Energy Saving method with Reduced Feedback in OFDM Relay System

In order to reduce uplink feedback and save the two hop link energy consumption in the orthogonal frequency division multiplexing (OFDM) relay system, this paper proposed a reduced uplink feedback and saved energy (RFSE) method. Firstly, set the feedback thresholds for relay and base station based on the probability of user feedback outage. Secondly, adjust the feedback threshold according to the change of channel state, and determine whether feedback the information to base station in order to reduce system feedback and ensure the feedback stabilization. Finally, adjust the transmit powers of base station and relay separately to reduce system energy consumption concerning the rate of two-hop relay system. The simulation results show that RFSE algorithm not only reduces system feedback and ensure system feedback stabilization，but also greatly reduces energy consumption compared with semi-distributed scheduling scheme which is used to reduce the feedback of channel state information.