Improved error recovery in an X.25 packet receiver

Conventional X.25 packet protocols demand 100% reception of incoming bits, based on a CRC checksum transmitted with each packet. On the other hand, in a point-to-point radio link, ASCII text messages may still be readable, despite occasional bit errors. An alternative repeat-request protocol is suggested, based on "less than 100%" reception. In such cases, while the totally error-free nature of packet radio is compromised, the channel throughput will improve, as fewer retransmissions will be required. A repeat request will be issued only if received packets fail a number of consistency checks, independently of the transmitted CRC (cyclic redundancy check) byte. An enhanced packet error recovery scheme is also suggested, based on a back-to-front analysis of the received bits, as a means of recovering from bit slips caused by faulty bit synchronization or erroneous bit de-stuffing during decoding