A communication system which has a plurality of mobile terminals and a base station, each of the mobile terminals and/or base station comprising a medium access control sub-layer, upper layers of the medium access control sub-layer, and a lower layer of the medium access control sub-layer, wherein the medium access control sub-layer is configured to perform self-basic functions in response to basic function execution requests or functions associated with the upper layers or lower layer in response to requests therefrom. According to the present invention, the communication system can provide a compatible multimedia communication service even if an originating terminal and a terminating terminal employ different communication manners, they are available from different manufacturers or they are operated by different communication service operators.