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Communications, IEE Proceedings-

Issue 4 • Date Aug 1994

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Displaying Results 1 - 13 of 13
  • Performance analysis of ATM switches using priority schemes

    Publication Year: 1994 , Page(s): 248 - 254
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    B-ISDN is expected to support diverse applications ranging from low bit rate communications between terminals and host computers to the broadcasting high resolution TV signals. One of the most promising approaches for the B-ISDN is the asynchronous transfer mode (ATM) where all information (such as voice, data, image and video) is divided into fixed length data format, called cells, and these cells are asynchronously transmitted through the network. ATM networks must provide multimedia services with diversified traffic flow characteristics and quality requirements, thus priorities are given to different classes of services. To achieve the requirement of each class, a suitable priority management scheme is needed. The authors propose a priority management scheme to achieve the delay requirement and the packet loss rate requirement of each class. The analytical process uses a Markov chain to analyse the average delay time and the packet loss rate of each class. A computing algorithm is proposed to generate the states of the Markov chain and the corresponding transition probability matrix automatically. The results indicate that the proposed priority management scheme provides a real-time service for the time constrained class, and the required buffer size in the switches can be greatly reduced when the control parameter is appropriately chosen View full abstract»

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  • Performance of joint frequency phase modulation over Rayleigh fading channels

    Publication Year: 1994 , Page(s): 241 - 247
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    Joint frequency-phase modulation (JFPM) is a constant envelope digital modulation technique where both the frequency and phase of the signal are varied. The authors consider the problems of signal design, receiver structure, bandwidth efficiency and the probability of error performance with coherent or noncoherent detection of JFPM signals over Rayleigh fading channels. A noncoherent receiver for the JFPM signals is introduced, and an exact expression for the bit error rate is obtained. Error rate performance using diversity techniques in a Rayleigh fading channel is evaluated. Results show that JFPM performs better than conventional noncoherent M-ary FSK or M-ary DPSK of comparable bandwidth efficiency View full abstract»

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  • Concatenated codes using multilevel structures for PSK signalling over the Rayleigh fading channel

    Publication Year: 1994 , Page(s): 233 - 236
    Cited by:  Patents (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    The authors investigate the application of concatenated codes to the Rayleigh fading channel using M-PSK modulation. To obtain a variety of diversity levels, the authors propose several concatenated schemes where the inner codes are multilevel codes. This approach yields high diversity with low complexity, essentially providing soft decision decoding performance on Reed-Solomon codes View full abstract»

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  • Performance analysis for a convolutionally coded DPSK meteor-burst communication system

    Publication Year: 1994 , Page(s): 223 - 228
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    The performance analysis of a convolutionally encoded DPSK MBC system is based on the time-varying SNR model, and the statistical nature of the burst duration and the decaying time constant. The performance is evaluated in terms of the average bit error rate, the throughput, the average waiting time, and the, system complexity. The average bit error rate is stressed, whereas only maximum acceptable BER is used as a parameter in earlier literature. The results obtained by this method are more accurate than that obtained by the classical methods. The new results are about 1 dB more optimistic in terms of minimum SNR. The performance of the convolutional coding-DPSK combination is compared with that of a Reed-Solomon coding-DPSK combination. The comparison shows that,for similar performance, the CC-DPSK combination has a much smaller system complexity, and for similar complexity the soft-decision decoded-CC-DPSK has a much better performance View full abstract»

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  • Connectivity properties of a random radio network

    Publication Year: 1994 , Page(s): 289 - 296
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    Pure and routing-algorithm-based connectivities of random radio networks are studied by theoretical analyses and computer simulation respectively. The `magic number' of average neighbours of each station from connectivity point of view is obtained View full abstract»

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  • Alternative to NASA's concatenated coding system for the Galileo mission

    Publication Year: 1994 , Page(s): 229 - 232
    Cited by:  Papers (1)  |  Patents (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Because of delays in the Galileo mission an enhanced coding gain was required, compared to the gain achieved by the concatenated system recommended by CCSDS. NASA has met the requirement by exchanging the inner convolutional memory, rate 1/2 code with a memory 14, rate 1/4 code, whereby an enhanced coding gain of 1.6 dB can be obtained if infinite interleaving is assumed. To obtain this enhanced coding gain the complexity for the inner decoder is increased by at least 256 times. The author proposes an alternative system with a slightly larger enhanced coding gain obtained at interleaving degree 16, i.e. by a system which can be implemented in practice. The overall complexity is, however, at least 25 times smaller than the complexity for the system implemented by NASA View full abstract»

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  • Transmission of compressed voice over integrated services frame relay networks: priority service and adaptive buildout delay

    Publication Year: 1994 , Page(s): 265 - 274
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    Voice packets must be delivered within a time constraint to be played out at the receiver, and the simplicity of frame relay (FR) protocols makes this difficult to achieve with a low loss rate for integrated traffic. Highly compressed voice is more sensitive to losses than uncompressed voice and also changes the nature of the traffic in a FR network because of the short length of the voice frames. Priority for voice is shown to be highly desirable to achieve high voice performance where low-speed access links may be used for integrated service traffic. Packetised voice transmission also requires that the receiver compensate for the random queuing delays experienced by each voice packet. The packetised voice protocol (PVP) achieves this by using delay stamps created in packet switching nodes at the packet level, but this is not possible in FR networks because they have no packet level. The authors propose an adaptive buildout delay mechanism which requires no action by the switching nodes, meets the requirements of random delay compensation with acceptable loss rates, and achieves shorter end-to-end voice delay than the PVP View full abstract»

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  • Error correction capabilities of binary mapped Reed-Solomon codes with parity bits appended to all symbols

    Publication Year: 1994 , Page(s): 209 - 211
    Cited by:  Papers (1)  |  Patents (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    It is shown that the class of binary codes obtained from an RS code over GF(2m) with a parity bit appended to each RS-code symbol in GF(2m) can be decoded very efficiently by an RS decoding algorithm which corrects both errors and erasures. The error correction capabilities of this-modified class of codes are discussed. It turns out that some subcodes of this class are competitive with the best-known quadratic-residue codes with similar parameters. Also this class of codes inherits the burst error correction capability from the original RS code View full abstract»

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  • Two-centre tree topologies for metropolitan area networks

    Publication Year: 1994 , Page(s): 280 - 288
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    A two-centre binary tree (BT) can be constructed by linking the root nodes of two binary trees. Variations can also be constructed by making additional linkages within the two-centre binary tree. Three of these variations, referred to as the quaternary tree (QT), the X-tree (XT) and the ring tree (RT), are studied. Comparisons using performance measures of traffic flows and path reliabilities are made with respect to the BT and some popular topologies in the literature. Various implementations issues that take advantage of these tree networks are then proposed and discussed. The study indicates that the variants of the two-centre trees are viable topologies for the implementation of a metropolitan area network (MAN) View full abstract»

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  • Optimum modulation and diversity for DS-SS communication over Rayleigh fading channels subject to pulse burst interference

    Publication Year: 1994 , Page(s): 237 - 240
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    Results of optimum modulation and coding for MPSK and MDPSK signals transmitted over fading channels and subject to high level interference are presented. The author uses the exact expressions of the probability of error for the uncoded M-ary modulations. However, the analysis of optimum diversity (repetition code) is carried out by a Chernoff bound approximation. Simple expressions are derived to determine the optimum modulation and diversity in terms of the channel parameters. To examine the validity of approximations used throughout, exact analysis of the coded bit-error rate is found numerically, and the results are compared. It is concluded that the exact and the Chernoff bound analysis yield the same results for the optimum modulation and coding and there exist an optimum modulation and coding for each value of signal-to-noise ratio. The results are particularly useful for power and bandwidth limited channels View full abstract»

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  • Sequential decoding of convolutional codes by a compressed multiple queue algorithm

    Publication Year: 1994 , Page(s): 212 - 222
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (780 KB)  

    The conventional multiple stack algorithm (MSA) is an-efficient approach for solving erasure problems in sequential decoding. However, the requirements of multiple stacks and large memory make its implementation difficult. Furthermore,the MSA allows only one stack to be in use at a time: the ether stacks will stay idle until the process in that stack is terminated. Thus it seems difficult to implement the MSA with parallel processing technology. A two-stack scheme is proposed to achieve similar effects to the MSA. The scheme greatly reduces the loading for data transfer and I/O complexity required in the MSA, and makes parallel processing possible. An erasure-free sequential decoding algorithm for convolutional codes, the compressed multiple-queue algorithm (CMQA), is introduced, based on systolic priority queue technology, which-can reorder the path metrics in a short and constant time. The decoding speed will therefore be much faster than in traditional sequential decoders using sorting methods. In the CMQA, a systolic priority queue is divided into two queues by adding control signals, thereby simplifying implementation. Computer simulations show that the CMQA outperforms the MSA in bit error rate, with about one-third the memory requirement of the MSA View full abstract»

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  • Design and performance analysis of input-output buffering delta-based ATM switch with backpressure mechanism

    Publication Year: 1994 , Page(s): 255 - 264
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    A new delta-based ATM switch architecture is described that is based on expanding a delta network so that blocking is eased while preserving self routing and path uniqueness. The switch employs a combined external input-output buffering strategy, but operates-in such a way that output buffer overflows never happen. An analytical model, that takes into account this backpressure mechanism, is developed for arbitrary switch parameters, and computer simulations are used to assess the accuracy of the analysis. It is shown that a maximum throughput of above 0.90 can be achieved for a large-size switch using an expansion factor of 16. It is also shown that the backpressure mechanism can reduce the overall memory size needed to achieve a given cell loss performance, compared with the case where it is not used. The switch is shown to compare very well to-the-well-known knockout switch in terms of both performance and complexity. Finally, a distinctive feature of the proposed architecture is that internal node buffering can be used without disturbing cell sequencing View full abstract»

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  • Discrete queueing analysis of a star network

    Publication Year: 1994 , Page(s): 275 - 279
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    A discrete traffic analysis of a star-topology communication network is presented. Fast switching capabilities are assumed in the central hub. The communication network is modelled as a discrete queueing system. First-in/first-out (FIFO) and random (RND) policies are examined for selection of messages to be routed from inputs to outputs of the central hub. The case of an infinite number of users is also considered to provide a tight upper-bound on actual performance View full abstract»

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