Splitterless multicarrier modem

• US 6,266,348 B1
• Filed: 02/11/2000
• Issued: 07/24/2001
• Est. Priority Date: 10/10/1997
• Status: Expired due to Term

• Current Assignee: Intellectual Ventures II LLC (Intellectual Ventures LLC)
• Original Assignee: Aware Incorporated (Crowley Holdings Preferred LLC)
• Inventors: Krinsky, David M., Tzannes, Marcos, Tzannes, Michael A., Gross, Richard W., Greszczuk, John A.
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Elallam, Ahmed
• Application Number:
  US09/485,614
• Time in Patent Office: 529 Days
• Field of Search: 370/252, 370/271, 370/286, 370/410, 370/493, 370/494, 379/394, 455/67.6
• US Class Current: 370/493
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER
• CPC Class Codes: H04L 2025/03764 only during predefined intervals
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0042 intra-user or intra-terminal allocation
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/0058 Allocation criteria
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0085 when channel conditions change
• CPC Class Codes: H04L 5/0094 Indication of how sub-channels of the path are allocated
• CPC Class Codes: H04L 5/1438 Negotiation of transmission parameters prior to communication modified according to link quality H04L1/0001
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data

Abstract

A modem for use in Digital Subscriber Line communications transmits and receives data over the local subscriber loop in common with voice information over the loop, while avoiding the need for voice/data splitters. The modem responds to disruptions associated with “disturbance events” such as on-hook to off-hook transitions and the like by rapidly switching between pre-stored channel parameter control sets defining communications over the loop under varying conditions. In addition to changing parameter control sets responsive to a disturbance event, the modem may also change transmission power levels and other system parameters such as frequency domain equalizer characteristics. Further, provisions are made for reduced bandwidth communications under selected conditions.

Claims

1. In a modem communicating data over a multiplicity of discrete subchannels, each characterized by a bit allocation parameter defining the allocation of bits over the corresponding subchannel for communication over said subchannel comprising:

means for storing a first channel control table for allocating bits to said subchannels during a first communication condition;

means for storing a second channel control table for allocating bits to said subchannels during a second communication condition; and

means for switching between said tables on the detection of a defined event.

2. In a modem communicating data over a multiplicity of discrete subchannels, each characterized by a bit allocation parameter defining the allocation of bits over the corresponding subchannel for communication over said subchannel comprising:

A. means for storing a first channel control table for allocating bits to said subchannels during a first communication condition, wherein said first table specifies the communications capabilities of said modem during normal operation; and

B. means for storing a second channel control table for allocating bits to said subchannels during a second communication condition.

3. A modem according to claim 2 in which the bit allocations of second table are determined by adding noise margins to the determination of the bit allocations of the corresponding subchannels of said first table.

4. In a modem communicating data over a multiplicity of discrete subchannels, each characterized by a bit allocation parameter defining the allocation of bits over the corresponding subchannel for communication over said subchannel comprising:

A. means for storing a first channel control table for allocating bits to said subchannels during a first communication condition; and

B. means for storing a second channel control table for allocating bits to said subchannels during a second communication condition, wherein said second table specifies the communications capabilities of said modem during diminished operation.

5. In a modem communicating data over a multiplicity of discrete subchannels, each characterized by a bit allocation parameter defining the allocation of bits over the corresponding subchannel for communication over said subchannel comprising:

A. means for storing a first channel control table for allocating bits to said subchannels during a first communication condition; and

B. means for storing a second channel control table for allocating bits to said subchannels during a second communication condition, wherein said defined event includes signaling events comprising transitions between on-hook and off-hook conditions.

6. A modem according to claim 5 in which said first table defines communications in the absence of a signaling event.

7. A modem according to claim 6 in which said second table defines communications responsive to detection of a signaling event.

8. A modem according to claim 7 in which said switching means switches from said second table to said first table on detection of a signaling event indicative of cessation of a previously-detected signaling event.

9. In a modem communicating data over a multiplicity of discrete subchannels, each characterized by a bit allocation parameter defining the allocation of bits over the corresponding subchannel for communication over said subchannel comprising:

A. means for storing a first channel control table for allocating bits to said subchannels during a first communication condition; and

B. means for storing a second channel control table for allocating bits to said subchannels during a second communication condition, wherein said first and second tables are determined during an initialization session in which the communication capabilities of said subchannels are determined.

10. A modem according to claim 9 in which said first table is determined in the absence of interfering signaling conditions.

11. A modem according to claim 10 in which said second table is determined as a function of said first table.

12. A modem according to claim 11 in which the bit allocations of said second table are determined as a percentage of the bit allocations of said first table.

13. In a modem communicating data over a multiplicity of discrete subchannels, each characterized by a bit allocation parameter defining the allocation of bits over the corresponding subchannel for communication over said subchannel, comprising:

A. means for storing a first channel control table for allocating bits to said subchannels during a first communication condition; and

B. means for storing a second channel control table for allocating bits to said subchannels during a second communication condition, wherein said second channel control table is determined responsive to a plurality of signaling events created by a corresponding plurality of event-generating sources, each defining a channel control table specific to the given source, and comprises a composite table formed by selecting, for each subchannel, the minimum bit allocation for the corresponding subchannel of the table associated with each of the plurality of sources.

14. In a modem communicating data over a multiplicity of discrete subchannels, each characterized by a bit allocation parameter defining the allocation of bits over the corresponding subchannel for communication over said subchannel, the improvement comprising:

A. means for storing a first channel control table for allocating bits to said subchannels during a first communication condition; and

B. means for storing a second channel control table for allocating bits to said subchannels during a second communication condition, wherein said second channel control table is selected from a plurality of tables determined responsive to a plurality of signaling events created by a corresponding plurality of event-generating sources, each defining a channel control table specific to the given source.

15. A modem according to claim 14 which includes means for selecting one of said plurality of tables for use as said second table in accordance with the source generating an event.

16. In a modem communicating data over a multiplicity of discrete subchannels, each characterized by a bit allocation parameter defining the allocation of bits over the corresponding subchannel for communication over said subchannel, the improvement comprising:

A. means for storing a first channel control table for allocating bits to said subchannels during a first communication condition;

B. means for storing a second channel control table for allocating bits to said subchannels during a second communication condition;

C. means for redetermining said channel control tables while said modem is in either of said communication conditions; and

D. means for communicating a redetermined table to a second modem engaged in communication with said modem.

17. A modem according to claim 16 in which said communicating means communicates said redetermined table over a dedicated sub-subchannel selected from among said discrete subchannels.

18. A modem according to claim 16 in which said communicating means further communicates to said second modem information identifying the type of said redetermined table.

19. A modem for use in asymmetric digital subscriber line communications having both upstream and downstream communication subchannels formed from a plurality of subchannels, said loop adapted to carry both voice and data communications thereon, comprising:

means for storing a first table defining data communications between said modem and a second modem connected to said loop during a first communication state;

means for storing a second table defining data communications between said modem and said second modem during a second communication state;

means for detecting said selected events;

means for monitoring a selected characteristic of at least one of said communication subchannels during a plurality of communication intervals;

means for determining differences in the selected characteristic over said plurality of intervals; and

means for generating a signal initiating switching of said tables when said differences exhibit a defined pattern.

20. A modem according to claim 19 in which said pattern comprises an initial difference above a first threshold amount followed by at least a subsequent differences less than a second threshold amount.

21. A modem according to claim 20 in which said first threshold is greater than said second threshold.

22. A modem according to claim 21 in which said pattern comprises an initial difference above a first threshold amount followed by a plurality of subsequent differences less than a second threshold amount.

23. A modem according to claim 21 in which said characteristic comprises an error code error.

24. A modem according to claim 21 in which said characteristic comprises a signal-to-noise ratio.

25. A modem according to claim 20 in which said selected characteristic is monitored over at least one sub-subchannel.

26. A modem according to claim 20 in which said selected characteristic is monitored over a plurality of subchannels.

27. (Amended) A modem according to claim 26 which includes means for averaging the monitored values of said selected characteristic over said subchannels for use in comparing said initial difference to said first threshold.

28. A modem according to claim 26 which includes means for averaging the monitored values of said selected characteristic over said subchannels for use in comparing said subsequent difference to said second threshold.

29. A modem according to claim 19 in which said characteristic comprises a parameter of a pilot tone.

30. A modem according to claim 19 in which said switching means returns said modem to said first communication state on termination of the event causing the switching.

31. A modem according to claim 19 in which said generating means causes transmission of a switch-control signal over one of said subchannels in response to detection of a selected event.

32. A modem according to claim 19 in which said generating means causes transmission of a tone in response to detection of a selected event.

33. A modem for use in asymmetric digital subscriber line communications over a loop having both upstream and downstream communication channels formed from a plurality of subchannels, said loop adapted to carry both voice and data communications thereon, comprising:

A. means for storing a first table defining data communications between said modem and a second modem connected to said loop during a first communication state; and

B. means for storing a second table defining data communications between said modem and said second modem during a second communication state, specifies wherein said first table establishes a data rate greater than that of said second table.

34. A modem according to claim 33 in which said tables define the number of bits transmitted over the respective subchannels.

35. A modem according to claim 34 in which said events comprise signaling events selected from the group comprising off-hook on-hook, ringing, and busy.

36. A modem for use in asymmetric digital subscriber line communications over a loop having both upstream and downstream communication channels formed from a plurality of subchannels, said loop adapted to carry both voice and data communications thereon, comprising:

A. means for storing a first table defining data communications between said modem and a second modem connected to said loop during a first communication state;

B. means for storing a second table defining data communications between said modem and said second modem during a second communication state;

C. means for emitting into said loop a test signal for probing the return characteristics of transmissions into the loop by said modem; and

D. means for limiting the power level of said transmissions in accordance with the measured return characteristics.

37. A modem according to claim 36 in which said probe comprises a tone at a defined amplitude and frequency and in which the measured return characteristics comprise at least one characteristic selected from the group comprising the amplitude and frequency of the signal returned to said modem in response to emission of said tone.

38. A modem according to claim 36 in which said probe comprises a plurality of tones at defined amplitudes and frequencies and in which the measured return characteristics comprise at least one characteristic selected from the group comprising the amplitudes and frequencies of the signal returned to said modem in response to emission of said tone.

39. A modem for use in asymmetric digital subscriber line communications over a loop having both upstream and downstream communication channels formed from a plurality of subchannels, said loop adapted to carry both voice and data communications thereon, comprising:

A. means for storing a first table defining data communications between said modem and a second modem connected to said loop during a first communication state;

B. means for storing a second table defining data communications between said modem and said second modem during a second communication state; and

equalizers for equalizing the transmission characteristics of said subchannels and in which said tables define;

(1) coefficients of time domain equalizers,

(2) coefficients of frequency domain equalizers or

(3) coefficients of digital echo cancellers.

40. A modem for use in asymmetric digital subscriber line communications over a loop having both upstream and downstream communication channels formed from a plurality of subchannels, said loop adapted to carry both voice and data communications thereon, comprising:

A. means for storing a first table defining data communications between said modem and a second modem connected to said loop during a first communication state, wherein said first table is determined during an initialization process in the absence of a selected event; and

B. means for storing a second table defining data communications between said modem and said second modem during a second communication state.

41. A modem according to claim 40 in which said second table is determined during an initialization process in the presence of a selected event.

42. A modem according to claim 41 in which said second table is redetermined responsive to occurrence of a selected event.

43. A modem according to claim 42 in which redetermined tables are communicated from a given modem to other modems with which it is in communication during a quiescent state.

44. A method of transmitting data over a wire line through upstream and downstream channels, respectively, from first and second pluralities of discrete-frequency subchannels, comprising the steps of:

A. storing at least first and second parameter sets defining data communications over said channels under at least two different communication conditions;

B. selecting a parameter set for use in communications in accordance with the prevailing communication condition, wherein said selecting step includes the step of monitoring communications on said line and transmitting and selecting said parameter set in accordance with said monitoring.

45. The method of claim 44 in which said monitoring step includes the step of measuring at least one communication indicium on said at least one subchannel.

46. The method of claim 45 in which said at least one indicium is selected from the group comprising signal to noise ratios, error rates, and the amplitude and frequency of tones.

47. A method of transmitting data over a wire line through upstream and downstream channels, respectively, from first and second pluralities of discrete-frequency subchannels, comprising the steps of:

A. storing at least first and second parameter sets defining data communications over said channels under at least two different communication conditions;

B. selecting a parameter set for use in communications in accordance with the prevailing communication condition; and

C. transmitting over said line a signal that identifies the parameter set to be selected.

48. The method of claim 47 in which said signal is transmitted on a subchannel intermediate said upstream and downstream channels.

49. A method of transmitting data over a wire line through upstream and downstream channels, respectively, from first and second pluralities of discrete-frequency subchannels, comprising the steps of:

A. storing at least first and second parameter sets defining data communications over said channels under at least two different communication conditions;

B. selecting a parameter set for use in communications in accordance with the prevailing communication condition; and

C. receiving over said line a signal that identifies the parameter set to be selected.

50. The method of claim 49 in which said signal is received on a subchannel intermediate said upstream and downstream channels.

51. A method of transmitting data over a wire line through upstream and downstream channels, respectively, from first and second pluralities of discrete-frequency subchanels, comprising the steps of:

A. storing at least first and second parameter sets defining data communications over said channels under at least two different communication conditions;

B. selecting a parameter set for use in communications in accordance with the prevailing communication condition, wherein said first parameter set defines communications over said line in the absence of a disturbance event and said second parameter set defines communications over said line in the presence of a disturbance event.

52. A method of transmitting data over a wire line through upstream and downstream channels, respectively, from first and second pluralities of discrete-frequency subchannels, comprising the steps of:

A. storing at least first and second parameter sets defining data communications over said channels under at least two different communication conditions;

B. selecting a parameter set for use in communications in accordance with the prevailing communication condition, wherein said parameter sets include at least one parameter set from the group comprising subchannel bit allocations and subchannel gains.

54. The method of claim 52 in which said parameter sets include a first section for use in transmitting data over said line and a second portion for receiving data over said line.

53. A method of transmitting data over a wire line through upstream and downstream channels, respectively, from first and second pluralities of discrete-frequency subchannels, comprising the steps of:

A. storing at least first and second parameter sets defining data communications over said channels under at least two different communication conditions;

B. selecting a parameter set for use in communications in accordance with the prevailing communication condition, wherein said parameter sets include at least one parameter set from the group comprising subchannel frequency domain coefficients, time domain coefficients, and echo cancellation coefficients.