# 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:
- 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:
- 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:
- Journal:
- 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 Field | Value | Language |
---|---|---|

dc.contributor.author | Xia, Minghua | en |

dc.contributor.author | Wu, Yik-Chung | en |

dc.contributor.author | Aissa, Sonia | en |

dc.date.accessioned | 2012-11-10T09:02:38Z | - |

dc.date.available | 2012-11-10T09:02:38Z | - |

dc.date.issued | 2012-04-01 | en |

dc.identifier.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. | en |

dc.identifier.issn | 1536-1276 | en |

dc.identifier.doi | 10.1109/TWC.2012.020812.110311 | en |

dc.identifier.uri | http://hdl.handle.net/10754/251674 | en |

dc.description.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. | en |

dc.language.iso | en | en |

dc.publisher | Institute of Electrical and Electronics Engineers (IEEE) | en |

dc.relation.url | http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6151774 | en |

dc.rights | Archived with thanks to IEEE Transactions on Wireless Communications | en |

dc.title | Non-Orthogonal Opportunistic Beamforming: Performance Analysis and Implementation | en |

dc.type | Article | en |

dc.contributor.department | Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division | en |

dc.contributor.department | Communication Theory Lab | en |

dc.identifier.journal | IEEE Transactions on Wireless Communications | en |

dc.eprint.version | Publisher's Version/PDF | en |

dc.contributor.institution | Department of Electrical and Electronic Engineering, University of Hong Kong, Hong Kong | en |

dc.contributor.institution | INRS, University of Quebec, Montreal, QC, Canada | en |

dc.contributor.affiliation | King Abdullah University of Science and Technology (KAUST) | en |

kaust.author | Xia, Minghua | en |

kaust.author | Aissa, Sonia | en |

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