IEE Proceedings - Communications
Volume 148, Issue 3, June 2001
Volumes & issues:
Volume 148, Issue 3
June 2001
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- Author(s): S. K. Shin ; S.I. Lee ; S.P. Lee
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 125 –131
- DOI: 10.1049/ip-com:20010284
- Type: Article
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125
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Iterative decoding of parallel concatenated codes, also known as turbo codes, can provide tremendous coding gain approximating to the Shannon limit. Application of turbo coding techniques to block codes gives many advantages, due to the finite code length of the constituent codes and their ease of modification. The authors investigate the application of the trellis decoding method to block turbo codes, since one of the most easy and efficient ways of providing soft output at the decoder is incorporation of the trellis decoding method. The soft output Viterbi algorithm is mainly considered, with performance improvement techniques. The authors propose efficient reduced search algorithms in which the decoder complexity can be reduced about ten times with less than 0.1 dB degradation in coding gain. - Author(s): C.-S. Chou and D.W. Lin
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 132 –138
- DOI: 10.1049/ip-com:20010271
- Type: Article
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p.
132
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Space–time Viterbi equalisation for wireless communication has received much interest recently. The authors consider the associated signal and receiver design for improved transmission performance at high baud rates. Three techniques are proposed; two concern signal design and one concerns receiver design. First, special kinds of sequences called the min-norm training sequences are used for channel estimation. These sequences can minimise the mean-square estimation error in uncorrelated AWGN environments. Secondly, the authors consider using unequal power levels for the training signal and the data signal, with a higher power level for the former. They derive a mathematical expression for the optimal power ratio. Thirdly, a channel estimation method using reduced channel length is proposed. This method can reduce the channel estimation error in low SNR environments. Small-scale Monte Carlo simulations are conducted to investigate the performance gain of these techniques in wireless transmission. The results show varying degrees of advantage under different conditions. - Author(s): S.K. Oh
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 139 –143
- DOI: 10.1049/ip-com:20010176
- Type: Article
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139
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Simple iterative methods for blind maximal ratio combining based on a maximum likelihood principle and finite alphabet properties inherent in digital communication systems are presented. These methods can provide accurate estimates of channel parameters even with a small subset of data. The channel parameters and the data sequence are estimated simultaneously. Two methods, the joint combining and data sequence estimation method and the pre-combining and blind phase estimation method, are presented. Efficient initialisation schemes that can assure the convergence to the global optimum are presented. Simulation results demonstrate the performance of the two methods in terms of the symbol error rate and the estimated accuracy of the channel parameters. - Author(s): J.-L. Chen and H.-C. Chao
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 144 –148
- DOI: 10.1049/ip-com:20010247
- Type: Article
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144
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To provide cellular data services with QoS provisions, a shared resource scheme, based on optimisation theory and LaGrange λ-calculus, has been developed. This scheme can generate a fair schedule for a diverse mix of traffic with diverse QoS requirements in a limited radio spectrum. The authors define the acceptance indication (AI) as the QoS measurement of the shared resource scheme. The experimental results show that as much as 2.5% improvement in the mean acceptance rate is obtained relative to other existing schemes. - Author(s): R. Bose and A. Kumar
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 149 –153
- DOI: 10.1049/ip-com:20010276
- Type: Article
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p.
149
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Co-channel interference is of great concern when planning modern cellular communication systems. The commonly used seven-cell frequency reuse pattern is based on the fact that the carrier to interference ratio (C/I) should be higher than 18 dB, which is based on subjective tests (W.C.Y. Lee, 1995). A scheme based on trellis coded modulation (TCM) is proposed which enables the system to perform satisfactorily even at reduced levels of C/I. The proposed scheme gives the flexibility to use four or three cell repeat patterns, thus substantially increasing the spectral efficiency of the system. The scheme proposes the use of different TCMs in the different co-channel cells. Simulation results have shown that for a four-cell repeat pattern, the proposed scheme resulted in a bit error rate of 10-5 or better, with an outage probability of 0.86%. - Author(s): J. Thomas
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 155 –162
- DOI: 10.1049/ip-com:20010268
- Type: Article
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Iterative minimum mean square error (MMSE) demodulation of coded direct sequence code division multiple access (CDMA) uplink channels suppresses multiuser interference over a wide range of user signal powers, by iteratively exchanging soft information between an MMSE multiuser detector and a bank of single-user decoders. The iterative feedback of soft information from the decoders allows the demodulator to suppress (via the MMSE paradigm) and subtract (as in parallel subtractive cancellation) interference from other users in the same cell. It also displays remarkable near–far resistance by functioning like a successive interference subtractor across iterations. Using multiple sensors at the demodulator improves its baseline performance and provides increased user capacities now via both array processing and refinements across iterations. Most remarkably, iterative and array processing allow increasing the ratio of the bandwidth expansion incurred by coding to that incurred by spreading. This is a very useful property in practical systems where user populations typically vary with time. Lower rate codes (with correspondingly lower spreading factors, to satisfy restrictions on the allowable total bandwidth expansion) are obviously helpful in lightly loaded systems. With the proposed (nonlinear) demodulation technique they also aid in improved in-cell user separation via soft-decoded feedback to the detector in the second and subsequent iterations, along with the additional initial spatial separation provided by multisensor arrays. They also serve to mitigate the effects of residual in-cell and out-of-cell interference in the final decoded estimates. - Author(s): H.K. Sim and D.G.M. Cruickshank
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 163 –168
- DOI: 10.1049/ip-com:20010275
- Type: Article
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p.
163
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The maximum-likelihood sequence estimation (MLSE) multiuser detector has very good performance but at the expense of the exponentially increasing number of states with the number of users. A scheme that exploits the feature of power-equality in the downlink to reduce the number of states involved has been previously proposed by the authors. In the paper, the folded-trellis detector is combined with MLSE. The main idea here is to use the folded trellis which has a linear complexity to preselect a subset of the bit-combinations and then apply MLSE to this much smaller set. - Author(s): A.K. Koukos ; A.F. Evagelatos ; J. Kamaras ; K. Orphanidou
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 169 –174
- DOI: 10.1049/ip-com:20010065
- Type: Article
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p.
169
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An ATM traffic shaper is presented which regulates the traffic injected into the ATM networks by enforcing specific traffic parameter values that have been agreed upon between the user and the network. It realises preventive flow control functions through a new effective rate control algorithm, adaptive to traffic characteristics. It has been designed to support data communication services. The proposed scheme is presented in detail, and its system functionality and implementation aspects are discussed. Possible applications and model extensions are also discussed. - Author(s): F. Zhao ; M. Hanawa ; M. Takahara
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 175 –180
- DOI: 10.1049/ip-com:20010127
- Type: Article
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p.
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The performance of the CAC scheme based on the periodic measurement of traffics (PMT) using statistical bandwidth in ATM networks is studied. The proposed PMT CAC scheme implements the dynamic admission control which can be applied to the distinct delay-sensitive variable-bit-rate sources. Since the estimated bandwidth and buffer resources can be allocated adaptively by the aggregate traffic measurement, the proposed PMT CAC scheme has great flexibility in the bandwidth allocation according to the network status. Simulation results show that the higher the burst of cell arrivals become, the greater the multiplexing gain that can be obtained. The proposed scheme is expected to be less overly conservative than conventional methods, so that the network resource utilisation can be greatly improved. - Author(s): D.I. Choi and Y. Lee
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 181 –187
- DOI: 10.1049/ip-com:20010115
- Type: Article
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p.
181
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Bursty traffic such as voice, video and graphics is supported in ATM networks and requires different quality of service (QoS). To meet the various QoS requirements of bursty traffic, a dynamic priority queue with two types of traffic is proposed and analysed. It is assumed that the traffic in each type arrives at the system according to a Markovian arrival process to describe its burstiness. The service order is determined by the queue-length-threshold scheduling policy with a Bernoulli schedule. Using the supplementary variable method, performance measures such as loss and delay are derived. Some numerical examples are presented to show the effects of the scheduling policy on the performance. - Author(s): J.A. Carrasco ; V. Suñé ; S. Mahevas ; G. Rubino
- Source: IEE Proceedings - Communications, Volume 148, Issue 3, p. 188 –196
- DOI: 10.1049/ip-com:20010285
- Type: Article
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p.
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The authors describe and solve a Markov model of the leaky bucket ATM generic flow control mechanism. The model has a space cardinality which grows quickly with its parameters and is challenging to solve. Exploiting the cyclic nature of the model, the authors develop a methodology which allows them to efficiently solve instances of the model with 3 905 134 states and 53 869 532 transitions using 29.8 Mbyte of memory and 222 Mbyte of disc storage. The CPU utilisation is high (between 70% and 90%). The methodology is new and can be easily extended to any kind of finite cyclic Markov models.
Evaluation of block turbo code performance with the reduced search trellis decoding method
Signal design and receiver dimensioning for space–time Viterbi equalisation
Class of blind maximal ratio combining methods for digital communication systems
Fair resource sharing scheduling for cellular data services with QoS provisioning
Reducing frequency reuse distance in cellular communications using trellis coded modulation
Impacting the coding-spreading trade-off in multiuser CDMA with iterative MMSE demodulation
Sub-optimum MLSE detector with a folded state-transition trellis preselection stage
Traffic shaping system for ATM networks — supporting PC interface functions
Multiple-criteria call admission control scheme for ATM networks
Performance analysis of a dynamic priority queue for traffic control of bursty traffic in ATM networks
Model of the leaky bucket ATM generic flow control mechanism: a case study on solving large cyclic models
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