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On the capacity of frequency-selective channels in training-based transmission schemes

Vikalo, Haris and Hassibi, Babak and Hochwald, Bertrand and Kailath, Thomas (2004) On the capacity of frequency-selective channels in training-based transmission schemes. IEEE Transactions on Signal Processing, 52 (9). pp. 2572-2583. ISSN 1053-587X. doi:10.1109/TSP.2004.832020.

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Communication systems transmitting over frequency-selective channels generally employ an equalizer to recover the transmitted sequence corrupted by intersymbol interference (ISI). Most practical systems use a training sequence to learn the channel impulse response and thereby design the equalizer. An important issue is determining the optimal amount of training: too little training and the channel is not learned properly, too much training and there is not enough time available to transmit data before the channel changes and must be learned anew. We use an information-theoretic approach to find the optimal parameters in training-based transmission schemes for channels described by a block-fading model. The optimal length of the training interval is found by maximizing a lower bound on the training-based channel capacity. When the transmitter is capable of providing two distinct transmission power levels (one for training and one for data transmission), the optimal length of the training interval is shown to be equal to the length of the channel. Further, we show that at high SNR, training-based schemes achieve the capacity of block-fading frequency selective channels, whereas at low SNR, they are highly suboptimal.

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Additional Information:© 2004 IEEE. Reprinted with permission Manuscript received November 19, 2002; revised September 15, 2003. [Posted online: 2004-08-16] The associate editor coordinating the review of this manuscript and approving it for publication was Prof. Nicholas D. Sidiropoulos.
Subject Keywords:Block fading, frequency-selective channels, intersymbol interference
Issue or Number:9
Record Number:CaltechAUTHORS:VIKieeetsp04
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3280
Deposited By: Archive Administrator
Deposited On:25 May 2006
Last Modified:08 Nov 2021 19:54

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