Multiuser MIMO capacity with limited feedback trellis exploration based precoder

In this paper, a linear trellis based precoder technique is proposed for maximizing multiuser MIMO capacity. We consider MIMO multiple access channel with inter symbol interference (ISI). We use the trellis exploration algorithm to form a precoding matrix that minimizes the interference from other users by allocating power in the appropriate eigen modes for each user. Employing a finite number of phases, the precoder matrix for each user is first custom designed at the receiver. Then a bit sequence indicating the phase indices of the optimized precoding matrix for the corresponding user is fed back to the transmitter. We show that under limited feedback, the sum rate capacity achieved is comparable to the optimal sum-rate capacity employing the well-known water filling solution with complete channel knowledge at the transmitter for spatio-temporal vector coding (STVC). Our simulations for various multiuser MIMO cases, show that the per user precoding strategy achieves desirable performance gain with limited feedback and equal user power allocation in terms of ergodic capacity.