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US3648237A
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Apparatus and method for obtaining synchronization of a maximum length pseudorandom sequence
Assignee: International Business Machines Corp
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Filing: 1969-02-28
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Granted: 1972-03-07
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Expires: 1989-02-28
Abstract
Abstract An apparatus and method for obtaining synchronization of a maximum length pseudorandom sequence included within input data. The apparatus comprises means for generating a predicted pseudorandom sequence, means for comparing the pseudorandom sequence with the input data and means for determining from said comparison whether said predicted pseudorandom sequence and said input data are the same. The method employed is a bit-by-bit comparison between the predicted values of a predicted pseudorandom sequence and the incoming values of the input data, synchronization is indicated when a predetermined number of successive comparisons are obtained, where said predetermined number of successive comparisons is less in number than the maximum length of the specified maximum length pseudorandom sequence.
Inventors
- 👤 Alexander H Frey Jr
- 👤 Burton E Schlosburg
- 👤 Ralph E Tygielski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 18:17
CPC Classifications
H; H04; H04L; H04L7/00; H04L7/04; H04L7/041; H04L7/043
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
363 words
An apparatus for obtaining synchronization from input data by identifying a specific maximum length pseudorandom sequence included within said input data, and by obtaining a point of referEnce within said specified maximum length pseudorandom sequence, said specific maximum length pseudorandom sequence having a length z where z 2n-1, n 0, 1, 2 . . . comprising: a prediction sequence generator for generating a predicted pseudorandom sequence as a function of said input data; a comparator for comparing said predicted pseudorandom sequence with said input data on a bit-by-bit serial basis, said comparator generating a compare output when the two bits being compared are the same and a no-compare output when the two bits being compared are not the same; a first control means for determining a SYNC/NO-SYNC condition; a first detecting means connected to said comparator for detecting the occurrence of y successive compare outputs from said comparator thereby signifying that the input data is the specific maximum length pseudorandom sequence, said first detecting means generating a sync output upon the occurrence of said y successive compare outputs from said comparator, said first control means generating a SYNC condition upon the occurrence of said sync output; a second detecting means connected to said prediction sequence generator for detecting a selected bit pattern in said prediction sequence generator after said first control means has generated said SYNC condition, said second detecting means generating a reference output which establishes the desired reference point for said specific maximum length pseudorandom sequence; a third detecting means connected to said comparator for detecting a loss of synchronization after said first control means has generated said SYNC condition, said third detecting means generating a no-sync output which indicates a loss of sync, said first control means generating a NO-SYNC condition upon the occurrence of said no-sync output; a second control means connected to said first control means for connecting said input data as the input to said prediction sequence generator under a NO-SYNC condition of said first control means, said second control means connecting the predicted sequence of said prediction sequence generator as an input from said prediction sequence generator under a SYNC condition of said first control means.
Claim 2
Independent Claim
363 words
An apparatus for obtaining synchronization from input data by identifying a specific maximum length pseudorandom sequence included within said input data, and by obtaining a point of referEnce within said specified maximum length pseudorandom sequence, said specific maximum length pseudorandom sequence having a length z where z 2n-1, n 0, 1, 2 . . . comprising: a prediction sequence generator for generating a predicted pseudorandom sequence as a function of said input data; a comparator for comparing said predicted pseudorandom sequence with said input data on a bit-by-bit serial basis, said comparator generating a compare output when the two bits being compared are the same and a no-compare output when the two bits being compared are not the same; a first control means for determining a SYNC/NO-SYNC condition; a first detecting means connected to said comparator for detecting the occurrence of y successive compare outputs from said comparator thereby signifying that the input data is the specific maximum length pseudorandom sequence, said first detecting means generating a sync output upon the occurrence of said y successive compare outputs from said comparator, said first control means generating a SYNC condition upon the occurrence of said sync output; a second detecting means connected to said prediction sequence generator for detecting a selected bit pattern in said prediction sequence generator after said first control means has generated said SYNC condition, said second detecting means generating a reference output which establishes the desired reference point for said specific maximum length pseudorandom sequence; a third detecting means connected to said comparator for detecting a loss of synchronization after said first control means has generated said SYNC condition, said third detecting means generating a no-sync output which indicates a loss of sync, said first control means generating a NO-SYNC condition upon the occurrence of said no-sync output; a second control means connected to said first control means for connecting said input data as the input to said prediction sequence generator under a NO-SYNC condition of said first control means, said second control means connecting the predicted sequence of said prediction sequence generator as an input from said prediction sequence generator under a SYNC condition of said first control means.
Claim 3
Dependent Claim
108 words
An apparatus as set forth in claim 1 wherein said prediction sequence generator comprises: an n stage shift register, each of said n stages of said shift register having an output, the input to said shift register being the input of said prediction sequence generator; an exclusive OR circuit connected to selected stages of said shift register such that the output of said exclusive OR circuit will be the specific maximum length pseudorandom sequence to be identified when said specific maximum length pseudorandom sequence is inputted as input data to said shift register, the output of said exclusive OR circuit being the output of said prediction sequence generator.
Claim 4
Dependent Claim
37 words
An apparatus as set forth in claim 1 wherein said third detecting means further comprises a first means for conditioning said third detecting means to operate only after said second detecting means has generated said reference output.
Claim 5
Independent Claim
168 words
A method of obtaining synchronization from input data which includes a specific maximum length pseudorandom sequence, said specific maximum length sequence being y bits long where y 2n-1, comprising the steps of: identifying said specific maximum length sequence in said input data by; generating a prediction pseudorandom sequence from said input data; comparing said prediction pseudorandom sequence with said input data on a bit-by-bit serial basis, generating a compare or no-compare signal for each said comparison, detecting when x successive compare signals occur, when x is less than y, generating a sync signal when x successive compares have been detected which indicate that said specific maximum length pseudorandom sequence has been identified; establishing a point of reference in said specific maximum length pseudorandom sequence by: detecting in said prediction pseudorandom sequence a given bit pattern, generating a reference signal when said given bit pattern in said prediction pseudorandom sequence is detected which indicates that a point of reference in said specific maximum length pseudorandom sequence has been detected.
Claim 6
Independent Claim
168 words
A method of obtaining synchronization from input data which includes a specific maximum length pseudorandom sequence, said specific maximum length sequence being y bits long where y 2n-1, comprising the steps of: identifying said specific maximum length sequence in said input data by; generating a prediction pseudorandom sequence from said input data; comparing said prediction pseudorandom sequence with said input data on a bit-by-bit serial basis, generating a compare or no-compare signal for each said comparison, detecting when x successive compare signals occur, when x is less than y, generating a sync signal when x successive compares have been detected which indicate that said specific maximum length pseudorandom sequence has been identified; establishing a point of reference in said specific maximum length pseudorandom sequence by: detecting in said prediction pseudorandom sequence a given bit pattern, generating a reference signal when said given bit pattern in said prediction pseudorandom sequence is detected which indicates that a point of reference in said specific maximum length pseudorandom sequence has been detected.
Claim 7
Dependent Claim
73 words
A method as set forth in claim 4 wherein the step of generating a prediction pseudorandom sequence comprises the steps of: storing successive overlapping groups of n bits of said input data, generating a prediction bit for each said successive overlapping group of n bits in accordance with the same criterion that was used to generate said specific maximum length pseudorandom sequence, outputting successively said prediction bits to form said prediction pseudorandom sequence.
Claim 8
Dependent Claim
41 words
A method as set forth in claim 5 wherein the step of comparing comprises the step of: comparing the n+1 bit of said input data with the prediction bit that was generated from the preceding n bits of said input data.
Claim 9
Dependent Claim
66 words
A method of synchronization as set forth in claim 4 further comprising the step of: determining loss of synchronization by, comparing said prediction pseudorandom sequence with said input data on a bit-by-bit serial basis, generating a compare or no-compare signal for each comparison, comparing the relative occurrences of said compare and no compare signal with a predetermined value to obtain an indication of loss of synchronization.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-03-07 | 1975-09-06 | 1976-03-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-07 | 1979-09-06 | 1980-03-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-07 | 1983-09-06 | 1984-03-07 | $7700.00 | Window Closed / Lapsed |