Joint Power Allocation for Nonregenerative MIMO-OFDM Relay Links

We consider a two-hop MIMO-OFDM communication scheme with a source, a relay, and a destination. The relay is assumed to be nonregenerative (or amplify-and-forward (AF)). We assume channel state information at each transmitter (CSIT), source and relay. We present a jointly optimized power allocation (PA) over the subchannels in space and frequency domain at source and relay with a joint transmit power constraint. The PA is based on a high SNR approximation of the SNR expression at the destination. In the low SNR regime, the performance is still very tight to the optimal rate. The presented PA can be computed with low computational complexity and achieves a considerable performance gain compared to a uniform PA at source and relay. To further enhance the performance of the considered scheme, all subchannels, in space and frequency domain, of the source to relay and relay to destination channel are paired according to their actual magnitude