Sung-Hwa Hong

A multi-hop reservation method for end-to-end latency performance improvement in asynchronous MAC-based wireless sensor networks

Duty cycling is a common mechanism for achieving energy efficiency in WSNs. Over the past several years a number of researchers have proposed low-power duty-cycle MAC protocols, but the tradeoff between energy efficiency and latency has been remained a challenging issue. We propose the Express-MAC protocol (EX-MAC) which can guarantee the requirement of the end-to-end transmission latency while conserving energy in a wireless sensor network using asynchronous duty cycling. To achieve low latency operation, EX-MAC employs a wakeup time reservation that utilizes a short preamble scheme to reduce end-to-end latency and to minimize energy consumption. Also, EX-MAC supports multi-hop applications through a cross-layering API, and it provides convergecast packets with unidirectional interfaces to optimize performance and to support reconfiguration routing. In this paper, we first introduce WSNs and the problems in existing MAC protocols. Then we propose the EXMAC protocol for low end-to-end latency and power efficiency in WSNs. From simulation results, it is proven that EX-MAC is able to adjust its wakeup time reservation for convergecast traffic and to guarantee the requirement of endto- end latency.

An efficient data gathering routing protocol in sensor networks using the integrated gateway node

In the future ubiquitous home network, sensors will collect various home environment data in the home. Since the sensor nodes are equipped with small, often irreplaceable, batteries with limited power capacity, it is essential that the network be energy-efficient in order to maximize its lifetime. Our study, described in this paper, was divided into two classes: the primary class was to set a gateway-selection level and the secondary class was to propose an offer of a home automation using a routing technique centered on a sensor network to set a flooding level. The proposed scheme is to increase the life time of the sensor network with the integrated gateway node. The IGN increases the life time of the network to integrate the multiple gateway nodes.