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Communications, IEE Proceedings-

Issue 1 • Date Feb 2003

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Displaying Results 1 - 11 of 11
  • Frame-alignment procedures for STM-1 frame

    Page(s): 37 - 44
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    The paper presents a novel approach to frame-alignment analysis. A universal model for out-of-frame procedures is presented and statistical parameters are derived. The synchronisation pattern structure is analysed using the bifix indicators. Different parameters for in- and out-of-frame procedures are considered. The results are applied to the STM-1 frame, for which the optimal framing strategy is proposed. View full abstract»

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  • Improved IEEE802.11 PCF performance using silence detection and cyclic shift on stations polling

    Page(s): 45 - 51
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (521 KB)  

    The authors propose a cyclic shift polling method that can be used along with silence detection on IEEE802.11 wireless LANs for increasing the number of supported voice communications. The method spreads the total voice packet rejection rate to all active stations in order to increase the number of stations that experience specific voice quality. The cyclic shift polling method is implemented only at the access point of each wireless LAN and does not require any modifications to the existing access protocol. Analytic expressions and comparative numerical results are presented for the performance of the IEEE802.11 point co-ordination function. The analysis shows how the cyclic shift polling method along with silence detection on the mobile stations can be used for increasing the number of supported voice calls. View full abstract»

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  • Optimum bandwidth limitation method to overcome GVD-based effect in practical fibre-optic transmission systems

    Page(s): 64 - 68
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (409 KB)  

    The paper describes an optical duobinary modulation scheme that reduces the waveform distortion caused by the effect of group velocity dispersion (GVD) and the combined self-phase modulation (SPM)-GVD effect as generated in non-dispersion shifted fibre (NDSF) with a length of over 300 km at 5 Gbit/s. Measured and simulated eye-opening penalties are used to compare the optical duobinary modulation scheme to the conventional non-return-to-zero (NRZ) intensity modulation scheme. A comparison of duobinary modulation with a duobinary filter against NRZ intensity modulation with a full-cosine roll-off filter shows that the former yields a compact spectrum even in the case of a single pulse, which needs the broadest bandwidth. NDSF repeaterless transmission at 5 Gbit/s and 363 km without dispersion compensation is established to confirm the effectiveness of the optical duobinary modulation scheme. View full abstract»

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  • Capacity of a wideband multirate CDMA system with multiservice in the presence of fading and power-control error

    Page(s): 59 - 63
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (397 KB)  

    The interference-modelling capacity analysis method developed by Gilhousen et al. (1991) is modified to make it appropriate for investigating the capacity of a variable spreading gain (VSG) DS-CDMA system with multiservice in the presence of fading (both shadow fading and multipath fading) and power-control error. With this analytical model, the uplink capacity estimate of an integrated voice and long constraint delay data (LCD) services system is obtained. The capacity estimate is the maximum number of concurrent voice users and LCD users that the system can support while their required QoS are met. Further studies are made of the effects of power allocation, power-control error and receiver diversity on system capacity. View full abstract»

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  • Signature-based approach to fair document exchange

    Page(s): 21 - 27
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (623 KB)  

    The authors aim to present a protocol for fair document exchange between two parties, that incorporates a signature scheme based method for the recovery of a document decryption key. The principal idea for such key recovery is based on a verifiable and recoverable encryption of a key. This means that any party can verify the correctness of the key encrypted without actually viewing the key, and the party can be assured that a designated party can decrypt the encrypted key to recover the original key. A DSA (digital signature algorithm) is applied as an example to demonstrate how to implement such key encryption based on an off-line semi-trusted third party. The third party is off-line as they do not participate in an exchange in normal situations, and semi-trusted in the sense that they may misbehave but do not conspire with any party involved in the exchange. The main contribution of the paper is that it presents a fair document exchange protocol which is more efficient, simpler and easier to implement in comparison with related work. View full abstract»

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  • Cell delay modelling and comparison of iterative scheduling algorithms for ATM input-queued switches

    Page(s): 11 - 16
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (422 KB)  

    Mathematical cell delay modelling and performance comparison of four iterative scheduling algorithms for ATM input-queued switches are carried out. The iterative round robin with multiple classes (IRRM-MC) algorithm is compared to iterative round robin with slip (iSLIP), parallel iterative matching (PIM) and simplified PIM (SPIM) algorithms. By using Bernoulli arrivals a mathematical cell delay model is proposed for the algorithms. The developed model is compared to the simulation to verify the extension of the model fitness. The algorithms are compared according to cell delay and throughput performances. The comparison is also carried out using on-off types of arrivals. The algorithms are severely degraded by this type of source but it is shown that the use of service class priority is a good scheduling policy to satisfy cell delay constraints while keeping high throughput, even when the switch is submitted to bursty traffic. The comparison shows that an input switch based on the IRRM-MC algorithm is a flexible one and suited to easily satisfying the QoS of each class of service. View full abstract»

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  • Cyclic redundancy checks with factorable generators

    Page(s): 17 - 20
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (359 KB)  

    Applications are proposed for cyclic redundancy checks (CRCs) that have factorable rather than primitive generator polynomials. Suitable encoding and decoding methods are developed. Factored-generator CRCs are then compared with tandem CRCs that have an inner code and outer code. When the factors of the generator are used as the generators of the inner and outer codes, the two kinds of CRCs have much in common, although their codewords are different. The differences are such that the factored-generator CRC offers an architectural advantage over the tandem CRC, in that the factored-generator CRC enables symmetric partial decoding, which is useful in mixed-transmission-media and point-to-multipoint systems. View full abstract»

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  • Auto-controlled algorithm for slotted ALOHA

    Page(s): 53 - 58
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    A multiple power level transmission system increases the maximum throughput by selecting the power levels randomly, showing the same behaviour as the standard slotted ALOHA, where the throughput decreases abruptly at higher traffic load conditions. An auto-controlled slowly decreasing throughput algorithm for slotted ALOHA is developed. Herein, a mobile terminal can transmit any packet at a higher probability at the lower power levels that increases the probability of only one packet at the highest power levels and thereby augmenting the capture probability. If the traffic load is high, the probability of interfering packets at the same slot increases. Consequently, the transmission probability at the lower power levels increases and the probability of exactly one packet at the highest power levels remains unaltered. As a result, the system is automatically controlled, since it does not need any extra information about the network. Therefore, it is very attractive from an implementation point of view for the emerging mobile networking environment. Extensive comparisons show that the proposed auto-controlled algorithm demands remarkable throughput performance compared with the traditional random power level selection algorithm particularly with a very high retransmission probability. View full abstract»

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  • Least bit error rate adaptive nonlinear equalisers for binary signalling

    Page(s): 29 - 36
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (535 KB)  

    The paper considers the problem of constructing adaptive minimum bit error rate (MBER) neural network equalisers for binary signalling. Motivated from a kernel density estimation of the bit error rate (BER) as a smooth function of training data, a stochastic gradient algorithm called the least bit error rate (LBER) is developed for adaptive nonlinear equalisers. This LBER algorithm is applied to adaptive training of a radial basis function (RBF) equaliser in a channel intersymbol interference (ISI) plus co-channel interference setting. A simulation study shows that the proposed algorithm has good convergence speed, and a small-size RBF equaliser trained by the LBER can closely approximate the performance of the optimal Bayesian equaliser. The results also demonstrate that the standard adaptive algorithm, the least mean square (LMS), performs poorly for neural network equalisers, because the minimum mean square error (MMSE) is clearly suboptimal in the equalisation setting. View full abstract»

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  • Delay bound of youngest serve first (YSF) aggregated packet scheduling

    Page(s): 6 - 10
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (381 KB)  

    A simple scalable aggregated traffic scheduling scheme is proposed, called the 'youngest serve first' (YSF) algorithm. It is shown analytically that YSF can provide bounded end-to-end delay time with high link utilisation that may not be possible for the first-in first-out (FIFO) scheme. View full abstract»

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  • Guaranteeing service rates for cell-based schedulers with a grouping architecture

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (383 KB)  

    Packet fair queueing (PFQ) algorithms are packetised versions of generalised processor sharing (GPS), which is an idealised fluid scheduling model with desirable properties in terms of delay bound and fairness. To support a large number of sessions with diverse bandwidth requirements, the grouping architecture, which is scalable, has been proposed to approximate PFQ algorithms. The authors analyse the relationship between the guaranteed service rates and utilisation for cell-based schedulers with the grouping architecture. Based on this analysis, call admission control (CAC) schemes are proposed to provide the guaranteed service rate for each session, and their performance is evaluated and compared in terms of computational complexity. View full abstract»

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