Preserving QoS in wireless ad hoc networks

Quality of service (QoS) support in ad hoc networks relies on admission control to prevent the network from congestion. The collision rate that is experienced by each node on a link plays an important role on the decision made by admission control due to its impact on the available bandwidth estimation. However, most of the existing QoS support schemes in ad hoc networks neglected the fact that the collision rate might change greatly after a new flow is set up in the network. In this study, we use a process called soft admission control to assess the change of collision rate and promptly reject the flows that tend to cause evident collision increase. The basic idea is to admit an incoming flow along a link temporally on the first instance and then to monitor the change of the collision rate on this link for a given period of time, based on which the final decision (fully admission or rejection) is reached. This will ensure that impairment to the QoS of existing flows does not occur.