A reliable link quality-based RPL routing for Internet of Things

RPL (IPv6 Routing Protocol for Low power and Lossy Networks) is the pseudo-standard routing protocol for Internet of Things. RPL employs a customizable objective function to optimize the routing. The default objective functions used in RPL are i) OF0 (Objective Function Zero) and ii) MRHOF (Minimum Rank with Hysteresis Objective Function). The OF0 is based on the routing metric hop count, whereas the MRHOF uses the ETX metric. They both do not measure the actual link quality. The link quality is directly related to the reliability of the network. The quality of the link can be estimated through methods that are both hardware and software based. The software-based methods are easy to implement and to ensure the reliability of the network. There are different software-based link quality estimation methods; the prominent methods among them are ETX and Link Quality Level (LQL). The ETX is a method of approximation of the transmitted packets. It uses probe packets to predict the expected transmission count, and it may not accurately reflect the link quality. The proposed Link Quality-Based Objective Function (LQBOF) makes use of the LQL metric which provides better link estimation values than the ETX method. The proposed method intends to provide a more reliable routing based on the link quality. The LQL is estimated through a metric called Packet Reception Rate (PRR). The LQL is calculated and ranked as values from 1 to 7, reflecting the best and worst link quality, respectively. The estimated LQL value is linked with the default ETX in computing the best path. This method intends to increase the reliability of the network. The reliability of the objective function is evaluated with the performance metrics packet delivery ratio, power consumption, throughput, convergence time, control traffic overhead and hop count.