Power allocation and link combining methods for DSTTD-based two-path relay systems

In this paper, we propose a double space-time transmit diversity (DSTTD)-based two-path relay system with power allocation and link combining methods. The two-path relaying protocol can restore spectral efficiency decreased due to the half-duplexing at the relay nodes and the DSTTD method can appropriately achieve the diversity gain from the two paths. To circumvent severe performance degradation caused by error propagation through the relays, power allocation is considered by maximizing an achievable rate of the system. For the performance enhancement with low complexity, two estimates from the direct-and relay-links are combined at the destination node with combining weights derived from the effective receive signal-to-noise ratios (SNRs) of the links. The performance evaluation shows that the proposed system can provide significant performance enhancement compared to the conventional point-to-point and half-duplex relay communications in any SNR region.