Block transmit-receiving device and block transmission method

SN examination section examination portion (101) in a packet in units of transmission data SN monitor, SN packet before SN packet comparing transmission target, and as a transmission target, and outputs the comparison result and transmits the data to CID selection section (102 ). CID selection section (102) is selected according to the comparison result output from SN examination section (101) CID, added to the transmission data, and outputs the header compression unit (104). CRC bit calculation unit (103) calculates CRC bits according to the header information. Header compression section (104) based on the packet information comparison result and the transmission packet storage unit (105) stored in the determined header compressed form of header contains SN and CRC bits is compressed, is output together with the transmission data to the transmission unit (106). Transmission packet storage unit (105) transmits a packet through the memory.