Cooperative Diversity using Soft Decision and Distributed Decoding

Cooperative communications techniques exploit the spatial diversity of wireless radio channel by forming antenna arrays in order to achieve Multiple Input Multiple Output (MIMO) performance in multi-user single-antenna environment. The improvements can be in terms of higher data rate, lower transmission power, or increase coverage in the network. In this paper we propose a new cooperative relaying concept using soft information and distributed turbo decoding. The relay regenerates a Log-Likelihood Ratios (LLRs) using a Soft Input Soft Output (SISO) decoder, then forwards this a posteriori information to the destination in its soft form yielding a likelihood for every source transmitted bit. At destination, the forwarded bits serve as a priori information to assist the iterative turbo decoding. Our results show that the gain achievable using the conventional cooperative diversity is obtained through our schemes with less amount of overhead.