An Efficient QoS-Based Uplink Scheduling Scheme for IEEE 802.16e Mobile Stations

The IEEE 802.16e-2005 standard for broadband wireless access provides a rich quality of service (QoS) framework suitable for supporting a multitude of services. In IEEE 802.16e, the uplink resource allocation is based on a request-grant mechanism where a mobile stations (MS) requests allocations of transmission opportunities from the base station (BS). Every frame, the BS decides the amount of resources to be granted for each uplink connection according to its QoS parameters. While the grant is decided on a connection basis, the BS aggregates the grants allocated for all connections of each MS and adds a single entry for each MS in the allocation MAP message. Two main challenges exist for scheduling at the MS side: the first is how to divide the grant among the connections according to their declared QoS parameters and requested bandwidth and the second is to be able to perform this operation prior to the arrival of the subsequent allocation from the BS. In this paper, we describe a new efficient scheme for mobile station uplink scheduling that meets these challenges. The scheme is a hierarchical credit-based algorithm based on the deficit round robin method. The algorithm is designed to prevent bandwidth stealing and starvation of low-priority connections. We provide simulation results that show the excellent performance of the scheme even under extreme overload conditions. The results show the isolation of service classes and the stability of the scheme.