Energy allocation strategies for LLR-based selection relaying in cooperative transmission

Selection relaying (SR) achieves the powerful benefits of multi-antenna systems without the need for physical arrays. It is theoretically shown that when the relay measures log-likelihood ratio (LLR) instead of signal-to-noise ratio (SNR) to decide whether or not to forward the recovered symbols to the destination, the performance of SR with equal energy allocation is drastically improved. In this paper, we propose two energy allocation strategies based on long-term fading statistics without increasing implementation complexity as well as causing the loss of spectral efficiency to complete the framework for LLR-based SR and further enhance its performance.