A relay handoff algorithm in cooperative diversity system

Cooperative communication can significantly improve the performance of wireless network through the help of relay nodes. Choosing a good relay is very important in cooperation. However, for user mobility, both inter-user channel and channel between relay and destination will vary quickly. So relay will not be used all the time. It will be changed when it is no longer suitable to be a relay. A relay handoff algorithm based on energy gain and direction information is proposed in this paper. In this algorithm, handoff is performed when the energy gain of the working relay falls below the threshold and the energy gain of the best relay exceeds the energy gain of the working relay by a variable hysteresis level assisted by direction information. The simulation and analytical results show that this algorithm can reduce the average number of handoffs while keeping the energy gain at a good level .