Antenna selection and power control in MIMO systems with continuously varying channels

Existing limited feedback methods for Multiple- Input Multiple-Output (MIMO) systems focus largely on block fading conditions whereas, in practice, channels change continuously over time. In this paper, we investigate adaptive transmission over a continuously varying channel (CVC). A combination of Kalman channel tracking, truncated channel inversion (TCI) antenna selection, and power control, is used to achieve bit error rates that are lower than those obtained with existing schemes. Using Kalman filtering for pilot-based channel tracking as well as decision-directed channel tracking, our scheme achieves about 3.6 dB gain over the eigen-mode antenna selection scheme and 1.5 dB gain over the unitary precoding scheme, when operating at a BER of 10^-5.