Cooperative Communication System Performance Analysis And Power Allocation

Cooperative communication realizes spatial diversity advantages in a distributed manner, in which the wireless nodes help each other relay information and form a virtual MIMO array. Since this transmission technique can provides significant performance gains in terms of link reliability, spectral efficiency, system capacity, and transmission range, the analysis and designing of cooperative communication wireless systems has been widely studied over the last couple of years, making the introduction and integration of cooperative communication into the next generation wireless standards LTE-A become pressing for designing an efficient and reliable fully-distributed wireless network. Nonetheless, there are various technical challenges and open issues to be resolved before this promsing concept becomes an integral part of the modern wireless communication devices.In cooperative wireless networks, power resources for each node are limited. In consequence, the optimal power allocation is a hot key technique to achieve the full potentials of relay-assisted transmission promised by the information-theoretic results. In the past, optimal power allocations of classic three-node two-hop cooperative systems have been studied. In this dissertation, we not only study optimal power allocations of three-node two-hop cooperative systems, but also study optimal power allocations of complex multi-branch two-hop cooperative systems, solving the problem of power allocations of multi-branch two-hop systems and presenting a comprehensive framework for solving the power allocation problem.Firstly, the approach of amplify and forward protocol, the system equivalent channel model and signal mathematical expressions are introduced. Then we analysis symbol error rate and channel capacity for three-node two-hop, multi-branch two-hop systems of AF, and the index of symbol error rate has been verified by simulations. Secondly, we detail three approaches of decode and forward protocol, the system equivalent channel models and signal mathematical expressions, give the analysis of symbol error rate and channel capacity for three-node two-hop, multi-branch two-hop systems of DF, and the indicator of symbol error rate has been verified by simulations. Finally, the problem of optimal relay selection in cooperative systems is discussed; based on the analysis of system performances, optimal power allocations related to symbol error rate and system capacity are respectively proposed. Moreover, the results show that performances for AF and DF systems have been significantly improved by our methods.