Preemption mechanisms for push-to-talk in ad hoc networks

Using push-to-talk applications in ad hoc networks is not straightforward. There are no inherent mechanisms to support priority of the voice traffic, to avoid great jitter and packet loss in face of large background traffic loads. This paper presents three preemption mechanisms that can be applied to support push-to-talk traffic in multi-hop ad hoc networks. The mechanisms differ in the way the background traffic is treated: discard, buffering and inter-scheduling. It is shown that there is a trade-off between the impact on the background traffic and the service for the push-to-talk traffic. Discarding or buffering the background traffic leaves the push-to-talk traffic with very little impact by the background traffic, while inserting the low priority packets in the interval between the high priority packets incurs some cost to the push-to-talk traffic.