Abstract: A method and device for dynamically changing transmission parameters of broadcast messages transmitted and received by a mobile unit. The method and device include monitoring transmission channel characteristics; dynamically adjusting the transmission parameters of a message based on the monitored transmission channel characteristics; and broadcasting the message using the adjusted transmission parameters. The transmission parameters may include one or more of transmission power, error code rate, and modulation rate. The transmission channel characteristics include one or more of the group consisting of received message density, channel congestion, detected number of message collisions, and signal to interference ratio.

Abstract: A system for electronic toll collection from a vehicle including an electronic tag for capturing information including a number of passengers in the vehicle and an electronic tag identification, a wireless transmitter for transmitting the captured information; and a wireless receiver for receiving the captured information. The system further includes a toll computer for determining a toll fee for the vehicle based on the received number of passengers and a time of day. The wireless transmitter may be an IR or RF transmitter. The toll computer determines the toll fee for the vehicle based on the received number of passengers, and one or more of the time of day, the day and the traffic information.