Apparatus method, and software modem for utilizing envelope delay distortion characteristics to determine a symbol rate and a carrier frequency for data transfer

• US 5,870,429 A
• Filed: 06/17/1996
• Issued: 02/09/1999
• Est. Priority Date: 06/17/1996
• Status: Expired due to Term

• Current Assignee: ARRIS Enterprises LLC (CommScope Holding Company, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Verma, Sanjeev, Moran, John L. III, Brown, William Leslie
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): DEPPE, BETSY LEE
• Application Number:
  US08/664,757
• Time in Patent Office: 967 Days
• Field of Search: 375/222, 375/219, 375/225, 375/227, 375/285, 375/377, 375/224, 370/252, 370/327.6, 455/67.3, 455/63, 455/73, 379/93.32, 379/93.33
• US Class Current: 375/222
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0019 in which mode-switching is based on a statistical approach

Abstract

An apparatus, software modem, and method for a data communications device, such as a modem (100, 101), to determine a symbol rate and carrier frequency, from a received probe signal, for optimizing a bit rate for data transmission and reception. The various embodiments utilizing a processor (108) or a digital signal processor (106) receive a probe signal, which also typically contains noise and other distortions, particularly envelope delay distortion. The various method and apparatus embodiments then determine a variance of the envelope delay distortion, either directly or indirectly as a correlate of attenuation distortion or as a correlate of a selected transmit pre-emphasis filter specified under the ITU V.34 protocol. The variance of the envelope delay distortion is then utilized to eliminate or disable certain symbol rates and corresponding carrier frequencies in the determination of an optimal symbol rate and carrier frequency for data transmission and reception.

Claims

1. A method of determining a symbol rate for data transmission and reception from a plurality of symbol rates to form a selected symbol rate, from a transmitted probe signal received via a channel, the transmitted probe signal having a sequence of a plurality of tones having predetermined frequency, amplitude and phase characteristics, the transmitted probe signal having a predetermined frequency spectrum, the transmitted probe signal received to form a received probe signal having a plurality of sets of received probe tones, each set of received probe tones having a plurality of probe tone frequencies, a proposed data rate selected from a plurality of data rates from the received probe signal, the method comprising:

(a) determining a variance of an envelope delay distortion parameter over the predetermined frequency spectrum from the received probe signal;

(b) when the proposed data rate is greater than a first predetermined data rate and when the variance of the envelope delay distortion parameter is greater than a first predetermined variance, disabling a first symbol rate from the plurality of symbol rates to form a plurality of remaining symbol rates; and

(c) determining the selected symbol rate for data transmission and reception from the plurality of remaining symbol rates.

2. The method of claim 1, further comprising:

(d1) determining a carrier frequency corresponding to the selected symbol rate to form a corresponding carrier frequency.

3. The method of claim 2 wherein the selected symbol rate and corresponding carrier frequency corresponds to an optimal data rate of the plurality of data rates.

4. The method of claim 1, further comprising:

(d2) repeating step (b) for additional symbol rates of the plurality of symbol rates prior to determining step (c).

5. The method of claim 1 wherein step (b) further comprises:

(b1) when the proposed data rate is greater than a second predetermined data rate and when the variance of the envelope delay distortion parameter is greater than a second predetermined variance, disabling a second symbol rate from the plurality of symbol rates to form the plurality of remaining symbol rates.

6. The method of claim 1 wherein the envelope delay distortion parameter is determined as a correlate of an attenuation distortion parameter.

7. The method of claim 1 wherein the envelope delay distortion parameter is determined as a correlate of a selected transmit pre-emphasis filter.

8. The method of claim 7 wherein the selected transmit pre-emphasis filter is determined as a function of a ratio of spectrum values.

9. The method of claim 1 wherein the variance of the envelope delay distortion parameter is determined for an upper 1000 Hz portion of the predetermined frequency spectrum.

10. The method of claim 1 wherein the determination of the variance of the envelope delay distortion parameter is a correlate of determining whether the channel is an ADPCM channel.

11. An apparatus for data transmission and reception, the apparatus having an initial training period for determining a symbol rate for data transmission and reception from a plurality of symbol rates to form a selected symbol rate, from a transmitted probe signal received via a channel, the transmitted probe signal having a sequence of a plurality of tones having predetermined frequency, amplitude and phase characteristics, the transmitted probe signal having a predetermined frequency spectrum, the transmitted probe signal received to form a received probe signal having a plurality of sets of received probe tones, each set of received probe tones having a plurality of probe tone frequencies, a proposed data rate selected from a plurality of data rates from the received probe signal, the apparatus comprising:

a data access arrangement coupleable to the channel to receive the transmitted probe signal, to form a received probe signal;

an analog-digital converter coupled to the data access arrangement to sample and convert the received probe signal to form a plurality of sets of received probe tones; and

a processor coupled to the analog-digital converter to receive the plurality of sets of received probe tones, the processor responsive through a set of program instructions to determine a variance of an envelope delay distortion parameter over the predetermined frequency spectrum from the received probe signal;

when the proposed data rate is greater than a first predetermined data rate and when the variance of the envelope delay distortion parameter is greater than a first predetermined variance, the processor further responsive to disable a first symbol rate from the plurality of symbol rates to form a plurality of remaining symbol rates and to determine the selected symbol rate for data transmission and reception from the plurality of remaining symbol rates.

12. The apparatus of claim 11, wherein the processor is further responsive to determine a carrier frequency corresponding to the selected symbol rate to form a corresponding carrier frequency.

13. The apparatus of claim 11, wherein the selected symbol rate and corresponding carrier frequency corresponds to an optimal data rate of the plurality of data rates.

14. The apparatus of claim 11, wherein the processor is further responsive, when the proposed data rate is greater than a second predetermined data rate and when the variance of the envelope delay distortion parameter is greater than a second predetermined variance, to disable a second symbol rate from the plurality of symbol rates to form the plurality of remaining symbol rates.

15. The apparatus of claim 11, wherein the processor is further responsive to determine the envelope delay distortion parameter as a correlate of an attenuation distortion parameter.

16. The apparatus of claim 11, wherein the processor is further responsive to determine the envelope delay distortion parameter as a correlate of a selected transmit pre-emphasis filter.

17. The apparatus of claim 16, wherein the processor is further responsive to determine the selected transmit pre-emphasis filter as a function of a ratio of spectrum values.

18. The apparatus of claim 11, wherein the processor is further responsive to determine the variance of the envelope delay distortion parameter for an upper 1000 Hz portion of the predetermined frequency spectrum.

19. An apparatus for data transmission and reception, the apparatus having an initial training period for determining a symbol rate for data transmission and reception from a plurality of symbol rates to form a selected symbol rate, from a transmitted probe signal received via a channel, the transmitted probe signal having a sequence of a plurality of tones having predetermined frequency, amplitude and phase characteristics, the transmitted probe signal having a predetermined frequency spectrum, the transmitted probe signal received to form a received probe signal having a plurality of sets of received probe tones, each set of received probe tones having a plurality of probe tone frequencies, the apparatus comprising:

a data access arrangement coupleable to the channel to receive the transmitted probe signal, to form a received probe signal;

an analog-digital converter coupled to the data access arrangement to sample and convert the received probe signal to form a plurality of sets of received probe tones; and

a processor coupled to the analog-digital converter to receive the plurality of sets of received probe tones, the processor responsive through a set of program instructions to determine a proposed data rate selected from a plurality of data rates from the received probe signal and to determine a selected transmit pre-emphasis filter from a plurality of transmit pre-emphasis filters from the received probe signal;

the processor further responsive, when the proposed data rate is greater than a first predetermined data rate and when the selected transmit pre-emphasis filter is greater than a first predetermined pre-emphasis level, to disable a first symbol rate from the plurality of symbol rates to form a plurality of remaining symbol rates and to determine the selected symbol rate for data transmission and reception from the plurality of remaining symbol rates.

20. The apparatus of claim 19, wherein the processor is further responsive to determine a carrier frequency corresponding to the selected symbol rate to form a corresponding carrier frequency.

21. The apparatus of claim 19, wherein the selected symbol rate and corresponding carrier frequency corresponds to an optimal data rate of the plurality of data rates.

22. The apparatus of claim 19, wherein the processor is further responsive, when the proposed data rate is greater than a second predetermined data rate and when the selected transmit pre-emphasis filter is greater than a second predetermined pre-emphasis level variance, to disable a second symbol rate from the plurality of symbol rates to form the plurality of remaining symbol rates.

23. The apparatus of claim 19, wherein the processor is further responsive to determine the selected transmit pre-emphasis filter as a correlate of the envelope delay distortion.

24. The apparatus of claim 23, wherein the processor is further responsive to determine the selected transmit pre-emphasis filter as a function of a ratio of spectrum values.

25. A software modem for data transmission and reception, the software modem stored as a set of program instructions on a computer readable medium, the software modem utilizable in conjunction with a computer having an initial training period for determining a symbol rate for data transmission and reception from a plurality of symbol rates to form a selected symbol rate, from a transmitted probe signal received via a channel, the transmitted probe signal having a sequence of a plurality of tones having predetermined frequency, amplitude and phase characteristics, the transmitted probe signal having a predetermined frequency spectrum, the transmitted probe signal received to form a received probe signal having a plurality of sets of received probe tones, each set of received probe tones having a plurality of probe tone frequencies, a proposed data rate selected from a plurality of data rates from the received probe signal, the software modem comprising:

means for determining a variance of an envelope delay distortion parameter over the predetermined frequency spectrum from the received probe signal;

when the proposed data rate is greater than a first predetermined data rate and when the variance of the envelope delay distortion parameter is greater than a first predetermined variance, means for disabling a first symbol rate from the plurality of symbol rates to form a plurality of remaining symbol rates; and

means for determining the selected symbol rate for data transmission and reception from the plurality of remaining symbol rates.

26. The software modem of claim 25, further comprising:

means for determining a carrier frequency corresponding to the selected symbol rate to form a corresponding carrier frequency.

27. The software modem of claim 25, further comprising:

when the proposed data rate is greater than a second predetermined data rate and when the variance of the envelope delay distortion parameter is greater than a second predetermined variance, means for disabling a second symbol rate from the plurality of symbol rates to form the plurality of remaining symbol rates.

28. The software modem of claim 25, further comprising:

means for determining the envelope delay distortion parameter as a correlate of an attenuation distortion parameter.

29. The software modem of claim 25, further comprising:

means for determining the envelope delay distortion parameter as a correlate of a correlate of a selected transmit pre-emphasis filter.