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.