公开(公告)号：DE2645778A1

公开(公告)日：1977-06-30

申请号：DE2645778

申请日：1976-10-09

Applicant: IBM

Inventor： BOUDREAU PAUL EMILE ,  MOORE BRIAN BARRY

IPC: H04L1/22 ,  G06F13/00 ,  H04L5/22 ,  H04L12/437 ,  H05K10/00 ,  H04L11/16 ,  H04L25/02

公开(公告)号：DE2447255A1

公开(公告)日：1975-06-12

申请号：DE2447255

申请日：1974-10-03

Applicant: IBM

Inventor： BOUDREAU PAUL EMILE ,  BRODD WYNENE DONALD ,  DONNAN ROBERT ANDERSON

IPC: H03M13/00 ,  G06F11/10 ,  H03M7/40 ,  H03M13/03 ,  H04L1/00 ,  H04L1/10

Abstract: In the transmission of variable length frames of digital information separated by one or more flag sequences, a block check is generated and appended to the information bits at the transmitter. The block check is generated by Exclusive OR'ing a predetermined non-zero number to the high order information bits and generating (n-k) check digits according to a cyclic error detecting code. The (n-k) check digits are Exclusive OR'd with an (n-k) bit non-zero number to produce the block check. At the receiver, the first mentioned non-zero number is added to the high order information bits and an (n-k) digit number is generated according to the same cyclic error detecting code used at the transmitter. This number is checked to see if it conforms to a predetermined number indicating error-free transmission. Utilizing the above approach, transmission errors in or near the flag sequence are detected, as well as those which may occur in the information field.

公开(公告)号：DE2320422A1

公开(公告)日：1973-11-29

申请号：DE2320422

申请日：1973-04-21

Applicant: IBM

Inventor： BOUDREAU PAUL EMILE ,  CHIEN ROBERT TIENWEN ,  PECK CHARLES CLYDE

IPC: H03M13/00 ,  H03M13/09 ,  H03M13/17 ,  H03K13/32

Abstract: If digital data sequences of length n bits are successively encoded for protection against error by appending to each block of n bits in a sequence of r check bits, the r check bits being calculated from the n bits of the block by iteratively dividing the data stream, by a generator polynomial g(x) prior to each transmission and then by iteratively dividing the data sequence and remainder by a scrambler polynomial S(x), then the apparent error E(x) at the receiver due to channel error e(x), after descrambling (multiplying) by polynomial S(x), is represented by the relation E(x) = S(x) e(x). When scrambling polynomial S(x) is of the form S(x) = 1 + x, then each channel error is replaced by two adjacent errors, hence E(x) = (1 = x) e(x). All single and odd errors are nevertheless detectable in such circumstances by modifying g(x) such that g(x) = (1 + x)m 1 t(x). Furthermore, burst type channel error of length >/= b is detectable, in addition to all single and odd errors, if the scrambler polynomial S(x) assumes the form S(x) = (1 + x)m f(x) and the generator polynomial is modified so that g(x) = (1 + x)m 1 t(x) where f(x) and t(x) are polynomials having an odd number of terms and relatively prime and t(x) is of degree >/= b.