Tone detection for signals sent through a vocoder
First Claim
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1. A method for detecting a tone in a signal received from a vocoder, comprising carrying out the following steps using a processor-based tone detector:
- performing a spectral energy analysis on the signal;
determining a center frequency for the signal; and
determining that tone is present if a result of the spectral energy analysis meets at least one selected criterion and if the center frequency is within a selected range of frequencies that includes a primary frequency of the tone.
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Abstract
A tone detector and associated method for use with EVRC-B and GSM vocoders to enable reliable detection of system connect tones over a wireless communication system. The tone detection method examines a number of sequential data frames of the signal received from the vocoder and determines that the tone is present if the spectral energy at frequencies around the tone is much higher than that at neighboring frequencies and if the calculated center frequency of the data frames is at or near the frequency of the tone.
14 Citations
20 Claims
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1. A method for detecting a tone in a signal received from a vocoder, comprising carrying out the following steps using a processor-based tone detector:
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performing a spectral energy analysis on the signal; determining a center frequency for the signal; and determining that tone is present if a result of the spectral energy analysis meets at least one selected criterion and if the center frequency is within a selected range of frequencies that includes a primary frequency of the tone.
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2. A method for detecting a tone in a signal received from a vocoder, comprising carrying out the following steps using a processor-based tone detector:
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(a) carrying out the following steps (a1) through (a3) for each of plurality of different portions of the signal; (a1) determining an energy characteristic of a portion of the signal at each of a first plurality of selected frequencies that together comprise a first group of frequencies; (a2) determining an energy characteristic of the portion of the signal at each of a second plurality of selected frequencies that together comprise a second group of frequencies; (a3) determining a relationship between a combination of the energy characteristics for the first group of frequencies and a combination of the energy characteristics for the second group of frequencies; and (b) determining a center frequency for the first group of frequencies; and (c) determining that the tone is present in the signal if the relationship meets at least one selected criterion and if the center frequency is within a selected range of frequencies that includes a primary frequency of the tone. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for detecting a tone in a signal received from an Enhanced Variable Rate Codec-B (EVRC-B) or Global System for Mobile Communications (GSM) vocoder, comprising carrying out the following steps using a processor-based tone detector:
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(a) providing a first frequency set containing a plurality of discrete frequencies located near the tone; (b) providing a second frequency set containing a plurality of discrete frequencies, some of which are located below all the frequencies in the first frequency set and others of which are located above all the frequencies in the first frequency set; (c) carrying out the following steps (c1) through (c3) for each of plurality of sequential data frames of the signal; (c1) determining an energy value for the first frequency set; (c2) determining an energy value for the second frequency set; (c3) determining an energy ratio using the energy values for the first and second frequency sets; (d) determining a center frequency for the sequential data frames; and (e) determining that the tone is present in the signal if the energy ratio meets at least one selected criterion and if the center frequency is within a selected range of frequencies that includes a primary frequency of the tone. - View Dependent Claims (19, 20)
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Specification