Shozo Komaki

A hierarchical image transmission system for multimedia mobile communication

This paper proposes a new mobile image transmission system based on the hierarchical modulation scheme for achieving a high quality and high speed digital image transmission in a band-limited fading channel. The proposed system uses a hierarchical QAM (quadrature amplitude modulation) scheme to give unequal transmission reliability depending on the significance of DCT (discrete cosine transform) based compressed images. Computer simulation results show that the proposed system is an effective high-quality and high-speed image transmission technique in the band-limited fading channel.

Proposal of adaptive wireless cell configuration for RoF-DAS over WDM-PON system

Radio on fiber (RoF) - distributed antenna system (DAS) over wavelength division multiplexing - passive optical network (WDM-PON) with multiple - input multiple - output (MIMO) has been proposed as a next generation radio access network (RAN). This system employs optical time division multiplexing (OTDM) over one WDM channel to multiplex and transmit various types of wireless interfaces such as 3.9G, Wireless LAN and WiMAX. A combination of star and bus topologies has employed to cover a wider service area. The optical transmission loss is caused notably at remote base stations (RBSs) quipped on a WDM bus link. The loss is relatively small, but at the RBS far from the center station (CS), the RBS suffers the large accumulated loss, so the reduction of cell size provides the increasing of the number of RBSs, causes the degradation of the SNR of RoF link. This paper addresses this trade-off problem, and considers the application to the actual service area by the channel capacity investigation of RoF-DAS over WDM-PON with computer simulation. Then, this paper focuses on the flexibility of RoF-DAS over WDM-PON, considers the adaptive wireless cell configuration according to population fluctuations of day and night, or densely populated areas and sparsely populated areas, respectively.