocations have been made in some countries via spectrum auctions (e.g. in the UK, Holland and Germany) or beauty contests (in France and Italy). The opportunity has also been taken to increase competition by allowing new operators into the bands as well as extending existing operator licences. These new systems will comprise microcells as well as macrocells in order to deliver the higher capacity services efficiently. 3G and 2G will continue to coexist for some time with optimisation of service provision between them. Various modes of delivery will be used to improve coverage in urban, suburban and rural areas, with satellite (and possibly HAPS—high altitude platform stations) playing a role.
Already, as we move from 2G to 3G the convergence of communications and computing is central to the realisation of the new generation of services and applications. Digital technology enables dynamic adaptation of systems, and intercommunicating software embedded in networks and terminals allows efficient control of the new networks. This is accentuated as we move from 3G to 4G, extending the range and bit rate of services and bringing about the convergence of fixed, mobile and broadcast networks, service provision and terminal types.
This paper introduce the basic ideas and thinking behind the second phase research programme (1999-2003) of the UK’s Virtual Centre of Excellence in Mobile and Personal Communications (Mobile VCE) in the form of ‘visions for 4G’. A Visions Group has been set up to produce and maintain an evolving picture of 4G and to communicate these ideas down to the work areas and researchers. The aim is to provide an umbrella vision to harmonise the research work in the various areas.
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