A congestion control method for a communication system supporting layered radio channel structure for communication between at least a first communication device and a second communication device that offers a first and second types of service with corresponding first and second priority orders. The messages between devices include a preamble and a payload with each message being separated by at least a minimum allowable period. The first communication device generates a physical layer message pertaining to the first type of service, senses the radio channel idle for at least a period corresponding to the minimum allowable period between two messages, and transmits the physical layer message including a preamble indicative of the type of service the message pertains. The content of the preamble is detected by the second communication device within a communication range irrespective of the decoding state of the payload of the transmitted message.