Equalization Techniques for Distributed Space-Time Block Codes With Amplify-and-Forward Relaying

摘要

In this paper, we investigate equalization methods for cooperative diversity schemes over frequency-selective fading channels. Specifically, we consider three equalization schemes proposed originally for conventional space-time block codes (STBC) and extend them to distributed STBC in a cooperative transmission scenario with amplify-and-forward relaying. The distributed STBC equalization schemes are named after their original counterparts as distributed time-reversal (D-TR) STBC, distributed single-carrier (D-SC) STBC, and distributed orthogonal frequency division multiplexed (D-OFDM) STBC. The underlying orthogonality of distributed STBC results in decoupled data streams at the receiver side allowing low-complexity implementations. Without loss of generality, we consider a single-relay scenario where the source-to-relay $Srightarrow R$, relay-to-destination $Rrightarrow D$, and source-to-destination $Srightarrow D$ links experience possibly different channel delay spreads. Under the assumption of perfect power control for the relay terminal and high signal-to-noise ratio (SNR) for the underlying links, our performance analysis demonstrates that D-TR-STBC, D-SC-STBC, and coded D-OFDM-STBC schemes are able to achieve a maximum diversity order of $min(L_{1},L_{3})+L_{2}+2$ where $L_{1}$, $L_{2}$, and $L_{3}$ are the channel memory lengths for $Srightarrow R$, $Srightarrow D$, and $Rrightarrow D$ links, respectively. This illustrates that the minimum of the multipath diversity orders experienced in $Srightarrow R$ and $Rrightarrow D$ links becomes the performance bottleneck for the relaying path. For the case of a nonfading relaying path where line-of-sight propagation is possible in either one of these underlying links, we demonstrate that diversity orders of $L_{1}+L_{2}+2$ and $L_{3}+L_{2}+2$ are achievable assuming nonfading $Srightarrow R$ and $Rrightarrow D$ links, respectively. An extensive Monte Carlo simulation study is presented to corroborate the analytical results and to provide detailed performance comparisons among the three candidate equalization schemes.