An Analytical Model of Energy-Aware RPL for Wireless Sensor Networks

Battery-operated Wireless Sensor Networks (WSNs) deployed in wide and remote areas are difficult to maintain as replacing their batteries in such scenarios is a daunting task. Thus, there is a need to make use of self-sustaining energy harvesting sensor nodes. However, the Routing Protocol for Low Power and Lossy Networks (RPL), the de facto standard routing protocol for WSNs, assumes that there is a constant supply of energy for all sensors, and that it does not use energy as its routing metric. Therefore, there is a need to modify RPL to factor in energy in its routing metric to improve the network lifetime. This study addresses this problem by dynamically converting the energy level of a node into an additive penalty to the ETX metric used by RPLs Minimum Rank Hysteresis Objective Function (MRHOF). RPL is modeled using a modified version of the Bellman-Ford algorithm. Assuming we use a lossless channel and we implement aggressive parent-switching, we have found out in our analytical model simulations that the Average Charge Cycle times and Time of First Node Death increase up to 2.5 times longer as compared to standard RPL for a simple, four node diamond topology. There is also the consequence of child nodes being disconnected from the network due to the energy balancing in the parent nodes, which lowers the total Packet Delivery Ratio up to 10% lower than standard RPL for the simple diamond topology. However, this is balanced out by the increase in Sending Rate of the parent nodes by up to 20% due to longer lifetimes. Thus, the total number of packets received from the entire network is up to 8% higher for the experiment topology.