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On the performance of cell-free massive MIMO relying on adaptive NOMA/OMA mode-switching

On the performance of cell-free massive MIMO relying on adaptive NOMA/OMA mode-switching
On the performance of cell-free massive MIMO relying on adaptive NOMA/OMA mode-switching
The downlink (DL) of a non-orthogonal-multiple-access (NOMA)-based cell-free massive multiple-input multipleoutput (MIMO) system is analyzed, where the channel state information (CSI) is estimated using pilots. It is assumed that the users are grouped into multiple clusters. The same pilot sequences are assigned to the users within the same clusters whereas the pilots allocated to all clusters are mutually orthogonal. First, a user’s bandwidth efficiency (BE) is derived based on his/her channel statistics under the assumption of employing successive interference cancellation (SIC) at the users’ end with no DL training. Next, the classic max-min optimization framework is invoked for maximizing the minimum BE of a user under peraccess point (AP) power constraints. The max min user BE of NOMA-based cell-free massive MIMO is compared to that of its orthogonal multiple-access (OMA) counter part, where all users employ orthogonal pilots. Finally, our numerical results are presented and an operating mode switching scheme is proposed based on the average per-user BE of the system, where the mode set is given by Mode = { OMA, NOMA }. Our numerical results confirm that the switching point between the NOMA and OMA modes depends both on the length of the channel’s coherence time and on the total number of users.
Cell-free massive MIMO, NOMA, convex optimization, max-min bandwidth efficiency
0090-6778
792-810
Bashar, Manijeh
5a511947-acb0-4f32-b40f-d8320a7eb7f8
Cumanan, Kanapathippillai
a9828323-a7c0-48d7-8e45-bd938ab70bd7
Burr, Alister
1801e82f-181a-4e2f-8507-ca92170a4e60
Ngo, Hien Quoc
dd9952d6-f840-4f31-84ab-68d2e5357849
Hanzo, Lajos
66e7266f-3066-4fc0-8391-e000acce71a1
Xiao, Pei
976b4b13-a282-4e48-919d-beec8a94396d
Bashar, Manijeh
5a511947-acb0-4f32-b40f-d8320a7eb7f8
Cumanan, Kanapathippillai
a9828323-a7c0-48d7-8e45-bd938ab70bd7
Burr, Alister
1801e82f-181a-4e2f-8507-ca92170a4e60
Ngo, Hien Quoc
dd9952d6-f840-4f31-84ab-68d2e5357849
Hanzo, Lajos
66e7266f-3066-4fc0-8391-e000acce71a1
Xiao, Pei
976b4b13-a282-4e48-919d-beec8a94396d

Bashar, Manijeh, Cumanan, Kanapathippillai, Burr, Alister, Ngo, Hien Quoc, Hanzo, Lajos and Xiao, Pei (2020) On the performance of cell-free massive MIMO relying on adaptive NOMA/OMA mode-switching. IEEE Transactions on Communications, 68 (2), 792-810, [8895763]. (doi:10.1109/TCOMM.2019.2952574).

Record type: Article

Abstract

The downlink (DL) of a non-orthogonal-multiple-access (NOMA)-based cell-free massive multiple-input multipleoutput (MIMO) system is analyzed, where the channel state information (CSI) is estimated using pilots. It is assumed that the users are grouped into multiple clusters. The same pilot sequences are assigned to the users within the same clusters whereas the pilots allocated to all clusters are mutually orthogonal. First, a user’s bandwidth efficiency (BE) is derived based on his/her channel statistics under the assumption of employing successive interference cancellation (SIC) at the users’ end with no DL training. Next, the classic max-min optimization framework is invoked for maximizing the minimum BE of a user under peraccess point (AP) power constraints. The max min user BE of NOMA-based cell-free massive MIMO is compared to that of its orthogonal multiple-access (OMA) counter part, where all users employ orthogonal pilots. Finally, our numerical results are presented and an operating mode switching scheme is proposed based on the average per-user BE of the system, where the mode set is given by Mode = { OMA, NOMA }. Our numerical results confirm that the switching point between the NOMA and OMA modes depends both on the length of the channel’s coherence time and on the total number of users.

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Accepted/In Press date: 27 October 2019
e-pub ahead of print date: 11 November 2019
Published date: February 2020
Keywords: Cell-free massive MIMO, NOMA, convex optimization, max-min bandwidth efficiency

Identifiers

Local EPrints ID: 435680
URI: http://eprints.soton.ac.uk/id/eprint/435680
ISSN: 0090-6778
PURE UUID: c026263b-673f-4207-b7ea-06a59381ce4e
ORCID for Lajos Hanzo: ORCID iD orcid.org/0000-0002-2636-5214

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Date deposited: 18 Nov 2019 17:30
Last modified: 28 Apr 2022 01:34

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Contributors

Author: Manijeh Bashar
Author: Kanapathippillai Cumanan
Author: Alister Burr
Author: Hien Quoc Ngo
Author: Lajos Hanzo ORCID iD
Author: Pei Xiao

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