Distributed approaches for exploiting multiuser diversity in wireless networks

Xiangping Qin*, Randall A. Berry

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

99 Scopus citations


In wireless fading channels, multiuser diversity can be exploited by scheduling users to transmit when their channel conditions are favorable. This leads to a sum throughput that increases with the number of users and, in certain cases, achieves capacity. However, such scheduling requires global knowledge of every user's channel gain, which may be difficult to obtain in some situations. This paper addresses contention-based protocols for exploiting multiuser diversity with only local channel knowledge. A variation of the ALOHA protocol is given in which users attempt to exploit multiuser diversity gains, but suffer contention losses due to the distributed channel knowledge. The growth rate of the sum throughput for this protocol is characterized in a backlogged system under both short-term and long-term average power constraints. A simple "fixed-rate" system is shown to be asymptotically optimal and to achieve the same growth rate as in a system with an optimal centralized scheduler. Moreover, asymptotically, the fraction of throughput lost due to contention is shown to be 1/e. Also, in a system with random arrivals and an infinite user population, a variation of this ALOHA protocol is shown to be stable for any total arrival rate, given that users can estimate the backlog.

Original languageEnglish (US)
Pages (from-to)392-413
Number of pages22
JournalIEEE Transactions on Information Theory
Issue number2
StatePublished - Feb 2006


  • Distributed algorithms
  • Multiuser diversity
  • Opportunistic communications
  • Random access
  • Scheduling
  • Slotted ALOHA
  • Wireless networks

ASJC Scopus subject areas

  • Information Systems
  • Computer Science Applications
  • Library and Information Sciences

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