A packet including data and a cyclic redundancy check code is encoded by using a selectable one of N scrambling codes (N>1). The encoded packet is transmitted and received, then decoded N times by using the N scrambling codes. The cyclic redundancy check code is used to decide which one of the N scrambling codes enabled the encoded packet to be decoded correctly, and the correctly decoded data are used. Packets with different formats, in particular with headers of different lengths, can be distinguished by the use of different scrambling codes, so that different formats can be employed without the need to transmit extra data to indicate which format has been used.