Optimal waveform design for MIMO relaying

Non-regenerative MIMO relaying between a source and a destination is studied in this paper. Optimal weighting matrix operating on baseband signals (waveforms) at the relay is found that maximizes the capacity between the source and the destination. Relay channels with or without direct link between the source and the destination are considered. The optimal relay exploits the knowledge of the channel matrix between the source and the relay and the channel matrix between the relay and the destination. The optimal weighting matrix can be considered as a matched filter along the singular vectors of the channel matrices. Such a non-regenerative relay can be deployed in mobile ad hoc networks as well as in cellular networks.