Traffic-aware routing for real-time communications in wireless multi-hop networks

In this paper, we propose a novel traffic-aware routing metric for real-time communications (RTC) in wireless multi-hop networks. Our routing metric, path predicted transmission time (PPTT), is designed to choose a high-quality path for RTC flow between a source and a destination. PPTT can serve as both single-radio and multi-radio routing metric for RTC flow. RTC has critical quality of service (QoS) requirements in terms of delay, bandwidth and so on. Traditional measurement-based routing schemes ignore the interference from the coming RTC flow itself (i.e. self-traffic), so they may choose the inefficient path to serve the coming RTC flow due to the inaccurate quality estimation of the transmission path. PPTT takes explicit consideration of both self-traffic and neighbouring traffic interfering with the RTC flow, and thus offers an accurate estimation of path transmission delay. Through differentiating the links by the wireless channel/radio they are using, PPTT has the capability to choose a high-quality path for the coming RTC flow in both single-radio and multi-radio networks. To evaluate the performance, we implement PPTT scheme and study its performance in a wireless multi-hop testbed consisting of 32 nodes equipped with two IEEE 802.11a/b/g combo cards, and we also conduct extensive simulations with different random topologies in network simulator NS-2 for a more comprehensive comparison. The results of simulation and experiment show that this routing metric outperforms other non-traffic-aware one such as expected transmission count (ETX) and weighted cumulative expected transmission time (WCETT) in terms of delay and goodput in both. single-radio and multi-radio wireless networks. Copyright (C) 2006 John Wiley & Sons, Ltd.