Voice band data rate detector

• US 4,912,765 A
• Filed: 09/28/1988
• Issued: 03/27/1990
• Est. Priority Date: 09/28/1988
• Status: Expired due to Fees

• Current Assignee: COMSAT Corporation (Reorganized ISA SA)
• Original Assignee: Communications Satellite Corporation (Reorganized ISA SA)
• Inventors: Virupaksha, Krishnamoorthy
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Merecki, John A.
• Application Number:
  US07/250,188
• Time in Patent Office: 545 Days
• Field of Search: 370/84, 375/122, 375/25-34, 381/29-40
• US Class Current: 704/229
• CPC Class Codes: H04B 14/068 with adaptive feedback

Abstract

An apparatus for detecting the modulation rate of voice-band data signals. The detector determines the level occupancy L_p, the partial entropy E_p, and the zero-crossing count N_zc for the input signal and compares these values with threshold values to determine the data rate.

Claims

1. An apparatus for detecting the data rate of input data signals, comprising:

means for normalizing said input data signals;

means for calculating the zero-crossing count N_zc of said input data signals;

means for Adaptive Differential Pulse Code Modulation (ADPCM) conversion of the output of said normalizing means to produce an ADPCM output having plural quantization levels;

a plurality of counting means for counting the number of times each of said quantization levels is used in said ADPCM output;

means for determining a partial level count L_p of the ADPCM output based on the outputs of fewer than all of said plurality of counting means;

means receiving at least some of the outputs of said plurality of counting means for determining the partial entropy E_p for said input data signals;

first means for comparing said partial level count L_p to a threshold level count and providing a first comparison output;

second means for comparing said partial entropy value E_p to a threshold entropy value and providing a second comparison output; and

third means for comparing said zero-crossing count N_zc to a zero-crossing threshold and providing a third comparison output;

means for determining said data rate in accordance with said first, second and third outputs.

2. An apparatus as claimed in claim 1, wherein if said partial level count L_p is greater than said threshold level count then an output signal indicating said data rate of said input data signals is greater than a predetermined data rate is generated.

3. An apparatus as claimed in claim 2, wherein if said partial level count L_p is not greater than said threshold level count then said partial entropy value E_p is compared to said threshold entropy value, and if said partial entropy value E_p is not greater than said threshold entropy value, an output signal indicating said data rate of said input data signals is less than said predetermined data rate is generated.

4. An apparatus as claimed in claim 3, wherein if said partial entropy value E_p is greater than said threshold entropy value then said zero-crossing count N_zc is compared to a pair of threshold zero-crossings, and if said zero crossing count N_zc is greater than a first one of said pair of threshold zero-crossings and less than the other of said pair of threshold zero-crossings, then an output signal indicating said data rate of said input data signals is equal to said predetermined data rate is generated.

5. An apparatus as claimed in claim 4, wherein if said zero crossing count N_zc is either not greater than said first one of said pair of threshold zero-crossings or not less than said other of said pair of threshold zero-crossings, then an output signal indicating said data rate of said input data signals is less than said predetermined data rate is generated.

6. An apparatus as claimed in claim 5, wherein a channel encoder is selected based on said output signals.

7. An apparatus as claimed in claim 1, wherein said detecting apparatus is disposed on a plurality of digital signal processing chips.

8. An apparatus as claimed in claim 7, wherein said means for normalizing said input data signals and said means for calculating the zero-crossing count are disposed on a first one of said plurality of digital signal processing chips.

9. An apparatus as claimed in claim 8, wherein said means for ADPCM conversion is disposed on a second one of said plurality of digital signal processing chips.

10. An apparatus as claimed in claim 9, wherein said plurality of counting means, said means for determining a partial level count L_p, said means for determining the partial entropy E_p for said input data signals, said first means for comparing said partial level count L_p, said second means for comparing said partial entropy value E_p, and said third means for comparing said zero-crossing count N_zc are disposed on a third one of said plurality of digital signal processing chips.

11. An apparatus as claimed in claim 1, wherein said detecting apparatus is disposed on a single digital signal processing chip.

12. An apparatus as claimed in claim 1, wherein said output of said normalizing means is a 13-bit linear Pulse Code Modulation (PCM) signal.

13. An apparatus as claimed in claim 1, wherein said output of said ADPCM conversion means is a 4 bit/sample ADPCM signal.

14. An apparatus as claimed in claim 13, wherein said plurality of counting means equals four.

15. An apparatus as claimed in claim 14, wherein the outputs of only two of said plurality of counting means are used for determining said partial level count L_p.