No abstract

No abstract

No abstract

Nowadays “Internet of Things” or IoT becomes the most popular technology in the Internet system. Types of devices and sensors have been connected as a network of devices and sensors. While a wireless sensor network is a traditional network of sensors that can be considered as a beginning point of IoT systems. Currently, these sensor data are not only exchanged within a local network but also are delivered to other devices in the Internet. Consequently, well-known organizations such as IEEE, IETF, ITU-T and ISO/IET are trying to set standards for wireless sensor devices in IoT systems. The recommended standard utilizes many of internet stack standards such as CoAP, UDP and IP. However, the traditional design of WSNs is to avoid using internet protocol in the system to reduce transmission overhead and power consumption due to resource limitation. Fortunately, the current technology in both hardware and software allow the internet standard to sufficiently operate in a small sensor.  In this paper, we propose a MAC protocol named CU-MAC to efficiently support IoT standard that need request-respond communication or bi-direction communication. CU-MAC uses multi-channel communication to perform continuous and bi-directional data transfer at low duty-cycle. It also has a mechanism to overcome the hidden terminal problem. We evaluated the performance of CU-MAC on both simulation and real testbed based on Contiki OS. The result shows that CU-MAC outperforms other existing MAC protocols in term of packet delivery ratio at 98.7% and requires lower duty-cycle than others to operate in the high traffic environment.

Mobile phone is now becoming a necessary gadget in our daily life. Mobile applications have been proposed to advance the function of mobile phone. Location service application is a kind of mobile application that provides location information such as current location of the mobile phone. GPS is the popular technology for location service on mobile phone because many models of mobile phone are embedded with GPS sensor. Although GPS can provide high accuracy over outdoor scenario, GPS cannot provide good accuracy in indoor environment because the GPS signal from GPS satellites is blocked by the structure of building. The indoor localization systems have been proposed to address the above-mentioned problem. Many indoor localization systems require costly back-end server to process location. Moreover, the devices need to connect to the back-end servers to request the service. In this paper, we propose a serverless indoor localization system for mobile phone platform. The proposed system does not need any support from back-end server. The localization is processed on mobile phone. The system is developed as an Android application, utilizing Wi-Fi signal to determine the current location of mobile phone and uses mobile ad hoc network to disseminate the current location to other users in the system. The proposed system achieves accuracy up to 83.43% when the system is deployed in the twofloors building, which is the experimental site.