Partially Cooperative MIMO Channels with Scaled Identity Transmit Covariance

Recently, there has been a great deal of interest on the performance of MIMO wireless systems as the MIMO fading channel offers an increase in capacity and reliability over that of a SISO channel. When channel state information is not known at the transmitter, the level of performance obtained depends on the degree of cooperation between the transmit antennas. With no cooperation between the antennas, horizontally coded spatial multiplexing is diversity suboptimal since each message bit is encoded and transmitted by only one antenna. An optimal scheme, on the other hand, codes message bits across all transmit antennas. This work generalizes and quantifies the level of cooperation between transmit antennas with the cooperation parameter R c and then finds upper and lower bounds for the achievable data rates for such a system using a scaled identity transmit covariance matrix. These bounds are found to be tight for certain values of Rc and the data rate Rt. Finally, these bounds are useful in computing the outage probability and diversity order of partially cooperative MIMO systems when channel state information is not known at the transmitter