Pulse or digital communications – Spread spectrum – Direct sequence
Patent
1986-11-28
1989-07-11
Buczinski, Stephen C.
Pulse or digital communications
Spread spectrum
Direct sequence
3401462, 375114, H04L 700, G05B 100
Patent
active
048478776
ABSTRACT:
The invention relates to a method and an apparatus for the fast detection of a predetermined pattern of n bits embedded in a serial bit stream. The n bits are adjacent or regularly distributed over the bit stream, and form a unique word which may in particular be used as a synchronization pattern, the detection of which allows to conclude that a synchronization status has been reached within the signal detected at a reception node. The method consists in detecting first a synchronization root, which is a subset of n' consecutive bits of the unique word. Then, succeeding potential bits of the unique word are detected from the serial bit stream, and each potential bit of the unique word is compared to the corresponding bit of the stored unique word. At each match, a counter is incremented, and when the count of the consecutive matches reaches a predetermined number, the unique word is said to be detected. However, if a mismatch occurs in a comparison step before the right count is reached, it is immediately derived that the unique word has not yet been detected, and the search process is reset. Thus, a non-detection of the unique word can be evidenced very early and accordingly, a substantial amount of time can be saved in the detection, since in the average, it is not necessary to go through n comparison steps to conclude a non-detection of the unique word. The method and apparatus according to the invention find an advantageous application in the detection of a synchronization pattern included in a Time Division Multiplexed signal, said pattern comprising n bits distributed over the TDM signal in a predetermined sequence.
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Buczinski Stephen C.
Hoel Johnh E.
International Business Machines - Corporation
Wallace Linda J.
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