Methods and apparatus for verifying transmit power levels in a signal point limited transmission system

• US 20010000705A1
• Filed: 12/18/2000
• Published: 05/03/2001
• Est. Priority Date: 05/11/1998
• Status: Active Grant

• Current Assignee: Modern Telecom Systems, LLC (Ideahub, Inc.)
• Original Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Inventors: Olafsson, Sverrir
• Granted Patent: US 6,359,932 B2
• Time in Patent Office: Days
• US Class Current: 375/295
• CPC Class Codes: H04L 25/4927 using levels matched to the quantisation levels of the channel
• CPC Class Codes: H04L 5/1453 of modulation type
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors

Abstract

A pulse code modulation modem system utilizes the same total average transmit power formula for designing signal point constellations and for verifying that the transmit power of the signal point constellations are within a designated maximum power limit. The transmit power of the signal point constellations designed by the client modem is also calculated by the server modem to verify that the transmit power limit imposed upon the server modem is not exceeded. In addition, the modem system is capable of designating a transmit power limit associated with one or more training signal points or a training sequence for use during a training mode.

Claims

1. A method for verifying transmit power levels in a signal point limited transmission system having a first device configured to communicate with a second device over a communication channel, said method comprising the steps of:

receiving a plurality of signal points at said first device, said plurality of signal points having a first computed transmit power less than or equal to a transmit power limit, said first computed transmit power being calculated in accordance with a predetermined power calculation formula;

calculating, in accordance with said predetermined power calculation formula, a second computed transmit power of said plurality of signal points; and

determining whether said second computed transmit power is less than or equal to said transmit power limit, said determining step being performed by said first device.

2. A method according to

claim 1

, wherein said first computed transmit power is less than said transmit power limit.

3. A method according to

claim 1

, wherein said second computed transmit power is less than said transmit power limit.

4. A method according to

claim 1

, further comprising the steps of:

generating, in accordance with said predetermined power calculation formula, said transmit power limit, said calculating step being performed by said first device; and

sending said transmit power limit from said first device to said second device.

5. A method according to

claim 4

, wherein said generating step generates a total average transmit power limit.

6. A method according to

claim 1

, further comprising the steps of:

accepting said plurality of signal points when said determining step determines that said second computed transmit power is less than or equal to said transmit power limit; and

rejecting said plurality of signal points when said determining step determines that said second computed transmit power is greater than said transmit power limit.

7. A method according to

claim 1

, wherein said first computed transmit power is associated with an upper bound calculation with respect to said predetermined power calculation formula.

8. A method according to

claim 1

, wherein said calculating step calculates said second computed transmit power in accordance with a lower bound calculation with respect to said predetermined power calculation formula.

9. A method according to

claim 1

, further comprising the step of selecting said predetermined power calculation formula from a plurality of formulas.

10. A method according to

claim 9

, wherein said selecting step is responsive to current operating characteristics of said transmission system.

11. A method according to

claim 1

, further comprising the step of generating said transmit power limit in accordance with said predetermined power calculation formula and in response to at least one of:

a computational tolerance of said first device;

a regulatory limit imposed upon said first device; and

operational characteristics of said communication channel.

12. A method for verifying transmit power levels in a signal point limited transmission system having a first device configured to communicate with a second device over a communication channel, said method comprising the steps of:

receiving, at said second device, a transmit power limit calculated in accordance with a predetermined power calculation formula;

selecting at least one signal point constellation such that said at least one signal point constellation has a first computed transmit power less than or equal to said transmit power limit, said first computed transmit power being calculated in accordance with said predetermined power calculation formula;

transmitting said at least one signal point constellation from said second device to said first device; and

prompting said first device to verify that the transmit power of said at least one signal point constellation is less than or equal to said transmit power limit.

13. A method according to

claim 12

, further comprising the steps of:

calculating, in accordance with said predetermined power calculation formula, a second computed transmit power of said at least one signal point constellation; and

determining whether said second computed transmit power is less than or equal to said transmit power limit, said determining step being performed by said first device.

14. A method according to

claim 13

, further comprising the step of initiating a data communication session utilizing said at least one signal point constellation.

15. A method according to

claim 14

, wherein said initiating step is performed when said determining step determines that said second computed transmit power is less than or equal to said transmit power limit.

16. A method according to

claim 12

, wherein said first computed transmit power is associated with an upper bound calculation with respect to said predetermined power calculation formula.

17. A method according to

claim 12

, further comprising the step of selecting said predetermined power calculation formula from a plurality of formulas.

18. A method according to

claim 17

, wherein said selecting step is responsive to current operating characteristics of said transmission system.

19. A data communication system for performing signal point limited transmissions, said system comprising:

a first device and a second device configured to communicate with one another over a communication channel;

means for selecting at least one signal point constellation such that said at least one signal point constellation has a first computed transmit power less than or equal to a transmit power limit, said first computed transmit power being calculated by said second device in accordance with a predetermined power calculation formula; and

means for verifying that the transmit power of said at least one signal point constellation is less than or equal to said transmit power limit, said first device comprising said means for verifying.

20. A data communication system according to

claim 19

, wherein said means for selecting is configured to select said at least one signal point constellation such that said first computed transmit power is less than said transmit power limit.

21. A data communication system according to

claim 19

, wherein said means for verifying is configured to verify that the transmit power of said at least one signal point constellation is less than said transmit power limit.

22. A data communication system according to

claim 19

, wherein said first computed transmit power is associated with an upper bound calculation with respect to said predetermined power calculation formula.

23. A data communication system according to

claim 19

, wherein said first device further comprises means for calculating said transmit power limit in accordance with said predetermined power calculation formula.

24. A data communication system according to

claim 23

, wherein said means for calculating is configured to calculate a total average transmit power limit.

25. A data communication system according to

claim 19

, wherein said first device further comprises a first transmitter configured to send said transmit power limit to said second device.

26. A data communication system according to

claim 19

, wherein said second device further comprises a second transmitter configured to send said at least one signal point constellation to said first device.

27. A data communication system according to

claim 19

, wherein said means for verifying comprises:

means for calculating, in accordance with said predetermined power calculation formula, a second computed transmit power of said at least one signal point constellation; and

means for determining whether said second computed transmit power is less than or equal to said transmit power limit.

28. A data communication system according to

claim 27

, wherein said means for calculating calculates said second computed transmit power in accordance with a lower bound calculation with respect to said predetermined power calculation formula.

29. A data communication system according to

claim 19

, further comprising means for selecting said predetermined power calculation formula from a plurality of formulas.

30. A data communication system according to

claim 29

, wherein said means for selecting is configured to select said predetermined power calculation formula in accordance with current operating characteristics of said transmission system.

31. A data communication system according to

claim 19

, wherein said first device further comprises means for generating said transmit power limit in accordance with said predetermined power calculation formula and in response to at least one of:

a computational tolerance of said first device;

a regulatory limit imposed upon said first device; and

operational characteristics of said communication channel.

32. A data communication system for performing signal point limited transmissions, said system comprising:

a first device and a second device configured to communicate with one another over a communication channel;

means for sending a transmit power limit from said first device to said second device; and

means for selecting at least one training signal point amplitude having a total average transmit power less than or equal to a transmit power limit, said second device comprising said means for selecting.

33. A data communication system according to

claim 32

, wherein said first device further comprises means for generating a training sequence comprising a plurality of signal points corresponding to said at least one training signal point amplitude.

34. A data communication system according to

claim 33

, wherein said means for generating assigns positive and negative polarities to said plurality of signal points.

35. A data communication system according to

claim 32

, wherein:

a training signal point amplitude is represented by a number of digital bits; and

said means for selecting is configured to select said at least one training signal point amplitude in accordance with a predetermined bit assignment for at least one of said number of digital bits.

36. A data communication system according to

claim 32

, wherein said means for selecting is configured to select said at least one training signal point amplitude in response to the presence of a digital impairment within said communication channel.

37. A data communication system according to

claim 32

, wherein said means for selecting is configured to favor the selection of training signal point amplitudes having relatively higher average transmit powers.

38. A data communication system according to

claim 32

, wherein said means for selecting selects said at least one training signal point amplitude such that said at least one training signal point amplitude has a total average transmit power less than said transmit power limit.

39. A method for designating transmit power levels associated with a training mode in a signal point limited transmission system having a first device configured to communicate with a second device over a communication channel, said method comprising the steps of:

entering a training mode between said first device and said second device;

sending a transmit power limit from said first device to said second device;

receiving at least one training signal point amplitude at said first device, said at least one training signal point amplitude having an average transmit power less than or equal to said transmit power limit; and

generating a training sequence comprising a plurality of signal points corresponding to said at least one training signal point amplitude.

40. A method according to

claim 39

, wherein said receiving step receives one training signal point amplitude.

41. A method according to

claim 40

, wherein said generating step assigns positive and negative polarities to said plurality of signal points.

42. A method according to

claim 40

, wherein:

said one training signal point amplitude is represented by a number of digital bits; and

said number of digital bits are selected in response to the presence of a digital impairment within said communication channel.

43. A method according to

claim 39

, further comprising the step of generating said transmit power limit in response to at least one of:

a computational tolerance of said first device;

a regulatory limit imposed upon said first device; and

operational characteristics of said communication channel.

44. A method for designating transmit power levels associated with a training mode in a signal point limited transmission system having a first device configured to communicate with a second device over a communication channel, said method comprising the steps of:

entering a training mode between said first device and said second device;

receiving, at said second device, a transmit power limit;

selecting at least one training signal point amplitude having an average transmit power less than or equal to said transmit power limit; and

transmitting said at least one training signal point amplitude from said second device to said first device.

45. A method according to

claim 44

, further comprising the step of receiving, at said second device, a training sequence comprising a plurality of signal points corresponding to said at least one training signal point amplitude.

46. A method according to

claim 44

, wherein said selecting step selects one training signal point amplitude.

47. A method according to

claim 46

, wherein:

said one training signal point amplitude is represented by a number of digital bits; and

said selecting step selects said one training signal point amplitude in accordance with a predetermined bit assignment for at least one of said number of digital bits.

48. A method according to

claim 44

, wherein said selecting step is responsive to the presence of a digital impairment within said communication channel.

49. A method according to

claim 44

, wherein said selecting step is biased toward training signal point amplitudes having relatively higher average transmit powers.