### Abstract

OFDM can provide frequency diversity gain for point-to-point communications over frequency-selective slow fading channel. Recent works show that OFDM may also form a flexible and efficient multiple access method, which is often referred to OFDMA. However, the user outage probability and the optimal frequency diversity gain in OFDMA systems are not known. In this paper, random bipartite graph is used to model and analyse the multi-user subcarrier allocation problem over frequency-selective slow fading channels. Our aim is to minimize the user outage probability as well as guarantee fairness by dynamic allocating various subcarrier to each user. An optimal subcarrier allocation algorithm, which we shall refer to as the Hungarian method with random vertices rotation, is introduced to achieve these objectives. A simple but effective approximation equation for user outage probability is then derived. It is shown that the optimal frequency diversity gain in OFDMA system is the same as the point-to-point OFDM system. In particular, the frequency diversity gain does not decay as the number of users increases.

Original language | English |
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Title of host publication | 2008 IEEE Global Telecommunications Conference, GLOBECOM 2008 |

Pages | 3805-3809 |

Number of pages | 5 |

DOIs | |

Publication status | Published - 2008 |

Externally published | Yes |

Event | 2008 IEEE Global Telecommunications Conference, GLOBECOM 2008 - New Orleans, LA, United States Duration: 30 Nov 2008 → 4 Dec 2008 |

### Other

Other | 2008 IEEE Global Telecommunications Conference, GLOBECOM 2008 |
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Country | United States |

City | New Orleans, LA |

Period | 30/11/08 → 4/12/08 |

### Fingerprint

### ASJC Scopus subject areas

- Electrical and Electronic Engineering

### Cite this

*2008 IEEE Global Telecommunications Conference, GLOBECOM 2008*(pp. 3805-3809). [4698505] https://doi.org/10.1109/GLOCOM.2008.ECP.730

**Achieving high frequency diversity with subcarrier allocation in OFDMA systems.** / Bai, Bo; Chen, Wei; Cao, Zhigang; Letaief, Khaled.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*2008 IEEE Global Telecommunications Conference, GLOBECOM 2008.*, 4698505, pp. 3805-3809, 2008 IEEE Global Telecommunications Conference, GLOBECOM 2008, New Orleans, LA, United States, 30/11/08. https://doi.org/10.1109/GLOCOM.2008.ECP.730

}

TY - GEN

T1 - Achieving high frequency diversity with subcarrier allocation in OFDMA systems

AU - Bai, Bo

AU - Chen, Wei

AU - Cao, Zhigang

AU - Letaief, Khaled

PY - 2008

Y1 - 2008

N2 - OFDM can provide frequency diversity gain for point-to-point communications over frequency-selective slow fading channel. Recent works show that OFDM may also form a flexible and efficient multiple access method, which is often referred to OFDMA. However, the user outage probability and the optimal frequency diversity gain in OFDMA systems are not known. In this paper, random bipartite graph is used to model and analyse the multi-user subcarrier allocation problem over frequency-selective slow fading channels. Our aim is to minimize the user outage probability as well as guarantee fairness by dynamic allocating various subcarrier to each user. An optimal subcarrier allocation algorithm, which we shall refer to as the Hungarian method with random vertices rotation, is introduced to achieve these objectives. A simple but effective approximation equation for user outage probability is then derived. It is shown that the optimal frequency diversity gain in OFDMA system is the same as the point-to-point OFDM system. In particular, the frequency diversity gain does not decay as the number of users increases.

AB - OFDM can provide frequency diversity gain for point-to-point communications over frequency-selective slow fading channel. Recent works show that OFDM may also form a flexible and efficient multiple access method, which is often referred to OFDMA. However, the user outage probability and the optimal frequency diversity gain in OFDMA systems are not known. In this paper, random bipartite graph is used to model and analyse the multi-user subcarrier allocation problem over frequency-selective slow fading channels. Our aim is to minimize the user outage probability as well as guarantee fairness by dynamic allocating various subcarrier to each user. An optimal subcarrier allocation algorithm, which we shall refer to as the Hungarian method with random vertices rotation, is introduced to achieve these objectives. A simple but effective approximation equation for user outage probability is then derived. It is shown that the optimal frequency diversity gain in OFDMA system is the same as the point-to-point OFDM system. In particular, the frequency diversity gain does not decay as the number of users increases.

UR - http://www.scopus.com/inward/record.url?scp=67249102157&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=67249102157&partnerID=8YFLogxK

U2 - 10.1109/GLOCOM.2008.ECP.730

DO - 10.1109/GLOCOM.2008.ECP.730

M3 - Conference contribution

SN - 9781424423248

SP - 3805

EP - 3809

BT - 2008 IEEE Global Telecommunications Conference, GLOBECOM 2008

ER -