A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> c) Lexical-Based Composition Enhancements <s> Simulators for wireless sensor networks are a valuable tool for system development. However, current simulators can only simulate a single level of a system at once. This makes system development and evolution difficult since developers cannot use the same simulator for both high-level algorithm development and low-level development such as device-driver implementations. We propose cross-level simulation, a novel type of wireless sensor network simulation that enables holistic simultaneous simulation at different levels. We present an implementation of such a simulator, COOJA, a simulator for the Contiki sensor node operating system. COOJA allows for simultaneous simulation at the network level, the operating system level, and the machine code instruction set level. With COOJA, we show the feasibility of the cross-level simulation approach. <s> BIB001 </s> A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> c) Lexical-Based Composition Enhancements <s> Available wireless sensor networks targeting the domain of healthcare enables the development of new applications and services in the context of E-Health. Such networks play an important role in several scenarios of patient monitoring, particularly those where data collection is vital for diagnosis and/or research purposes. However, despite emerging solutions, wearable sensors still depend on users' acceptance. One proposed solution to improve wearability relies on the use of smaller sensing nodes, requiring more energy-efficient networks, due to smaller room available for energy sources. In such context, smaller wireless sensor network nodes are required to work long time periods without human intervention and, at the same time, to provide appropriate levels of reliability and quality of service. Satisfaction of these two goals depends on several key factors, such as the routing protocol, the network topology, and energy efficiency. This paper offers a solution to increase the network lifetime based on a new Energy-Aware Objective Function used to design a Routing Protocol for Low-Power and Lossy Networks. The proposed Objective Function uses the Expected Transmission Count Metric and the Remaining Energy on each sensor node to compute the best paths to route data packets across the network. When compared with state of the art solutions, the proposed method increases the network lifetime by 21% and reduces the peaks of energy consumption by 12%. In this way, wireless sensor network nodes wearability can be improved, making them smaller and lighter, while maintaining the required performance. <s> BIB002
A lexical composite based OF named an energy-aware objective function (EAOF) for RPL protocol is introduced in BIB002 . In this study, the authors highlight the issue that current RPL objective functions do not use energy-based metrics. They proposed combining the ETX metric with the residual energy of nodes in order to build a topology that is energy-efficient and reliable. A node running EAOF must first select a subset of nodes with the lowest ranks, calculated based on ETX, from its neighbors. Then, the node with the maximum residual energy is selected from this subset as a preferred parent. The parameter MAX-ETX is introduced to limit the size of the ETX-based subset from which the preferred parent is selected according the application requirements. In addition, the parameter MIN_ENER is proposed to introduce a hysteresis value when switching parents based on energy in order to ensure network stability. The study uses the popular Cooja BIB001 simulator with Contiki  to validate the proposed objective function and compare it with the ContikiRPL implementation of the ETX-based MRHOF in terms of Packet Reception Ratio (PRR), energy efficiency and network lifetime. It is shown that EAOF significantly improves the network lifetime and balances energy consumption compared to RPL MRHOF, with a negligible impact on reliability. A slight degradation in PRR is attributed to EAOF sometimes favoring balanced paths over high quality paths to enhance network lifetime.