Optimum Threshold for SNR-Based Selective Digital Relaying Schemes in Cooperative Wireless Networks

Abstract

Abstract-We study selective digital relaying schemes where the relay may choose to retransmit or to remain silent based on the qualities of the links between the source, relay and the destination. We first analyze a baseline scheme, called static relaying, where the relaying decisions are based only on the average signal-to-noise ratio (SNR) values of all the links. The second scheme, dynamic relaying, allows the relay to make decisions based on the instantaneous SNR of the source-relay link and average SNRs of the relay-destination and source-destination links. We show that, in dynamic relaying the optimal strategy to minimize the average end-to-end bit error rate is a threshold rule on the instantaneous SNR of the source-relay channel. In this case, the optimal threshold value is a function of average SNR of relay-destination and source-destination channels. We derive closed-form expressions for the optimal threshold and the bit error performance achieved by this threshold. We show that dynamic relaying can provide significant performance advantage over static relaying.

Asymptotic BER Analysis of Threshold Digital Relaying Schemes in Cooperative Wireless Systems

“…The second upper bound, receive diversity, is obtained by assuming that the S-R link is error-free, i.e., BER Rx2 e2e = P{E coop }, where P{E coop } is given in (7).…”

“…The BER of TDR schemes in a network with multi-antenna relays using a similar threshold function was studied by Adinoyi and Yanikomeroglu in [5]. In [7] the optimal threshold functions that minimize e2e BER have been derived analytically. It is shown that if the threshold is selected properly, TDR can improve the BER performance significantly compared to the simple relaying, where the relay always forwards the received data.…”

Low-Complexity Decoding Algorithms for Distributed Space-Time Coded Regenerative Relay Systems

“…Step 1: Find the l that makes D k + λ k,l is maximum for the chosen k, where λ k,l ∈ P and is calculated by (4). (3) Step 2: Fix l and find a D n ∈ C which makes D n + λ n,l is maximum.…”

“…Therefore, in this paper, we treat DMF as the object to be studied for regenerative relay networks. However, DMF relay has an important disadvantage, which is the error produced in relay's Maximum Likelihood demodulation degrades the effective SNR at the destination significantly, which is called error propagation [4]. For distributed space-time coding system in regenerative relay networks, the degradation is more drastic [5,6].…”

Relay-Induced Error Propagation Reduction for Decode-and-Forward Cooperative Communications

“…Hence, various methods have been proposed for mitigating the effects of error propagation imposed by the RN [9], [10]. In this paper, two methods are studied.…”