The Wireless Ad-Hoc Network for Shiojiri is an urban network being deployed with the objective to serve the community of Shiojiri city. In this work, we use data collected in test experiments on the actual field to find optimal topologies, minimizing the cost given by the number of required transponders for several possible threshold values of strength of the packets sent from the terminals. The results presented here provide valuable information about the reliability of the expected service, give alternatives to the decision maker, and help the designer to set up threshold parameters at the transponders.

An interframe coding system is described which is capable of transmitting a 4-MHz National Television System Commission (NTSC) color television signal. 6.3 Mbit/s transmission gives acceptable picture quality for video telephone or conference TV use. The NTSC color television signal is converted into a timedivision multiplex (TDM) signal which is composed of time-compressed chrominance and luminance signal in sequence. This signal is encoded using a frame-difference coder of the kind that has been used for black-and-white television signals. A field-repeating technique is introduced into the coder, to prevent a buffer memory from overflowing and to improve picture quality. Statistical investigations show that the presence of the timecompressed chrominance signal gives less than 10 percent increase in the amount of information generated by picture movements; this increase scarcely affects the picture quality.