MIMO cooperative diversity strategies for frequency selective fading relay channels

This paper presents a family of cooperative diversity strategies for the fading relay channel in an initially frequency flat fading environment. The relay channel used in this paper operates in what is termed as MIMO cooperative diversity mode, where the source transmits to both relay and destination terminals in the first instance. Both the source and relay then transmit to the destination in the second instance. Initially the current cooperative diversity frameworks are extended to consider system constraints to make a direct and fair comparison with the single-hop case. In-particular a power constraint is put on the system and the optimal transmit power levels are presented. The framework is then extended to consider the frequency selective channel by consider an Orthogonal Frequency Division Multiplexing (OFDM) framework. The amount of collision in frequency can be varied and then analysed. This paper shows that full collision is the preferred transmission scheme.