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Communications, IEE Proceedings-

Issue 6 • Date Dec 1998

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Displaying Results 1 - 11 of 11
  • Performance analysis of an FFH/BFSK self-normalising receiver under multitone jamming

    Page(s): 431 - 436
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    Analytical expressions for bit-error probability are derived for a fast frequency-hopping binary frequency-shift-keying (FFH/BFSK) spread-spectrum (SS) communication system based on Taylor-series expansion. The FFH system employs a soft-decision self-normalising receiver against the worst-case multitone jamming (MTJ) and additive white Gaussian noise (AWGN). The authors' analysis, validated by the simulation results, shows that the band MTJ is generally more harmful than the corresponding independent MTJ. Unlike the soft-decision linear-combining receiver, the worst-case partial-band jamming (PBJ) causes slightly poorer bit-error-rate (BER) performance than the corresponding worst-case band MTJ for the self-normalising receiver with diversity. The BER performance of the self-normalising receiver is shown to be significantly better than that of the soft-decision linear-combining receiver under the conditions of the worst-case band MTJ and AWGN View full abstract»

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  • Code acquisition with diversity combining for FFH/MFSK spread spectrum systems

    Page(s): 437 - 444
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    Pseudonoise code acquisition based on hard-decision and clipped diversity combining is investigated for fast frequency-hopped MFSK systems under the effects of white Gaussian noise, band multitone jamming and multipath fading. Multipath fading may affect the signal or jamming channel or both. An analytical method is developed to evaluate the mean acquisition time and the operating characteristics of the acquisition system for various jamming and channel conditions. Numerical results show that the time diversity offered by a fast hopper can provide a significant performance improvement and may be indispensable in some cases to obtain a satisfactory performance; the clipped diversity combining outperforms the hard-decision diversity combining, and under some jamming and channel conditions the performance difference of these two methods can be significant; and multipath fading on the signal path degrades the acquisition performance. 1-4 dB degradation is observed, whereas fading on the jamming path reduces the effectiveness of a jamming signal. Computer simulations are also conducted to substantiate the analytical results View full abstract»

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  • Transmission modelling of ENCAP-OQPSK radio links

    Page(s): 419 - 425
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    Offset quaternary PSK-type (OQPSK) digital modulation schemes are strongly recommended for radio transmission within land mobile and/or satellite communication systems requiring good power/bandwidth tradeoffs and low-cost, power-efficient implementations. The ENCAP-OQPSK design method (encoded-amplitude-and-phase) previously proposed by the authors was shown to provide a wide class of OQPSK-type schemes of practical interest; a flexible, digital transmitter implementation can be directly based on the encoding rules of this design method. The paper deals with the transmission modelling of radio links where ENCAP-OQPSK modulators are employed. In spite of the apparent complexity of the encoding rules, it was possible to define an appropriate signal model, both accurate and user-friendly. In fact, the nonlinearly modulated ENCAP-OQPSK signals can always be exactly represented as a sum of linear OQPSK-type components. Similar representations, also exact, can be adopted for any signal obtained by filtering and/or nonlinear amplification of the signals. This modelling approach simplifies spectral computations and performance evaluations, and is quite accurate, in general, when the sum of the two main linear components is used to approximate the transmitted signals View full abstract»

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  • MQAM modulation and RS codes for SS-CDMA communication over Rician fading channels

    Page(s): 414 - 418
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    The use of bandwidth efficient high level modulation systems such as quadrature-amplitude modulation (MQAM) and multiphase (MPSK), together with Reed-Solomon (RS) codes, provides substantial coding gain on fading channels. The author derives the optimum modulation and coding parameters of RS coded MPSK and MQAM schemes. The transmission channel is subject to flat Rician fading and spread-spectrum code-division multiple-access (SS-CDMA) interference. For RS codes defined over GF(M m), the encoded symbols are mapped to the signal points of an expanded set with cardinality of M such that each RS code symbol consists of concatenation of m M-ary symbols. It is shown that there is an optimum selection of m which minimises the bit-error rate. The Gaussian approximation is used to derive a simple expression of the probability of error (Pc) using RS codes. Finally, the optimum modulation and coding parameters which optimise the bit-error performance are obtained by setting partial derivatives of Pc to zero and solving the resulting equations. It is shown that the optimum choice of modulation and coding parameters depends on the channel interference and fading conditions. Although exact analysis can be used, the present approach yields a general solution, and optimum design parameters can be related to channel conditions View full abstract»

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  • Analysis of DPSK nonlinear combiner over fading channels with impulse noise

    Page(s): 406 - 413
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    Analysis of the performance of an L-diversity DPSK nonlinear combiner in frequency nonselective Rayleigh fading channels with impulse noise is presented. By employing the characteristic function, asymptotic and approximate bit error probabilities are derived. Analysis and simulation results indicate that by equipping a nonlinear element in the equal-gain combiner, the new detector can effectively combat impulse noise and fading View full abstract»

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  • Performance analysis of priority leaky bucket scheme with queue-length-threshold scheduling policy

    Page(s): 395 - 401
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    The leaky bucket scheme is a promising method that regulates input traffic for preventive congestion control in ATM networks. One of the important problems in ATM networks is meeting the quality of service requirements for real-time and non-real-time traffic. The authors propose a priority leaky bucket scheme with queue-length-threshold scheduling policy. The motivation of this proposed leaky bucket scheme is to meet the quality of service for real-time traffic while providing more improved services for non-real-time traffic. Using the embedded Markov chain method, the authors obtain the joint distribution of the queue lengths, the loss probability and the mean waiting time. Numerical results show the effects of the system parameters such as the buffer size and the token pool size on the performance of the proposed scheme View full abstract»

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  • Multiparty videoconferencing on multi-drop VP-based SONET/ATM rings: performance analysis

    Page(s): 389 - 394
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    A type of multiparty videoconferencing in VP-based SONET/ATM ring networks under the minimum hop routing rule is analysed. For this type of conference, only the video and voice of the current speaker are broadcast to other conferees. A queueing model is presented. Conference blocking probabilities and video freeze probabilities are derived and are shown to be in close agreement with the simulation results View full abstract»

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  • Optimising indoor base-station locations in coverage- and interference-limited indoor environments

    Page(s): 445 - 450
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    Investigations into optimising the locations of base stations in an indoor wireless communications network are reported. The method is based on introducing quality-of-service criteria and using these to form an objective function in an optimisation scheme. Using this approach both coverage- and interference-limited environments are handled. Results are provided based on an accurate propagation prediction model to estimate local mean signal power. These demonstrate that significant improvements in quality of service can be obtained by optimising the locations of base stations View full abstract»

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  • Channel assignment of cellular mobile systems with nonuniform cells

    Page(s): 451 - 456
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    The degree of co-channel interference and the required number of channels are used as the difficulty degree in assigning channels in cellular mobile systems with nonuniform cells. To minimise the total number of channels required, a heuristic algorithm is proposed with the requirement-exhaustive strategy definitions of assignment difficulty degree. In the experiments, the results obtained with the authors' algorithm are compared with near-optimal assignment results. The performance of the algorithm with various types of difficulty degree under different conditions is investigated. The one which gives the minimum total number of channels required in the channel assignment strategy is used and compared with the lower bound using the seven-cell frequency reuse pattern View full abstract»

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  • Incomplete locator polynomials and redundant iterations reduction in the Welch-Berlekamp algorithm

    Page(s): 402 - 405
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    A concept named `incomplete locator polynomial' is introduced as a replacement for the traditional approach. Theorems for finding the incomplete locators were established when the Welch-Berlekamp algorithm (1986) was employed for decoding Reed-Solomon codes, and an incomplete iteration strategy of decoding Reed-Solomon codes, based on finding incomplete locator polynomials is presented, by which the redundant iterations in the Welch-Berlekamp algorithm are reduced significantly View full abstract»

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  • Adaptive MLSE of QAM signals over frequency nonselective Rayleigh fading channels

    Page(s): 426 - 430
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    Maximum likelihood sequence estimation (MLSE) of QAM signals over frequency nonselective Rayleigh fading channels is examined. Adaptive prediction filters are applied to reduce the computational complexity related to the design of the prediction filters. The error performance of this receiver is evaluated through computer simulations. It is found that the superior error performance of the 16 star QAM signals over 16-DPSK for coherent detection is preserved for MLSE when adaptive prediction filters are used View full abstract»

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