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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of wireless information networks 1 (1994), S. 239-252 
    ISSN: 1572-8129
    Keywords: Flat fading ; quadrature amplitude modulation ; slow frequency hopping ; time-division-multiple-access
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract High performance and reasonable complexity have made pilot-symbol-assisted modulation (PSAM) of great practical interest in mobile communications. However, no previous work has investigated PSAM in burst-mode operation which is commonly encountered in multiple-access schemes (time-division or slow-frequency-hopped system). This paper examines the burst structure design problem in a frequency-flat fading environment. The explicit relationship between error performance and the design parameters, including pilot allocation, frequency offset, Doppler spread, and modulation scheme, is explored. Periodic pilot insertion commonly used for continuous transmission produces degraded performance in burst-mode operation. A new, unequal-pilot-spacing burst architecture is proposed in this paper to achieve better error performance. This work also focuses on the potential performance improvement of a frequency offset estimator and a Doppler spread estimator. The results show that an improvement up to 2.5 dB in SNR/bit can be attained by a Doppler spread estimator. A significant frequency offset can produce an irreducible error floor or a severe reduction in the throughput rate if no compensation is implemented. The performance degradation investigated in this paper can be used to determine the specification of the frequency offset estimator and the Doppler spread estimator used in conjunction with PSAM.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of wireless information networks 1 (1994), S. 131-139 
    ISSN: 1572-8129
    Keywords: QAM modulation ; differential encoding ; Rayleigh fading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper presents some closed-form bit error probability expressions for coherent demodulation of both Gray coded and differentially decoded Gray coded QAM modulations in nonfading and frequency nonselective Rayleigh fading channels. These results demonstrate that as QAM constellation sizes get larger the BEP degradation due to differential encoding and decoding becomes negligible.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Wireless networks 4 (1998), S. 507-514 
    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract We present a novel symbol-by-symbol Bayesian multiuser detector for cochannel interference cancellation in TDMA cellular communications. To begin with, we present the usual composite signal model consisting of the desired signal, interferer, channel parameters and channel noise. Then, we derive the soft output interference cancellation algorithm (SICA) to compute fixed-lag maximum a posteriori (MAP) estimates of the data symbols of the desired user, using a fixed lookahead of D observations. In the process, the interferer symbols are treated as nuisance parameters and averaged out. The complexity of the SICA is exponential in the length of the combined channel at the receiver. Subsequently, we present a simple, yet effective, technique for complexity reduction without significant performance degradation. We apply the algorithm to some typical scenarios, using the IS-136 TDMA standard, to demonstrate its interference suppression capabilities. In this paper, we assume that all relevant channel parameters are known. Hence, our results should be viewed as representing the best possible performance that can be obtained with the SICA in the scenarios considered.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of wireless information networks 2 (1995), S. 41-54 
    ISSN: 1572-8129
    Keywords: Conditional decision feedback estimator ; delay spread ; Doppler spread ; cochannel interference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper applies the Bayesian conditional decision feedback estimator (BCDFE) to rapidly fading frequency selective channels. The BCDFE is a model-based deconvolution algorithm which jointly estimates the transmitted data and channel parameters. The BCDFE smoothly transitions between trained and blind operation and consequently provides robust performance in rapidly fading channels. We provide a brief derivation of the BCDFE and characterize the performance on the land mobile radio channel. We assess the BCDFE's principle design characteristics and the resulting performance in both transient and steady-state operation. The effects of delay spread, Doppler spread, and cochannel interference on the bit error probability performance are also presented. The BCDFE demonstrates many of the desirable characteristics of an equalizer for mobile radio.
    Type of Medium: Electronic Resource
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