Researches To Resource Allocation Algorithms On Relay Networks

With the development of wireless communication technologies and the requirements of wireless transmission data rates and quality of service, the vital problem is how to guarantee the quality of communication due to the multi-path fading.Recently, multi-input and multi-output (MIMO) technology which has obvious advantage in the area of anti-multi-path fading is becoming a promising technology to improve the commutation rate and quality. However, because of the limit of size, power and cost, disposing multiple antennas in mobile terminal is unpractical.Therefore, cooperation diversity which is a new form of spatial diversity technology was proposed.Till now, various cooperative schemes have been proposed, such as amplify-and-forward (AF), decode-and-forward (DF), code cooperation(CC) and so on. Comparing with other cooperative scheme,AF is the simplest scheme that each relay only directly amplifies and forwards the received signals to the destination node. Furthermore, AF could still achieve full spatial diversity orders to increase the network reliability. Therefore, AF has been attracted a lot of attention.In this paper, we focus on the traditional half-duplex fixed AF cooperative system and study the problem of "when to cooperate" and resource allocation. Firstly, we present an approximate optimum power allocation method (OPA) to maximize the upper bound of ergodic capacity. Then in static wireless network, we study the problem of relay selection and power allocation. The simulation results show that the OPA method can significantly improve the ergodic capacity and reduce the symbol error ratio(SER) than equal power allocation method.Finally, inspired by OPA method, we propose two novel jointly relay selection and power allocation algorithms:S-AR algorithm and S-OR algorithm. The two jointly algorithms aim to optimize ergodic capacity in AF cooperative diversity communication.Through Monte Carlo simulation, we draw the conclusion that jointly relay selection and power allocation algorithms have better throughput performance than that of parallel-relay scheme.Furthermore, S-AR algorithm is better than S-OR algorithm when throughput of the cooperative-diversity system is considered.