Distributed SCH selection for concurrent transmissions in IEEE 1609.4 multi-channel VANETs

The IEEE 1609.4 standard allows a single radio device to utilize multiple channels by alternating control channel (CCH) and service channel (SCH). During the SCH interval, the RTS/CTS/data/ACK handshake can be triggered to transmit large size of data without the hidden node problem. However, it can cause the exposed node problem that hinders concurrent transmissions, which is fatal in highly dynamic VANETs. Even though judicious SCH selection in a multi-channel environment can mitigate the exposed node problem, IEEE 1609.4 does not specify how to select a SCH, which can cause the randomly selected SCHs to be biased. Conforming to the current standards, we therefore propose a novel scheme that enables the exposed vehicles to avoid selecting the same SCH by piggybacking a candidate SCH selection within the optional field of the basic safety message. Through extensive simulations, it is verified that the average throughput can be improved by up to 26%.