Method of configuring and dynamically adapting data and energy parameters in a multi-channel communications system

• US 6,075,821 A
• Filed: 12/16/1997
• Issued: 06/13/2000
• Est. Priority Date: 12/16/1997
• Status: Expired due to Term

• Current Assignee: Realtek Semiconductor Corp.
• Original Assignee: Integrated Telecom Express, Inc.
• Inventors: Liu, Ming-Kang, Chen, Chunta, Kao, Chiihsin
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GHAYOUR, MOHAMMAD H
• Application Number:
  US08/991,449
• Time in Patent Office: 910 Days
• Field of Search: 375/260, 375/295, 375/219, 375/222, 375/225, 379/93.08, 370/235, 370/231
• US Class Current: 375/260
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

An adaptive process for optimizing the bit and energy configurations of data sub-channels in a multi-channel data transmission signal is disclosed. The inventive process is preferably embodied in one or more microcode routines executable by a high speed digital signal processor. A first routine initializes the transmission system, while a second routine adaptively changes system parameters as necessary to accommodate channel performance changes, varying target bit rates, etc. Both of the routines monitor, analyze and store sub-channel signal-to-noise characteristics, determine theoretical bit capacity loading, evaluates power performance margin, and optimize sub-channel configurations based on a series of iterative calculations intended to maximize the overall system power performance margin for any given target data rate. Alternatively, for a given power performance margin, the achieved data rate can be maximized. To achieve these results, a number of non-zero bit sub-channels (N_CH) are remembered from iteration to iteration, which results in a more optimal loading of the sub-channels. A unique new approach is also disclosed for deciding which of the sub-channels should be disabled to have a zero bit loading. If adjustments to bit loadings are required to achieve a particular initial target rate, those sub-channels which will have the least effect on the overall system performance margin are adjusted first, so that compliance with system performance margin requirements is better achieved. In addition, an "iteration criteria" count can be incorporated in the process to ensure that sub-channel loadings can be effectuated (at least to a very close order) in a predetermined and controlled fashion. The resulting bit/energy loadings can be adjusted to be fully compliant with applicable Discrete Multi-Tone (DMT) implementations of Asymmetric Digital Subscriber Loop (ADSL) protocols.

Claims

1. A method of configuring and adaptively changing sub-channel characteristics of a high speed multi-channel transmission system, which system is intended to transmit data at a data rate R using N sub-channels, said method comprising the steps of:

(a) determining K signal-to-noise values associated with K sub-channels, where K≦

N; and

(b) determining data capacities of each of the K sub-channels based on an evaluation of the following parameters;

i) the K signal-to-noise values; and

ii) said data rate R; and

iii) a number N_ch of the K sub-channels having a non-zero bit capacity; and

wherein the data capacities are determined in one or more iterations of step (b) and N_ch is re-calculated during each iteration.

2. The method of claim 1, wherein during step (b) minimum (b_min (i)) and maximum (b_max (i)) bit loadings for each of the K sub-channels are also calculated and considered in determining the data capacities.

3. The method of claim 2, wherein during step (b) power modification factors e_min (i) and e_max (i) for each of the K sub-channels are also calculated and considered in determining the data capacities.

5. The method of claim 1, wherein the data capacities are also determined based on a consideration of maximum transmission power P for such system.

6. The method of claim 5, wherein during step (b) power adjustment values for the sub-channels are also used in determining the data capacities, the power adjustment values corresponding to a function of the following:

space="preserve" listing-type="equation">(e.sub.max (i)-e.sub.min (i))/(b.sub.max (i)-b.sub.min (i))

where b_min (i) and b_max (i) are calculated minimum and maximum bit loadings respectively for each of the K sub-channels, and e_min (i) and e_max (i) are sub-channel power modification factors associated with such minimum and maximum bit loadings.

7. The method of claim 6, wherein a value of transmission power to be used in said system is adjusted based on an evaluation of a sorted set of the power values.

8. The method of claim 7, wherein a value of the bit rate to be used in said system is adjusted in accordance with adjustments made to the transmission power.

9. The method of claim 1, wherein the system achieves said data rate R by generating an interval during two iterations of step (b), the interval consisting of two different values {B_min, B_max } which bound (B_min <

B<

B_max) a target value B, where B=R/R_symbol, and where R_symbol is a constant.

10. The method of claim 9, wherein the two different values B_min, B_max are generated based on an estimated value of a power margin (γ

_m) for said system.

11. The method of claim 10, wherein a power margin γ

_min is associated with B_min, a second power margin γ

_max is associated with B_max, and said data rate is based on computing an iterative power margin γ

_m =√

γ

_min *√

γ

_max.

12. The method of claim 1, wherein a bit error rate γ

_b for each sub-channel can be varied.

13. The method of claim 1, wherein the data capacities are dynamically adapted in response to changes in characteristics of a transmission channel used by the transmission system.

14. The method of claim 1 wherein the data capacities are dynamically adapted in response to changes in said data rate R for the transmission system.

4. The method of 3, wherein N_ch is determined as a function of b_min (i), b_max (i), e_min (i) and e_max (i).

15. A method of initializing and adapting sub-channel parameters of a high speed multi-channel transmission system, which system is intended to transmit data at a data rate R using K sub-channels, said method comprising the steps of:

(a) determining K signal-to-noise values associated with K sub-channels, where K≦

N; and

(b) determining initial rough data capacities for each of the K sub-channels based on an evaluation of the following parameters;

i) the K signal-to-noise values; and

ii) said data rate R; and

iii) an iteration criteria count M; and

wherein the initial rough data capacities are determined in M or fewer iterations of step (b);

(c) thereafter adaptively determining optimized data capacities for such sub-channels as needed.

16. The method of claim 15, wherein a number N_ch of the K sub-channels having a non-zero bit capacity are calculated during iterations of step (b) and used to determine the optimal data capacities.

17. The method of claim 15, wherein a setup time for establishing a communications link can be controlled by varying the iteration criteria count.

18. The method of claim 15, wherein a rate R'"'"' approximately equal to R is effectuated during step (b), and said rate R is effectuated during step (c).

19. The method of claim 15, wherein power adjustment values for the sub-channels are used in determining the optimized data capacities, the power adjustment values being a function of the following:

space="preserve" listing-type="equation">(e.sub.max (i)-e.sub.min (i))/(b.sub.max (i)-b.sub.min (i))

where b_min (i) and b_max (i) are related to calculated minimum and maximum bit loadings respectively for each of the K sub-channels, and e_min (i) and e_max (i) are related to sub-channel power modification factors associated with such minimum and maximum bit loadings.

20. The method of claim 15, wherein the system is initialized and/or adapted to achieve said data rate R by generating an interval consisting of two different values {B_min, B_max } during the M or fewer iterations of step (b), which values bound (B_min <

B_target <

B_max) a target value B_target, where B_target =R/R_symbol, and where R_symbol is a constant.

21. The method of claim 20, wherein after the two different values B_min, B_max are generated in step (b), a value of a power margin (γ

_m) for said system is also iterated so that an associated data rate R'"'"' for the power margin will converge in value to said data rate R.

22. The method of claim 21, wherein a power margin γ

_min is associated with B_min, a second power margin γ

_max is associated with B_max, an iterative power margin γ

'"'"'_m =√

γ

_min *√

γ

_max is iteratively computed during one or more iterations, and the data rates associated with the iterative power margin converge to said data rate R during such iterations.

23. The method of claim 15, wherein during step (c) the data capacities are dynamically adapted in response to changes in characteristics of a transmission channel used by the transmission system.

24. The method of claim 15 wherein during step (c) the data capacities are dynamically adapted in response to changes in target data rate R for the transmission system.

25. A method of initializing and adapting a high speed transmission system to achieve a data rate R using K sub-channels and with an overall target output power value P, said method comprising the steps of:

(a) determining signal to noise values associated with some or all of said sub-channels; and

(b) calculating a proposed minimum (b_min) and a proposed maximum (b_max) bit loading for the data capacities of sub-channels that are not disabled; and

(c) calculating an output power value P'"'"' associated with such proposed loading; and

(d) if P'"'"'>

P, removing bit capacity in sorted order from those sub-channels which have the greatest differential in power between loadings in which they carry b_min or b_max ; and

wherein the bit capacity is removed during an initialization procedure or adaptation procedure until P'"'"' is substantially equal to P;

(e) calculating a proposed data rate R'"'"' to be used in said system based on the results of steps (b)-(d).

26. The method of claim 25, further wherein during step (e) R'"'"' is compared to R, and if R'"'"' is less than R, steps (b)-(e) are repeated until R'"'"' is substantially equal to R and P'"'"' is substantially equal to P.

27. The method of claim 26, wherein during step (e) if R'"'"'≠

R, an adjustment is made to system power margin (γ

_m) so that in later iterations R'"'"' will converge to R.

28. The method of claim 25, wherein a number N_ch of non-disabled sub-channels is calculated prior to step (b).

29. A method of initializing and adapting a high speed multi-channel transmission system to achieve a target data rate R using K sub-channels, said method comprising the steps of:

(a) determining signal to noise values and nominal data capacities associated with some or all of said sub-channels during an initialization procedure; and

(b) determining optimal data capacities for the sub-channels in one or more iterations of a fine tuning procedure until said data rate R is achieved, the optimal data capacities being calculated based on an evaluation and comparison of power margin variation associated with varying the data capacity for each of such sub-channels.

30. The method of claim 29, wherein during step (b), when an achieved data rate is less than said data rate, a power margin factor F₊₁ (i) relating to an excess power margin of sub-channel is computed, and data capacity is added to the sub-channels in order beginning with the sub-channels with larger power margin factors until said data rate is achieved.

31. The method of claim 29, wherein during step (b), when an achieved data rate is greater than said target data rate, a power margin factor F_-1 (i) relating to a power margin in such sub-channel is computed, and data capacity is optionally removed from the sub-channels in order beginning with the sub-channels with smaller power margins until said target rate is achieved.

32. The method of claim 31 wherein during step (b) a number N_ch of non-disabled sub-channels is calculated and used for determining the optimal data capacities.

33. The method of claim 29, wherein the data capacities are dynamically adapted in response to changes in characteristics of a transmission channel used by the transmission system.

34. The method of claim 30 wherein the data capacities are dynamically adapted in response to changes in target data rate R for the transmission system.

35. A method of maximizing a rate B_total in a high speed multi-channel transmission system during an initialization process and further during an adaptation process, which system is intended to transmit data using K sub-channels, and constrained to use a total transmission power P, and a power margin γ

_m, said method comprising the steps of;

(a) determining signal-to-noise values associated with some or all of said sub-channels; and

(b) determining which of the K sub-channels should be disabled;

(c) determining a proposed minimum (b_min) and a proposed maximum (b_max) bit loading for the data capacities of sub-channels that are not disabled; and

(d) determining an output power value P'"'"' and power modification factors, e_max and e_min associated with such proposed bit loadings; and

(e) replacing b_max with b_min, and e_max with e_min, for one or more sub-channels, until P'"'"'≦

P;

whereby B_total =Σ

b_max for all the sub-channels, and is maximized during both of said initialization and adaptation processes for such values of P and γ

_m.

36. The method of claim 35, wherein the operation of replacing b_max with b_min and e_max with e_min is done in descending order according to a sorting of the sub-channels based on a function related to the following for each sub-channel:

space="preserve" listing-type="equation">(e.sub.max -e.sub.min)/(b.sub.max -b.sub.min).

37. The method of claim 35, wherein B_total can be adjusted to achieve a different rate B_target by performing an additional step (f):

estimating an adjustment Δ

γ

_m to said power margin γ

_m, and repeating steps (b)-(e).

38. The method of claim 37, wherein convergence to said rate B_target is achieved by performing a step (g):

repeating steps (b)-(f) until two values of B_total, namely, B_min and B_max, bound B_target (B_min <

B_target <

B_max).

39. The method of claim 38, further including a step (h):

computing a new B_total and a system power margin γ

_m '"'"' which is a function of γ

_min and γ

_max, where γ

_min and γ

_max are performance margins associated with B_min and B_max respectively.

40. The method of claim 39 further including a step (i):

letting γ

_m '"'"'=√

γ

_min *√

γ

_max and repeating step (h) until B_total converges to B_target.

41. The method of claim 39, wherein the data capacities are dynamically adapted in response to changes in characteristics of a transmission channel used by the transmission system.

42. The method of claim 39 wherein the data capacities are dynamically adapted in response to changes in said symbol target data rate for the transmission system.

43. A method of maximizing a power performance margin γ

_m in a high speed multi-channel transmission system, during an initialization process and further during an adaptation process, which system is intended to transmit data using K sub-channels and a rate B_target, said method comprising the steps of;

(a) determining signal-to-noise values associated with some or all of said sub-channels; and

(b) determining which of the K sub-channels should be disabled;

(c) determining a proposed bit loading for the data capacities of sub-channels that are not disabled based on a nominal power performance margin γ

_m and

(d) calculating a difference Δ

B=B_total -B_target, where B_total is an achieved rate based on the proposed bit loading; and

(e) calculating a new nominal power performance margin γ

'"'"'_m based on Δ

B; and

(f) replacing γ

_m with γ

'"'"'_m and repeating steps (b) through (e) as necessary until Δ

B=0;

wherein γ

_m is maximized during both of said initialization and adaptation processes for said rate B_target.

44. The method of claim 43, wherein during step (f), convergence to said rate B_target is achieved by performing by repeating steps (b)-(f) until two values of B_total, namely, B_min and B_max, bound B_target (B_min <

B_target <

B_max).

45. The method of claim 44, wherein during step (f), after B_min and B_max are computed, γ

_m '"'"' is derived from an iterated function of γ

_min and γ

_max, where γ

_min and γ

_max are performance margins associated with B_min and B_max respectively.

46. The method of claim 43, wherein the data capacities are dynamically adapted in response to changes in characteristics of a transmission channel used by the transmission system.

47. The method of claim 43 wherein the data capacities are dynamically adapted in response to changes in said target symbol data rate for the transmission system.

48. A method of implementing both an initiation procedure and an adaptation procedure for configuring a high speed transmission system using K sub-channels which system can be set to either a first mode achieving a maximum data rate, or a second mode achieving a maximum power performance margin, said method comprising the steps of:

(a) determining signal-to-noise values associated with some or all of said sub-channels; and

(b) determining which of the K sub-channels should be disabled; and

(c) determining a proposed bit loading for the data capacities of sub-channels that are not disabled based on a nominal power performance margin γ

_m ; and

(d) when said first mode is selected, setting said system to use a maximum data rate which is based on the results of step (c) and thereafter terminating said initialization or adaptation procedure; and

(e) when said second mode is selected, calculating a difference Δ

B=B_total -B_target, where B_total is an achieved rate based on the proposed bit loading, and B_target is a target rate for said system; and

(f) calculating a new nominal power performance margin γ

'"'"'_m based on Δ

B; and

(g) replacing γ

_m with γ

'"'"'_m and repeating steps (b), (c), (e) and (f) as necessary until Δ

B=0 thereby maximizing γ

_m for the given value of B_target and thereafter terminating said initialization or adaptation procedure.

49. The method of claim 48, wherein during step (g), convergence to said target rate B_target is achieved by performing by repeating steps (b) (e), (e) and (f) until two values of B_total, namely, B_min and B_max, bound B_target (B_min <

B_target <

B_max).

50. The method of claim 49, wherein during step (g), after B_min and B_max are computed, γ

_m '"'"' is derived from an iterated function of γ

_min and γ

_max, where γ

_min and γ

_max are performance margins associated with B_min and B_max respectively.

51. A method of initializing and adapting a high speed multi-channel transmission system, which system is intended to transmit data using K sub-channels, said method comprising the steps of:

(a) determining signal-to-noise values associated with some or all of said sub-channels; and

(b) determining a proposed minimum (b_min) and a proposed maximum (b_max) bit loading for the data capacities of sub-channels; and

(c) determining power modification factors, e_max and e_min associated with such proposed bit loadings; and

(d) disabling deficient sub-channels by evaluating b_max, b_min, e_max and e_min ; and

(e) loading only non-disabled sub-channels with data;

wherein said system is configured during an initialization process and an adaptation process to only to use non-disabled sub-channels for data transmissions.

52. The method of claim 51, wherein during step (d), a sub-channel is disabled if both b_max and b_min are below a predetermined bit capacity threshold.

53. The method of claim 52, wherein during step (d), sub-channel is disabled if b_min is less than a predetermined bit capacity threshold, and e_max is greater than a predetermined power factor value.

54. A method of configuring a high speed multi-channel transmission system, which system is intended to transmit data using K sub-channels, said method comprising the steps of:

(a) determining signal-to-noise values associated with some or all of said sub-channels; and

(b) determining a proposed minimum (b_min) and a proposed maximum (b_max) bit loading for the data capacities of sub-channels; and

(c) determining power modification factors, e_max and e_min associated with such proposed bit loadings; and

(d) disabling deficient sub-channels by evaluating b_max,b_min, e_max and e_min ; and

(e) loading only non-disabled sub-channels with data;

wherein said system is configured only to use non-disabled sub-channels for data transmissions.

55. The method of claim 54 wherein during step (d), a sub-channel is disabled if both b_max and b_min are below a predetermined bit capacity threshold.

56. The method of claim 55, wherein during step (d), sub-channel is disabled if b_min is less than a predetermined bit capacity threshold, and e_max is greater than a predetermined power factor value.