Indoor MIMO System Research Articles

A compact dual‐polarized cavity‐backed annular slot antenna for indoor mimo systems

ABSTRACTA unidirectional, dual‐polarized multi‐input multi‐output (MIMO) antenna is designed for indoor 2.4‐GHz WLAN application. The proposed antenna consists of a cavity‐backed annular slot and two inverted microstrip fed lines which are mutually orthogonal. To further suppress the cross polarization levels and enhance the ports isolation, two grounded strips, being opposite to the microstrip lines of the same size, are introduced above the annular slot. Meanwhile, a conductor pillar is loaded into the back cavity. The experimental results show that this antenna has the ports isolation of more than 28 dB and the cross‐polarized levels of less 30 dB than the copolarization over the working band. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:384–388, 2015

Effect of Polarization on the Correlation and Capacity of Indoor MIMO Channels

We describe a simple multiple-input/multiple-output (MIMO) channel measurement system for acquiring indoor MIMO channel responses. Four configurations of the polarization diversity antenna, referred to asVVV,YYH,YVYandVHH, were studied in terms of the capacity of indoor MIMO systems. Measurements were taken for a3×3MIMO system in the 2.4 GHz band. In addition, the channel capacity, singular-value decomposition, and correlation coefficient were used to explain the effects of various polarization schemes on MIMO fading channels. We also propose an analysis method for polarization channel capacity; this method includes the normalization of the received power and polarization effect for different polarization schemes. The validation of the model is based upon data collected in both light-of-sight (LOS) and non-light-of-sight (NLOS) environments. From the numerical simulation results, the proposed analysis method was close to measurements made in an indoor environment.

Channel capacity study of polarization reconfigurable slot antenna for indoor MIMO system

AbstractThis article presents a polarization reconfigurable slot antenna with compact feed.Fed by dual modes of coplanar waveguide, a dual orthogonal linear polarization is excited in the slot and controlled by two PIN diodes. The proposed antenna has been built and its reflection coefficient, radiation pattern, gain were tested. The capacity performance in an indoor wireless local area network scenario was measured by using two proposed antennas as access point in a 2 × 2 multi‐input multi‐output system. The results show the advantage of polarization reconfigurable antennas in channel capacity, especially at the condition of non‐line‐of‐sight. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1209–1213, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26014

A Low-Profile Dual-Polarized Directional Antenna for Enhancing Channel Capacity in Indoor MIMO Systems

The use of directional antenna and polarization diversity techniques has been reported to achieve good MIMO performance. Low-profile, small structures are required to configure the MIMO antenna with these techniques. First, we assume downlink transmission in indoor MIMO systems and present the design guidelines for the radiation pattern to obtain large channel capacity by the ray-tracing method. We then propose a uni-directional, dual-polarized MIMO antenna with a thickness of 0.24λ based on the design guidelines. The proposed antenna consists of dipole antennas mounted horizontally to the ground plane and cavity backed slot antennas for vertical polarization. We apply the proposed antenna to 2 × 2 MIMO transmission and demonstrate the effectiveness of channel capacity enhancement in an actual environment. The improvement factor is revealed to be +16.2% with place averaged value compared to sleeve antenna configuration.

Use Channel Reconfiguration Technique to Improve the Spatial Multiplexing Gain of MIMO Systems

Multiple-input-multiple-output (MIMO) wireless systems can not always have full spatial multiplexing gain due to the channel correlation problem caused by various factors such as the coupled antenna elements, and the key-hole effect of the propagation environment. In this paper, we proposed a channel reconfiguration technique to combat the rank deficiency problem of the involved MIMO wireless channels that can not afford high-order multiplexing gains. In the proposed approach, each mobile station can simultaneously receive several independent data streams from multiple base stations through a set of MMSE-based receive beamformers to suppress the multiple access interferences. Making use of the receive beamforming, which virtually produce the effect of a single antenna at each receive mobile, makes the transmit base station possible to reconfigure the MIMO downlink channel and then pre-cancel the co-channel interferences. The proposed signal processing mechanism that iteratively optimized the MMSE receive weights and the transmit precoders, which brings the reconfigured MIMO system about the high data throughput seen only with indoor MIMO systems having rich wireless channels. It is shown that as compared to the conventional MIMO system, the M4 system can achieve a significantly higher capacity which is proportional to the number of the linked base stations.

Measurements of MIMO Indoor Channels at 1800 MHz with Multiple Indoor and Outdoor Base Stations

This paper proposes several configurations for multiple base stations in indoor MIMO systems and compares their performance. The results are based on channel measurements realized with a MIMO testbed. The receiver was moved along several routes and floors on an office building. Both outdoor and indoor locations are considered for the transmitters or base stations, which allow the analysis of not only indoor but also outdoor-to-indoor environment. The use of 2 base stations with different system level combinations of the two is analyzed. We show that the 2 ×4 configuration with base station selection provides almost as good performance as a 4 × 4 full water-filling scheme when the 2 base stations are placed at different locations. Also the spatial correlation properties for the different configurations are analyzed and the importance of considering path loss when evaluating capacity is highlighte.

Effect of Antenna Locations on Indoor MIMO System

The effect of antenna locations on multiple-input-multiple-output (MIMO) communication system in the line of sight (LOS) and the nonline of sight (NLOS) indoor environments is investigated by a numerical hybrid method of the method of moments (MoM) and the finite difference time domain (FDTD) method. The channel capacity, the received power and the effective degrees-of-freedom (EDOF) of multipaths of MIMO system are statistically analyzed. It is found that the channel capacity of indoor MIMO system is affected significantly by the antenna locations. However, in the case of ignoring of path loss, MIMO channel capacity in NLOS indoor environment is almost independent of antenna locations