Research On Relay Cooperation Diversity Modes And Their Power Optimization Allocation

The thought of relay cooperation diversity technology is based on transmitting the signal to destination through source and relay cooperation, in order to achieve diversity gain and improve system performance. However, different diversity mode has different diversity gain and performance improvement. As to quite diversity modes with good performance, we investigate outage probability and BER performance of two types (non-feedback and feedback) of relay cooperative diversity modes, and then propose two improved diversity modes with better performance, where Improved SDF in non-feedback type and Improved Feedback-SDF in feedback type. Result show that improved diversity modes proposed initially here has better performance over other diversity modes in both outage probability and BER, achieving full diversity effect seeing from BER.The other hand, under the total transmitting power constrain, optimizing the power of source and relay can enhance diversity gain and improve system performance significantly through relay cooperation. Most of research on power optimization allocation at present achieve limited system performance enhancement, and have disadvantages of single optimization criterion based on and not fairly good comprehensive performance. Therefore, We propose a power optimization scheme based on minimizing the outage probability but lower BER as much as possible according to channel state under the total transmit power constrain. We use this scheme to optimize power allocation of two types of relay cooperative diversity modes, to improve the performances of both outage probability and BER significantly by final power optimization result. Furthermore, another power optimization scheme of AF and DF based on minimizing the approximated expression of outage probability in high SNR according to average channel state is presented here and compared our scheme. Results show that the performances of outage probability and BER have been improved significantly by power optimization. Meanwhile in AF and DF modes, results demonstrate that in improving the performance of both outage probability and BER, the scheme proposed here is better than the referring scheme. Although the scheme of power optimization allocation investigated here is based on the system of three-end transmitting model with single relay, it can extend to the power optimization allocation of the system based on two-hop transmitting model with several relays by slight modification.