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Sequence Number for Error Detection in a Fixed Format

IP.com Disclosure Number: IPCOM000076144D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 17K

Publishing Venue

IBM

Related People

Chien, RT: AUTHOR [+3]

Abstract

This is a method for minimizing the loss of synchronism in the digital data transmission of fixed format and fixed length messages, occasioned by the inadvertent gain or loss of bits. The method comprises the steps of: adding the message bit count M. to the sequence number N(i) of the ith message at the transmitter; and comparing at the receiver the modified sequence number M(i) + N(i) with the sum of the sequence number N(i-1) of the i/th/ -1 message and the bit count M'(i) made by the receiver. A mismatch between the two sums is indicative of error.

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Sequence Number for Error Detection in a Fixed Format

This is a method for minimizing the loss of synchronism in the digital data transmission of fixed format and fixed length messages, occasioned by the inadvertent gain or loss of bits. The method comprises the steps of: adding the message bit count M. to the sequence number N(i) of the ith message at the transmitter; and comparing at the receiver the modified sequence number M(i) + N(i) with the sum of the sequence number N(i-1) of the i/th/ -1 message and the bit count M'(i) made by the receiver. A mismatch between the two sums is indicative of error.

The shortening or lengthening of a message may arise as a function of automatically inserting or extracting a bit opposite to that of a predetermined number of consecutive matching bits. The performance of the method can be evaluated by the following argument.

Let P(i) be the probability that the data sequence changed its length by K bits and let P(2) be the probability that the modified sequence number changed by K as a result of the error. Then the probability of undetected error is

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