Sensor Networks

Protocols for Ubiquitous Computing

"Ubiquitous Computing" was first articulated by Mark Weiser in 1988, then it has been spreading in many research areas, especially sensor network and human interface. Advances in small-sized wireless devices, embedded microprocessor designs, and limited-power smart sensors present research challenge in several aspects including network protocols (MAC layer, network layer, and transport layer), energy efficiency, distributed databases and security. However, no any work gives good enough solution for all of these issues. Our laboratory is working on developing new protocol including security for ubiquitous computing.

Security for Ubiquitous Computing

While recent research in ubiquitous computing has focused on network protocols, energy efficiency, and distributed databases, there is much less attention given to security. However, in many applications the security aspects are as important as performance and low energy consumption.Security in sensor network (confidentiality, authentication and integrity) is a challenging problem because asymmetric key cryptosystems are unsuitable for resource constrained sensor nodes. Therefore, our research is not only network protocol for ubiquitous computing, but also security issue.

Home-area Networks

We are working on developing communication software for home network based on power-line networking, wireless networking and phone-line networking.

Network Measurement

Because the amount of traffic often changes in best-effort network, available bandwidth and delay also vary widely. This affects end-to-end performance so much. We use one-way delay together with loss to analyze and measure the end-to-end performance of the network. Such measurement is useful for routing and rate control in overlay network. One of our previous work is to detecting congestion from the variation of ROTT (Relative One-way Trip Time). ROTT is relative value, therefore, we can avoid the effect of skew between the clocks at the sender and the receiver.

Reference: Y. Tobe, Y. Tamura, A. Molano, S. Ghosh, and H. Tokuda, " Achieving Moderate Fairness for UDP Flows by Path-Status Classification," IEEE Annual Conf. on Local Computer Networks (LCN 2000), Nov. 2000.

Currently, we cooperate with RIPE and perform one-way delay (absolute value) measurement between many hosts in Europe. We are working on using these measurements to analyze Internet characteristics such as bandwidti