Yasuhiko Inoue

A priority control method for wireless multi-hop access using IEEE 802.11 DCF mechanism

Multi-hop communication systems have been widely studied and many of them are based on the IEEE 802.11 WLAN system. The paper explains the problem of throughput degradation of a relay station when IEEE 802.11 DCF is adopted in multi-hop communications. The relay stations lose some of their capacity compared to stations that are not relaying the data of other stations. Because all stations, under the CSMA/CA protocol, have equal transmission opportunity, the relay stations have to send packets from other terminals. We propose an autonomous priority control method that changes the contention window size depending on the number of relay stations and the number of hops to ensure that relay stations are offered the same transmission capacity as regular stations in the service area. Then its performance is evaluated by computer simulations.

Development of traffic control mechanisms for IEEE 802.11 wireless LANs without QoS support functionality

This paper proposes a traffic control scheme to support real-time traffic over the IEEE 802.11 wireless LAN systems that do not have QoS support functionality. The main features of the proposed scheme are bandwidth control for each flow and load balancing between access points by using information of data link, network and transport layers. The proposed scheme was implemented on a Linux machine which is called traffic controller. The traffic controller connects a high capacity backbone network and an access network and the access points of wireless LAN are attached to the access network. We evaluated the performance of the proposed traffic controller and confirmed that the communication quality of real-time traffic would be greatly improved by using this technique.

Wireless download agent for high-capacity wireless LAN based ubiquitous services

We propose a wireless download agent which effectively controls the point at which a download starts for providing a comfortable mobile computing environment. A user can get the desired data with the wireless download agent while walking through a service area without stopping. We conducted simulations to evaluate its performance in terms of throughput, download period, and probability of successful download. Our results show that the proposed scheme very well suits the wireless download agent in high-speed wireless access systems with many users. Furthermore, we describe the use of the proposed scheme considering the randomness of the walking directions of users.