The Internet of Things (IoT) paradigm is assumed to be a major component in the present and future Internet, with forecasts claiming a humongous number of devices connected in the near future, and applications fields spanning from agriculture, to healthcare. Despite this, the standardization efforts have not yet resulted in widely adopted standards, and the market is fragmented into multiple solutions both at physical and communication protocol levels. Moreover, IoT systems exacerbate the usual test bed limitations, e.g., scalability (very large number of devices), hardware compatibility, space, and price. Due to the above problems, simulation tools become an extremely interesting tool for studying IoT systems both for academia (new algorithms), standardization (new protocols), and industry (what-if analysis). In this paper we will discuss what are the most relevant features and models that a simulation tool like ns-3 should prioritize to enable the above-mentioned needs from academia, standardization, and industry, and if they are achievable in the short, medium, or long term.

The IEEE 802.15.4 is a popular standard used in wireless sensor networks (WSNs) and the Internet of Things (IoT) applications. In these networks, devices are organized into groups formally known as personal area networks (PAN) which require a bootstrap procedure to become operational. Bootstrap plays a key role in the initialization and maintenance of these networks. For this reason, this work presents our implementation and performance analysis for the ns-3 network simulator. Specifically, this bootstrap implementation includes the support of three types of scanning mechanisms (energy scan, passive scan, and active scan) and the complete classic association mechanism described by the standard. Both of these mechanisms can be used independently by higher layers protocols to support network initialization, network joining, and maintenance tasks. Performance evaluation is conducted in total network association time and packet overhead terms. Our source code is documented and publicly available in the latest ns-3 official release.

Spatially unbalanced energy consumption among sensors is the most important issue in Wireless Sensor Networks (WSNs). This uneven energy consumption can significantly reduce network lifetime. The use of sink mobility with constrained paths and decreasing the message flood by limiting the flood area can help to improve the energy efficiency in WSNs. Maximum Amount Shortest Path routing (MASP) is an efficient protocol using this idea. MASP is proactive (table-driven) in nature and tries to collect the largest amount of data with least energy. MASP makes use of constrained paths for the trajectories of mobile sinks and divides the deployed sensor nodes into independent zones to construct the routing tables. In this paper we discuss the implementation of MASP and conduct a performance evaluation of it using the ns-3 network simulator.