Side trip multi-path routing protocol for spatial node failure tolerance in data-gathering WSNs

In severe disaster environments, wireless sensor networks (WSNs) need to be tolerant to spatial node failure due to external factors such as bomb attack and river overflow. The aim of this paper is to realize data-gathering WSNs that keep the data collection ratio as high as possible while keeping system lifetime as long as possible. This paper proposes not only a multipath data gathering protocol called “Side Trip (ST)” scheme to enhance spatial node-failure tolerance, but also an improved version of ST scheme called “Side Trip with Network Coding (STNC)” scheme which utilizes inter-flow XOR network coding to reduce redundant packets without affecting the system lifetime significantly. In data-gathering WSNs, nodes further from a sink node tend to relay fewer packets. In the ST scheme, a node establishes another secondary path which, for some distance, passes through nodes the same hop count away from the sink in order to spatially separate the path from the primary path. In the STNC scheme, redundant packets from different source nodes are network-coded into an encoded packet in order to reduce the number of redundant packets. We compare the ST scheme, STNC scheme, and two existing multipath protocols, i.e., H-SPREAD (hybrid-secure protocol for reliable data delivery) scheme and Sub-branch Multipath Routing Protocol (SMRP) scheme, by means of a self-developed simulator. The results show that STNC scheme and ST scheme offer enhanced tolerance to node-failure compared to H-SPREAD scheme and SMRP scheme with no significant impact on system lifetime.