Bidirectional Cooperative Relay Strategies for Transmitted Reference Pulse Cluster UWB Systems

In this paper, several bidirectional cooperative relay strategies for transmitted reference pulse cluster ultrawideband systems are proposed, followed by the bit error rate (BER) performance analyses for each of them. First, three bit-level channel quality indicators (CQIs) are proposed, which reflect the transmission quality depending on the multipath channel and the instantaneous noise. Suppose the channel remains unchanged for a period of time, a long-term CQI is also presented that depends only on the multipath channel but independent of noise. Second, based on the defined CQIs, relay cooperation strategies are proposed, analyzed, simulated, and compared. It is shown that the bit-level strategies outperform the long-term relay selections and the direct relay combining at the cost of higher complexity at the relay nodes. Min-Max relay selection and outage-based relay selection and combining achieve the best performance. Furthermore, analytical results are consistent with simulation, which validates the BER analysis. This study provides guidelines in the selection of a relay cooperation strategy with consideration of the performance and complexity tradeoff.