A parametric approach to optimal soft signal relaying in wireless parallel-relay systems

This paper proposes an optimal estimate-forward strategy, termed Z-forwarding, for 2-hop parallel-relay systems. The previous tanh-forwarding strategy, which is optimized for the single-relay system is shown to be no longer optimal for a parallel-relay system. Instead, a new, parametrically-optimize...

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Bibliographic Details
Main Authors: Xuanxuan Lu, Jing Li, Yang Liu
Format: Conference Proceeding
Language:English
Subjects:
AWGN channels
Bit error rate
Fading
Maximum likelihood decoding
Maximum likelihood estimation
Relays
Signal to noise ratio
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Summary:This paper proposes an optimal estimate-forward strategy, termed Z-forwarding, for 2-hop parallel-relay systems. The previous tanh-forwarding strategy, which is optimized for the single-relay system is shown to be no longer optimal for a parallel-relay system. Instead, a new, parametrically-optimized Z-forwarding strategy is proposed, where the relay re-transmits a nonlinear but piece-wise linear function of the log-likelihood ratio (LLR) of the source signal. By analytically formulating the end-to-end bit error rate (BER), optimal thresholds that minimize the BER are computed as a function of all the source-relay and relay-destination channels. Maximum likelihood (ML) detector is also developed for the destination to recoup all the diversity gains from the multiple relays. It is shown that Z-forwarding strategy delivers a performance comparable to tanh-forwarding in a single relay system, but considerably better than tanh-forwarding (as well as amplify-forward and decode-forward) in a parallel-relay system.
ISSN:1520-6149
2379-190X
DOI:10.1109/ICASSP.2014.6854099