IEE Proceedings - Communications
Volume 144, Issue 4, August 1997
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Volume 144, Issue 4
August 1997
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- Author(s): A.Z. Tirkel ; C.F. Osborne ; T.E. Hall
- Source: IEE Proceedings - Communications, Volume 144, Issue 4, p. 217 –220
- DOI: 10.1049/ip-com:19971379
- Type: Article
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p.
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The paper examines the origin of high crosscorrelation between m-sequences of the same length by exhaustive examination of all pairs of sequences for n < 18. It is shown that, for composite lengths, there exist forced agreements between terms of the sequences. This leads to long-range order or correlation bias for particular decimations relating the sequences and the relative sequence phases. Decimations leading to biased correlations are predictable. For such bias, one of the sidelobes occurs for characteristic phase alignment. The small, but finite, discrepancy between the predicted and observed sidelobe maxima is analysed and is found to be due to the partitioning of sequence terms at characteristic phase. Sequences of nonprime length are found to exhibit considerable diversity in their cyclotomic set structure and closed-form expressions for the crosscorrelation at characteristic-phase alignment. By contrast, these are particularly simple for Mersenne-prime lengths, where it is found that suppression of peak sidelobes by at least 3 dB is achieved by avoiding characteristic-phase alignment. The impact of the theory developed in the paper on CDMA is that sequences with biased correlation, and hence high sidelobes, are predictable and therefore avoidable. - Author(s): Y. Lin and S.H. Tu
- Source: IEE Proceedings - Communications, Volume 144, Issue 4, p. 221 –228
- DOI: 10.1049/ip-com:19971348
- Type: Article
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The multiple stack algorithm (MSA), devised by Chevillat and Costello, is an efficient algorithm for erasurefree decoding of long constraint length convolutional codes. In the MSA, substack size and the number of transferred survivors (or successors) are assumed to be small. Lower error probabilities can be achieved by increasing the first stack size and/or increasing the computational limit. A large storage capacity for survivors is required to prevent memory overflow and achieve a low error probability. The authors present a modified MSA, in which the storage capacity for survivors is kept as a constant, while the substacks are arranged in a ring-like structure to handle the overflow problem of storage for survivors. In addition, the substack size and the number of transferred survivors are made large to improve performance. The performance of the modified MSA in decoding a convolutional code with constraint length m = 23 is investigated and compared with the performance of the unmodified MSA. - Author(s): J.Y. Lee and C.K. Un
- Source: IEE Proceedings - Communications, Volume 144, Issue 4, p. 229 –236
- DOI: 10.1049/ip-com:19971179
- Type: Article
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In future high-speed integrated networks asynchronous transfer mode (ATM) switches should be able to accommodate diverse types of applications with different quality of services (QOS) and traffic requirements. Thus some types of priority control schemes are needed in ATM switches to increase the utilisation of switches and satisfy the QOS of each traffic type. The authors consider a nonblocking input and output queueing ATM switch with capacity m in which two classes of traffics are admitted. Each input queue adopts one of two space-priority mechanisms, partial push-out and partial buffer sharing, which assign priorities for buffer access to each traffic type according to its loss probability constraints. The distribution of input queue length and loss probabilities of each traffic class are obtained using the matrix-geometric solution method and their performances compared. Numerical analysis and simulation indicate switch utilisation with space-priority mechanisms satisfying the QOS of each traffic class is much higher than that of the switch without control and the required buffer size is reduced while satisfying the same QOS. The partial push-out scheme has somewhat higher throughput than the partial buffer sharing scheme but the latter is preferred to the former owing to its lower implementation complexity. - Author(s): M. Conti and E. Gregori
- Source: IEE Proceedings - Communications, Volume 144, Issue 4, p. 237 –246
- DOI: 10.1049/ip-com:19971261
- Type: Article
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Analytical models are an important tool in providing a quantitative analysis of computer and communication systems. Matrix analytic techniques provide exact solutions for a general class of stochastic models named M/G/1-type models. These models can be used to study, for example, network switches with correlated arrival traffic and/or complex scheduling algorithms. However, the modelling effort using this technique can be difficult and time-consuming. The modelling effort can be drastically reduced by using appropriate software tools. In the paper, the authors present the software library MG1TYPE for the analysis of M/G/1-type Markov chains. MG1TYPE is general, robust and computationally efficient. It provides a range of performance measurement figures including the distribution of the steady-state probabilities and its moments. Applications of MG1TYPE in the analysis of relevant computer communication problems are presented. - Author(s): M.W. Janoska and T.D. Todd
- Source: IEE Proceedings - Communications, Volume 144, Issue 4, p. 247 –255
- DOI: 10.1049/ip-com:19971349
- Type: Article
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Future photonic LANs and MANs may be based upon single-hop architectures using wavelength division multiplexing (WDM) and passive star coupling. Recently, however, single-hop designs have been introduced which use a hierarchical structure employing simple wavelength routing functions. A salient feature of this type of network is that a set of wavelengths can be reused locally, while maintaining full single-hop connectivity through a different set of globally shared wavelengths. In such a network, wavelength routing divides the system into separate local and remote subnetworks, which may be accessed from each station by a single tunable transmitter. As a result, media access protocol operation can be implemented independently for each subnetwork, or it may be coupled between levels. These two options are investigated, focusing on remote subnetwork performance. Since global connectivity is achieved using a single set of remote wavelengths, it is important that they are efficiently used. The proposed protocols implement different forms of dynamic movable boundary TDMA, using various request/allocation mechanisms motivated by the channel controller approach. It is shown that, in such networks, remote channel efficiency can be improved significantly through a strong coupling of local and remote system operation. - Author(s): A.I. Giortzis and L.F. Turner
- Source: IEE Proceedings - Communications, Volume 144, Issue 4, p. 257 –264
- DOI: 10.1049/ip-com:19971249
- Type: Article
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The fixed channel assignment problem (CAP) is formulated as an integer linear programming problem with compatibility and requirement constraints. The proposed formulation is general and has been extended for the case of maximum packing fixed channel assignment problems. For the solution of the resulting formulation a special branch and bound algorithm has been used. The exploitation of the problem's special structure can improve the computational efficiency of the algorithm used. The model has been applied to a number of different benchmark problems that have appeared in the literature. The examples presented show that using the proposed formulation and a specially designed branch and bound algorithm, it is possible to solve optimally and efficiently fairly large channel assignment problems. - Author(s): P.I. Dallas and F.-N. Pavlidou
- Source: IEE Proceedings - Communications, Volume 144, Issue 4, p. 265 –273
- DOI: 10.1049/ip-com:19971243
- Type: Article
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Performance analysis is carried out for a cluster of a M-ary orthogonal DS/CDMA cellular system. The bit error rate (BER) is evaluated for both the forward and the reverse link, considering a wideband frequency selective channel with Rayleigh fading and lognormal shadowing. Both cases of power control (perfect and imperfect) within each cell are examined. Coherent and noncoherent RAKE receivers are studied for the forward and the reverse link, respectively, through appropriate numerical techniques calculating the target integrals. Owing to the channel model complexity, an equivalent lognormal distribution has to be introduced to make the calculations more convenient. An increased user accommodation capability, in comparison with the one cell study, results from the overall analysis of the system. - Author(s): X.H. Chen and H.K. Sim
- Source: IEE Proceedings - Communications, Volume 144, Issue 4, p. 275 –280
- DOI: 10.1049/ip-com:19971247
- Type: Article
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p.
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The authors propose a novel multiuser detection scheme for synchronous DS/CDMA systems, the orthogonal decision-feedback detector (ODFD), which performs equally well as the decorrelating decision-feedback detector (DDFD) but with a much reduced complexity. The ODFD employs a match filter bank matching to a set of orthonormal sequences which are generated by the Gram–Schmidt orthogonalisation procedure based on spreading codes. The ODFD algorithm involves only the orthonormal coefficient matrix which requires no frequent recalculations even when system parameters change. Successive decision-feedback detection is performed immediately at the output of the ODFD match filter bank without the transform matrix which is required in the DDFD. - Author(s): M. Boloorian and J.P. McGeehan
- Source: IEE Proceedings - Communications, Volume 144, Issue 4, p. 281 –288
- DOI: 10.1049/ip-com:19971248
- Type: Article
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p.
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The effects of feedback DC offset and gain/phase imbalance on the performance of the Cartesian feedback linear transmitter are described. A method for the automatic removal of these effects is presented and its validity confirmed by simulation results. The relevant theoretical background is also discussed.
Effects of bias and characteristic phase on the crosscorrelation of m-sequences
Modified multiple stack algorithm for decoding convolutional codes
Performance analysis of space-priority mechanisms in an input and output queueing ATM switch
Software library for analysing M/G/1-type systems and its application in computer network performance evaluation
Coupled reservation protocols for hierarchical single-hop photonic networks
Application of mathematical programming to the fixed channel assignment problem in mobile radio networks
Cluster design of M-ary orthogonal DS/CDMA cellular system with Rayleigh fading and lognormal shadowing
Novel synchronous CDMA multiuser detection scheme: orthogonal decision-feedback detection and its performance study
Automatic removal of Cartesian feedback transmitter imperfections
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