# A Reference Model for Monitoring IoT WSN-Based Applications
## 1 Introduction  
The Internet of Things (IoT) can be defined as an infrastructure of interconnected objects, people, systems and information resources together with intelligent services to allow them to process information of the physical and the virtual world and react accordingly [1]. IoT is also defined by the Organisation for Economic Co-operation and Development (OECD) as the convergence between Information and Communications Technology (ICT) and the economy on a grand scale [2]. As an enabling technology that provides support of existing and new applications, services and devices, the impact of IoT on day-to-day life of people and its environments may not be bounded at this time. One of the main characteristics of IoT is that the objects must be context-aware. Many IoT applications require that the \"things\" know their environmental conditions, and adjust their behavior to them and to the other objects that are nearby. In this way, Wireless Sensor Networks (WSNs) can be considered the extension of the Internet toward the physical environment in the IoT, and thus they are one of the most valuable parts of any IoT system. WSNs are formed by many small devices, called motes, that are able to acquire information about their environment through sensing elements called transducers, process the obtained data and transmit it to a data center in order to store and collaboratively process it. Thus, WSNs correct behavior is fundamental for the correct operation, and maybe the future success, of IoT applications. However, although WNS designs show good performance and behavior when being evaluated in controlled environments, experience has shown that their deployment in real environments results in poorer performance and behavior [3]. It is therefore necessary to improve this behavior, and for that, to have more accurate information of the internal WSN operation [3; 4; 5]. This information may be obtained by the utilization of appropriate tools, the so called WSN Monitoring Platform (WSN-MP) being the most suitable. A WSN-MP is a distributed system which monitors the operation of a WSN, by means of a set of devices and/or modules which acquire information from different elements of the WSN (from the motes, wireless network, gateways, and even communication channel), and then collects, analyzes and presents it to the user to provide internal information about the WSN's operation. Many efforts have been carried out to debug the operation of WSNs, but as explained in the next section, those efforts have resulted in specific tools that only can be applied to specific WSNs, while cooperation between heterogeneous WSNs is a key issue in IoT applications. The use of WSN-MP may help in all the states of the life-cycle of a WSN. WSN researchers may use a WSN-MP to perform comparative analysis on new proposals. Designers may select the most suitable techniques for the requirements of any application. When deploying a WSN, the enhanced debugging capabilities added by the WSN-MP are unbeatable. The deployment is much easier when the correct functioning of the motes can be verified in-situ. During operation, malfunctions may be diagnosed without stopping the system, and the redesign of the system can use more detailed information about current functioning. In addition, these tools can become fundamental in the standardization and certification of applications based on the WSN. With these goals in mind, WSN-MPs are an increasingly important research line, a fact corroborated by the publication of a large number of papers on this area in the scientific literature. The study of these proposals has shown the great disparity of different WSN-MPs and the lack of methodology for their analysis and design, which leads to the fact that each proposal uses different ad-hoc solutions. Additionally, we conclude that there is a set of different issues that every WSN-MP must solve to be functional, and the different solutions of these problems could be combined in order to obtain the appropriate characteristics for the desired Monitoring Platform.