Non-Orthogonal Opportunistic Beamforming: Performance Analysis and Implementation

Handle URI:
http://hdl.handle.net/10754/251674
Title:
Non-Orthogonal Opportunistic Beamforming: Performance Analysis and Implementation
Authors:
Xia, Minghua; Wu, Yik-Chung; Aissa, Sonia
Abstract:
Aiming to achieve the sum-rate capacity in multi-user multi-antenna systems where $N_t$ antennas are implemented at the transmitter, opportunistic beamforming (OBF) generates~$N_t$ orthonormal beams and serves $N_t$ users during each channel use, which results in high scheduling delay over the users, especially in densely populated networks. Non-orthogonal OBF with more than~$N_t$ transmit beams can be exploited to serve more users simultaneously and further decrease scheduling delay. However, the inter-beam interference will inevitably deteriorate the sum-rate. Therefore, there is a tradeoff between sum-rate and scheduling delay for non-orthogonal OBF. In this context, system performance and implementation of non-orthogonal OBF with $N>N_t$ beams are investigated in this paper. Specifically, it is analytically shown that non-orthogonal OBF is an interference-limited system as the number of users $K \to \infty$. When the inter-beam interference reaches its minimum for fixed $N_t$ and~$N$, the sum-rate scales as $N\ln\left(\frac{N}{N-N_t}\right)$ and it degrades monotonically with the number of beams $N$ for fixed $N_t$. On the contrary, the average scheduling delay is shown to scale as $\frac{1}{N}K\ln{K}$ channel uses and it improves monotonically with $N$. Furthermore, two practical non-orthogonal beamforming schemes are explicitly constructed and they are demonstrated to yield the minimum inter-beam interference for fixed $N_t$ and $N$. This study reveals that, if user traffic is light and one user can be successfully served within a single transmission, non-orthogonal OBF can be applied to obtain lower worst-case delay among the users. On the other hand, if user traffic is heavy, non-orthogonal OBF is inferior to orthogonal OBF in terms of sum-rate and packet delay.
KAUST Department:
Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division; Communication Theory Lab
Citation:
Xia M, Wu Y-C, Aissa S (2012) Non-Orthogonal Opportunistic Beamforming: Performance Analysis and Implementation. IEEE Trans Wireless Commun 11: 1424-1433. doi:10.1109/TWC.2012.020812.110311.
Publisher:
Institute of Electrical and Electronics Engineers (IEEE)
Journal:
IEEE Transactions on Wireless Communications
Issue Date:
1-Apr-2012
DOI:
10.1109/TWC.2012.020812.110311
Type:
Article
ISSN:
1536-1276
Additional Links:
http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6151774
Appears in Collections:
Articles; Communication Theory Lab; Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorXia, Minghuaen
dc.contributor.authorWu, Yik-Chungen
dc.contributor.authorAissa, Soniaen
dc.date.accessioned2012-11-10T09:02:38Z-
dc.date.available2012-11-10T09:02:38Z-
dc.date.issued2012-04-01en
dc.identifier.citationXia M, Wu Y-C, Aissa S (2012) Non-Orthogonal Opportunistic Beamforming: Performance Analysis and Implementation. IEEE Trans Wireless Commun 11: 1424-1433. doi:10.1109/TWC.2012.020812.110311.en
dc.identifier.issn1536-1276en
dc.identifier.doi10.1109/TWC.2012.020812.110311en
dc.identifier.urihttp://hdl.handle.net/10754/251674en
dc.description.abstractAiming to achieve the sum-rate capacity in multi-user multi-antenna systems where $N_t$ antennas are implemented at the transmitter, opportunistic beamforming (OBF) generates~$N_t$ orthonormal beams and serves $N_t$ users during each channel use, which results in high scheduling delay over the users, especially in densely populated networks. Non-orthogonal OBF with more than~$N_t$ transmit beams can be exploited to serve more users simultaneously and further decrease scheduling delay. However, the inter-beam interference will inevitably deteriorate the sum-rate. Therefore, there is a tradeoff between sum-rate and scheduling delay for non-orthogonal OBF. In this context, system performance and implementation of non-orthogonal OBF with $N>N_t$ beams are investigated in this paper. Specifically, it is analytically shown that non-orthogonal OBF is an interference-limited system as the number of users $K \to \infty$. When the inter-beam interference reaches its minimum for fixed $N_t$ and~$N$, the sum-rate scales as $N\ln\left(\frac{N}{N-N_t}\right)$ and it degrades monotonically with the number of beams $N$ for fixed $N_t$. On the contrary, the average scheduling delay is shown to scale as $\frac{1}{N}K\ln{K}$ channel uses and it improves monotonically with $N$. Furthermore, two practical non-orthogonal beamforming schemes are explicitly constructed and they are demonstrated to yield the minimum inter-beam interference for fixed $N_t$ and $N$. This study reveals that, if user traffic is light and one user can be successfully served within a single transmission, non-orthogonal OBF can be applied to obtain lower worst-case delay among the users. On the other hand, if user traffic is heavy, non-orthogonal OBF is inferior to orthogonal OBF in terms of sum-rate and packet delay.en
dc.language.isoenen
dc.publisherInstitute of Electrical and Electronics Engineers (IEEE)en
dc.relation.urlhttp://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6151774en
dc.rightsArchived with thanks to IEEE Transactions on Wireless Communicationsen
dc.titleNon-Orthogonal Opportunistic Beamforming: Performance Analysis and Implementationen
dc.typeArticleen
dc.contributor.departmentComputer, Electrical and Mathematical Sciences and Engineering (CEMSE) Divisionen
dc.contributor.departmentCommunication Theory Laben
dc.identifier.journalIEEE Transactions on Wireless Communicationsen
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.institutionDepartment of Electrical and Electronic Engineering, University of Hong Kong, Hong Kongen
dc.contributor.institutionINRS, University of Quebec, Montreal, QC, Canadaen
dc.contributor.affiliationKing Abdullah University of Science and Technology (KAUST)en
kaust.authorXia, Minghuaen
kaust.authorAissa, Soniaen
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