Impact of relay location to SER performance with different power allocation methods in cooperative system

In this paper, we analyze the symbol-error-rate (SER) performance for a two-user amplify-and-forward cooperative system. The closed-form SER formulation and corresponding upper bound with PSK signals are derived first. Moreover, we develop an optimum power allocation for the cooperative system to minimize the SER. With the optimum and equal power allocation methods, we discuss the impact of relay location to the SER performance by making use of a characteristic ellipse topology. With the equal power allocation, the SER curve shows an interesting symmetric characteristic and the optimum relay location is just in the middle with respect to the source and destination, while the optimum relay location is near the destination with the optimum power case.