Event triggered change of access service class in a random access channel

For transmitting and receiving data communication device (1) and corresponding communication method and communication system. The can be in communication system for wireless or wired communication system, providing comprises multiple access resource random access channels. Is divided into at least two access resource groups the access resource, respectively corresponding to a corresponding to the access probability different access service. The communication device (1) comprises a selector (5), transmitting device (3) and detection device (6). The detection device (6) detects the open-close special event, wherein the communication device (1) for accessing business category conversion for the access service category.