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The assignment of 10 MHz in the UHF band (715 to 725 MHz) for ITS inter-vehicle communication systems was decided in the Japan Telecommunications Council report on June 27, 2007. The purpose of this bandwidth assignment is to avoid head-on collisions in intersections and other areas with reduced visibility by allowing vehicles to inform each other of their locations through 720MHz radio wave transmissions. The bandwidth assignment will take effect on July 25, 2012. CSMA is the dominant protocol in inter-vehicle communication systems, but serious degradation in performance caused by the hidden node problem is a concern. This study proposes and evaluates a new media access protocol designed for dealing with this problem. The study computes the range of occurrence of hidden nodes in a head-on collision scenario. The study indicates the amount of influence that those nodes have while evaluating the simulated packet arrival rates of both the proposed protocol and the conventional protocol. The study concludes that the proposed protocol is superior.

Shigeyuki Asami
Kunimitsu Arai