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.

Reducing location-dependent interference in distributed antenna systems operating in multiple-input, multiple-output (MIMO) configuration, and related components, systems, and methods

Abstract: Components, systems, and methods for reducing location-based interference in distributed antenna systems operating in multiple-input, multiple-output (MIMO) configuration are disclosed. Interference is defined as issues with received MIMO communications signals that can cause a MIMO algorithm to not be able to solve a channel matrix for MIMO communications signals received by MIMO receivers in client devices. These issues may be caused by lack of spatial (i.e., phase) separation in the received MIMO communications signals. Thus, to provide phase separation of received MIMO communication signals, multiple MIMO transmitters are each configured to employ multiple transmitter antennas, which are each configured to transmit in different polarization states. In certain embodiments, one of the MIMO communications signals is phase shifted in one of the polarization states to provide phase separation between received MIMO communication signals. In other embodiments, multiple transmitter antennas in a MIMO transmitter can be offset to provide phase separation.

Iterative Joint Channel Estimation and Multi-User Detection for Multiple-Antenna Aided OFDM Systems

Abstract: Multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems have recently attracted substantial research interest. However, compared to single-input-single-output (SISO) systems, channel estimation in the MIMO scenario becomes more challenging, owing to the increased number of independent transmitter-receiver links to be estimated. In the context of the Bell layered space-time architecture (BLAST) or space division multiple access (SDMA) multi-user MIMO OFDM systems, none of the known channel estimation techniques allows the number of users to be higher than the number of receiver antennas, which is often referred to as a "rank-deficient" scenario, owing to the constraint imposed by the rank of the MIMO channel matrix. Against this background, in this paper we propose a new genetic algorithm (GA) assisted iterative joint channel estimation and multi-user detection (GA-JCEMUD) approach for multi-user MIMO SDMA-OFDM systems, which provides an effective solution to the multi-user MIMO channel estimation problem in the above-mentioned rank-deficient scenario. Furthermore, the GAs invoked in the data detection literature can only provide a hard-decision output for the forward error correction (FEC) or channel decoder, which inevitably limits the system's achievable performance. By contrast, our proposed GA is capable of providing "soft" outputs and hence it becomes capable of achieving an improved performance with the aid of FEC decoders. A range of simulation results are provided to demonstrate the superiority of the proposed scheme.

Degrees of Freedom of Two-Hop Wireless Networks: Everyone Gets the Entire Cake

Abstract: We show that fully connected two-hop wireless networks with K sources, K relays, and K destinations have K degrees of freedom both in the case of time-varying channel coefficients and constant channel coefficients (in which case the result holds for almost all values of constant channel coefficients). Our main contribution is a new achievability scheme which we call Aligned Network Diagonalization. This scheme allows the data streams transmitted by the sources to undergo a diagonal linear transformation from the sources to the destinations, thus being received free of interference by their intended destination. In addition, we extend our scheme to multihop networks with fully connected hops, and multihop networks with MIMO nodes, for which the degrees of freedom are also fully characterized.

Optical Wireless MIMO Experiments in an Industrial Environment

Abstract: This paper reports on a field trial in a robotic manufacturing cell. Channel measurements and transmission experiments were conducted, assisting the development of a light-emitting diode-based optical wireless communication (OWC) system tailored for the needs of industrial wireless applications. These are moderate data rates, reliability, and low latency. Since dedicated radio spectrum is hardly available, the usage of light is an interesting alternative. Due to its spatial confinement, OWC links provide enhanced security and are difficult to jam from outside a building—a particularly interesting property for industrial applications. We performed broadband distributed $8\times 6$ multiple-input multiple-output (MIMO) channel measurements in a manufacturing cell. Results confirm that the signal-to-noise ratio is sufficient if a line-of-sight (LOS) is available and bandwidth is limited to a few megahertz. However, small movements and rotations may lead to sudden fades of 10–20 dB, when an LOS is blocked. To improve reliability, antenna diversity concepts are applied. Results show that for reliable communication, MIMO diversity schemes are indispensable as it increases the probability of a free LOS significantly. Based on these insights, we suggest an OWC design tailored to industrial wireless applications.

Joint wireless information and energy transfer in massive distributed antenna systems

Abstract: In mobile communications, two potentially ground-breaking ideas have emerged in recent years: massive MIMO antenna technology, which delivers enormous information rates, and wireless energy transfer (WET), which makes remote charging of mobile users possible. This article realizes the huge potential of combining the two for high wireless information transfer (WIT) and WET. In particular, to maximize the synergy, the distributed version of massive MIMO (known as massive distributed antenna system, MDAS) is advocated to go with the joint wireless information and energy transfer (JWIET) system capable of both WIT and WET. We present the opportunities in MDAS-JWIET, and discuss research trends in MDAS with several architectures involving WET and WIT.