A Simple Distributed Multihop Diversity Relaying Scheme Based on Repetition

A new multihop relaying scheme based on repetition transmission is developed. The performance in Rayleigh fading of the proposed system with amplify-and-forward (AF) and decode-and-forward (DF) relaying is studied. In AF relaying systems, the source re-transmits the same signal in every three time slots, each relay simply amplifies and forwards the received signal, and the destination employs maximal ratio combining (MRC). In DF relaying systems, the source re-transmits the same signal in subsequent time slots, each relay detects the received signal based on square-law selection combining and then forwards the estimated signal, and the destination employs MRC or square-law combining. Using simple closed-form bounds on the average error probability, it is shown that the proposed repetition-based multihop transmission systems with AF relaying and DF relaying achieve diversity order equal to the number of repetitions. Numerical results are provided to assess the tightness of the proposed bounds. It is shown that repetition-based DF relaying systems achieve better symbol error rate performance than repetition-based AF relaying systems in medium to large SNRs. It is also shown that DF relaying systems with balanced links employing square-law combining at the destination achieve almost the same performance as those employing MRC. In addition, the throughputs of various multihop transmission systems are obtained. It is seen that multihop transmission systems employing a DF relaying scheme achieve higher throughput than multihop transmission systems employing an AF relaying scheme.