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Methods and apparatus for detecting a cellular digital packet data (CDPD) carrier

  • US 5,574,750 A
  • Filed: 09/14/1993
  • Issued: 11/12/1996
  • Est. Priority Date: 09/14/1993
  • Status: Expired due to Term
First Claim
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1. A method for detecting an overlay signal in a channel of a primary system, wherein said overlay signal is associated with an overlay system that shares a frequency allocation with the primary system, wherein the primary system has a plurality of channels in which the overlay signal might be present at any given time, and wherein the overlay signal is characterized by a predetermined expected value, the method comprising the steps of:

  • (a) sampling a received signal in at least one channel to obtain a predetermined number of samples for said at least one channel;

    (b) computing an error value for each sample, said error value based on a difference, if any, between a sample value and said predetermined expected value;

    (c) determining a minimum error value;

    (d) determining a reference value;

    (e) determining a ratio of said minimum error value to said reference value; and

    (f) making a decision as to whether the received signal is an overlay signal on the basis of at least said ratio, wherein said decision is made by comparing said ratio to a threshold value.

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