Interference channel sum rate optimization on the Grassmann manifold

The problem of truncated unitary precoder design for the Multiple-Input Multiple-Output Interference Channel (MIMO-IC) is investigated. A simple gradient ascent method is utilized over the Grassmann manifold to maximize the sum rate achieved over the MIMO-IC. Since such optimization methods are not guaranteed to converge to the global solution, we also introduce an implementation of simulated annealing for the problem at hand and compare the performance of the two methods. The results show that the gradient on the Grassmann manifold provides gains over existing methods such as max-SINR, in particular when asymmetric channels are considered and the achieved performance is comparable to that achieved by more complex methods not restricted to unitary constraints. Furthermore it performs close to the simulated annealing method at low SNR regime.