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Communications, IEE Proceedings-

Issue 2 • Date Apr 1996

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Displaying Results 1 - 9 of 9
  • Hybrid-ARQ system for HF channels based on codeword partitioning

    Publication Year: 1996
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    A technique by which the codewords of an error-correcting code are partitioned to obtain an error-detecting code with half the original length is described. It is intended to be used in a hybrid-ARQ system for achieving high throughput on HF channels. Performance evaluations of examples based on BCH and RS codes are also provided View full abstract»

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  • Sojourn time analysis of prioritised DQDB (IEEE802.6) MAN with bursty traffic input

    Publication Year: 1996 , Page(s): 112 - 116
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    The sojourn time of the prioritised DQDB MAN with bursty traffic input is studied. The expression of the mean sojourn time of the message transmitted at the higher priority level is given. After an investigation of the transient behaviour of a related random walk process, the sojourn time of the packet at the lower priority level is derived. The authors obtain the expression for the mean sojourn time of the message with the lower transmission priority. The conclusions drawn are that the mean sojourn time of the message at either higher or lower priority, is approximately a linear function of the mean message length, and a marked performance improvement is obtained by adopting the higher priority level for the user, especially when the lower-priority traffic load from the downstream users is heavy View full abstract»

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  • Discrete-time analysis of the leaky bucket scheme with threshold-based token generation intervals

    Publication Year: 1996 , Page(s): 105 - 111
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    In the ATM network, the leaky bucket scheme is a promising method that regulates the input traffic for preventive congestion control. In order to satisfy the loss probability constraint of more bursty input traffic, it is known that the leaky bucket scheme with a static token generation interval requires a larger data buffer and token pool size. This causes an increase in the mean waiting time for the input traffic to pass the leaky bucket scheme, which would be inappropriate for real time traffic such as voice and video. The authors present the leaky bucket scheme with threshold-based token generation intervals in which the token generation interval changes according to the buffer occupancy. The proposed leaky bucket scheme is analysed in the discrete-time case by assuming the arrival process to be a Markov-modulated Bernoulli process (MMBP). The authors show that the quality of service (QoS) of the input traffic is satisfied with a smaller data buffer and token pool size in the proposed leaky bucket scheme View full abstract»

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  • Digital transmission using multimode phase-continuous chirp signals

    Publication Year: 1996
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    In a spread-spectrum system the transmitted signal is spread over a wide frequency band, often much wider than the minimum bandwidth needed for the information to be conveyed. The concept of varying the modulation index of a continuous phase FSK (i.e. CPFSK) waveform is applied to digital transmission using chirp signals. These multimode chirp waveforms are described and their ability to perform over the coherent Gaussian channel is examined. It is shown that the dual-mode phase-continuous chirp signals out perform monomode signals by nearly 0.8 dB, when corresponding high-SNR 5-bit optimum minimum-bit-error-probability receivers are employed. A low-complexity suboptimum average matched filter receiver for multimode chirp signals is examined and explicit expressions for its performance are given View full abstract»

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  • Reduced-state trellis and its decoding for full-response CPM

    Publication Year: 1996
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    A new reduced-state trellis and Viterbi decoding for binary full-response continuous phase modulation (FRCPM) are derived. The theoretical and simulated error-rate performance of the reduced-state trellis decoding is presented. It is shown that the reduced-state trellis decoding of FRCPM with small modulation index can provide almost the same error-rate performance as the original-state trellis decoding at high signal-to-noise ratio View full abstract»

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  • Evaluation of efficient trellis methods for soft decision decoding of Reed-Solomon codes

    Publication Year: 1996
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    Various novel trellis decoding methods are suggested that make it easy to incorporate soft decision methods for Reed-Solomon codes. For each decoding method the advantages and disadvantages are pointed out. The performance and computational efficiency of each decoder are estimated using simulation on an AWGN channel. From the simulation results the best of these trellis decoding schemes is suggested for particular codes and particular applications View full abstract»

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  • Preventive flow control method for packet video

    Publication Year: 1996
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Broadband ISDN (B-ISDN) networks utilising asynchronous transfer mode (ATM) are expected to provide the transport infrastructure for broadband multiservice applications. A preventive flow control method suitable for video services within an ATM network is presented. In this method each video encoder employs a model of the aggregate traffic of all sources sharing the virtual path with the heaviest traffic. The aggregate traffic is modelled knowing the mean, peak-to-mean and the number of sources passing through the bottleneck link of the transmission path. Once the encoder's estimate of the aggregate traffic has reached a certain level of the channel capacity, it adjusts its bit rate accordingly. The impact of self flow control on both coding and network performance is investigated. It is shown that both network performance and perceived image quality are optimised for a threshold level corresponding to an estimated traffic of 80% of the channel rate View full abstract»

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  • Optical power distribution in wireless infrared LANs

    Publication Year: 1996
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    The problem of optical power distribution in a wireless, in-room, local-area network based on IR technology is studied. The distribution of optical power in an office room or shop floor environment produced by a grid of light sources is examined. The influence in the uniformity of power distribution of factors, such as radiant intensity, pattern of the light sources and number of transmitters is studied. The optimum number of transmitters is calculated as a function of the room size. The data presented could be useful to the designer of an in-room IR communication system View full abstract»

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  • Fast adaptive polynomial I and Q predistorter with global optimisation

    Publication Year: 1996
    Cited by:  Papers (6)  |  Patents (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    High spectral efficiency modulation methods such as quadrature amplitude modulation are of considerable interest for future mobile communication systems. These methods are highly sensitive to transmitter power amplifier nonlinearities. The linearity of a power amplifier can be improved by using an adaptive nonlinear predistorter. A modified version of a previously reported polynomial lineariser is presented which has a faster rate of convergence by an order of magnitude. Faster convergence is achieved using postdistorter polynomial functions of two variables. The price is a 30% higher computation load for a predistorter having six coefficients. It is shown analytically that the gain and phase errors in the output demodulator used for adaptation of the predistorter simply result in a phase offset equal to the phase error. Adaptability of the proposed lineariser with changes in the power amplifier, predistorter quadrature modulator and the output demodulator are tested. The results show that the lineariser can adapt to these changes. The effect of the rotation of the demodulated output signal phase on convergence is studied. It is shown that the optimum value for this rotation is in the range of 15 to 70°. Spectrum-spreading results for different values of output back-off are included View full abstract»

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