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By Topic

Communications, IEE Proceedings-

Issue 1 • Date Feb 1996

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Displaying Results 1 - 9 of 9
  • Serving system with the correlated component of overflow traffic having changed serving intensity

    Publication Year: 1996 , Page(s): 1 - 4
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The serving model of two Poisson traffic distributions in the first choice trunk group has been explicitly solved, whereupon the rejected calls of one of the traffic distributions are directed to a second trunk group and are served with changed serving intensity. This problem is encountered in situations where; owing to requesting a connection through several nodes on the alternative route of a circuit switching network, the mean occupation time is increased, or when this time is reduced due to the existence of the information about the increased cost of using the alternative route. The analytical solutions for the losses, state probabilities and overflow traffic moments are the generalisation of the solutions of some simpler overflow traffic models View full abstract»

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  • Optimum time diversity for channels subject to pulse-burst interference

    Publication Year: 1996 , Page(s): 43 - 46
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    Results of optimum time diversity for Gaussian and Rayleigh fading channels subject to pulse-burst interference of large power and duty-cycle λ are presented. For NC-BFSK and DPSK signals the Chernoff upper bound is used to obtain expressions of the optimum diversity and the average bit error rate. Both hard-decision and soft-decision decoding are considered. It is particularly shown that the optimum diversity obtained using exact analysis and the Chernoff upper bound are nearly equal, and that the results are valid for conventional as well as spread-spectrum systems. It is concluded that the optimum time diversity known as the repetition code can be used as an effective countermeasure against pulsed interference of high power. With optimum diversity, the exponential relation between power and bandwidth is recovered for both the Gaussian and Rayleigh channels. Using soft-decision decoding, the combined effect of pulse-burst interference and the noncoherent combining loss is a reduction in the effective signal/noise ratio by factors of (I-λ0.25) and (1-λ)2 for Gaussian and Rayleigh channels, respectively. For Gaussian channels, exact analyses show that hard-decision decoding results in an additional loss of 2 dB for λ→0, increasing to 3 dB as λ→1. Using the Chernoff upper bound, hard-decision decoding results in an additional loss of 3 dB for all values of λ. For Rayleigh channels with optimum diversity, hard-decision decoding is 3 dB inferior to soft-decision decoding View full abstract»

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  • Discrete-time model for digital communications over a frequency-selective Rician fading WSSUS channel

    Publication Year: 1996 , Page(s): 37 - 42
    Cited by:  Papers (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    The paper develops a discrete-time model for digital communications via a frequency-selective Rician fading, wide-sense-stationary uncorrelated-scattering (WSSUS) channel with arbitrary pulse shaping and receiver filtering. As a special case, the discrete-time model is also applicable to a frequency-selective Rayleigh fading WSSUS channel. The model is expressed in the form Ξk=Nk+Σbk-mgm(t), where Ξk is the complex-valued receiver output, bk-m is the transmitted symbol, Nk is the complex-valued output noise due to AWGN, and gm(t) is the time-varying gain of bk-m. Statistical characteristics of Nk and g m(t) are derived. It is found that {Nk} is a zero-mean complex Gaussian sequence, and gm(t)s∀m follow a wide-sense-stationary, jointly complex Gaussian random process. Simple closed-form formulas computing statistical parameters of Nk and gm(t)s are derived. Several aspects regarding the use of the proposed model to analytic works and efficient computer simulations are discussed. Finally, three illustrative examples are given View full abstract»

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  • Destructive collision-free protocol for distributed DS/CDMA wireless networks using code-sensing and chip-rate-division techniques

    Publication Year: 1996 , Page(s): 47 - 55
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (812 KB)  

    In the paper a spreading code protocol (the code-sensing R3 code protocol) designed for wireless local networks is proposed and its performance is analysed. In a network adopting the protocol, destructive collisions among terminals are minimised by utilising the busy code-sensing and dual chip-rate techniques in transmissions of the REQ and ACK/data packets. A two-dimensional continuous-time Markov model is applied to study the behaviour of the protocol. The results show that a respectable improvement in throughput-delay performance can be achieved by the proposed protocol when compared to those previously reported in the literature View full abstract»

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  • Type-1 hybrid ARQ scheme with time diversity for binary digital FM cellular radio

    Publication Year: 1996 , Page(s): 29 - 36
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    A type-1 hybrid automatic-repeat-request (ARQ) scheme with time diversity combining is proposed and its performance analysed for binary digital FM (BFM) mobile radio communications. Time diversity combining is achieved by exploiting the packet retransmission nature inherent in the ARQ scheme. The ARQ scheme employs a high-rate error-correcting code with either hard-decision decoding or soft-decision decoding. Received signal envelopes are sampled and used as channel state information (CSI) in the decoding process. Numerical results on the system throughput and decoded bit error rate (BER) are presented as functions of average information signal-to-noise ratio, average information signal-to-interference ratio, and random FM noise View full abstract»

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  • Analysis of bandwidth allocation schemes for transmission of VBR video traffic on a FODA satellite network

    Publication Year: 1996 , Page(s): 12 - 20
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (872 KB)  

    FODA (FIFO ordered demand assignment), an access protocol for satellite networks based on a TDMA technology, is designed to support integrated services. To this end, FODA provides two types of service: synchronous and asynchronous; only the users of the synchronous service have guaranteed bandwidth. In the paper the authors focus on the synchronous service alone and investigate static bandwidth allocation strategies which satisfy the quality of service (QoS) requirements (i.e. a limited transfer delay and a packet loss rate <10-6) for the transmission of the data generated by a variable bit rate (VBR) video codec. By solving an analytical model it is shown that, due to the stringent QoS constraints, the amount of reserved bandwidth for VBR video applications must be much higher than their throughput. Hence a portion of low-priority traffic (e.g. EDP data) can be transmitted on the FODA synchronous services to utilise the satellite link to the maximum extent. Via simulation, the authors analyse, for the bandwidth allocation schemes which provide an acceptable QoS for high-priority traffic, the QoS available to low-priority users View full abstract»

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  • Adaptive differential detection for M-ary DPSK

    Publication Year: 1996 , Page(s): 21 - 28
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    The adaptive differential detection (adaptive DD) of M-ary DPSK signals is proposed in which the phase reference for differential detection is estimated using the least mean square algorithm with step size optimally adapted to changing channel conditions. The Viterbi algorithm and decision feedback algorithm are applied to effectively perform the maximum likelihood detection of the transmitted phase sequence. The bit error rate (BER) performance of adaptive DD is evaluated by computer simulations of 4DPSK in additive Gaussian noise (AWGN) and Rayleigh fading channels. In AWGN channels, BER performance close to that of coherent detection with differential decoding is achieved with performance loss of only 0.3 dB. In Rayleigh fading, the irreducible BER owing to fading Doppler spread can be reduced almost by half compared with conventional DD without prior knowledge of fading statistics View full abstract»

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  • Synchronised call handoff performance model

    Publication Year: 1996 , Page(s): 56 - 60
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    The performance of a synchronised call handoff algorithm called the `hierarchical optimisation handoff algorithm' (HOHA) is analysed. New results are presented with the derivation of an analytical model which describes the behaviour of the HOHA and provides an upper bound on its performance View full abstract»

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  • Queueing system with queue length dependent service times and its application to cell discarding scheme in ATM networks

    Publication Year: 1996 , Page(s): 5 - 11
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    The authors analyse a queueing system MMPP/G1,G2 /1/B with queue length dependent service times. The arrival process of customers is assumed to be a Markov-modulated Poisson process (MMPP), and the distribution of service time of customers is G1 or G2, dependent on the queue length at the service initiation epoch. The authors obtain the queue length distribution both at departure epochs and at arbitrary times, and then obtain the loss probability and the mean waiting time. They apply their results to the cell discarding (CD) scheme operating at the output of a buffer for voice traffic in ATM networks. They also give some numerical examples to show the effects of the CD scheme View full abstract»

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