On Scalability of FDD-Based Cell-Free Massive MIMO Framework
Cell-free massive multiple-input multiple-output (MIMO) systems have the potential of providing joint services, including joint initial access, efficient clustering of access points (APs), and pilot allocation to user equipment (UEs) over large coverage areas with reduced interference. In cell-free...
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| Format: | Article |
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MDPI AG
2023-08-01
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| Series: | Sensors |
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| Online Access: | https://www.mdpi.com/1424-8220/23/15/6991 |
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| author | Beenish Hassan Sobia Baig Saad Aslam |
| author_facet | Beenish Hassan Sobia Baig Saad Aslam |
| author_sort | Beenish Hassan |
| collection | DOAJ |
| description | Cell-free massive multiple-input multiple-output (MIMO) systems have the potential of providing joint services, including joint initial access, efficient clustering of access points (APs), and pilot allocation to user equipment (UEs) over large coverage areas with reduced interference. In cell-free massive MIMO, a large coverage area corresponds to the provision and maintenance of the scalable quality of service requirements for an infinitely large number of UEs. The research in cell-free massive MIMO is mostly focused on time division duplex mode due to the availability of channel reciprocity which aids in avoiding feedback overhead. However, the frequency division duplex (FDD) protocol still dominates the current wireless standards, and the provision of angle reciprocity aids in reducing this overhead. The challenge of providing a scalable cell-free massive MIMO system in an FDD setting is also prevalent, since computational complexity regarding signal processing tasks, such as channel estimation, precoding/combining, and power allocation, becomes prohibitively high with an increase in the number of UEs. In this work, we consider an FDD-based scalable cell-free network with angular reciprocity and a dynamic cooperation clustering approach. We have proposed scalability for our FDD cell-free and performed a comparative analysis with reference to channel estimation, power allocation, and precoding/combining techniques. We present expressions for scalable spectral efficiency, angle-based precoding/combining schemes and provide a comparison of overhead between conventional and scalable angle-based estimation as well as combining schemes. Simulations confirm that the proposed scalable cell-free network based on an FDD scheme outperforms the conventional matched filtering scheme based on scalable precoding/combining schemes. The angle-based LP-MMSE in the FDD cell-free network provides <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>14.3</mn><mo>%</mo></mrow></semantics></math></inline-formula> improvement in spectral efficiency and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>11.11</mn><mo>%</mo></mrow></semantics></math></inline-formula> improvement in energy efficiency compared to the scalable MF scheme. |
| first_indexed | 2024-03-11T00:16:54Z |
| format | Article |
| id | doaj.art-d3c2517884f448f0ada236c66e24a3f0 |
| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-03-11T00:16:54Z |
| publishDate | 2023-08-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Sensors |
| spelling | doaj.art-d3c2517884f448f0ada236c66e24a3f02023-11-18T23:37:13ZengMDPI AGSensors1424-82202023-08-012315699110.3390/s23156991On Scalability of FDD-Based Cell-Free Massive MIMO FrameworkBeenish Hassan0Sobia Baig1Saad Aslam2Department of Electrical Engineering, The Islamia University of Bahawalpur, Bahawalpur 63100, PakistanDepartment of Electrical and Computer Engineering, Energy Research Center, COMSATS University Islamabad, Lahore Campus, Lahore 54000, PakistanDepartment of Computing and Information Systems, School of Engineering and Technology, Sunway University, Petaling Jaya 47500, Selangor, MalaysiaCell-free massive multiple-input multiple-output (MIMO) systems have the potential of providing joint services, including joint initial access, efficient clustering of access points (APs), and pilot allocation to user equipment (UEs) over large coverage areas with reduced interference. In cell-free massive MIMO, a large coverage area corresponds to the provision and maintenance of the scalable quality of service requirements for an infinitely large number of UEs. The research in cell-free massive MIMO is mostly focused on time division duplex mode due to the availability of channel reciprocity which aids in avoiding feedback overhead. However, the frequency division duplex (FDD) protocol still dominates the current wireless standards, and the provision of angle reciprocity aids in reducing this overhead. The challenge of providing a scalable cell-free massive MIMO system in an FDD setting is also prevalent, since computational complexity regarding signal processing tasks, such as channel estimation, precoding/combining, and power allocation, becomes prohibitively high with an increase in the number of UEs. In this work, we consider an FDD-based scalable cell-free network with angular reciprocity and a dynamic cooperation clustering approach. We have proposed scalability for our FDD cell-free and performed a comparative analysis with reference to channel estimation, power allocation, and precoding/combining techniques. We present expressions for scalable spectral efficiency, angle-based precoding/combining schemes and provide a comparison of overhead between conventional and scalable angle-based estimation as well as combining schemes. Simulations confirm that the proposed scalable cell-free network based on an FDD scheme outperforms the conventional matched filtering scheme based on scalable precoding/combining schemes. The angle-based LP-MMSE in the FDD cell-free network provides <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>14.3</mn><mo>%</mo></mrow></semantics></math></inline-formula> improvement in spectral efficiency and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>11.11</mn><mo>%</mo></mrow></semantics></math></inline-formula> improvement in energy efficiency compared to the scalable MF scheme.https://www.mdpi.com/1424-8220/23/15/6991cell-freemassive MIMOscalable FDDangular reciprocitydynamic cooperation clustering |
| spellingShingle | Beenish Hassan Sobia Baig Saad Aslam On Scalability of FDD-Based Cell-Free Massive MIMO Framework Sensors cell-free massive MIMO scalable FDD angular reciprocity dynamic cooperation clustering |
| title | On Scalability of FDD-Based Cell-Free Massive MIMO Framework |
| title_full | On Scalability of FDD-Based Cell-Free Massive MIMO Framework |
| title_fullStr | On Scalability of FDD-Based Cell-Free Massive MIMO Framework |
| title_full_unstemmed | On Scalability of FDD-Based Cell-Free Massive MIMO Framework |
| title_short | On Scalability of FDD-Based Cell-Free Massive MIMO Framework |
| title_sort | on scalability of fdd based cell free massive mimo framework |
| topic | cell-free massive MIMO scalable FDD angular reciprocity dynamic cooperation clustering |
| url | https://www.mdpi.com/1424-8220/23/15/6991 |
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