The future of third-generation wireless networking is discussed. The vision of the third generation is a single set of standards that can meet a wide range of wireless access applications. Third-generation systems, in harmony with broadband integrated services digital networks, will use shared resources to convey many information types. A single network architecture will serve its users efficiently in many environments, including moving vehicles, indoor and outdoor public areas, residences, offices, and factories. A study of a switching architecture, referred to as a cellular packet switch, and a packet transmission technique, referred to as a packet reservation multiple access is discussed. By means of a design example, it is shown how these techniques can work together to meet some of the demands of third-generation systems. >

Cellular packet communications

Single- and Multi-carrier Quadrature Amplitude Modulation Principles and Applications for Personal Communications, WLANs and Broadcasting L. Hanzo Department of Electronics and Computer Science, University of Southampton, UK W. Webb Motorola, Arlington Heights, USA formerly at Multiple Access Communications Ltd, Southampton, UK T. Keller Ubinetics, Cambridge Technology Centre, Melbourn, UK formerly at Department of Electronics and Computer Science, University of Southampton, UK Motivated by the rapid evolution of wireless communication systems, this expanded second edition provides an overview of most major single- and multi-carrier Quadrature Amplitude Modulation (QAM) techniques commencing with simple QAM schemes for the uninitiated through to complex, rapidly-evolving areas, such as arrangements for wide-band mobile channels. Targeted at the more advanced reader, the multi-carrier modulation based second half of the book presents a research-orientated outlook using a variety of novel QAM-based arrangements. * Features six new chapters dealing with the complexities of multi-carrier modulation which has found applications ranging from Wireless Local Area Networks (WLAN) to Digital Video Broadcasting (DVB) * Provides a rudimentary introduction for readers requiring a background in the field of modulation and radio wave propagation * Discusses classic QAM transmission issues relevant to Gaussian channels * Examines QAM-based transmissions over mobile radio channels * Incorporates QAM-related orthogonal techniques, considers the spectral efficiency of QAM in cellular frequency re-use structures and presents a QAM-based speech communications system design study * Introduces Orthogonal Frequency Division Multiplexing (OFDM) over both Gaussian and wideband fading channels By providing an all-encompassing self-contained treatment of single- and multi- carrier QAM based communications, a wide range of readers including senior undergraduate and postgraduate students, practising engineers and researchers alike will all find the coverage of this book attractive.

Single- and Multi-carrier Quadrature Amplitude Modulation : Principles and Applications for Personal Communications, WLANs and Broadcasting

Time division multiple access (TDMA) is a classic approach to multiple access in digital cellular wireless communications systems. The authors summarize a number of frequency and time slot allocation techniques for enhancing the capacity and flexibility of TDMA-based systems. They also describe how the problems of fading, delay spread, time variability and interference affect TDMA systems, and how they may he countered and even exploited by appropriate techniques of detection, diversity, coding, adaptive equalization and slow frequency hopping (FH). It is worth emphasizing that the use of one of these techniques, slow random FH, results in a system that is in effect a hybrid of TDMA and code division multiple access (CDMA). >

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Time division multiple access methods for wireless personal communications

A mobile telephone system multiplexes plural voice traffic channels on a single carrier using a TDMA protocol. The capacity of the mobile telephone system is increased by assigning voice traffic capacity, not on a conversation basis, but on an information burst basis. In order to avoid compromising the voice transmission capacity, control signals (for the allocation and deallocation of both forward and reverse traffic channels) are sent using multiple diversity, i.e. both time and frequency. In addition, to increase the number of available control channels, a control channel comprises a sub-divided portion of an otherwise equivalent voice traffic slot. For reverse allocation requests, which are transmitted over a contention access channel, power diversity is used in addition to time and frequency diversity.

Method for exploitation of voice inactivity to increase the capacity of a time division multiple access radio communications system

The authors present a simulation study of an adaptive receiver, based on the concept of maximum-likelihood sequence estimation (MLSE), which compensates for the heavy selective distortions caused by multipath propagation. The receiver includes a matched filter and a modified Viterbi processor and is suitable for implementation in a digital form. It operates adaptively, in a training mode at the beginning of each burst, as well as in a tracking mode during message detection. This makes the receiver robust both to fast Doppler shifts and to a large frequency offset. Simulation results are presented which show the performance in different multipath environments, with echo delay in excess of 20 mu s and vehicle speed up to 250 km/h. >

An adaptive MLSE receiver for TDMA digital mobile radio

Digital transmission on a mobile radio channel requires sophisticated adaptive reception techniques. Two classes of non-linear adaptive equalization structures are studied in the present paper: the Maximum Likelihood Sequence Estimation (MLSE) and the Decision Feedback Equalizer (DFE). A coherently detected GMSK modulation has been assumed, with a 300 kb/s bit rate in a TDMA frame structure. Simulation results are presented with different kinds of static or dynamic multipath patterns. The results show that acceptable performance around the threshold objective of BER = 1% can be achieved without excessive complexity with both schemes. A further benefit will be provided by the use of FEC coding not considered here. At this point a direct comparison between the two structures may not be fair, because optimization work has not yet been completed to put both of them in optimal operating conditions.

Adaptive equalization in TDMA mobile radio systems

Diversity receiver structures are discussed in the context of a digital mobile radio system using time division multiple access (TDMA). Both selection diversity and combining diversity are considered. Simulation results are presented, with reference to the European GSM (Groupe Speciale Mobile) system, taking into account frequency selective Rayleigh fading and cochannel interference. Receiver structures and simulation results provide useful information for a performance/complexity tradeoff. It is shown that an estimate of signal quality, based on the TDMA preamble processing, can substantially improve the performances in any of the examined schemes, particularly in the interference-limited environment. >

Evaluation of diversity schemes in TDMA digital mobile radio

The performance of the diversity receiver that has been designed in the Italtel laboratories for the Groupe Speciale Mobile (GSM) digital mobile system is described. In the Italtel scheme, the base station receiver will systematically contain the diversity option to improve the network resistance to noise and interference. Simulation results show a very effective action of the adopted diversity scheme against interference. The effect of the correlation of the various signals and the improvement that can be achieved with a three-branch receiver have also been considered. The reported results offer a wide range of possible solutions, making it possible to find the most satisfactory tradeoff between performance improvement and implementation complexity. >

R. D'Avella

Papers

An adaptive MLSE receiver for TDMA digital mobile radio

Adaptive equalization in TDMA mobile radio systems

Evaluation of diversity schemes in TDMA digital mobile radio

A diversity receiver for the Pan-European mobile digital system