Receive antenna selection for polarized antennas

Receive antenna selection for polarized antennas,Aamir Habib,Christian Mehlfuhrer,Markus Rupp

Receive antenna selection for polarized antennas   (Citations: 1)
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In this work we analyze the combined effects of array orientation/rotation and antenna cross polarization discrimination on the performance of dual-polarized systems with receive antenna selection. We start our analysis with a 1 out of N selection and extend it to M out of N receive antenna selection, for which we derive numerical expressions for the effective channel gains. These expressions are valid for small values of M and N , and approximately valid for higher values of M and N. Our analysis shows that robustness against rotation increases as the number of selected antennas is increased. We conclude from our analysis that M needing to be at least 1/2 of N , the maximum effective channel gain can be attained. Keywords-Antenna Selection, XPD, Array orientation, Array rotation. I. INTRODUCTION In the analysis of multiple-input multiple-output (MIMO) systems, an array of vertical antennas is normally consid- ered when the receiver has no space limitations. In compact portable devices, such as mobile handsets and laptops, if a spatial array of vertical antennas is realized, high correlation between the closely spaced antenna elements severely effects the performance. Applying dual polarized antennas at the receiver or at the transmitter proves effective in alleviat- ing performance loss due to low correlation between the antenna elements. Antenna selection, when combined with dual-polarized antennas, enables compact devices to exploit the benefits of the MIMO architecture with only a nominal increase in complexity. Also there can be a leakage of power from one antenna to another. This effect is known as antenna Cross Polarized Discrimination (XPD), and is eminent in both co-located dual-polarized antenna arrays and spatially separated antenna arrays. The effect of correlation is more dominant in closely spaced antenna arrays and less dominant in systems with dual-polarized antennas. XPD is due to non- ideal antenna polarization patterns. Because of this leakage, a simple rotation in the antenna array causes a mismatch in the incoming incident Electro-Magnetic (EM) wave. The amount of this leakage has an impact on the overall performance of the system (1). Multiple Dual Polarized (DP) antennas are strong candidates to be put into practice in 3GPP Long Term Evolution (LTE) (2) systems. A. Motivation and Contribution receive antenna is employed, a further benefit is the mitigation of polarization mismatch caused by the random orientation of portable devices. Increased hardware complexity is a con- siderable disadvantage for deploying MIMO. Conventional MIMO systems require one down-conversion/up-conversion radio frequency (RF) chain for each antenna element. While the antenna elements themselves do not increase transceiver costs significantly, the RF chains are a very significant cost factor. Antenna subset selection techniques help in cost re- duction for MIMO deployment, while maintaining full MIMO diversity benefits. In this work multiple co-located (fed from the same point) receive antennas are considered. We apply Receive Antenna Selection (RAS), starting with 1 out of 2 selection and then extend our work to 1 out of N receive antennas. Finally, the results are generalized for the M out of N selection case to study the limits on performance. The combined effect of array rotation, power imbalance, and M out of N receive antenna selection is studied. Analysis and simulation is performed for flat Rayleigh fading channels. Accurate expressions and approximate bounds for the effective channel gains are provided for a generic M out of N selection. A simple Maximum Ratio Combiner (MRC) is applied at the receiver for signal detection. Robustness analysis is presented for a generic M out of N receive antenna selection by finding the CDF of the effective channel gains through simulations. From limiting values of effective channel gains, a minimum antenna set (M,N) is found. To the best of our knowledge the features enumerated above have not been analyzed collectively for a MIMO system in literature.
Published in 2011.
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