Receiver-coordinated zero-forcing distributed transmit nullforming

A coherent cooperative communication system is proposed in which a distributed array of transmit nodes forms a beam at a desired receiver while simultaneously steering nulls at several protected receivers. Coherent transmission is achieved through a receiver-coordinated protocol where the receivers in the system use state-space channel tracking and provide feedback to the transmit cluster to facilitate distributed transmission. Analytical estimates for the performance degradation in the nulls due to channel estimation errors are verified by simulations. Numerical results demonstrate that the technique is effective even with low channel measurement overhead, infrequent measurement intervals, and feedback latency.