IEE Proceedings - Communications
Volume 145, Issue 5, October 1998
Volumes & issues:
Volume 145, Issue 5
October 1998
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- Author(s): X.-H. Peng and P.G. Farrell
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 289 –296
- DOI: 10.1049/ip-com:19982283
- Type: Article
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p.
289
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An approach is introduced towards generalised threshold decoding, in which the threshold value is not necessarily a majority element. This approach can help extend the threshold decoding method to more types of code in order to benefit from having low decoding complexities. With the motivation of finding codes decodable by applying the general threshold decoding rule, a class of block codes, called parity-check-based codes, is investigated. The method of constructing this class of codes differs from traditional approaches, i.e. the encoding procedure is based on the given parity-check symbols, instead of information symbols, with the aim of having a simple decoding algorithm. Better code performance can be achieved with some of these codes than those using similar decoding methods. - Author(s): J.-G. Zhang ; W.C. Kwong ; S. Mann
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 297 –303
- DOI: 10.1049/ip-com:19982286
- Type: Article
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p.
297
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The authors construct a new family of 2n codes, called 2n extended prime codes, for all-optical code-division multiple access (AOCDMA) applications. Such 2n codes are obtained by ‘extending’ prime codes. As a result, the cross-correlation constraint of the new codes is equal to one, as opposed to two in the original prime codes or 2n prime codes. Moreover, the bit error rate (BER) of AOCDMA systems using the new codes is analysed. It is shown that the new codes can support a larger number of active users than the 2n prime codes for a given BER. - Author(s): T. Kwon and J. Song
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 304 –308
- DOI: 10.1049/ip-com:19982282
- Type: Article
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p.
304
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A user-chosen password is not appropriate for a shared secret by which an authenticated key exchange protocol is operated. This is because users choose their passwords so that they can be easily memorised and can be typed using an alphabetic keyboard or a numeric keypad. Therefore, the password becomes a weak secret which is vulnerable to guessing attacks. However, users prefer to utilise the short easily memorised passwords. Several protocols, which are resistant to guessing attacks, have been developed to overcome this problem. However, they are inefficient in terms of the computation and communication costs. As a more practical solution, the authors propose new authenticated key exchange protocols by reducing the number of random numbers, cipher operations, and protocol steps. To achieve this goal, they deliberately use a one-time pad and a strong one-way hash function in their protocols. - Author(s): R.M.A.P. Rajatheva and E. Shwedyk
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 309 –315
- DOI: 10.1049/ip-com:19982290
- Type: Article
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p.
309
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The application of convolutional codes for finite intersymbol interference (ISI) channels is considered. The performance of a bandlimited communication system in the presence of additive white Gaussian noise depends on the minimum Euclidean distance dmin between different signal sequences. To further increase dmin, convolutional or trellis coding could be used. Search results indicate that the encoder with the best free distance does not always give the best coded distance when combined with an ISI channel. It has been seen from the results for several ISI channels that moderate coding gains can be obtained if the channel and the encoder are properly matched. Furthermore, it has been observed that if the channel is a maximum distance one, then the resulting coded distance is usually higher than that for a non-maximum distance channel. - Author(s): S. Chen ; B. Mulgrew ; E.S. Chng ; G.J. Gibson
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 316 –322
- DOI: 10.1049/ip-com:19982281
- Type: Article
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Decision feedback in a decision feedback equaliser (DFE) performs a space translation that maps the DFE onto a transversal equaliser in the translated observation space. Properties of DFEs can therefore be analysed more easily by exploiting this geometric translation property. This approach is used to analyse the conventional DFE that employs a linear combination of the channel observations and the past decisions (the linear-combiner DFE). It is demonstrated that the usual minimum mean square error (MMSE) solution does not achieve the full performance potential of the linear-combiner DFE structure. A bit error rate (BER) expression for the linear-combiner DFE with binary signalling is obtained, and a method is proposed to optimally set the coefficients of the linear-combiner DFE. The performance of this minimum-BER (MBER) linear-combiner DFE is much closer to that of the optimal Bayesian DFE, compared with the MMSE linear-combiner DFE. - Author(s): S.K. Patra and B. Mulgrew
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 323 –330
- DOI: 10.1049/ip-com:19982284
- Type: Article
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p.
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The authors investigate the problem of channel equalisation in the presence of co-channel interference (CCI), intersymbol interference and additive white gaussian noise. The optimal Bayesian decision feedback equaliser decision function for this problem is derived and an elegant fuzzy implementation of the optimal solution is proposed. This fuzzy implemented equaliser is able to provide performance close to the optimal equaliser with a substantial reduction in computational complexity. The equaliser consists of a fuzzy equaliser with an input processing block for co-channel compensation. This preprocessor can be used under severe-to-moderate CCI and can be removed under low CCI conditions. Simulation studies demonstrate the performance of the fuzzy equaliser developed. - Author(s): B.D. Choi ; D.I. Choi ; Y. Lee ; D.K. Sung
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 331 –336
- DOI: 10.1049/ip-com:19982288
- Type: Article
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A discrete-time priority queueing system is studied, in which two different classes of fixed-length packet-trains arrive according to independent batch geometric streams. The packets in each packet-train arrive at the rate of one packet per slot (train arrivals), resulting in a correlated arrival stream. The service time of one packet is deterministic of one slot. The motivation for the work comes from ATM networks with diverse traffic sources and correlated packet arrival stream. Using the probability generating function method, the joint distribution of queue lengths and the waiting time distribution are obtained for each class. Numerical results are presented. Comparision is made with the case of ‘batch arrivals’, where all packets of a packet-train arrive simultaneously at the buffer. - Author(s): S. Fragiacomo ; C. Matrakidis ; A. Popplewell ; J. O'Reilly
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 337 –341
- DOI: 10.1049/ip-com:19982278
- Type: Article
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p.
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Conventional simulation techniques are not suitable for modern low bit error rate communication systems, since significant computational power is required to achieve statistically significant results. Two novel simulation techniques are presented, which reduce the time required without affecting the performance. These are based on channel noise statistics, and generate error events without simulating a prohibitively large number of code words. This reduces the total number of code words that must be simulated, depending on the error correcting power of the code. The reduction in the simulation time required is two orders of magnitude, compared with conventional simulation techniques. - Author(s): C.R. Lin
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 342 –346
- DOI: 10.1049/ip-com:19982279
- Type: Article
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p.
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Traditionally, multihop wireless networks focus on datagram and mobility services. The packet radio network (PRNET), for example, was a very important contribution in that it provided a conceptually simple, distributed, reliable, totally asynchronous solution to the problem. PRNET handled datagram traffic reasonably well, but did not offer efficient multimedia support. Recently, several mobile, multimedia, multihop (M3) wireless network architectures have been developed, which assume some form of synchronous, time division infrastructure. The synchronous time frame leads to efficient multimedia support implementations. However, it introduces more complexity and is less robust in the face of mobility and channel fading. The author examines the impact of synchronisation on wireless M3 network performance. First, he introduces MACA/PR, an asynchronous network based on the collision avoidance MAC scheme employed in the IEEE 802.11 standard. Then, he evaluates and compares several wireless packet networks ranging from the total asynchronous PRNET to the synchronised cluster TDMA network. He examines the tradeoffs between time synchronisation and performance in various traffic and mobility environments. - Author(s): H.C.B. Chan and V.C.M. Leung
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 347 –354
- DOI: 10.1049/ip-com:19982285
- Type: Article
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p.
347
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Dual-bus metropolitan area networks (MANs) are well suited to provide broad-band network access and network interconnection over a city area by functioning as distributed broadband multiplexers between existing corporate/public networks, multi-media terminals, and broadband integrated services' digital networks employing an asynchronous transfer mode. The authors address the important problem of integrating time-sensitive and non-time-sensitive traffic over MANs. In the proposed integration scheme, time-sensitive variable bit-rate isochronous (VBRI) traffic, such as voice and video, is statistically multiplexed over the MAN by a novel, reservation-arbitrated (RA) access protocol, while non-time-sensitive asynchronous traffic, such as data, is transported over the residual bandwidth by queue-arbitrated access. RA access allows a VBRI traffic source to capture and reserve some isochronous channels on a bandwidth-on-demand basis. Compared to previously proposed reservation protocols, RA access is fair, provides a better isochronous transport service, and is compatible to the slot format of the existing IEEE 802.6 MAN standard. The system performance is analysed by an approximate theoretical model and computer simulations. Results indicate that the proposed integration scheme can be engineered to meet the stringent quality of service requirements of the time-sensitive VBRI traffic, while providing a satisfactory service to the non-time-sensitive data traffic and ensuring efficient bandwidth utilisation. - Author(s): M.L. Sim ; E. Gunawan ; C.B. Soh ; B.H. Soong
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 355 –362
- DOI: 10.1049/ip-com:19982291
- Type: Article
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p.
355
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The authors consider the performance of a reverse link DS/CDMA system with fast closed loop power control algorithms. For power control purposes, the received signal-to-interference ratio (SIR) must be measured. A simple procedure is proposed for estimating received SIR which does not need much calibration. The result shows that the BER performance is sensitive to the feedback delay or the inverse of the power control updating frequency. The power control mechanism is effective provided that the power control command updating frequency is ten times higher than the Doppler frequency. A step-size of 2 dB for the single step-size power control algorithm is found to be optimal for the mobile unit's velocity, which is uniformly distributed in the range 0–100 km/h. It was also found that the BER performance is very sensitive to the power control command channel error rate in the range 10-1–10-2. This suggests that the system designer should concentrate on minimising this error to improve the overall performance. Lastly, if a multiple step-size power control algorithm is to be implemented, two power control command bits would perform better than one, three, or more bits in a mobile channel environment. - Author(s): J. Lee ; R. Tafazolli ; B.G. Evans
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 363 –369
- DOI: 10.1049/ip-com:19982280
- Type: Article
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p.
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The performance is investigated of cellular hybrid FD/CDMA (frequency division/code division multiple access) with the overlapped carrier allocation (OCA) scheme in the reverse link of a cellular radio system. Of primary interest are the effect of chip waveform, the number of carriers and the degree of overlapping between adjacent carriers on the system capacity. To take into account the bandlimited waveform, the analysis is conducted in the frequency domain. It is shown that OCA compensates for capacity loss incurred in the subdivision of the available spectrum for frequency division multiplexing, and that it also achieves even higher capacity for chip waveforms with a smooth spectral shape at no extra system complexity while the merits of FD/CDMA are still fully exploited. - Author(s): X.H. Chen ; T. Lang ; J. Oksman
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 371 –377
- DOI: 10.1049/ip-com:19982289
- Type: Article
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p.
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The authors study a multiple chip-rate DS/CDMA system and its spreading code dependent performance. The multiple chip-rate technique is useful in some CDMA applications needing extra divisions among users in addition to code division to support variable data rate applications, such as multimedia systems. The study is applicable to both synchronous and asynchronous multiple chip-rate CDMA systems. A co-channel interference model based on correlation statistics for deriving bit error rate of a dual-chip-rate CDMA system is introduced considering various spreading codes, such as m-sequence, Gold, Gold-like, Kasami and Walsh codes. The results show that Gold code families are most suitable for the use in the dual-chip-rate CDMA system. - Author(s): G. Ruiz ; T.L. Doumi ; J.G. Gardiner
- Source: IEE Proceedings - Communications, Volume 145, Issue 5, p. 378 –387
- DOI: 10.1049/ip-com:19982292
- Type: Article
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p.
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It is likely that global mobile communications will call for interoperability between terrestrial and satellite systems based on nongeostationary constellations. In view of the high mobility of the satellite cells, the teletraffic analysis of the resulting integrated system appears a complex problem. The performance analysis of such a network, where moving satellite cells overlay clusters of terrestrial cells for the provision of services to dual-mode and satellite-only mobile terminals is presented. The approach followed makes use of results from studies of hierarchical mobile networks and of recent results from the teletraffic analysis of nongeostationary satellite mobile radio systems. In particular, the use of Markov-modulated Poisson-processes to model overflow traffic, combined with an iterative approach used in the analysis of the mobile satellite system, has enabled the provision of measures for blocking, handover failures, overflow traffic rejection and forced terminations when different overflow strategies are employed. Analytical work is supported by examples.
Threshold decoding and a new class of threshold decodable codes
Construction of 2n extended prime codes with cross-correlation constraint of one
Authenticated key exchange protocols resistant to password guessing attacks
Convolutional coding for bandlimited channels
Space translation properties and the minimum-BER linear-combiner DFE
Fuzzy implementation of a Bayesian equaliser in the presence of intersymbol and co-channel interference
Priority queueing system with fixed-length packet-train arrivals
Novel accelerated simulation techniques for low bit error rate communication systems
Multimedia transport in multihop wireless networks
Reservation arbitrated access for efficient service integration over dual-bus metropolitan area networks
Characteristics of closed loop power control algorithms for a cellular DS/CDMA system
Performance of hybrid OCA–FD/CDMA for cellular mobile communications
Multiple chip-rate DS/CDMA system and its spreading code dependent performance analysis
Teletraffic analysis of an integrated satellite/terrestrial mobile radio system based on nongeostationary satellites
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