### Abstract

OFDMA is a potential technology that can flexibly allocate subcarriers while providing diversity gain to multiple users. In our recent work [1], we showed a surprising result that the maximum frequency diversity gain in OFDMA systems is equal to the number of independent subcarriers, i.e., the same as that in point-to-point OFDM systems despite of the fact that multiple users will share a common set of subcarriers. However, the diversity gain only characterizes the first-order outage performance in the high SNR regime, and the outage performance in the low SNR regime, which is very important in practice, is still an open problem. In this paper, we first formulate the subcarrier allocation problem in OFDMA systems as a random bipartite graph model. Then, a more precise outage probability is derived in the high SNR regime using a high-order analysis of the maximum matching on a random bipartite graph. An approximate outage probability in the low SNR regime is also obtained by studying the complement of a random bipartite graph. It is then demonstrated that the coefficient of the second-order term in the outage probability expression is zero except for the scenario of two users with two or three subcarriers.

Original language | English |
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Title of host publication | GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference |

DOIs | |

Publication status | Published - 1 Dec 2009 |

Event | 2009 IEEE Global Telecommunications Conference, GLOBECOM 2009 - Honolulu, HI, United States Duration: 30 Nov 2009 → 4 Dec 2009 |

### Publication series

Name | GLOBECOM - IEEE Global Telecommunications Conference |
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### Other

Other | 2009 IEEE Global Telecommunications Conference, GLOBECOM 2009 |
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Country | United States |

City | Honolulu, HI |

Period | 30/11/09 → 4/12/09 |

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### ASJC Scopus subject areas

- Electrical and Electronic Engineering

### Cite this

*GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference*[5425749] (GLOBECOM - IEEE Global Telecommunications Conference). https://doi.org/10.1109/GLOCOM.2009.5425749