IEE Proceedings - Communications
Volume 145, Issue 3, June 1998
Volumes & issues:
Volume 145, Issue 3
June 1998
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- Author(s): S.W. Lee and D.H. Green
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 117 –125
- DOI: 10.1049/ip-com:19982073
- Type: Article
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p.
117
–125
(9)
The adoption of incoherent optical signal processing in CDMA LANs faces limitation of the absence of complementary elements which hinder the design of optical code sequences that are fully orthogonal to each other. Coherent optical processing has been shown to be able to overcome the limitation. The paper looks at the coding aspect of CDMA LANs with coherent optical processing. The architectures of encoder/decoder and their basic phase properties are described. Based on the phase properties, methods of generating families of optical phase codes with good correlation properties are presented. The phase code families generated are then compared with optical codes used in incoherent systems, in terms of codelength, family size and correlation properties. From the comparison, it is shown that, generally, phase codes exhibit more desired features in these aspects than the conventional optical codes, and, therefore, render higher data rate and more secured transmission. - Author(s): M. Diab
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 126 –132
- DOI: 10.1049/ip-com:19981799
- Type: Article
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p.
126
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The author develops a new systolic architecture for the decoding of single-burst error-correcting cyclic codes (SBECCC). The well known decoding procedure for these codes, based on the error-trapping technique, is expressed by means of uniform recurrence equations to be implemented using systolic arrays. The decoder uses the generator polynomial of the code. For an (n, k) SBECCC, with a burst-error correcting capability l, the decoder consists of (n + k – 1) cells arranged into a serial-in serial-out one-dimensional feed-forward systolic array. The decoder has the following advantages: it does not contain any feedback connection; it is easily reconfigurable for variable code parameters n, k and l and changes in the choice of the generator polynomial. - Author(s): Z. Fan and P. Mars
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 133 –140
- DOI: 10.1049/ip-com:19982080
- Type: Article
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p.
133
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(8)
It is demonstrated how fast and accurate estimates of quality-of-service (QOS) parameters can be obtained for an ATM multiplexer queueing model fed by multiple Markovian traffic sources. This has been achieved by constructing a simple approximation of the buffer overflow probability, which involves computation of two parameters based on the theory of large deviations. Upper bounds on other QOS parameters, such as cell loss ratio, mean cell delay and cell delay variance, can all be derived from this estimate. It is shown that this approximation is much more accurate than the pure effective bandwidth one, which ignores the statistical multiplexing gain due to a large number of sources. One attraction of the proposed method is that the speed of computation of this approach is independent of the size of the system. Thus the authors' analytical techniques can be implemented fast enough for real-time admission control in ATM networks. - Author(s): J.S. Choi and C.K. Un
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 141 –144
- DOI: 10.1049/ip-com:19981931
- Type: Article
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p.
141
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The performance of the preemptive priority queueing strategy in an input queueing switch with two priority classes is considered. A new queueing model is proposed which consists of two independent input buffers with separate head of line (HOL) queues. This model takes account of the priority queue structure as well as the influence of the preemptive priority scheme for output contention. By applying the approximation techniques of the flow conservation rule and an equivalent queueing model, the authors obtain the queue length distribution, delay and maximum throughput in closed-form without using any heuristic adjustments. The results are compared with those of results of Chen and Guérin (1991), and verified with simulations. - Author(s): Y.-S. Lin ; C.B. Shung ; J.-C. Chen
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 145 –151
- DOI: 10.1049/ip-com:19981875
- Type: Article
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p.
145
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The knockout switch architecture has been found attractive for large-scale switch implementations because of its satisfactory cell loss performance, with constant output buffer speed-up independent of switch dimension. The per port hardware complexity of a knockout concentrator, however, does grow linearly with the switch dimension. In the paper, several approaches are investigated to reduce the hardware complexity of the knockout concentrator while retaining the cell loss performance. A bufferless hierarchical concentrator architecture with reduced hardware complexity is derived. The concentrator complexity can be further reduced by introducing buffers in the concentrator, and the trade-off is analysed. Furthermore, output grouping may be applied in the buffered hierarchical concentrator to reduce the per port complexity. Two large-scale switch design examples are derived using the proposed design approaches, producing a complexity reduction ranging from 1.2% to 89.7%. - Author(s): B.D. Choi ; B.-C. Shin ; K.B. Choi ; D.H. Han ; J.S. Jang
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 152 –158
- DOI: 10.1049/ip-com:19982077
- Type: Article
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p.
152
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The authors consider a single server priority queueing system with two priority classes of customers. The work is motivated for performance analysis of multiplexing video and data in communication networks, where videos at cell level arrive according to a two-state Markov-modulated Poisson process (MMPP) and data arrive according to a Poisson process. With the supplementary variable method, the authors explicitly obtain the steady-state joint generating function of the queue lengths of each class. They also investigate the queue lengths of each class by a technique of Markov-modulated fluid flow (MMFF). In comparison with the MMPP model, the MMFF model provides computationally simple procedures and results. Numerical results show that performance measures obtained with the MMFF model are quite close to those with the MMPP model. - Author(s): H.C.B. Chan and V.C.M. Leung
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 159 –167
- DOI: 10.1049/ip-com:19981960
- Type: Article
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p.
159
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To address the problem of video communications over 802.6 MANs, a reservation-arbitrated (RA) access protocol is proposed which allows a variable-bit-rate video source to reserve isochronous channels on a bandwidth-on-demand basis. The paper explains the general method of RA access, compares four different schemes of acquiring incremental bandwidth in response to a reservation request, and evaluates the performance of RA access by simulations using two video-source models. Results indicate that RA access provides fair service under a cyclic capturing mechanism, permits statistical multiplexing while providing nearly isochronous transport service, allows a video source to adapt to its reserved bandwidth during network congestion, and facilitates the implementation of layered video coding techniques. - Author(s): C.A. Pantjiaros ; J.A. Wylie ; J. Brown ; G.F. Gott ; P.J. Laycock
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 168 –174
- DOI: 10.1049/ip-com:19981711
- Type: Article
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p.
168
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Since 1982, a programme of research has undertaken the measurement, analysis, and mathematical modelling of occupancy across the entire high frequency (HF) spectrum at the times of the solstices, and this work has been published. Since the establishment of an automated, remotely controlled UK measurement system in 1989, occupancy measurements have been made at nominally fortnightly intervals. The authors present mathematical models based on these frequent measurements made during the period 1990 to 1997, when the 12-month moving average sunspot number varied from about 160 to 10. The models incorporate the parameters field strength threshold, frequency, measurement bandwidth, sunspot number and week of year. - Author(s): L. Wolfe
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 175 –179
- DOI: 10.1049/ip-com:19982006
- Type: Article
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p.
175
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A method is suggested for finding only those source inputs that are sufficient for computing the capacity of large communications channels. An efficient algorithm is proposed to implement the method. The suggested approach has application in finding the capacity of large telecommunications channels, such as those with intersymbol interference, which are computationally intensive. A discrete memoryless channel provides an example of the application of the algorithm. - Author(s): G. Fairhurst ; S.L. Pang ; P.S. Wan
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 180 –185
- DOI: 10.1049/ip-com:19982079
- Type: Article
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p.
180
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An adaptive convolutional code-rate system for packet data is presented which adapts the level of coding to overcome the effect of varying levels of noise. The system utilises the frame structure of packet data to synchronise adaption and uses a parallel decoding technique to ensure a hitless changeover between a number of different coding rates. The issues concerning the design are discussed in detail, including the resynchronisation of the Viterbi decoders, and the estimation of the level of noise. The system has been implemented using off-the-shelf components and tested over a range of error conditions and introduces only a low per-packet overhead. One important application is to counter the effect of a rain fade on a satellite communication link. A considerable improvement in the link throughput has been observed for a satellite link which suffers from typical rain fades. - Author(s): I.W. Band and D.G.M. Cruickshank
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 186 –190
- DOI: 10.1049/ip-com:19982074
- Type: Article
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p.
186
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The authors compare methods of reducing the co-channel interference on a DS-CDMA downlink signal by employing convolutional coding at the base station and a Viterbi decoder as the initial estimator for a parallel cancellation scheme. The combination of a matched filter and the Viterbi algorithm is shown to afford increased performance compared to equivalent bandwidth systems which do not use forward error correction. The use of a Wiener filter to collapse the spectrum of the spread signal leads to even greater capacity improvements. The systems discussed may be implemented with an affordable increase in receiver complexity and processing delay. - Author(s): S. Salous ; N. Nikandrou ; N.F. Bajj
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 191 –196
- DOI: 10.1049/ip-com:19982078
- Type: Article
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p.
191
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The theory of chirp sounding is briefly reviewed. This is followed by the description of a digital mobile radio chirp sounder which is implemented using direct digital frequency synthesisers (DDFS), field programmable gate arrays and microcontrollers. The gate arrays and the microcontroller provide the user interface via either a keypad or a PC, generate the programming words for the DDFS and two phase-locked-loop (PLL) synthesisers, synchronise the transmitter’s sweep to the receiver’s sweep and implement a beat-frequency-oscillator DDFS. Results demonstrate that the digital chirp sounder provides full programmability of the various chirp waveform parameters, bandwidths up to 90 MHz which are suitable for both indoor and outdoor environments, offline processing to obtain different channel characteristics, and moderate averaging to obtain a dynamic range better than 35 dB. - Author(s): A.J. Coulson ; A.G. Williamson ; R.G. Vaughan
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 197 –202
- DOI: 10.1049/ip-com:19981991
- Type: Article
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p.
197
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Probability distribution functions (PDFs) are discussed for characterising narrowband fading processes in mobile radio communications. In particular, the effects of short-term channel variations (fast fading), and longer term channel variations (shadow fading) are discussed in relation to commonly used PDFs. A channel model is proposed to represent the mixture of these processes, and is shown to be well represented by the Suzuki PDF. Difficulties in using the Suzuki PDF to predict system behaviour, in particular bit error rate (BER), are presented, and the use of the generalised gamma PDF is recommended. It is shown that this PDF represents channel behaviour as well as the Suzuki PDF, and that it is much more convenient for BER prediction. The accuracy of BER prediction using this PDF is demonstrated by computer simulation of digital radio transmission over Suzuki fading channels. - Author(s): ZangzhouFu
- Source: IEE Proceedings - Communications, Volume 145, Issue 3, p. 203 –211
- DOI: 10.1049/ip-com:19982029
- Type: Article
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p.
203
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A new kind of one-point-to-multipoint random access channel protocol called the acknowledgement-type random access and code division multiple access channel protocol (ACK-ALOHA-CDMA) is presented. It is particularly applicable to the data transmission of differential global positioning system (DGPS) deformation or disaster monitoring networks with a large number of monitoring stations distributed over a wide area. The characteristics of the channel are analysed in detail and computer simulation results are given. Several mathematical functions and conclusions useful for both system design and performance evaluation are obtained.
Coding for coherent optical CDMA networks
Systolic decoder for burst error-correcting codes
Fast and accurate estimation of ATM quality-of-service parameters with applications to call admission control
Delay performance of an input queueing packet switch with two priority classes
Design of knockout concentrators
Priority queue with two-state Markov-modulated arrivals
Evaluation of reservation-arbitrated access schemes for statistical multiplexing of variable-bit-rate video traffic over dual-bus metropolitan area networks
Extended UK models for high frequency spectral occupancy
Finding sufficient inputs to calculate communications channel capacity
Smart codec: an adaptive packet data link
Improving the capacity of CDMA systems using convolutional coding and interference cancellation
Digital techniques for mobile radio chirp sounders
Improved fading distribution for mobile radio
New channel access protocol for a wide area DGPS deformation monitoring network
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