Spatial Separation of Closely-Located Users in Measured Massive MIMO Channels
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...
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IEEE
2018-01-01
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| Series: | IEEE Access |
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| Online Access: | https://ieeexplore.ieee.org/document/8408797/ |
| _version_ | 1818331462678609920 |
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| author | Jose Flordelis Fredrik Rusek Xiang Gao Ghassan Dahman Ove Edfors Fredrik Tufvesson |
| author_facet | Jose Flordelis Fredrik Rusek Xiang Gao Ghassan Dahman Ove Edfors Fredrik Tufvesson |
| author_sort | Jose Flordelis |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-12-13T13:20:14Z |
| format | Article |
| id | doaj.art-2c0b7850323e4420bc6e18e668137d87 |
| institution | Directory Open Access Journal |
| issn | 2169-3536 |
| language | English |
| last_indexed | 2024-12-13T13:20:14Z |
| publishDate | 2018-01-01 |
| publisher | IEEE |
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| series | IEEE Access |
| spelling | doaj.art-2c0b7850323e4420bc6e18e668137d872022-12-21T23:44:25ZengIEEEIEEE Access2169-35362018-01-016402534026610.1109/ACCESS.2018.28543078408797Spatial Separation of Closely-Located Users in Measured Massive MIMO ChannelsJose Flordelis0https://orcid.org/0000-0002-3952-4579Fredrik Rusek1Xiang Gao2https://orcid.org/0000-0002-5410-4388Ghassan Dahman3https://orcid.org/0000-0002-9681-5655Ove Edfors4Fredrik Tufvesson5https://orcid.org/0000-0003-1072-0784Department of Electrical and Information Technology, Lund University, Lund, SwedenDepartment of Electrical and Information Technology, Lund University, Lund, SwedenNational Key Laboratory of Science and Technology on Communications, University of Electronic Science and Technology of China, Chengdu, ChinaÉcole de Technologie Supérieure, Montreal, CanadaDepartment of Electrical and Information Technology, Lund University, Lund, SwedenDepartment of Electrical and Information Technology, Lund University, Lund, SwedenWe 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.https://ieeexplore.ieee.org/document/8408797/Channel measurementsMassive MIMOspatial separation |
| spellingShingle | Jose Flordelis Fredrik Rusek Xiang Gao Ghassan Dahman Ove Edfors Fredrik Tufvesson Spatial Separation of Closely-Located Users in Measured Massive MIMO Channels IEEE Access Channel measurements Massive MIMO spatial separation |
| title | Spatial Separation of Closely-Located Users in Measured Massive MIMO Channels |
| title_full | Spatial Separation of Closely-Located Users in Measured Massive MIMO Channels |
| title_fullStr | Spatial Separation of Closely-Located Users in Measured Massive MIMO Channels |
| title_full_unstemmed | Spatial Separation of Closely-Located Users in Measured Massive MIMO Channels |
| title_short | Spatial Separation of Closely-Located Users in Measured Massive MIMO Channels |
| title_sort | spatial separation of closely located users in measured massive mimo channels |
| topic | Channel measurements Massive MIMO spatial separation |
| url | https://ieeexplore.ieee.org/document/8408797/ |
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