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

TL;DR

This paper analyzes the channel hardening rate of antenna selection schemes, showing they harden slower than MIMO but still offer significant multiuser scheduling gains, especially in low SINR scenarios.

Contribution

It provides an asymptotic analysis of antenna selection gain distribution and compares its channel hardening rate to MIMO, highlighting its advantages in low SINR regimes.

Findings

Antenna selection hardens at a rate of O(1/ log m)

Significant multiuser scheduling gain exists for antenna selection

Outperforms open loop MIMO in low SINR conditions

Abstract

For a multiple antenna system, we compute the asymptotic distribution of antenna selection gain when the transmitter selects the transmit antenna with the strongest channel. We use this to asymptotically estimate the underlying channel capacity distributions, and demonstrate 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 - O(1/ log m) for channel selection as opposed to O(1/ sqrt{m}) for MIMO, where m is the number of transmit antennas. Additionally, even without this scheduling gain, it is demonstrated that transmit antenna selection systems outperform open loop MIMO systems in low signal-to-interference-plus-noise ratio (SINR) regimes, particularly for a small number of receive antennas. This may have some implications on wireless system design, because most of the users in modern wireless systems have low SINRs