Past Research
Recent technological advances have enabled distributed micro-sensing for large scale information gathering through a network of tiny, low power devices or nodes equipped with programmable computing, multiple sensing, and communication capabilities. Because of their ease of deployment, ad hoc connectivity, and cost-effectiveness, these networks of sensor nodes, known as wireless sensor networks (WSNs), have been widely studied and usefully employed in many applications, such as environmental monitoring, embedded systems, and so on. The constraints of sensor nodes in terms of energy requirements, computing, and communication capabilities pose many challenges in the design and management of WSNs. These challenges necessitate energy-awareness at all layers of networking protocol stack.
My past research intention is to develop novel routing protocols to overcome these challenges. The overall objective is to maximize the functional lifetime of the network through the design of distributed and scalable algorithms. As data transmission and reception is the dominant factor determining energy consumption in a sensor network, the design of energy-aware routing protocols can lead to significant power conservation and hence improve the lifetime of an energy-stringent network such as a sensor network.
Adaptive Transmission Range Assignment Algorithm for In-routing Image Compression on WSNs
This work proposes an adaptive transmission range assignment algorithm for in-routing image compression over wireless sensor networks, called ARIC. I apply the concept of collaborative image compression to distribute the computational cost among the sensor nodes involved in a routing path between a source node and a base station. Then, I formulate the energy distribution as a mathematical optimization problem. I prove that the problem can be mapped to a 0-1 Multiple Choice Knapsack Problem (0-1 MCKP) and present a dynamic programming method to solve for the optimization solution. The proposed method allows the source sensor node to dynamically assign compression and communication tasks to appropriate sensor nodes according to their residual energy. Publication: SEATUC Symposium 2010, IEEE INDIN 2010, APSITT 2010.
A Transmission Range Adjustment to Avoid Energy Hole in Wireless Sensor Networks
In this work, the energy hole problem is modeled in wireless sensor networks, and a novel transmission range adjustment method is proposed to solve the problem. The goal of the work is to analyze the problem and to propose a dynamic algorithm that allows the transmission range of the sensor nodes to be varied as a function of their residual energy and distance to the base station, such that each individual node consumes its energy smoothly. This method contributes to the balancing of the energy consumption among sensor nodes, avoiding the energy holes problem and, thus, extending the network lifetime. Publication: ICCE 2010.
Multiple Targets Tracking in Wireless Sensor Networks
How to coordinate a randomly deployed WSN to efficiently track multiple targets in real time while conserving network resources and dealing with sensor nodes' constraints is a great challenge. The purpose of the research is to develop novel algorithms and implement a real experiment to track unknown multiple targets moving with varying speed. The objectives are to detect, identify (two crossing targets), and keep tracking of all targets, while reducing the tracking delay, increasing tracking accuracy, and extending the network lifetime. Publication: 2009 IEICE Society Communication Conference.
ARPEES Protocol
In the first research, I propose a novel adaptive routing protocol for WSNs, called ARPEES. The main aim is to find ways of energy efficient route setup and reliable relaying of data from the sensor nodes to the sink, so as to maximize the lifetime of the network. The main design features of the proposed protocol are energy efficiency, dynamic event clustering, and multi-hop relay, considering the trade-off relationship between the residual energy available of relay nodes and distance from the relay node to the base station. In this method, I consider energy and distance as the parameters in the proposed function to select relay nodes and finally select the optimal path among the cluster head, relay nodes, and the base station. The proposed protocol spreads the routing load between the source and destination nodes over a large number of sensor nodes in order to minimize disparity in the energy levels of the sensor nodes.
The main results of the research were published in IEICE Transactions on Communications (vol. E91-B, no. 9, pp. 2795-2805, September 2008), in the proceeding of 4th International Conference on Ubiquitous Robots and Ambient Intelligence (URAI 2007, Pohang, Korea, November 2007), 1st South East Asia Technical University Consortium (SEATUC) Symposium (Bangkok, Thailand , February 2007), IEICE Technical Report (vol.108, no.134, pp.83-88, July 2008), 2008 IEICE General Conference (BS-3-14, pp. S-36-S-37, March 2008), and 2007 Communications Society Conference of IEICE (BS-12-3, pp. S-154-S-155, September 2007).
MSCR Algorithm
In the second research, I define a maximum sensing coverage region problem (MSCR) and propose a completely localized and distributed algorithm to solve the problem, in which each sensor should decide, in a localized manner, to remain active or to enter sleep mode so that the maximum monitored area is fully covered by the minimum active sensors. In this method, sensor nodes are scheduled alternately between active and sleep modes while guaranteeing the k-coverage requirement over the whole working area, where k is a predetermined value that can be changed by users.
The main results of the work were published in Elsevier Computer Networks (Vol. 53, Issue 13, pp. 2275-2287, August 2009), in the proceeding of 2008 IEEE Sarnoff Symposium (New Jersey, USA, paper no. S3.5, April 2008) and 2009 IEICE General Conference (English Session, BS-4-32, pp. S-63-S-64, March 2009).
CoARPEES Protocol
In the third research, by integrating the MSCR algorithm and the ARPEES, I propose a new architecture of routing protocol considering the sensing coverage problem in high-density distributed WSNs. This realizes an efficient architecture that includes the eligibility of redundant sensor nodes, permits configurable QoS coverage parameters, and provides sufficient sensing coverage with balanced sensor energy and low communication overhead, each individually optimized to maximize the network lifetime. With the adaptive, distributed, and communication-efficient approach, we aim to spread out the energy consumption required for sensing data, forming clusters, selecting cluster heads, and relaying data to different sensor nodes, so as to achieve maximum sensing coverage with minimal energy consumption in the design and implementation of the routing protocols for WSNs.
The main results of this research were presented at the 2nd International Conference on Communications and Electronics (HUT-ICCE 2008, Hoi An, Vietnam, June 2008, IEEE Student Best Paper Award). Currently I am preparing to submit to another journal.
Optical burst switching for service differentiation in the next-generation optical internet
This research analyzed a critical issue involved in the optical burst switched networks,
namely contention resolution, and introduced a new approach called Burst Segmentation,
to reduce packet loss during contention resolution. The result is published at
