A Study of Energy Efficient Transparent Relay Using Cooperative Strategy

The purpose of a multi-hop relay in WiMAX system is to enhance cell coverage, throughput and system capacity. IEEE802.16j standard specifies a multi-hop relay and IEEE802.16m standard recently considers adopting a multi-hop relay. Besides, many research groups insist that cooperative communication including transparent relay saves energy as well as brings better performance. However, they don´t provide specific data for transparent relay in a realistic communication system such as WiMAX. In this paper, we study on how much power saving it can be achieved when using transparent relay with cooperative strategy. We firstly propose cooperative strategy for transparent relay in order to achieve diversity gain and then investigate how much gain we can achieve and how much power saving we can have in WiMAX model. The spectral efficiency of a distributed Alamouti scheme is N/2N sym/sec/Hz for transparent relay but the one of the proposed scheme is (N-1)/N sym/sec/Hz which is same as original purpose of transparent relay. In addition it is shown that transparent relay with cooperative strategy has up to 60% power saving under the given simulation configuration.