Improved training and training power allocation schemes for multi-relay AF networks

For a multi-relay amplify-and-forward (AF) network, an improved training scheme is proposed and the corresponding training power allocation problem is investigated for the individual channel estimation at the destination. Compared with a previous scheme where the training of the source-relay channels is conducted sequentially, the proposed scheme exploits the broadcast nature of the source-relay links to save training time and power. By analyzing the total mean square error (MSE) of all channel estimates and with the help of approximations, we derive a training power allocation solution among the source and the relays. Simulation results demonstrate that our improved training scheme and power allocation solution obtain lower total MSE than the existing schemes.