ISSN : 1796-2021
Volume : 4    Issue : 5    Date : June 2009

Joint Polling and Contention Based Feedback Algorithm to Exploit Multiuser Diversity
Yahya S. Al-Harthi
Page(s): 348-356
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One of the most promising approaches to boost the communication efficiency in wireless systems
is the use of multiuser diversity (MUDiv), where the fading of channels is exploited. The mechanism
of scheduling the user with the best channel condition is called opportunistic scheduling (OS). In
this paper we propose a joint polling and contention based feedback (JPCF) algorithm that exploits
MUDiv while reducing the feedback load. The guard time, which is between bursts, is divided into
minislots that alternate between polling-based feedback minislot (p-minislot) and contention-based
feedback minislot (c-minislot). During the minislot, users feedback their channel qualities if above a
predetermined threshold. We analyze the scheduling algorithm under slow Rayleigh fading
assumption and derive the closed-form expressions of the feedback load as well as the system
capacity. We also consider the delay resulting from the time needed to schedule a user and derive
the system throughput. The scheduling algorithm is compared with other scheduling algorithms.

Index Terms
Multiuser diversity, adaptive modulation, feedback load, spectral efficiency and probability of access