1. A method for decompressing a packet header, the method comprising: determining if decompression of a current packet header failed; determining a difference between a link layer sequence number (LL SN) of a previous correctly decompressed packet and a link layer sequence number (LL SN) of the current packet to provide repair information used for header decompression, if header decompression failed; and decompressing the header of the current packet using the repair information.