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Communications, IEE Proceedings-

Issue 2 • Date Apr 1999

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Displaying Results 1 - 12 of 12
  • Embedding channel coding in arithmetic coding

    Publication Year: 1999 , Page(s): 73 - 78
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    An arithmetic coding algorithm that incorporates channel coding is presented. For a source alphabet with m symbols, the selected m code points over the [0-1) interval have a desired minimum Hamming distance d min between them. The decoder utilises this dmin in conjunction with the self-synchronisation property of arithmetic coding and knowledge of the source statistics to recover the original sequence of symbols, in the presence of channel errors, without the use of known channel coding techniques. The selected dmin provides a desired error protection level. The introduced scheme is suitable for bandwidth-limited binary symmetric channels (BSCs) with moderate to high error rates View full abstract»

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  • Logical link control techniques for wireless ATM network

    Publication Year: 1999 , Page(s): 107 - 112
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    In wireless ATM networks, a logical link control (LLC) layer is necessary to mitigate the effect of errors caused by the radio channel before cells are released to the ATM network layer. The authors propose and evaluate some LLC techniques, compare the system performance for different packet lengths, and discuss the trade-off between complexity and performance. The lengths of the used packets in different conditions are suggested. Simulations for conventional ARQ and code combining ARQ in a Rayleigh fading environment are carried out, and the results indicate that code combining ARQ is a simple and efficient technique View full abstract»

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  • Learning algorithms for multicast routing

    Publication Year: 1999 , Page(s): 89 - 94
    Cited by:  Patents (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    It is shown how learning algorithms are used to grow shared multicast trees, in order to minimise some performance index such as the average received packet delay or path length. In particular, automata are used to select a core to send a join request to in a dynamic membership environment. The motivation is to improve the performance of shared multicast trees while retaining their attractive scaling properties. It is shown that in the single source (single group) case, automata converge to the optimal shortest path tree solution. For multiple sources, automata reach a `good' compromise solution. However, automata are most useful in heterogeneous scenarios where the resources are unevenly distributed, a situation which could easily arise due to consumption of resources by multiple priority traffic in future integrated-services networks View full abstract»

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  • In-service monitoring of quality of service in ATM networks using OAM cells

    Publication Year: 1999 , Page(s): 102 - 106
    Cited by:  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    Congestion conditions in ATM switches may cause gradual deterioration in the QoS. QoS monitoring, using OAM, can accurately measure the overall quality of monitored parameters to detect such deterioration before the service quality has dropped below an acceptable level. Several factors call affect the accuracy of the in-service QoS performance monitoring technique, such as the burstiness of the background traffic, network load, monitoring frequency, and bit rate. However, acceptable levels of accuracy can be achieved using OAM cells. Because of the fluctuations presented by VBR video, OAM cells can measure their characteristics more accurately than CBR video. Also, for low bursty background traffic, the cell delay variation (CDV) of VBR is higher than CBR. As the burstiness of the background traffic increases, the CDV of CBR grows faster than that of VBR. At high burstiness, the CDV of CBR is higher than VBR. For all background data burstiness, the first multiplexer of the network absorbs most of the CDV View full abstract»

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  • Automatically designed fuzzy system for connection admission control in ATM networks

    Publication Year: 1999 , Page(s): 113 - 119
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    Connection admission control (CAC) is a vital function for asynchronous transfer mode networks. A CAC algorithm should be simple, i.e. economically implementable and fast, and it should be efficient, i.e. allow statistical multiplexing. A solution based on an analytical queueing model is too CPU-intensive and cannot be applied online. The paper proposes a new scheme based on fuzzy logic. The aim is to predict online the cell loss ratio that a connection will exhibit if it is accepted into the network. The CAC scheme is based on a consideration of fuzzy logic and artificial neural networks (ANNs). The ANN is used in the learning phase to tune the fuzzy system automatically. The structure of the neuro-fuzzy system is discussed. A training set obtained by an analytical algorithm, namely the convolution algorithm, is used to develop a learning algorithm and to check the applicability of the technique View full abstract»

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  • Performance of an adaptive data-rate MBC system using different FEC codings and ARQ protocols

    Publication Year: 1999 , Page(s): 127 - 132
    Cited by:  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    The performance of meteor burst communication using adaptive data-rate modulation is analysed. The transmitted data-rate is a function of the channel state, and is varied in a such way that the probability of bit error is kept constant. Unlike other performance analyses, the message consists of data-packets, thus allowing more realistic ARQ protocols to be analysed. The performance of the system is given in terms of average throughput, probability of successful message completion in a given time span and average waiting time for different message lengths, with or without coding View full abstract»

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  • Approximate bit error probability analysis of 2PSK and 4PSK with partially coherent, symbol-by-symbol detection in carrier phase noise

    Publication Year: 1999 , Page(s): 120 - 126
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    The effect of carrier phase noise on the BEP of 2PSK and 4PSK with partially coherent, symbol-by-symbol detection is analysed using an approximate approach. Partially coherent detection is achieved using a decision-aided, maximum likelihood carrier phase estimator. The carrier phase noise is modelled as a Brownian motion. Assuming a small phase noise variance, it is shown that the Brownian phase noise, together with the additive, white, Gaussian channel noise, leads to a Gaussian phase error in the recovered reference and a random signal component for data detection. These results enable the BEP to be numerically evaluated, and the numerical results agree well with the results of computer simulations. Both the effects of carrier phase fluctuations on the matched filter output and the decorrelation of the carrier phase from one symbol interval to the next are taken into account View full abstract»

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  • Generalised FSMC model for radio channels with correlated fading

    Publication Year: 1999 , Page(s): 133 - 137
    Cited by:  Papers (22)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    Finite-state Markov channel (FSMC) models are useful for analysing radio channels with nonindependent fading, which give rise to bursty channel errors. In the paper the FSMC model is constructed by partitioning the dynamic range of the fade amplitude into finite number of intervals and representing each interval as a `state' in the model. Transitions between these channel states thus characterise the physical fading process. Based on the Nakagami-m distribution, a new analytical formulation for the state transition probability is presented and validated for channels with arbitrary degrees of time-interleaving. The resultant FSMC model is shown to be applicable to a wide range of practical fading channels, including diversity-combined channels and multicarrier channels View full abstract»

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  • Choice of high and low thresholds in the rate-based flow control scheme

    Publication Year: 1999 , Page(s): 95 - 101
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    In a rate-based flow control scheme, the important issue is how to determine congestion occurrence and congestion relief. The most common method is to set two thresholds of queue length, a high threshold and a low threshold. The values of these two thresholds seriously influence the system performance. Hence the authors present the concept of `best area' to determine how to set the high and low thresholds to guarantee good performance (i.e. cell loss probability is zero and utilisation is one, if it is possible). Some rules are also given to prevent unnecessary cell loss and under-utilisation, when good performance is not achieved due to too many connections or too large a propagation delay View full abstract»

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  • Reduction of decoding complexity of trellises for BCM

    Publication Year: 1999 , Page(s): 82 - 88
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    Block-coded modulation (BCM) combines bandwidth-efficient modulation techniques with error-correction capabilities to allow efficient data transmission over communication channels. The disadvantage of this technique, however, is the complexity of the trellis used in the Viterbi decoding process. The authors address this problem and propose a method for the reduction of decoding complexity. Optimal sectionalisation has been identified as an appropriate technique and it is applied to trellises of BCM schemes based on a set of new objective functions. The resulting sectionalisation algorithm has been applied to various BCM schemes including 4-PSK, 8-PSK and 16-PSK and a complexity reduction of approximately 20% is achieved. Extensive simulation has shown that both original and sectionalised trellises have the same performance over Rayleigh, K=6 Rician and K=10 Rician fading channels. Furthermore, a comparison between the considered BCM schemes and ring-TCM is provided in terms of code performance and decoding complexity View full abstract»

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  • Errors-and-erasures decoding of BCH codes

    Publication Year: 1999 , Page(s): 79 - 81
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    A Grobner basis algorithm for errors-and-erasures decoding of BCH codes that avoids computation of the modified syndrome polynomial is given. The decoding problem is viewed as an instance of a more general interpolation problem. The algorithm has the same computational complexity as the Berlekamp-Massey algorithm but is more efficient in hardware View full abstract»

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  • Forward-link analysis of cellular DS-CDMA over generalised fading channels using saddlepoint integration

    Publication Year: 1999 , Page(s): 138 - 143
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    The bit-error rate (BER) analysis of an asynchronous cellular direct-sequence code-division multiple-access (DS-CDMA) system with channel fading and random mobile locations often results in a multiintegral expression, even though the Gaussian approximation is applied. In the paper, saddlepoint integration (SPI) is proposed to simplify the analysis. The computational complexity grows only linearly with the number of interfering cells in the system, regardless of the number of mobiles in each cell. By making use of the derived expression, the BER performance for arbitrary Nakagami (1960) parameters and path-loss exponents is evaluated efficiently. Simulation results show that the SPI technique is accurate and reliable View full abstract»

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