Ordering in time: A new routing approach for wireless networks

The ordering of nodes with respect to destinations of interest by means of spatial information (e.g., distances, path constituency, complete or partial topology) has been a fundamental aspect of all routing protocols in wireless networks. This spatial ordering has also included the use of geographical or virtual coordinates denoting the location of nodes. We propose the use of ordering of nodes based on time rather than space, and without the need to establish any clock synchronization among nodes. We demonstrate for the first time that using the relative times when each node receives and transmits packets is sufficient to establish multiple loop-free paths to destinations, and that such time-based ordering renders more efficient loop-free routing than the spatial ordering of nodes. With the use of self-adjusted delays, nodes can manipulate their ordering so that the resulting routing choices are more robust to failures than routing choices based solely on times driven by the physical topology. Furthermore, we show that the problem of resetting sequence numbers, which is a network-wide operation with traditional spatial ordering, is trivial with temporal ordering. We introduce the Time Ordered Routing Protocol (TORP) and compare it against routing protocols based on spatial ordering to demonstrate that temporal ordering can lead to superior performance in multi-hop wireless networks.