Modified RPL Routing Protocol for Dense IOT Networks

Dense IoT-WSNs is a subtype of IoT-WSNs in which a high density of deployed nodes and data exchange is considered. Due to the capacity constraints of nodes in the IoT-WSN, the routing process requires a unique design to accommodate a large amount of data while saving its energy consumption. The Internet Engineering Task Force (IETF) creates a routing protocol for low-power lossy networks based on IPv6 to handle large numbers of nodes called RPL. RPL nodes rely on an objective function mechanism in route selection. Each objective function utilizes different metrics. The primary objective of this paper is to propose two modified RPL protocols to improve RPL performance over a dense network. The impact of the number of children is also investigated. The first proposed protocol is called ENCRPL. It used three metrics: energy level, number of neighbors, and a new metric, depending on the number of children. The second protocol, called NCERPL, is based on combining node and link metrics by using the numbers of neighbor nodes and children's nodes as node metrics and the expected transmission count (ETX) as a link metric. The proposed protocols are implemented and evaluated using Cooja simulator based on the Contiki-OS. Regarding energy consumption, the results show that the proposed protocols outperform RPL and the previously proposed protocol, called MET protocol. ENCRPL achieved a 93% improvement in energy saving over RPL with a density of 0.48 and 0.0075 nodes/m2. NCERPL provides about 14% improvement in energy saving over METRPL with 0.48 density and a 44% improvement with 0.0075 density. Both ENCRPL and NCERPL achieved higher performance regarding the number of dead nodes than RPL and METRPL with all scenarios. Considering packet delivery ratio and throughput, ENCRPL and NCERPL perform better than RPL with high-density scenarios.