A Study on Implementations of IoT System Frameworks

Abstract

본 논문은 다양한 응용의 IoT (Internet of Things) 시스템 구현에 요구되는 프레임 개발에 대한 연구를 다룬다. 먼저 홈 IoT 시스템 프레임워크 구축을 위해 Android 모바일 어플리케이션을 구현한 후 요구하는 서비스에 대한 요청을 처리하기 위해 백-엔드 애플리케이션도 개발한다. 그리고 홈에서 사용되는 정보가전기기들을 임베디드 시스템에 여러 종류의 센서 및 인터페이스로 연결하고 효율적인 통신 프로토콜을 적용하여 통신을 한다. 또한 웹 서비스의 경우 HTTP (Hypertext Transfer Protocol) 프로토콜을 사용하는 대신 CoAP (Constrained Application Protocol) 프로토콜을 사용한다. CoAP 메시지의 정보 필드는 각각의 정보가전기기의 특성에 따라 분류하여 독창적인 메시지포맷을 정의 및 구현한다. 그리고 CoAP 메시지의 전송과정에서 LEA (Lightweight Encryption Algorithm) 알고리즘을 응용하여 빠르고 간단한 보안메커니즘을 개발 및 적용한다 또한 Firebase Cloud Firestore 데이터베이스를 활용하여 해당 홈 IoT 시스템 사용자들에게 각종 사용정보를 축적하여 활용하도록 구성한다. 연구의 두 번째 부분은, 다른 유형의 IoT 시스템 프레임워크 구축으로 도로 위에서 달리는 차량이 자동적으로 해당지역 기반 제한속도 지켜 과속으로 인한 사고를 줄이는데 기여한다. 즉 셀룰러 네트워크 기술을 활용해 통신회사가 운영하는 셀 정보를 사용하여 각 차량은 해당지역의 제한속도를 파악해 이것을 자동적으로 지키는 IoT 제어 시스템이다. 먼저 GPS (Global Positioning System) 및 셀룰러 위치기반기술을 사용하여 각 차량의 위치를 파악 후 특정 셀 내의 해당영역에서 제한속도를 파악하고 차량속도를 제어하기 위한 ECU (Electronic Control Unit)를 구현한다. 그리고 차량의 기어박스에 연결된 속도센서가 차량속도 값을 전달 후 해당지역의 제한속도에 맞게 제어하는 시스템을 구현한다. 마지막으로, 제안된 두 IoT 시스템들이 모두 실제 상황에서 동작될 수 있도록 프로토타입 구현하여 성능을 확인한다.

This research can be divided into two main parts. The purpose of the first part of this research is to build a complete and easy-to-use framework for setting up controllable Internet of Things (IoT) Systems such as Home IoT Systems and Smart Farm Systems. We created a dynamic Android mobile application adaptable to the user’s preferences and to various systems of appliances-managing computers/microcontrollers, which we will refer generally as controllers. In addition, we developed a controller side application for handling requests sent from the mobile application as well as for making requests in certain circumstances. We used multiple sensors and devices to represent real-life appliances. It is aimed that nonprofessional users, with some references, can easily set up their own IoT system using this framework. In terms of application layer protocols, instead of using the traditional HTTP as Internet application protocol, we used the Constrained Application Protocol (CoAP), which is a web transfer protocol especially designed for lossy networks and for memory-limited and low power devices. Based on the structure of the controllers, we built our own message formats for better parsing of the requested services. On the top of that, we append security tags to all messages transmitted between the user and the system using the (Lightweight Encryption Algorithm) LEA security mechanism. Finally, we made use of the Firebase’s Cloud Firestore database to update certain information to all users in an IoT system. The second part of the research has the aim of using the technologies proposed previously such as Cloud, Android mobile application, CoAP, to another type of system that we structured. The system imposes an area-based threshold speed to vehicles, to mitigate accidents due to excessive or unsuitable speed. Although traffic lights, road signs, police and other security measures in place play different roles to ensure that each vehicle is running at the appropriate speed, the driver is free to speed up as much as he wants and, he might, in result, cause a great damage or a loss of humane life. This project provides a practical solution to this issue by limiting the driver’s freedom. On the one hand, the vehicle keeps its potentiality of running at high speed. On the other hand, it follows automatically the area’s rules and regulations. As cellular networks are almost omnipresent in inhabited places and where Global Positioning System (GPS) is seldom used, we primarily use this technology by setting in each cell a general threshold speed, and even within the cell, various speed limit values might be set. Each base station communicates with the vehicles within its cell and issues to each the appropriate speed. To specify a speed limit in a particular area within a particular cell, the GPS data of the vehicle might be optionally utilized. For controlling the vehicle’s speed based on an input value, an Electronic Control Unit (ECU) is used. To know the current speed of the vehicle for the ECU to take action, speed sensor connected to the vehicle’s gearbox is used. To ensure that the sensor is not sensing incorrectly, we use the positions of the vehicle and a timer to check the speed. Finally, we implemented a prototype to illustrate how the system might work in real-life.