An information frame comprised of a plurality of consecutive multiplex frames each having a given length, each multiplex frame comprised of a header and a succeeding radio link protocol (RLP) frame, said RLP frame including a transmission data, wherein at least one of the multiplex frames is comprised of a plurality of sub-multiplex frames, and each sub-multiplex frame is comprised of a header including a RLP service identifier and a length indication field for indicating a length of the transmission data, and a data block associated with the succeeding RLP frame.