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.

Design and analysis of linear distributed MIMO relaying algorithms

Abstract: The use of multiple antennas at both ends of a wireless link, also known as multiple-input multiple-output (MIMO) wireless, has been shown to offer significant improvements in the quality of communication in terms of both higher data rates and better reliability at no additional cost of spectrum or power. In this paper, MIMO communication in a wireless network is considered where multiple MIMO source-destination pair terminals simultaneously communicate through a large common set of MIMO relay terminals. With ever increasing demands for tetherless, ubiquitous and high data rate applications, there has been great interest in developing novel decentralised communication methods through distributed relaying techniques to enhance performance and enable more efficient usage of system resources. Distributed MIMO linear relaying techiques are designed that take advantage of local channel state information (CSI) at the relay terminals to simultaneously beamform multiple users' signals to their intended destinations. The merits of distributed MIMO relaying over direct transmissions through the analytical characterisation of the signal-to-interference ratio (SIR) statistics in the high and low signal-to-noise ratio (SNR) regimes are demonstrated and theoretical predictions are verified by numerical simulations. Finally, relay beamforming based on the quantised finite-rate feedback of the channel states is considered and the SIR degradation through Monte-Carlo simulations is quantified.

Prototype experience for MIMO BLAST over third-generation wireless system

Abstract: In this paper, a multiple-input-multiple-output (MIMO) extension for a third-generation (3G) wireless system is described. The integration of MIMO concepts within the existing UMTS standard and the associated space-time RAKE receiver are explained. An analysis is followed by a description of an actual experimental MIMO transmitter and receiver architecture, both realized on digital signal processors (DSPs) and FPGAs within a precommercial OneBTS base station. It uses four transmit and four receive antennas to achieve downlink data rates up to 1 Mb/s per user with a spreading factor of 32 and the UMTS chip rate of 3.84 MHz. Furthermore, different MIMO detectors are evaluated, comparing their performance and complexity. System performance is evaluated through simulations and indoor over-the-air measurements. Capacity and bit-error rate measurement results are presented.

Adaptive downlink multi-user MIMO wireless systems for correlated channels with imperfect CSI

Abstract: Multiple-input multiple-output (MIMO) wireless antenna systems provide increases in capacity without the need for additional spectrum or power. However the capacity increase is limited when the number of antennas at the receiver is fixed or restricted (due to mobile size constraints for example). To overcome this limitation multi-user MIMO can be used, which allows several users to be served simultaneously in frequency and time. A disadvantage of these multi-user MIMO systems, when used in the downlink however, is that they need accurate channel state information (CSI) at the transmitter and also uncorrelated channels among users. In this paper we investigate methods to address the problems of multi-user MIMO systems in spatially correlated channels. We adopt the concept of angle between subspaces to characterize the inter-user spatial correlation and adapt the algorithm to those conditions. We also investigate the impact of the accuracy of CSI at the transmitter (CSIT) and whether more limited CSI such as channel correlation information alone can be used to provide good multi-user MIMO performance. Results are presented as various simulated capacity measures and we use them to make comparisons between the various multi-user MIMO configurations

Physical Layer Authentication over MIMO Fading Wiretap Channels

Abstract: In a wide band and multipath rich environment, precise channel estimation allows authenticating the source and protecting the integrity of a message at the physical layer without the need of a pre-shared secret key. This allows also a reduction of the burden on the authentication protocols at higher layers. In this paper we develop an authentication scheme in the framework of hypothesis testing that suits a multiple wiretap channels environment with correlated fading, as is the case of multiple input multiple output (MIMO) systems and/or orthogonal frequency division multiplexing (OFDM) modulation. By allowing some degree of correlation among the channels, we formulate the optimal attack strategy for the cases of both single attempt and multiple repeated trials. For the latter scenario, due to the complexity of the optimal solution, we also develop a simpler suboptimal attack strategy. The performance of the proposed methods is evaluated in a MIMO/OFDM scenario and numerical results show the merits of the proposed approaches that can be adopted as a layer one authentication mechanism.

Optimal Space-Time Codes for the MIMO Amplify-and-Forward Cooperative Channel

Abstract: The amplify-and-forward cooperative diversity scheme is generalized to the MIMO channel. A family of space-time block codes for a half-duplex MIMO amplify-and-forward fading cooperative channel with N relays is constructed. The code construction is shown to achieve the optimal diversity-multiplexing tradeoff of the channel