Rate of Channel Hardening of Antenna Selection Diversity Schemes and Its Implication on Scheduling

For a multiple-antenna system, we find a simple and accurate expression for the asymptotic distribution of the antenna selection gain when the transmitter selects the transmit antenna with the strongest channel. We use this to estimate the underlying channel capacity distributions and obtain the approximate ergodic capacity. This estimate is compared with upper and lower bounds. This analysis demonstrates that unlike multiple-input/multiple-output ( MIMO) systems, the channel for antenna selection systems hardens at a slower rate, and thus a significant multiuser scheduling gain can exist -Theta(1/log m) for channel selection as opposed to Theta(1/root m) for MIMO, where m is the number of transmit antennas.