Multiple antenna channels with partial feedback

We consider flat-fading multiple antenna channels with t transmit and r receive antennas, which is modeled by an r x t complex matrix H. The first n eigenvectors of (HH)-H-dagger, where 0 less than or equal to n less than or equal to min(t, r), are assumed to be available at the transmitter as partial spatial information of channel. A transmission method was proposed which enables better use of the multiple-input multiple-output (MIMO) channels [1]. By using the transmission scheme, the MIMO channel can be decomposed into two parts: n parallel channels and a new small coupled MIMO channel. One reasonable coding strategy is to employ conventional time-domain only code for each of the parallel channels and a space-time code for the small MIMO channel. This paper focuses on deriving the channel capacity of the multiple antenna channels employing such a coding strategy. The results show that the proposed methods lead to systems wherein the amount of feedback information can be significantly reduced with a minor sacrifice of achievable transmission rate.