Yosuke Tamura

EFR: a retransmit scheme for TCP in wireless LANs

We propose a new, efficient fast retransmission (EFR) scheme for wireless LANs. Wireless LANs are becoming popular and providing an efficient protocol over a wireless link is important. In our experiments with the 2.4 GHz WaveLAN, the poor TCP performance observed was attributed to frequent expiration of the retransmission timer. To avoid unnecessary expiration of the retransmission timer, we propose a scheme in which fast retransmission is performed efficiently. The proposed modification only affects a TCP sender, and our version of TCP where the change is interoperable with existing TCP implementations. The change is especially effective in wireless LAN environments, where we have demonstrated significant improvements in throughput, 10-15%, via experiments.

Research into sensor networks and Web APIs - Urban navigation systems utilising sensor network data -

Sensor networks have recently been attracting the interest of both researchers and developers alike. Due to the advances in sensor and wireless device miniaturisation through MEMS technology, it is now possible to obtain environment information from difficult to reach places and expectations are high as to how this technology will be applied. When we considered sensor network applications, difficulties were forecast with respect to gathering the enourmous amounts of data from the monitored environment. However, we designed and developed a Web API for obtaining sensor data from sensor networks and, using a version of the Web API tailored for mobile phones, we developed a navigation system aimed at pedestrians. The system uses temperature sensor data to determine the most comfortable route for the user. All edges are weighted using the temperature sensor data and then an optimal route is computed using Dijkstrapsilas algorithm. In this paper we describe both the Web API and the navigation system.

NBQ: neighbor-state based queuing for adaptive bandwidth sharing

We propose the neighbor-state based queuing (NBQ) for improving the performance of flows sharing link bandwidth under various transfer protocols. Each router with NBQ informs the next upstream router of its link status. According to the received status, the NBQ dynamically sets the packet discard ratio of the non-adaptive flows. The NBQ reduces the wasted non-adaptive flows and provides available bandwidth for the adaptive flows. We have demonstrated dramatic improvements of the adaptive flows throughput using our scheme through simulations.