Power Allocation of Training Sequences for Cooperative OFDM Systems at the Relay

Considering the scene that in a street environment, there is no direct channel between the source node and the destination node because of distance or obstacles, and it needs some relay nodes to do the cooperative communications. In this paper, We propose a power allocation method for cooperative OFDM systems at the relay under spatial correlation circumstances. Based on the matrix formulation of narrowband cooperative channel, Broadband cooperative OFDM channel models was derived. Assuming that the relay has the knowledge of channel covariance, We allocate the power of training sequences that minimize the channel estimation Linear Minimum Mean Square Error (LMMSE). Simulation results show that the power allocation method have good MSE (Mean Square Error) performance in spatial correlations of channels. Compared with less consideration of spatial correlation power allocation method, the precision of method is closer to the CramérRao bound (CRB).