This paper presents the adaptation of a specific metric for the RPL protocol in the objective function MRHOF. Among the functions standardized by IETF, we find OF0, which is based on the minimum hop count, as well as MRHOF, which is based on the Expected Transmission Count (ETX). However, when the network becomes denser or the number of nodes increases, both OF0 and MRHOF introduce long hops, which can generate a bottleneck that restricts the network. The adaptation is proposed to optimize both OFs through a new routing metric. To solve the above problem, the metrics of the minimum number of hops and the ETX are combined by designing a new routing metric called SIGMA-ETX, in which the best route is calculated using the standard deviation of ETX values between each node, as opposed to working with the ETX average along the route. This method ensures a better routing performance in dense sensor networks. The simulations are done through the Cooja simulator, based on the Contiki operating system. The simulations showed that the proposed optimization outperforms at a high margin in both OF0 and MRHOF, in terms of network latency, packet delivery ratio, lifetime, and power consumption.

The wireless sensor networks (WSN) are immersed in multiple areas of knowledge and are the alternative that allows analyzing, solving, and preventing problems under different facets. The RPL protocol (IPv6 Routing Protocol for Low power a Lossy Networks) arises for the management of this type of network restricted by their physical capabilities through different rules and operations that simplify the communications and constructions of the WSN. Although RPL is an efficient and standardized protocol, it does not consider high traffic handling and presents severe problems regarding load balancing, which leads to service disruption. In this article, WRF-RPL is proposed as a protocol for considering load balancing over RPL to distribute communications and messages into a network topology to avoid one preferred parent's congestions. The proposed protocol aims to improve the network's lifetime and the packet delivery through source nodes to the sink in an energy-efficient manner. Different simulated scenarios were conducted over the Cooja simulator. The results show that WRF-RPL protocols outperform the standard RPL protocol over Network Lifetime, PDR, control message overhead, and energy consumption compared with other existing protocols.

This paper proposes a novel architecture named SBR, a software defined network (SDN) architecture using as a routing protocol RPL, a Protocol for Low-Power, and Lossy Networks for Internet of Things (IoT). The architecture includes the function SIGMA, an objective function used in IoT applications to take routing decisions. This research represents an effort to relate IoT and SDN. This association was developed using RPL-SIGMA to solve various IoT and Wireless Sensor Networks (WSN) problems. At the end, a comparison between SBR (SDN-RPL with SIGMA) and SDN-RPL (without SIGMA) was included. The simulations show that SBR has a better performance concerning packet loss, latency, and energy consumption over an architecture based on IoT without SIGMA. The simulation also demonstrates that SDN can be used to manage the IoT network efficiently.