Channel State Information-Aware Incremental Selection Hybrid Decode-Amplify-Forward by Unified Destination Scheduling

A channel status information (CSI)-aware incremental selection hybrid decode-amplify-forward (ISHDAF) relay cooperation is proposed by unified destination scheduling to both improve the spatial diversity gain and reduce the average transmission power. First, a cooperative threshold with a feasible prediction is derived by the criterion of maximum transmission rate at an acceptable transmission link quality. Second, the amplify-and-forward (AF), decode-and-forward (DF), and source retransmission are combined together to increase the diversity gain. Finally, the relay simply performs the cooperation according to feedback from the destination to simplify the architecture with improved spectrum efficiency and outage probability performance. The main contributions are as follows. By the unified destination scheduling, average transmission power is reduced and the spatial diversity gain is improved. Information-theoretic mutual propagation-related decision threshold is proposed by maximum average mutual information. Lower bound of the outage probability is derived for theoretical diversity analysis and error reduction. In addition, the joint transmission and power optimization are jointly obtained to properly arrange relay forwarding to avoid fast battery exhaustion in some relays of the critical path. Simulation results show that the proposed scheme has less power consumption and relay deployment costs than those of the current ISHDAF. When the relay distance factor ratio is 0.9 and the total system power is 10 w, it outperforms the ISHDAF by an average transmission power of approximately 1 w. Therefore, the proposed cooperation is especially suited for the power-limited Internet of things (IoT) with thin-client relays of both efficient power consumption and low outage probability.