Takefumi Hiraguri

Study of Power Saving Scheme Suitable for Wireless LAN in Multimedia Communication

Wireless LAN access is now being offered by small personal terminals in addition to laptops. Since these terminals have very limited battery capacity, wireless LAN interfaces that offer some form of power saving are essential. IEEE802.11. specifies PSM (Power save management); it reduces power consumption by suspending some communications functions. However, since Multicasting and Broadcasting are invariably received by all terminals regardless of PSM, the terminals unnecessarily consume electric power even if the terminal is not engaged in multicasting. This paper clarifies this problem, and proposes a scheme for reducing power consumption and the results of an experiment confirm its excellent performance.

Novel Frame Structures to Improve System Capacity and Latency Performance of a Time-Division Duplex Multihop Relay Wireless Access System

The multihop relay wireless access system is expected to eliminate dead spots by expanding Line-Of-Sight situations and to extend coverage at low cost. However, time-division duplex relay schemes that apportion the fixed length frame resources between the access and relay zones like the IEEE802.16j relay scheme suffer the problems of degraded system capacity and poor latency performance. This paper solve these problems by introducing two novel frame structures: Mixed bidirectional frame and Offset frame. Numerical simulations confirm that both frame structures offer better performance than the IEEE802.16j frame structure, in terms of total throughput, throughput of the last hop SS, and latency performance. The offset frame improves the performance most significantly compared to the IEEE 802.16j frame structure; total throughput is increased by 85%, DL/UL throughput of the last hop SS by 88/120% and DL/UL latency is reduced by 73/33%.