Power Allocation Strategies in Cooperative MIMO Networks

We examine the capacity of cooperative MIMO networks, specifically power allocation methods at the relay. Our principle finding is that power allocation using SVD and waterfilling at the source and the relay cannot achieve maximum capacity in cooperative MIMO networks. We find the optimal power allocation at the relay for the two antenna case when waterfilling is used for the direct path. A modified waterfilling power allocation method at the relay is used to increase the overall cooperative capacity when the relay is close to the source. The proposed power allocation method achieves high capacity gain in cooperative MIMO networks using a simple method when the relay has no channel information concerning the direct path. As the distance between the source and the relay increases, the outage probability at the relay plays an important role in cooperative networks. To improve the outage probability at the relay, we use a waterfilling method for the channel between the source and the relay. Finally, we compare the performance of five power allocation techniques for the multiple antenna case in terms of outage probability.