DelayCheck: Scheduling voice over multi-hop multi-channel wireless mesh networks

In this work, we consider the goal of scheduling the maximum number of voice calls in a TDMA-based multi-radio, multi-channel mesh network. One of the main challenges to achieve this goal is the difficulty in providing strict (packet-level) delay guarantees for voice traffic in capacity limited multi-hop wireless networks. In this context, we propose DelayCheck, an online centralized scheduling and call-admission-control (CAC) algorithm which effectively schedules constant-bit-rate voice traffic in TDMA-based mesh networks. DelayCheck solves the joint routing, channel assignment and link scheduling problem while satisfying the constraint. We formulate an offline version of this scheduling problem as an Integer Linear Program (ILP), the LP relaxation of which gives us an optimality upper bound. We compare the output of DelayCheck with the LP-based upper bound as well as with two state-of-the-art prior scheduling algorithms. DelayCheck performs remarkably well, accepting about 93% of voice calls as compared to LP-based upper bound. As compared to state-of-the-art algorithms, DelayCheck improves scheduler efficiency by more than 34% and reduces call rejections by 2 fold. We also demonstrate that DelayCheck efficiently exploits the number of channels available for scheduling. With implementation optimizations, we show that DelayCheck has low memory and CPU requirements, thus making it practical.