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Power Allocation Policies for Convolutional and Turbo Coded Systems Over Fading Channels

Rangarajan, Arun and Singh, Shialendra K and Sharma, Vinod (2003) Power Allocation Policies for Convolutional and Turbo Coded Systems Over Fading Channels. In: Conference on Convergent Technologies for Asia-Pacific Region TENCON 2003, 15-17 October, Bangalore,India, Vol.1, 155-159.


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In this paper we study adaptive power allocation (PA) policies for improving the performance of convolutional and turbo codes on fading channels. The transmitter has an average power constraint. The fading process can be continuous (e.g., Rayleigh distribution). Perfect channel state information at the transmitter (CSIT) and the receiver (CSIR) are assumed. For convolutional codes, we consider block (slow) fading and fast fading environments separately and propose new PA policies that reduce the BER. We do a comparative study of the proposed PA policies with commonly used policies, e.g. water filling, (truncated) channel inversion and an optimal policy proposed by Hayes (1968) for an uncoded system. For all the cases studied, we show that the proposed policies substantially outperform commonly used policies. Among existing policies, only Hayes' gives performance improvement over constant PA. We show that interleaving with PA can improve significantly the performance of coded systems on block fading channels. We also make the important observation that the improvements in BER obtained with PA increase with SNR, which is in sharp contrast to the negligible gain in channel capacity obtained with PA [6]. Since direct optimization for turbo codes is difficult, we use the policies derived for convolutional codes on the constituent convolutional codes of turbo codes and show that significant performance improvements can be obtained.

Item Type: Conference Paper
Publisher: IEEE
Additional Information: �©1990 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Keywords: Power allocation;Block fading;Fast fading; Inter leaving;Convolutional codes;Turbo codes
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 23 Dec 2005
Last Modified: 19 Sep 2010 04:22
URI: http://eprints.iisc.ac.in/id/eprint/4757

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