A new routing and connectivity availability metric of low duty cycle random sleep scheduled multi-hop wireless sensor networks

Abstract

Wireless sensor network (WSN) is attracting intensive interests in many application areas. In some scenarios such as monitoring of the coal-mining area or remote area, nodes seldom move and may switch from sleeping to waking mode to minimize power consumption. Energy conservation design for the network lifetime extension is the primary issue. By adopting sleep scheduling to keep low duty cycle can help reduce the energy consumption. Random sleep scheduling is a desirable mechanism for its simplicity and guaranteed stable low duty cycle. Moreover, the low duty cycle sleeping of nodes may destroy the connectivity of network. Most of existing WSN routing techniques are designed for fully connected networks assuming that the nodes of the routing path between source and destination are all available at the same time. Maintaining fully connected backbone involves high duty cycle and costly clock synchronization which consumes more energy. If certain delay is tolerant, partially connected routing can achieve successful packet forwarding in networks with the deficiency of connectivity. In this paper a new partially connected routing and simple random sleep scheduling scheme is proposed for WSN with low duty cycle. A continuous time Markov chains (CTMC) connectivity availability model is introduced to evaluate the end to end packet delivery ratio of multi-hop networks subjected to the impact of both frequent disconnection and random sleep latency. The proposed connectivity availability model can also be used as the key metric for route path selection to achieve stable and high performance. Deployment guidelines are given for WSN with random sleep scheduling policy satisfying reliability, timeliness and duty cycle requirements. By modeling and simulation, we find that as compared to the fully connected routing protocol, the partially connected routing design can achieve much higher packet delivery ratio and lower duty cycle within the tolerant delay. The computation and simulation validate the mechanism.