On linear pre-processing in multi-antenna systems

We study linear pre-processing for multi-antenna systems when the channel is perfectly known at the transmitter. In particular, the capacity of linear and adaptive channel inversion is compared to the optimum water-filling. When equal numbers of antennas are used at the transmitter and at the receiver, the outage probability with linear inversion is rather large. Outage is remarkably reduced when more antennas are used at the transmitter. Adaptive inversion approximates the water-filling capacity at small transmitter power and so it is robust against fading correlation. The average transmitter power with linear inversion depends on the numbers of antennas at the transmitter and at the receiver. For Rayleigh fading, we compare the bit error performance to V-BLAST.