Method and apparatus to detect and recover a pseudo-random sequence

• US 4,827,514 A
• Filed: 03/03/1988
• Issued: 05/02/1989
• Est. Priority Date: 09/03/1986
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ziolko, Eric F., Hennen, Harry A.
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US07/163,684
• Time in Patent Office: 425 Days
• Field of Search: 375/112, 375/113, 375/114, 375/116, 375/1, 380/48, 380/46
• US Class Current: 380/268
• CPC Class Codes: H04L 9/0656 Pseudorandom key sequence combined element-for-element with data sequence, e.g. one-time-pad [OTP] or Vernam's cipher
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner

Abstract

A synchronization detector is disclosed wherein a portion of the received data stream is parallel loaded into a sequence generating means. The sequence generating means provides a local synchronization sequence that is compared to the transmitted synchronization signal, and an error count is tallied. If the number of errors occurring in a predetermined "window" is below a predetermined threshold, a synchronization detect signal is asserted. However, if the errors in a predetermined window exceed the threshold, the sequence generating means is reloaded with another portion of the received data stream and the process is repeated until the synchronization detect signal is asserted.

Claims

1. A method for detecting and recovering a psuedo-random synchronization sequence from a received data stream comprising at least a portion of said pseudo-random sequence and an information signal, said method comprising the steps of:

(a) loading, in parallel, at least a portion of the data stream into a pseudo-random sequence generating means;

(b) generating a pseudo-random sequence;

(c) comparing at least a portion of said pseudo-random sequence to at least a portion of the data stream to provide an error indication;

(d) providing a detection signal if said error indication is at least below a predetermined threshold.

2. The method of claim 1, which includes the step of:

(e) repeating steps (a) through (d) if said error indication is above said predetermined threshold.

3. The method of claim 1, wherein step (a) comprises the steps of:

(a1) loading, serially, at least a portion of the data signal into a storage means to provide a temporary signal;

(a2) transferring, in parallel, at least a portion of said temporary signal into said pseudo-random sequence generating means.

4. The method of claim 1, wherein said comparing step comprises the step of summing, modulo two, said at least a portion of the data stream and said at least a portion of said pseudo-random sequence.

5. A method for detecting and recovering a pseudo-random synchronization sequence from a received data stream comprising at least a portion of said pseudo-random sequence and an information signal, said method comprising the steps of:

(a) loading, serially, at least a portion of the data signal into a storage means to provide a temporary signal;

(b) transferring, in parallel, at least a portion of said temporary signal into a pseudo-random sequence generating means;

(c) generating a pseudo-random sequence;

(d) comparing, by modulo two addition, at least a portion of said pseudo-random sequence to at least a portion of the data stream to provide an error indication;

(e) providing a detection signal if said error indication is at least below a predetermined threshold.

6. In a synchronous communication system, which transmits a data signal comprising at least a portion of a pseudo-random synchronization sequence and an information signal, a method for detecting and receiving said pseudo-random synchronization sequence, comprising the steps of:

at the transmitter;

(a) generating a first pseudo-random synchronization sequence;

(b) transmitting the data signal comprising at least a portion of said first pseudo-random synchronization signal and an information signal;

at the receivers;

(a) receiving the transmitted data signal to provide a received signal;

(b) loading, in parallel, at least a portion of said received signal into a sequence generating means;

(c) generating a second pseudo-random synchronization sequence;

(d) comparing at least a portion of said second pseudo-random synchronization sequence to at least a portion of said received signal to provide an error indication;

(e) providing a synchronization detection signal if said error indication is at least below a predetermined threshold.

7. The method of claim 6, which includes the step of:

(f) repeating steps (a) through (e) if said error indication is above said predetermined threshold.

8. The method of claim 6, wherein receiver step (a) comprises the steps of:

(a1) loading, serially, at least a portion of said received signal into a storage means to provide a temporary signal;

(a2) transferring, in parallel, at least a portion of said temporary signal into said pseudo-random sequence generating means.

9. The method of claim 6, wherein transmitter step (a) comprises transmitting said at least a portion of said first pseudo-random synchronization sequence as a preamble to said data signal.

10. The method of claim 6, wherein transmitter step (a) comprises transmitting said at least a portion of said first pseudo-random synchronization sequence as a postamble to said data signal.

11. The method of claim 6, wherein transmitter step (a) comprises interleaving said at least a portion of said first pseudo-random synchronization sequence with said information signal.

12. The method of claim 6, wherein receiver step (d) comprises the step of summing, modulo two, said at least a portion of said received signal and said at least a portion of said second pseudo-random synchronization sequence.

13. An apparatus for detecting and recovering a pseudo-random synchronization sequence from a received data stream comprising at least a portion of said pseudo-random sequence and an information signal, said apparatus comprising:

(a) loading means for loading, in parallel, at least a portion of the data stream into a pseudo-random sequence generating means;

(b) said pseudo-random sequence generating means for generating a pseudo-random sequence;

(c) means for comparing at least a portion of said pseudo-random sequence to at least a portion of the data stream to provide an error indication;

(d) means for providing a detection signal if said error indication is at least below a predetermined threshold.

14. The apparatus of claim 13, wherein said loading means comprises:

(a1) means for loading, serially, at least a portion of the data signal into a storage means to provide a temporary signal;

(a2) means for transferring, in parallel, at least a portion of said temporary signal into said pseudo-random sequence generating means.

15. An apparatus for detecting and recovering a pseudo-random synchronization sequence from a received data stream comprising at least said pseudo-random sequence and an information signal, said apparatus comprising:

(a) means for loading, serially, at least a portion of the data signal into a storage means to provide a temporary signal;

(b) means for transferring, in parallel, at least a portion of said temporary signal into a pseudo-random sequence generating means;

(c) said pseudo-random generating means for generating a pseudo-random sequence;

(d) means for comparing, by modulo two addition, at least a portion of said pseudo-random sequence to at least a portion of the data stream to provide an error indication;

(e) means for providing a detection signal if said error indication is at least below a predetermined threshold.