BER and Diversity Order Analysis of Distributed Alamouti´s Code with CSI-Assisted Relays

This paper focuses on the average bit error rate (BER) and diversity order analysis of the distributed Alamouti´s code in dissimilar cooperative networks with channel state information (CSI)-assisted relays. We first assume that the relays adopt the amplifying coefficient proposed in . Lower and upper bounds of the average BER of the distributed Alamouti´s code are derived. Those two bounds tightly bound the exact average BER. Then we show that, surprisingly, the distributed Alamouti´s code achieves only diversity order one when the relays use the amplifying coefficient proposed in . To resolve this problem, we propose a new threshold-based amplifying coefficient for the distributed Alamouti´s code based on the work in . This new amplifying coefficient makes the distributed Alamouti´s code achieve the full diversity order two. Moreover, based on three different CSI assumptions, four amplifying schemes are developed in order to determine the value of the threshold used in the new amplifying coefficient.