Antenna Selection in Polarization Reconfigurable MIMO (PR-MIMO) Communication Systems

TL;DR

The paper tackles improving MIMO performance by enabling polarization reconfigurability at each antenna element (PR-MIMO) and combining it with hybrid antenna selection (PR-HS-MIMO). It derives closed-form-like insights for optimal polarization at a link end and proposes an iterative pre-post coding scheme for joint polarization optimization, achieving significant capacity gains. Two PR-HS-MIMO schemes—element-wise and global polarization reconfiguration—are developed to balance performance and complexity, with simulations showing 3–5 dB SNR gains in PR-MIMO and about 3 dB in PR-HS-MIMO, along with improvements in channel capacity and SER distributions. The work demonstrates that polarization-aware adaptation yields meaningful practical benefits for scalable MIMO systems with limited RF chains and emphasizes the importance of accurate CSI for realizing these gains.

Abstract

Adaptation of a wireless system to the polarization state of the propagation channel can improve reliability and throughput. This paper in particular considers polarization reconfigurable multiple input multiple output (PR-MIMO) systems, where both transmitter and receiver can change the (linear) polarization orientation at each element of their antenna arrays. We first introduce joint polarization pre-post coding to maximize bounds on the capacity and the maximum eigenvalue of the channel matrix. For this we first derive approximate closed form equations of optimal polarization vectors at one link end, and then use iterative joint polarization pre-post coding to pursue joint optimal polarization vectors at both link ends. Next we investigate the combination of PR-MIMO with hybrid antenna selection / maximum ratio transmission (PR-HS/MRT), which can achieve a remarkable improvement of channel capacity and symbol error rate (SER). Further, two novel schemes of element wise and global polarization reconfiguration are presented for PR-HS/MRT. Comprehensive simulation results indicate that the proposed schemes provide 3 to 5 dB SNR gain in PR-MIMO spatial multiplexing and approximately 3 dB SNR gain in PRHS/ MRT, with concomitant improvements of channel capacity and SER.

Figures (12)

• Figure 1: PR-MIMO system with polarization reconfigurable antennas.
• Figure 2: Polarization-determinant ellipse and polarization-vector unit circle.
• Figure 3: System model of polarization reconfigurable hybrid antenna selection in MIMO (PR-HS-MIMO) communications
• Figure 4: Empirical histogram of $|h^{\rm eff}_{ij}|^2$ in PR-HS; the comparison of chi-square distribution with 4 degrees of freedom.
• Figure 5: Impact of $L_t$ on the mean of effective channel gain in PR-HS-MIMO systems.