Topic
Multi-user MIMO
About: Multi-user MIMO is a research topic. Over the lifetime, 10265 publications have been published within this topic receiving 227206 citations. The topic is also known as: multi user mimo & MU-MIMO.
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TL;DR: An interesting observation that by generating intended patterns, some simultaneous transmissions can be successfully decoded without degrading the effective throughput in original transmission is observed, and a DC-MAC is proposed to leverage this "free” coordination channel for efficient medium access in a multiple-user wireless network.
Abstract: Interference is a critical issue in wireless communications. In a typical multiple-user environment, different users may severely interfere with each other. Coordination among users therefore is an indispensable part for interference management in wireless networks. It is known that coordination among multiple nodes is a costly operation taking a significant amount of valuable communication resource. In this paper, we have an interesting observation that by generating intended patterns, some simultaneous transmissions, i.e., "interference,” can be successfully decoded without degrading the effective throughput in original transmission. As such, an extra and "free” coordination channel can be built. Based on this idea, we propose a DC-MAC to leverage this "free” channel for efficient medium access in a multiple-user wireless network. We theoretically analyze the capacity of this channel under different environments with various modulation schemes. USRP2-based implementation experiments show that compared with the widely adopted CSMA, DC-MAC can improve the channel utilization efficiency by up to 250 percent.
67 citations
Patent•
14 Dec 2010TL;DR: In this article, the MIMO base station is configured to switch between a single-user (SU)-MIMO mode and a multipleuser (MU) mode during communications with the plurality of MU devices based on multi-rank precoding matrix indicator (PMI) feedback received from at least one of the MU devices.
Abstract: In at least some embodiments, a system includes a multiple-input multiple-output (MIMO) base station and a plurality of MIMO user equipment (UE) devices in communication with the MIMO base station. The MIMO base station is configured to switch between a single-user (SU)-MIMO mode and a multiple-user (MU)-MIMO mode during communications with the plurality of MIMO UE devices based on multi-rank precoding matrix indicator (PMI) feedback received from at least one of the MIMO UE devices.
67 citations
TL;DR: 2-D unitary estimation of signal parameters via rotational invariance techniques (U-ESPRIT) algorithm is studied to jointly estimate elevation and azimuth information, and uniform rectangular array is selected to represent massive MIMO systems.
Abstract: With the rapid development of wireless communication networks, the need of massive Multiple-Input Multiple-Output (MIMO) to offer sufficient network capacity has become evident. As a part of array signal processing, direction-of-arrival (DoA) estimation is of vital importance to obtain directional information of sources and to enable the 3-D beamforming. In this paper, the performance of DoA estimation for massive MIMO systems is analyzed and compared using a low complexity algorithm. To be specific, 2-D unitary estimation of signal parameters via rotational invariance techniques (U-ESPRIT) algorithm is studied to jointly estimate elevation and azimuth information, and uniform rectangular array is selected to represent massive MIMO systems. The simulation results indicate that the U-ESPRIT algorithm works well for the massive MIMO systems. The performance has been evaluated with various types of antenna configuration and source numbers. Finally, the array resolution is adopted to analyze the performance of elevation and azimuth estimation and how to choose the appropriate antenna array configuration.
67 citations
TL;DR: Low-profile band-notched G-shaped ultra-wideband (UWB) multiple input multiple output (MIMO) antenna design for mobile terminals has been presented and demonstrates that the G- shaped MIMO antenna has nearly omnidirectional patterns, stable gain and good diversity performance besides having low-profile elements.
Abstract: Low-profile band-notched G-shaped ultra-wideband (UWB) multiple input multiple output (MIMO) antenna design for mobile terminals has been presented. In this context, two UWB MIMO antenna systems have been designed: The first is with square elements and the second is with G-shaped elements. An MIMO antenna with two symmetrical square elements each of 8 × 8 mm
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operating between 2.2 and 13.3 GHz was firstly designed for the UWB applications. Each square element was fed through a 50-Ω microstrip transmission line (MTL). A thin strip line was designed at the end of MTL to provide impedance matching. Although the isolation level between the elements was satisfactory for efficient MIMO implementation, a T-shaped strip on the ground was employed to further improve the isolation for low frequency. The frequency range of 4.4-6.2 GHz which is an important band of wireless local area network (WLAN) standard was then notched by forming a G-shaped structure on the square element. The performance of G-shaped antenna system was studied in terms of important antenna characteristics and MIMO parameters. The results demonstrate that the G-shaped MIMO antenna has nearly omnidirectional patterns, stable gain and good diversity performance besides having low-profile elements.
67 citations
Patent•
07 Feb 2014TL;DR: In this paper, a wireless network access point can operate as a closed loop MIMO device when communicating with a station that is operating as an open loop mIMO devices.
Abstract: A wireless network access point can operate as a closed loop MIMO device when communicating with a station that is operating as an open loop MIMO device. Transmit/receive chains in the access point are calibrated to support aggregate channel reciprocity.
66 citations