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Communications, IEE Proceedings-

Issue 1 • Date Feb 2002

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Displaying Results 1 - 10 of 10
  • Capacity-coverage analysis of TDD and FDD mode in UMTS at 1920 MHz

    Page(s): 51 - 57
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (759 KB)  

    In the Universal Mobile Telephony System (UMTS) the frequency division duplex (FDD) and time division duplex (TDD) modes have adjacent carriers at 1920 MHz. This creates adjacent channel interference (ACI) between the two different air interfaces. Since different duplexing modes are used, the implications for each system are different, with respect to capacity and coverage: these implications are investigated. The separation distance of the TDD and FDD base station and the load in each system are varied and a symmetrical speech service in both systems is considered, with non-ideal power control assumed. It is found that for an FDD cell radius of 1000 m, a TDD cell radius of 50 m and 10% maximal tolerable outage, the effects of ACI on capacity can be compensated by dynamically increasing the required power at each BS, without affecting the coverage View full abstract»

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  • Performance analysis of threshold based bandwidth allocation scheme for IP traffic on ATM networks

    Page(s): 29 - 35
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (597 KB)  

    The authors analyse a discrete-time based finite queueing model with deterministic service times and a Markov modulated batch Bernoulli process (MMBBP) as a bursty input traffic model in order to investigate the performance of a double threshold based dynamic bandwidth allocation scheme for IP traffic on ATM networks. It is assumed that the segmentation processing time devoted to each cell requires several slot times. In an MMBBP process, the arrivals during a slot time occur as batch Bernoulli processes with the batch size distributions varying according to the phases of a Markov chain. As performance measures, the packet loss probability and the mean packet delay of an arbitrary packet are obtained. Some numerical results are presented to show the performance of the dynamic bandwidth allocation scheme View full abstract»

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  • Interleaving and termination in unpunctured symmetric turbo codes

    Page(s): 6 - 12
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1162 KB)  

    The turbo code interleaver design problem is considered for large block sizes, where the effect of trellis termination is less marked. The performance is compared for various interleavers with a similar block size, including an implementation of the uniform interleaver. An optimised interleaver design technique based on simulated annealing is proposed. The results obtained show that the error performance may be significantly improved without increasing the delay. Finally, interleaver design for small turbo codes is considered. In this case it is shown that while correct termination improves the performance for an average interleaver, its effect on turbo codes with optimised interleavers is negligible. Using the proposed simulated annealing design technique it is easier to include restrictions which make the interleaver correctly-terminating or odd-even. While the S-random algorithm serves well for specifying interleaver spread, the authors believe that their algorithm is better suited for more. sophisticated design criteria View full abstract»

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  • Analysis of dynamic service separation with trunk reservation policy

    Page(s): 23 - 28
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (717 KB)  

    The paper is concerned with the analysis of dynamic service separation under the trunk reservation policy. In the framework of dynamic service separation, statistical multiplexing of cell streams from each service can be well captured by an equivalent capacity that may take a nonlinear form. The conventional trunk reservation policy is extended to consider the nonlinear equivalent capacity. Various connection admission control schemes are formulated to implement blocking equalisation and blocking prioritisation regimes. In particular, the fixed, state-dependent, and hybrid trunk reservation schemes are proposed and compared with the complete sharing scenario. To solve the call-blocking probabilities, a simple yet efficient approximation procedure is carried out, based on an extension of the linear approximation model. Numerical results are reported on the effectiveness of the formulated blocking equalisation and blocking prioritisation regimes, and the degree of accuracy of the proposed approximation procedure View full abstract»

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  • Carrier-frequency estimation for space-diversity reception over selective channels

    Page(s): 58 - 64
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (711 KB)  

    Carrier-frequency estimation for space-diversity reception over frequency-selective channels is discussed. Three estimation schemes based on training sequences are proposed. The first scheme employs arbitrary sequences and provides joint maximum likelihood (ML) estimates of the carrier frequency and the channel response. Its implementation is complex, but its accuracy achieves the Cramer-Rao bound. The second scheme is based on the ML criterion but employs periodic sequences to reduce the computational load. Periodic sequences are also used in the third scheme which is based on heuristic reasoning. Theoretical analysis and simulations are employed to assess the performance of the three estimation methods, and to show the improvements due to space diversity View full abstract»

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  • Destination-initiating path restoration protocol for wavelength-routed WDM networks

    Page(s): 18 - 22
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    Network survivability has been a crucial concern in wavelength-routed WDM networks. Due to the huge transmission capacity, a single network failure may cause a large amount of data loss, which would greatly degrade and even disrupt network services. In the paper, a destination initiating path restoration protocol is proposed for surviving single-link failures in wavelength routed WDM networks. Unlike existing path restoration protocols, the proposed protocol allows the destination node of a broken connection to initiate a connection restoration process. The objective is to reduce the connection restoration time so that a backup path can be provisioned rapidly for each broken connection that traverses a failed link. The major procedures of the protocol are described and its performance in terms of the connection restoration time is evaluated View full abstract»

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  • Decoding of generalised low-density parity-check codes using weighted bit-flip voting

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (670 KB)  

    A generalised low-density parity-check code (GLDPC) is a low-density parity-check code in which the constraint nodes of the code's graph are replaced with component or subcodes other than single parity checks. Gallager's (1963) bit-flipping algorithm for LDPCs is generalised to the class of GLDPCs with Hamming subcodes. The proposed weighted bit-flip voting (WBFV) method is iterative and uses only the hard decision decoder of the Hamming subcodes. Decoding of Hamming-based GLDPCs using WBFV has been simulated on the binary symmetric channel. Simulation results are presented showing the variation in performance with voting rule, graph construction and block length. In terms of the dependence of coding gains and complexity on the GLDPC block length, the proposed method is found to display a good performance to decoding complexity trade-off. The performance is found to compete well with other more conventional hard decision decoding schemes View full abstract»

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  • Blind equalisation technique based on an improved constant modulus adaptive algorithm

    Page(s): 45 - 50
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    A blind equalisation technique based on an improved constant modulus adaptive (CMA) algorithm is proposed. This technique can accomplish blind equalisation and carrier phase recovery simultaneously as well as easily switch between blind and decision-directed modes. It also takes advantage of the principle of minimum disturbance to avoid the gradient noise amplification problem and achieve improved stability and robustness with low computational complexity. It can be easily switched over to a decision-directed equalisation scheme whenever the error level is reasonably low to obtain higher convergence speed and lower residual intersymbol interference as well. Computer simulation results have indicated very attractive behaviour of the proposed technique, especially with respect to various noise characteristics and time-varying channels View full abstract»

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  • Coherent frequency/phase modulation scheme

    Page(s): 36 - 44
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (819 KB)  

    An L-phase-levelled coherent frequency/phase modulation (LCFPM) scheme is investigated. It is analysed for both spectral characteristics and bit error characteristics on the additive white Gaussian noise channel. Comparison with conventional joint frequency and phase modulations is conducted in terms of power and bandwidth efficiencies. Both uncoded and trellis coded modulation formats are considered. It is found that LCFPM is highly competitive in power and bandwidth efficiencies with conventional dual-frequency joint frequency and phase modulations after experimenting with different uncoded and trellis-coded pulsed formats View full abstract»

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  • Transmitter buffer behaviour of stop-and-wait ARQ schemes with repeated transmissions

    Page(s): 13 - 17
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    The statistical analysis of a number of previously proposed ARQ protocols of the stop-and-wait type is performed. Specifically, a method is described to find the tail distribution (i.e. the probability of exceeding a certain threshold) for the delay time of the transmitted data blocks and the queue or buffer occupancy at the transmitter side. A performance comparison of the schemes is given, based on both throughput and tail probability considerations View full abstract»

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