Prefiltered space-Time M-BCJR Equalizer for MIMO Frequency-Selective Channels. Fragouli, C., Al-Dhahir, N., Diggavi, S. N., & Turin, W. CISS, 2001.
abstract   bibtex   
This paper addresses the problem of soft equalization for time-variant frequency-selective channels. Such a channel arises in EDGE (Enhanced Data for GSM Evolution), third generation TDMA proposal, which employs 8-PSK modulation with a linearized GMSK pulse shaping filter that introduces strong intersymbol interference. The proposed equalization approach uses a prefilter to concetrate the effective channel power in a small number of taps, followed by a reduced complexity MAP equalizer to produce soft decision outputs. The MAP equalizer is based on the implementation of the M-algorithm in the log domain. The prefilter introduces residual intersymbol interference which degrades the performance of MAP when applied to the trellis of the shortened channel. However, the shape of the overall shortened channel impulse response allows the M-algorithm to approximate the prefiltered MAP performance with a small number of states. Based on this general framework, we investigate several enhancements, such as using a different prefilter for the forward and backward recursion, concatenating two trellis steps during decoding, and temporal oversampling. The performance is evaluated through simulations over the typical urban (TU) EDGE channel.
@article{fragouli_prefiltered_2001,
 abstract = {This paper addresses the problem of soft equalization for time-variant frequency-selective channels. Such a channel arises in EDGE (Enhanced Data for GSM Evolution), third generation TDMA proposal, which employs 8-PSK modulation with a linearized GMSK pulse shaping filter that introduces strong intersymbol interference. The proposed equalization approach uses a prefilter to concetrate the effective channel power in a small number of taps, followed by a reduced complexity MAP equalizer to produce soft decision outputs. The MAP equalizer is based on the implementation of the M-algorithm in the log domain. The prefilter introduces residual intersymbol interference which degrades the performance of MAP when applied to the trellis of the shortened channel. However, the shape of the overall shortened channel impulse response allows the M-algorithm to approximate the prefiltered MAP performance with a small number of states. Based on this general framework, we investigate several enhancements, such as using a different prefilter for the forward and backward recursion, concatenating two trellis steps during decoding, and temporal oversampling. The performance is evaluated through simulations over the typical urban (TU) EDGE channel.},
 type={4},
 author = {Fragouli, C. and Al-Dhahir, N. and Diggavi, Suhas N. and Turin, W.},
 journal = {CISS},
 tags = {channel_coding},
 title = {Prefiltered space-{Time} {M}-{BCJR} {Equalizer} for {MIMO} {Frequency}-{Selective} {Channels}},
 year = {2001}
}

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