###### Abstract  
The Internet of Things (IoT) paradigm is growing, affecting human life and aiming to solve problems in the real world, i.e., in education, healthcare, smart homes, intelligent transportation, and other areas. However, it is a fact that the development of IoT systems is complicated compared to that of traditional software systems, especially in relation to requirements engineering (RE). The RE of IoT systems is not implemented frequently due to their broad aspects, such as the variety of user needs, making these systems difficult to construct. In this sense, the use of IoT-based systems has not been well explored by the research community in order to provide well-planned proposals to improve the quality of their performance. In this work, we present a comprehensive and inclusive review of the RE of IoT-based systems. To accomplish this, a systematic mapping study (SMS) is presented to evaluate the use of parameters based on the existing literature. SMS is a methodology used for research in the medical field and has recently been implemented in software engineering (SE) to sort and organize research publications to gain knowledge on progress and identify research gaps. In this article, we aim to classify the existing research publications in the current scientific literature regarding RE proposals for IoT software systems and review their implications for future research. This will make it possible to establish lines of research in order to improve the quality of the development of future IoT systems. systematic mapping study; requirements engineering; Internet of Things; IoT software systems development +
Footnote †: journal: Medical Engineering  
1 Facultad de Informatica Mazatlan, Universidad Autonoma de Sinaloa, Mazatlan 82140, Mexico;  
[EMAIL_ADDRESS] (C.T.-B.) [EMAIL_ADDRESS] (A.Z.-C.)  
2 Escuela de Ingenieria Mazatlan, Universidad Autonoma de Sinaloa, Mazatlan 82140, Mexico;
(RE) phase, considering functional (FR) and non-functional requirements (NFRs). RE is a sub-discipline of software engineering (SE) and is concerned with establishing the goals, functionality, and constraints of hardware and software systems [13]. According to [14], RE is the part of SE that is applied to identify stakeholders' needs; they have documented an exhaustive set of phases such as analysis, specification, and validation in a requirements document. For RE, it is necessary to have synergy with customers to understand their specific needs. This activity helps the software development team collect sufficient information about the problem domain to define models for the solution domain. However, poor implementation of RE means that the final product will not satisfy the customer's expectations or, instead, it will not be used. Now, more than ever, there is an opportunity to implement well-planned and efficient IoT systems, not only on the shop floor, but with user goals and satisfaction in mind, since there is more access to IoT systems available now than ever. Nevertheless, there are great challenges involved in implementing RE. There is an absence of systematic methodological approaches to building IoT applications, especially for IoT-based RE. Despite the required complexity of such implementations in the real world, there is no reference guide in the context of RE to assist in implementing these systems. Consequently, it is essential to establish a baseline that can serve as a starting point when developing IoT systems, in order to develop reliable proposals that can be applied to the real world. Furthermore, this will satisfy user expectations since requirements and system elements are highly interconnected [15].