Abstract: An intermediate station produces, for an altered packet that includes multiple cells from a received packet and one or more altered cells that are substituted for the corresponding cells of the received packet, a .DELTA.-CRC remainder that is combined with the CRC remainder included in the received packet to produce a CRC remainder for the altered packet. The station first produces for each altered cell a bit pattern that has zeros in the bit positions in which the bits of the altered cell and the corresponding received cell match and ones in the bit position in which the two cells do not match. The station next encodes the bit patterns in accordance with the CRC code and produces corresponding .DELTA.-CRC values. It then manipulates the .DELTA.-CRC values to produce the .DELTA.-CRC remainder, and combines the .DELTA.-CRC remainder with the CRC remainder in the received packet. The result is the CRC remainder for the altered packet.

Abstract: A method of detecting errors and losses in transmitting digital information from a sending unit to a receiving unit, including the steps of: receiving header information indicating the transmission size from the sending unit at an early stage of the transmission process; counting the number of pieces of information transmitted while receiving the information; and comparing the result of the counting step with the size indicated in the header information. In one embodiment of the invention, the method is adapted for use with transmissions of information from an upper processor to a lower processor in a digital cellular system base station.