A scheduler for a wireless system

Abstract

This problem deals with the scheduling of data packets for different users who share a common wireless channel of limited capacity and who have different service time requirements. From a system point of view it is important to maintain a high throughput, that is, a high number of packets served per unit of time. However from a user point of view it is important to minimise the service time. This poses a trade-off problem, which is one of the goals we wish to analyse.

The wireless transmission channel alternates between good and bad states over time. While the channel is in a bad state the transmission of a packet fails and the packet needs to be retransmitted. When the state of the channel is good, packets are transmitted successfully and do not require retransmission. The system transmission efficiency or throughput might be defined as the number of data packets that can be transmitted successfully in a given time.

The scheduler we wish to study is designed to consider both the wireless channel conditions and the users' quality of service requirements. For this purpose users are assigned a credit every scheduling frame, which is a function of the wireless channel conditions and the quality of service required, which depends on the traffic class.