Compression method, transmitter and receiver for radio data communication

An SIP/SDP compression method, transmitter ( 510 ) and receiver ( 550 ) for communicating a message from the transmitter to the receiver by, at the transmitter, removing from the message element (s) thereof and inserting into the message an indication ( 200 ) of absence of the removed element (s); and, at the receiver, inserting into a message received from the transmitter element (s) pre-cached at the receiver in replacement for the element (s) whose absence is indicated. This provides a lightweight SIP/SPD compression scheme (LSSCS) that (i) removes the information redundancy generated at the application layer, and (ii) can achieve 100% compression efficiency for the redundant SIP and SDP URL fields.