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 S → R, relay-to-destination R → D, and source-to-destination S → 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(L1, L3+ L2 + 2 where L1, L2, and L3 are the channel memory lengths for S → R, S → D, and R → D→ links, respectively. This illustrates that the minimum of the multipath diversity orders experienced in S → R and R → 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 L1+L2+2 and L3+L2 +2 are achievable assuming nonfading S → R and R → 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.
- Cooperative diversity
- Distributed space-time block coding (STBC)
- Fading channels
- Pairwise error probability
ASJC Scopus subject areas
- Signal Processing
- Electrical and Electronic Engineering