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Performance Bounds for Bi-Directional Coded Cooperation Protocols (2008)
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BibTeX
@MISC{Kim08performancebounds,
author = {Sang Joon Kim and Patrick Mitran and Vahid Tarokh},
title = { Performance Bounds for Bi-Directional Coded Cooperation Protocols},
year = {2008}
}
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Abstract
In coded bi-directional cooperation, two nodes wish to exchange messages over a shared half-duplex channel with the help of a relay. In this paper, we derive capacity bounds for this problem for each of three protocols. The first protocol is a two phase protocol where both users simultaneously transmit during the first phase and the relay alone transmits during the second. In this protocol, our bounds are tight. The second protocol considers sequential transmissions from the two users followed by a transmission from the relay while the third protocol is a hybrid of the first two protocols and has four phases. In the latter two protocols the inner and outer bounds are not identical, and differ in a manner similar to the inner and outer bounds of Cover’s relay channel. Numerical evaluation shows that at least in some cases of interest our bounds do not differ significantly. Finally, in the Gaussian case with path loss, we derive achievable rates and compare the relative merits of each protocol in various regimes. This case is of interest in cellular systems. Surprisingly, we find that in some cases, the achievable rate region of the four phase protocol sometimes contains points that are outside the outer bounds of the other protocols.
Keyphrases
performance bound bi-directional coded cooperation protocol outer bound capacity bound phase protocol numerical evaluation network coding bi-directional communication second protocol considers sequential transmission third protocol first protocol path loss relay channel bi-directional cooperation cellular system index term cooperation achievable rate region various regime half-duplex channel relative merit first phase achievable rate gaussian case
