Performance evaluation of spatially multiplexed MIMO systems with subset antenna transmission in interference limited environments |
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Authors: | Shreeram Sigdel Witold A Krzymień |
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Affiliation: | (1) University of Alberta/TRLabs, Edmonton, AB, Canada |
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Abstract: | Transmit antenna selection in spatially multiplexed multiple-input multiple-output (MIMO) systems is a low complexity low-rate
feedback technique, which involves transmission of a reduced number of streams from the maximum possible to improve the error
rate performance of linear receivers. It has been shown to be effective in enhancing the performance of single-user interference-free
point-to-point MIMO systems. However, performance of transmit antenna selection techniques in interference-limited environments
and over frequency selective channels is less well understood. In this paper, we investigate the performance of transmit antenna
selection in spatially multiplexed MIMO systems in the presence of co-channel interference. We propose a transmission technique
for the downlink of a cellular MIMO system that employs transmit antenna selection to minimize the effect of co-channel interference
from surrounding cells. Several transmit antenna selection algorithms are proposed and their performance is evaluated in both
frequency flat and frequency selective channels. Various antenna selection algorithms proposed in the literature for single
user MIMO links are extended to a cellular scenario, where each user experiences co-channel interference from the other cells
(intercell interference) in the system. For frequency selective channels, we consider orthogonal frequency division multiplexing
(OFDM) with MIMO. We propose a selection algorithm that maximizes the average output SINR over all subcarriers. A method to
quantify selection gain in frequency selective channel is discussed. The effect of delay spread on the selection gain is studied
by simulating practical fading environments with different delay spreads. The effect of the variable signal constellation
sizes and the number of transmitted streams on the bit error rate (BER) performance of the proposed system is also investigated
in conjunction with the transmit antenna selection. Simulation results show that for low to moderate interference power, significant
improvement in the system performance is achievable with the use of transmit antenna selection algorithms. Even though the
gain due to selection in frequency selective channels is reduced compared to that in flat fading channels due to the inherent
frequency diversity, the performance improvement is significant when the system is interference limited. The performance improvement
due to reduced number of transmit streams at larger signal constellation sizes is found to be more significant in spatially
correlated scenarios, and the gain due to selection is found to be reduced with the increased delay spread. It is found that
employing transmit antenna selection algorithms in conjunction with adaptation of the number of transmitted streams and the
signal constellation sizes can significantly improve the performance of MIMO systems with co-channel interference. |
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Keywords: | MIMO systems Transmit antenna selection Co-channel interference Orthogonal frequency division multiplexing |
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