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Memoryless relay strategies for two-way relay channels

Cui, Tao and Ho, Tracey and Kliewer, Jörg (2009) Memoryless relay strategies for two-way relay channels. IEEE Transactions on Communications, 57 (10). pp. 3132-3143. ISSN 0090-6778.

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We propose relaying strategies for uncoded two-way relay channels, where two terminals transmit simultaneously to each other with the help of a relay. In particular, we consider a memoryless system, where the signal transmitted by the relay is obtained by applying an instantaneous relay function to the previously received signal. For binary antipodal signaling, a class of so called absolute (abs)-based schemes is proposed in which the processing at the relay is solely based on the absolute value of the received signal. We analyze and optimize the symbol-error performance of existing and new abs-based and non-abs-based strategies under an average power constraint, including abs-based and non-abs-based versions of amplify and forward (AF), detect and forward (DF), and estimate and forward (EF). Additionally, we optimize the relay function via functional analysis such that the average probability of error is minimized at the high signal-to-noise ratio (SNR) regime. The optimized relay function is shown to be a Lambert W function parameterized on the noise power and the transmission energy. The optimized function behaves like abs-AF at low SNR and like abs-DF at high SNR, respectively; EF behaves similarly to the optimized function over the whole SNR range. We find the conditions under which each class of strategies is preferred. Finally, we show that all these results can also be generalized to higher order constellations.

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Additional Information:© 2009 IEEE. Paper approved by G.-H. Im, the Editor for Equalization and Multicarrier Techniques of the IEEE Communications Society. Manuscript received April 28, 2008; revised October 12, 2008 and December 24, 2008. This work has been supported in part by DARPA grant N66001-06-C-2020, Caltechs Lee Center for Advanced Networking, the Okawa Foundation Research Grant, NSF grant CCF-0830666, and a gift from Microsoft Research. This paper has been presented in part at the IEEE International Conference on Communications, May 2008, Beijing, China [1], and in part at the Information Theory and Applications Workshop, Jan. 2008, San Diego, CA, USA.
Funding AgencyGrant Number
Defense Advanced Research Projects Agency (DARPA)N66001-06-C-2020
Caltech Lee Center for Advanced Networking UNSPECIFIED
Okawa Foundation Research GrantUNSPECIFIED
NSF CCF-0830666
Microsoft Research UNSPECIFIED
Subject Keywords:Two-way channel; wireless relay networks; functional analysis
Record Number:CaltechAUTHORS:20091104-153456802
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Official Citation:Tao Cui; Ho, T.; Kliewer, J., "Memoryless relay strategies for two-way relay channels," Communications, IEEE Transactions on , vol.57, no.10, pp.3132-3143, October 2009 URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16583
Deposited By: Tony Diaz
Deposited On:16 Nov 2009 17:47
Last Modified:22 Jun 2016 23:14

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