Master Thesis - Past Projects - Abstract

QoS-aware MAC layer protocol for wireless ad hoc networks

ID: LITH-IDA-EX--07/008--SE

Due to infrastructure-less deployment, wireless ad hoc networks are drawing a lot of interest. The users expect to run various types of applications over wireless ad hoc networks, like email, internet browsing, voice over IP networks and video streaming. Each of these applications has unique needs, characteristics and importance. As of today there is little support for Quality of Service (QoS) in wireless ad hoc networks. The aim of the thesis is to test and evaluate a prioritized MAC layer, where we allocate the wireless channel to the packets with higher priorities. Our strategy is to classify packets according to their criticality for the users, and to achieve an absolute priority-based bandwidth allocation by transmitting higher prioritized packets on the wireless channel first. Moreover, all nodes in the network should treat packets of a particular priority class in same manner. We modified the CSMA/CA protocol implementation in the Network Simulator (NS2) in order to introduce support for priority-based packet forwarding. Experiments indicate that our modifications enforce prioritized channel allocation. Due to our modifications, highly prioritized packets always occupy the channel first, as they have to wait for a shorter time interval before transmission. However, channel utilization is effected negatively when there are only low-prioritized packets to transmit, since these packets have to wait for a longer time before transmission.

Keywords: MAC layer, QoS, CSMA/CA, DIFS, Contention window

Author(s): Muhammad Azam Akram

Contact: Calin Curescu