Generalizing the Amplify-and-Forward Relay Gain Model: An Optimal SEP Perspective

Sainath, B and Mehta, Neelesh B (2012) Generalizing the Amplify-and-Forward Relay Gain Model: An Optimal SEP Perspective. In: IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, 11 (11). pp. 4118-4127.

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Abstract

Two models for AF relaying, namely, fixed gain and fixed power relaying, have been extensively studied in the literature given their ability to harness spatial diversity. In fixed gain relaying, the relay gain is fixed but its transmit power varies as a function of the source-relay channel gain. In fixed power relaying, the relay transmit power is fixed, but its gain varies. We revisit and generalize the fundamental two-hop AF relaying model. We present an optimal scheme in which an average power constrained AF relay adapts its gain and transmit power to minimize the symbol error probability (SEP) at the destination. Also derived are insightful and practically amenable closed-form bounds for the optimal relay gain. We then analyze the SEP of MPSK, derive tight bounds for it, and characterize the diversity order for Rayleigh fading. Also derived is an SEP approximation that is accurate to within 0.1 dB. Extensive results show that the scheme yields significant energy savings of 2.0-7.7 dB at the source and relay. Optimal relay placement for the proposed scheme is also characterized, and is different from fixed gain or power relaying. Generalizations to MQAM and other fading distributions are also discussed.

Item Type:	Journal Article
Publication:	IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS
Publisher:	IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Additional Information:	Copyright for this article belongs to IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, PISCATAWAY, USA
Keywords:	Cooperative systems;spatial diversity;relays;MPSK;MQAM;power constraint;modulation;fading channels;amplify-and-forward;symbol error probability;relay placement
Department/Centre:	Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited:	02 Jan 2013 07:53
Last Modified:	02 Jan 2013 07:53
URI:	http://eprints.iisc.ac.in/id/eprint/45592

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