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.

Conjugate Gradient-based Soft-Output Detection and Precoding in Massive MIMO Systems

Abstract: Massive multiple-input multiple-output (MIMO) promises improved spectral efficiency, coverage, and range, compared to conventional (small-scale) MIMO wireless systems. Unfortunately, these benefits come at the cost of significantly increased computational complexity, especially for systems with realistic antenna configurations. To reduce the complexity of data detection (in the uplink) and precoding (in the downlink) in massive MIMO systems, we propose to use conjugate gradient (CG) methods. While precoding using CG is rather straightforward, soft-output minimum mean-square error (MMSE) detection requires the computation of the post-equalization signal-to-interference-and-noise-ratio (SINR). To enable CG for soft-output detection, we propose a novel way of computing the SINR directly within the CG algorithm at low complexity. We investigate the performance/complexity trade-offs associated with CG-based soft-output detection and precoding, and we compare it to exact and approximate methods. Our results reveal that the proposed method outperforms existing algorithms for massive MIMO systems with realistic antenna configurations.

Hybrid Analog-Digital Millimeter-Wave MU-MIMO Transmission With Virtual Path Selection

Abstract: In this letter, we propose a low-complexity hybrid precoding and combining design for the millimeter-wave MU-MIMO transmission, applicable to both fully connected and sub-connected structures Analog precoding and combining schemes are first designed, where a joint approach, a decoupled approach, and a sub-optimal approach are proposed to harvest the array gain Virtual path selection is performed to maximize the channel gain of the analog effective channel Then, based on the effective channel, a low-dimensional zero-forcing precoding is applied in the baseband to manage the interference The simulation results show that the proposed techniques offer an enhanced performance-complexity tradeoff compared with both existing hybrid schemes and fully digital schemes

Method and apparatus for supporting single-user multiple-input multiple-output (su-mimo) and multi-user mimo (mu-mimo)

Abstract: Techniques for supporting data transmission with single-user multiple-input multiple-output (SU-MIMO) and multi-user MIMO (MU-MIMO) are described. A base station may transmit multiple data streams on a given time-frequency resource to a single user equipment (UE) for SU-MIMO or to multiple UEs for MU-MIMO. In an aspect, an antenna port assignment for a UE for MU-MIMO may be conveyed by reusing one or more fields of a downlink control information (DCI) format. In another aspect, a hierarchical two-tier structure may be used to convey an antenna port assignment for a UE for MU-MIMO. In yet another aspect, a UE may be configured via higher layer to report only channel quality indicator (CQI), or both CQI and precoding matrix indicator (PMI), when operating in a transmission mode supporting SU-MIMO and MU-MIMO. In yet another aspect, a UE may report CQI such that SU-MIMO and MU-MIMO can be supported for the UE.

Multiple antenna systems: their role and impact in future wireless access

Abstract: Multiple antennas play an important role in improving radio communications. In view of this role, the area of multiple antenna communication systems is in the forefront of wireless research. This article reviews two key related aspects of multiple antenna communication systems: multiple access interference mitigation at the receiver via multi-user beamforming; and space-time modulation and coding for MIMO systems. It is shown that both multi-user and MIMO receivers share similar signal processing and complexity tradeoffs.. Following that, a general unified framework for assessing different types of space-time modulation for MIMO systems is introduced. These space-time modulation methods are then compared in terms of Shannon capacity over multipath channels. Key MIMO system performance and implementation issues are also highlighted.

Approach to a unified SU-MIMO/MU-MIMO operation

Abstract: An apparatus and method to dynamically schedule user devices in a wireless communication system in single-user multiple-input multiple-output (SU-MIMO) or multiple-user multiple-input multiple-output (MU-MIMO) modes of operation. The dynamic scheduling employs an efficient differential reporting of channel state information that reduces uplink feedback overhead, whereby a base layer value of a channel quality indicator (CQI) is reported in conjunction with a CQI offset value. Antenna subset selection is also reported. The offset value reflects gains by detection with successive interference cancellation if multiple antennas are reported (rank>1), while it reflects the actual offset between single-layer SU-MIMO CQI and MU-MIMO CQI if a single antenna is reported. Scheduled SU-MIMO mode of operation is optimized for a user reporting either a single antenna or multiple antennas, whereas MU-MIMO operation is optimized for a user reporting a single antenna.