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.

Method and apparatus of transmitting a spatial stream for mu - mimo in a wireless local area network system

Abstract: A method of transmitting a spatial stream for multi user(MU) - mulitple input multiple output(MIMO) in a wireless local area network system, performed by a transmitter is provided. The method includes transmitting, to a receiver, a management frame including group information to assign or change a position of a plurality of spatial streams corresponding to each of a plurality of groups, and transmitting, to the receiver, a frame including at least one spatial stream, wherein the group information includes a plurality of group indicators and a plurality of spatial stream(SS) indicators, each of the plurality of group indicators indicating whether or not the receiver is a member of each of the plurality of groups, each of the plurality of SS indicators indicating a position of the plurality of spatial streams corresponding to each of the plurality of groups.

A MAC Protocol for MIMO Based IEEE 802.11 Wireless Local Area Networks

Abstract: An increasing number of wireless devices and services imposes higher demands for wireless networks' capacity. Likewise, contemporary bandwidth requirements of each user in the network rise significantly, being a mixture of traffic types such as Web surfing, file transfer protocol (FTP), video, video-teleconference, and voice. Multiple input-multiple output (MIMO) techniques are recognized as methods that can meet these requirements, since they significantly increase the capacity of wireless networks, without additional bandwidth or transmission power. With a MIMO physical layer (PHY), the transmission channel gets a layered structure. Consequently, support from higher layers with a cross-layer approach that provides efficient management of the channel's spatial layers, can significantly increase the network's performance on both link and system level. In this paper a high capacity medium access control (MAC) protocol for MIMO support is presented. The proposed protocol is based on IEEE 802.11 standard, and provides a flexible and scalable support for multiple antenna terminals, backwards compatible with legacy stations.

Two-Stage Constant-Envelope Precoding for Low-Cost Massive MIMO Systems

Abstract: Massive MIMO is a key technology to meet increasing capacity demands in 5G wireless systems. However, a base station (BS) equipped with $M\gg 1$ antennas requires $M$ radio frequency (RF) chains with linear power amplifiers, which are very expensive. In this paper, we propose a two stage constant-envelope (CE) precoding scheme to enable low-cost implementation of massive MIMO BS with $S\ll M$ RF chains and nonlinear power amplifiers. Specifically, the MIMO precoder at the BS is partitioned into an RF precoder and a baseband precoder. The RF precoder is adaptive to the slow timescale channel statistics to achieve the array gain. The baseband precoder is adaptive to the fast timescale low dimensional effective channel to achieve the spatial multiplexing gain. Both the RF and baseband precoders are subject to CE constraints to reduce the implementation cost and the peak-to-average power ratio of the transmit signal. The two stage CE precoding is a challenging non-convex stochastic optimization problem and we propose an online alternating optimization algorithm which can autonomously converge to a stationary solution without explicit knowledge of channel statistics. Simulations show that the proposed solution has many advantages over various baselines.

Chorus: truly distributed distributed-MIMO

Abstract: Distributed MIMO has long been known theoretically to bring large throughput gains to wireless networks. Recent years have seen significant interest and progress in developing practical distributed MIMO systems. However, these systems only distribute the transmission function across the multiple nodes. The control fabric that synchronizes the nodes to a common reference phase still fundamentally requires a single leader that all nodes in the network are capable of hearing. This paper presents Chorus, a truly distributed distributed-MIMO system. Chorus is leaderless - all nodes are peers, and jointly transmit the synchronization signal used by other nodes to synchronize to a common reference phase. The participation of all nodes in the network in the synchronization signal enables Chorus to scale to large networks, while being resilient to node failures or changes in network connectivity, and without imposing onerous management burdens on network administrators. We implement and evaluate Chorus and demonstrate that it can synchronize effectively without the need for a single leader, scale to large networks where no leader node can be heard by all others, and provide 2.7X throughput improvement over traditional leader-based systems.

Cross-Layer Optimization for MIMO-Based Wireless Ad Hoc Networks: Routing, Power Allocation, and Bandwidth Allocation

Abstract: MIMO-based communications systems have great potential to improve network capacity for wireless ad hoc networks. Due to unique physical layer characteristics associated with MIMO, network performance is tightly coupled with mechanisms at physical, link, and routing layers. So far, research on MIMO-based wireless ad hoc networks is still in its infancy and few results are available. In this paper, we consider the problem of jointly optimizing power and bandwidth allocation at each node and multi-hop/multi-path routing in a MIMO-based wireless ad hoc network. We develop a solution procedure to this cross-layer optimization problem and use simulations to validate the efficacy of this solution.