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.

Efficient jamming attacks on MIMO channels

Abstract: This paper investigates efficient jamming attacks against MIMO-enabled systems. Previous research has focused on jamming data transmissions. We instead focus on jamming channel sounding symbols, and introduce the MIMO Singularity Attack, which attempts to reduce the rank of the channel gain matrix estimate by the receiver through transmission of specific jamming signals. All MIMO systems need a method to estimate and equalize their channel, whether through channel reciprocity or sounding, and most modern OFDM-based MIMO waveforms use sounding via OFDM pilot tones. We develop the constraints associated with jamming MIMO sounding channels, and further describe how these attacks specifically impact data symbol estimates for OFDM pilot-based sounding systems.

Linear transceiver design for full-duplex multi-user MIMO system

Abstract: We focus on a full-duplex multi-user MIMO system where the base station (BS) serves multiple uplink and downlink users simultaneously. Both the BS and the mobile stations (MSs) are equipped with multiple antennas. The performance of the system is limited by the self-interference at the base station and the interference caused by the uplink users on the downlink users. To address this issue, we propose to jointly design the beamformers of the BS and MSs. An optimization problem is formulated to maximize the weighted sum data rate subject to maximum power constraints. Although the problem is non-convex, it can be solved via iterative minimization of weighted sum mean square error (MSE), and a stationary point of the problem can be obtained. Strategies to choose uplink and downlink users and to determine initial point for the optimization problem are also proposed. Simulation results show that the weighted sum data rate achieved by full-duplex system is substantially higher than that achieved by baseline half-duplex systems.

Distributed source model for short-range MIMO

Abstract: The plane-wave, or point-source, assumption has been used extensively in array signal processing, parameter estimation, and wireless channel modeling to simplify analysis. It is suitable for single-input-single-output (SISO) and single-input/multiple-output (SIMO) systems, because the rank of the channel matrix is one. However, for short-range multiple-input- multiple-output (MIMO) systems with line-of-sight (LOS), the point-source assumption affects the rank and singular value distribution of the MIMO channel matrix, and results in the underestimation of channel capacity, especially for element spacings exceeding a half wavelength. The short-range geometry could apply to many indoor wireless local area network (WLAN) applications. To avoid this under-estimation problem, the received signal phases must depend precisely on the distances between transmit and receive antenna elements. With this correction, the capacity of short-range LOS MIMO channels grows steadily as the element spacing exceeds half wavelength. We derive an empirically-based threshold distance below which the distributed source model is required for accurate performance estimation in ray tracing.

On Diversity and Multiplexing Gain of Multiple Antenna Systems with Transmitter Channel Information

Abstract: We quantify the multiplexing-diversity tradeoff of a multiple-input multiple-output (MIMO) system, when the channel state information (CSI) is known perfectly at the receiver and partially at the transmitter. The partial knowledge of CSI at the transmitter consists of the quantized value of one of the eigenvalues and perfect knowledge of eigenvectors of the channel matrix. The key result is that while multiplexing gain cannot be increased beyond minimum number of transmit and receive antennas, diversity order for each multiplexing gain can be substantially increased by using only a few bits of feedback at the transmitter. For example, with 1 bit of feedback in a 2× 3 system, for multiplexing gains of 0, 1, and 2, diversity gains of 42, 6, and 2 can be achieved, respectively. Thus, while the tradeoff between diversity advantage and multiplexing gain is still present, its behavior is significantly changed by channel knowledge at the transmitter. The major reason for this different tradeoff can be attributed to addition of long-term power control, which allows the transmitter to switch between modes for reducing outage and increasing throughput based on signal to noise ratio along different eigenvalues.

Energy Detection for MIMO Decision Fusion in Underwater Sensor Networks

Abstract: In this paper, we study the performance of the energy detector when considered for binary hypothesis decision fusion in underwater acoustic wireless sensor networks with a multiple-access reporting channel. Energy detection is appealing in terms of computational complexity and limited system knowledge requirements, i.e., channel state information, signal-to-noise ratio, and local performance of the sensors are not needed at the receiver side, then the interest for performance assessment over underwater acoustic channels arises. Here, we demonstrate that energy detection may be applied with good results to underwater sensor networks. The impact on the performance of various design parameters is considered, including sampling frequency, number of transmitting sensors, and number of receiving elements (hydrophones).