Abstract
We propose a new differential maximum-likelihood (DML) combiner for noncoherent detection of the differential amplify-and-forward (D-AF) relaying system in the time-selective channel. The weights are computed based on both the average channel quality and the correlation coefficient of the direct and relay channels. Moreover, we derive a closed-form approximate expression for the average bit error rate (BER), which is applicable to any single-relay D-AF system with fixed weights. Both theoretical and simulated results are presented to show that the time-selective nature of the underlying channels tends to reduce the diversity gains at the low-signal-to-noise-ratio (SNR) region, resulting in an asymptotic BER floor at the high-SNR region. Moreover, the proposed DML combiner is capable of providing significant BER improvements compared with the conventional differential detection (CDD) and selection-combining (SC) schemes.
Highlights
Cooperative communications has received much attention since it is capable of improving system performance and extending coverage
This paper has studied the error performance of the single-relay differential amplify-andforward (D-AF) system considering BPSK signaling over a time-selective fading channel
A differential diversity combiner was proposed, which can weigh the received signals of the direct and relay links based on the average channel quality and correlation coefficient
Summary
Cooperative communications has received much attention since it is capable of improving system performance and extending coverage. In [11], the impact of different CSI estimation rates on the error performance of a multirelay AF system employing maximal ratio that combines over the time-selective fading channel was studied. In [13]–[15], a conventional differential detection (CDD) scheme is proposed to combine the received signals at the destination. An approximate bit error rate (BER) expression for a single-relay D-AF system employing the selection-combining (SC) scheme in the time-selective channel is derived in [16]. A new differential maximum-likelihood (DML) combiner is proposed that is suitable for a time-selective channel with an arbitrary average channel gain. A novel universal closed-form approximate expression for the average BER is derived for the considered system with a general differential diversity combiner (i.e., with any fixed weights). O(x) is used to represent the high-order terms of x
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