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Spatial Separation of Closely-Located Users in Measured Massive MIMO Channels

Flordelis, Jose LU ; Rusek, Fredrik LU ; Gao, Xiang LU ; Dahman, Ghassan LU ; Edfors, Ove LU and Tufvesson, Fredrik LU (2018) In IEEE Access 6. p.40253-40266
Abstract

We investigate the ability of Massive multiple-input multiple-output (MIMO) systems to spatially separate up to eighteen users located close to one another in line-of-sight (LOS) propagation conditions, in both indoor and outdoor environments. For that, we use fully-synchronous measured channels at 2.6 GHz of single-antenna users moving within a small area and concurrently communicating with a base station (BS) equipped with a compact 128-port array. To quantify the degree of spatial user separability, we use three scalar metrics, namely, the achievable sum-rates, the condition number of the channel matrix, and the angle to interference factor. Our results show that Massive MIMO with zero-forcing (ZF) or regularized ZF (RZF) can... (More)

We investigate the ability of Massive multiple-input multiple-output (MIMO) systems to spatially separate up to eighteen users located close to one another in line-of-sight (LOS) propagation conditions, in both indoor and outdoor environments. For that, we use fully-synchronous measured channels at 2.6 GHz of single-antenna users moving within a small area and concurrently communicating with a base station (BS) equipped with a compact 128-port array. To quantify the degree of spatial user separability, we use three scalar metrics, namely, the achievable sum-rates, the condition number of the channel matrix, and the angle to interference factor. Our results show that Massive MIMO with zero-forcing (ZF) or regularized ZF (RZF) can spatially separate nine, even eighteen, concurrent users at practical SNR values even in the challenging case of dominant LOS propagation. In particular, signal-to-noise ratio losses relative to ideal (non-interfering and equally strong) channels can be reduced dramatically compared with standard multiuser MIMO systems, which typically have the same number of users as BS antennas. Our findings suggest that with RZF or ZF the ratio of BS antennas to number of served users should be at least three to four, to harvest most of the available spatial gains that the environment can offer. Although orthogonality and array gains complement each other, for the suggested ratios of antennas to users, the main contribution to improving system performance, measured in sum-rates, comes from the orthogonality gain.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Channel measurements, Massive MIMO, spatial separation
in
IEEE Access
volume
6
pages
14 pages
publisher
IEEE--Institute of Electrical and Electronics Engineers Inc.
external identifiers
  • scopus:85049797888
ISSN
2169-3536
DOI
10.1109/ACCESS.2018.2854307
language
English
LU publication?
yes
id
82e55a25-787f-4b58-b8e5-724b47fe8725
date added to LUP
2018-09-11 14:07:47
date last changed
2018-11-21 21:41:33
@article{82e55a25-787f-4b58-b8e5-724b47fe8725,
  abstract     = {<p>We investigate the ability of Massive multiple-input multiple-output (MIMO) systems to spatially separate up to eighteen users located close to one another in line-of-sight (LOS) propagation conditions, in both indoor and outdoor environments. For that, we use fully-synchronous measured channels at 2.6 GHz of single-antenna users moving within a small area and concurrently communicating with a base station (BS) equipped with a compact 128-port array. To quantify the degree of spatial user separability, we use three scalar metrics, namely, the achievable sum-rates, the condition number of the channel matrix, and the angle to interference factor. Our results show that Massive MIMO with zero-forcing (ZF) or regularized ZF (RZF) can spatially separate nine, even eighteen, concurrent users at practical SNR values even in the challenging case of dominant LOS propagation. In particular, signal-to-noise ratio losses relative to ideal (non-interfering and equally strong) channels can be reduced dramatically compared with standard multiuser MIMO systems, which typically have the same number of users as BS antennas. Our findings suggest that with RZF or ZF the ratio of BS antennas to number of served users should be at least three to four, to harvest most of the available spatial gains that the environment can offer. Although orthogonality and array gains complement each other, for the suggested ratios of antennas to users, the main contribution to improving system performance, measured in sum-rates, comes from the orthogonality gain.</p>},
  articleno    = {8408797},
  author       = {Flordelis, Jose and Rusek, Fredrik and Gao, Xiang and Dahman, Ghassan and Edfors, Ove and Tufvesson, Fredrik},
  issn         = {2169-3536},
  keyword      = {Channel measurements,Massive MIMO,spatial separation},
  language     = {eng},
  month        = {07},
  pages        = {40253--40266},
  publisher    = {IEEE--Institute of Electrical and Electronics Engineers Inc.},
  series       = {IEEE Access},
  title        = {Spatial Separation of Closely-Located Users in Measured Massive MIMO Channels},
  url          = {http://dx.doi.org/10.1109/ACCESS.2018.2854307},
  volume       = {6},
  year         = {2018},
}