A Hybrid Adaptive Protocol for Reliable Data Delivery in WSNs with Multiple Mobile Sinks

In this paper we deal with reliable and energy-efficient data delivery in sparse Wireless Sensor Networks with multiple Mobile Sinks (MSs). This is a critical task, especially when MSs move randomly, as interactions with sensor nodes are unpredictable, typically of short duration, and affected by message losses. In addition, multiple MSs can be simultaneously present in the sensor contact area making the minimum energy data delivery a complex optimization problem. To solve the above issues, in this paper we propose a novel protocol that combines efficiently erasure coding with an ARQ scheme. The key features of the proposed protocol are: (i) the use of redundancy to cope efficiently with message losses in the multicast environment, and (ii) the ability of adapting the level of redundancy based on feedbacks sent back by MSs through ACKs. We observed by simulation that our protocol outperforms an alternative protocol that relies only on an ARQ scheme, even when there is a single MS. We also validated our simulation results through a set of experimental measurements based on real sensor nodes. Our results show that the adoption of encoding techniques increases the lifetime of the sensor in the range [40% 55%] compared to standard simple ARQ approaches when applied to WSNs with Mobile Sinks.