On-line step-size calculation using signal power estimation and tone grouping of the frequency-domain equalizer for DMT-based transceiver

• US 20070127563A1
• Filed: 12/05/2005
• Published: 06/07/2007
• Est. Priority Date: 12/05/2005
• Status: Active Grant

• Current Assignee: National Taiwan University (Government of The Republic of China)
• Original Assignee: National Taiwan University (Government of The Republic of China)
• Inventors: Shiue, Muh-Tian, Wang, Chorng-Kuang, Wu, Chih-Feng, Wu, An-Yeu
• Granted Patent: US 7,602,844 B2
• Time in Patent Office: Days
• US Class Current: 375/229
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03687 of step size
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence

Abstract

An efficient method for calculating the step-sizes for a frequency-domain equalizer of a discrete-multitone communications system using signal power estimation and tone grouping (SPE-TG) while on-line. The SPE-TG method is used to calculate a plurality of subchannel step-sizes which are then stored in a lookup table. When on-line, the method uses signal power estimation to select step sizes for each tone, and uses these step sizes for frequency domain equalization. The SPE-TG method simplifies the calculations necessary for frequency domain equalization, thereby saving significant hardware and/or processing resources. The SPE-TG method is reliable and robust, and does not depend upon assumptions about the line, location, or channel.

Claims

1. A method for implementing a frequency-domain equalizer comprising:

generating a plurality of step sizes;

storing the plurality of step sizes in a lookup table;

selecting a step size of a subchannel from the plurality of step sizes in the lookup table according to a received signal power while on-line; and

applying the step size to the frequency-domain equalizer.

2. The method of claim 1 where generating the plurality of step sizes comprises:

selecting a signal to noise ratio gap value;

selecting a design margin value;

selecting a coding gain value;

calculating a baseband equivalent noise standard deviation value;

selecting a signal to noise ratio loss value; and

selecting a subchannel equivalent gain value.

3. The method of claim 1 where selecting the step size of the subchannel comprises:

determining an eta value from the signal to noise ratio loss value;

calculating a subchannel average input signal power value; and

dividing the eta value by the subchannel average input signal power value.

4. The method of claim 1 where generating the plurality of step sizes comprises taking a square of the subchannel equivalent gain value multiplied by the total signal to noise ratio gap multiplied by a square of the baseband equivalent noise standard deviation value multiplied by a scaling factor value, where the scaling factor value is calculated by subtracting one from two raised to an integer power, where the integer is selected from the range [2 . . . 16] inclusive.

5. The method of claim 1 further comprising approximating the plurality of step sizes as powers of two.

6. The method of claim 1 where selecting the step size of the subchannel from the plurality of step sizes in the lookup table according to a received signal power while on-line comprises:

calculating a signal power accumulation;

calculating an average received signal power;

comparing the average received signal power to a plurality of threshold values stored in a lookup table;

when a threshold value of the plurality of threshold values is greater than the average received signal power value, selecting the subchannel step size associated with a chosen threshold value of the lookup table where the average received signal power is greater than or equal to the chosen threshold value and where the average received signal power is less than all threshold values in a set of a plurality of threshold values larger than the chosen threshold value;

when each threshold value of the plurality of threshold values is less than the average received signal power value, selecting a maximum subchannel step size; and

when each threshold value of the plurality of threshold values is greater than the average received signal power, selecting a minimum subchannel step size.

7. A method for implementing a frequency-domain equalizer comprising:

generating a plurality of step sizes for a plurality of subchannels of a modem;

storing the plurality of step sizes in a lookup table; and

applying the plurality of step sizes to the frequency-domain equalizer.

8. The method of claim 7 further comprising:

selecting a signal to noise ratio gap value;

selecting a design margin value;

selecting a signal to noise ratio loss value; and

selecting a coding gain value.

9. The method of claim 7 where generating the plurality of step sizes of comprises:

calculating a baseband equivalent noise standard deviation value; and

calculating a subchannel equivalent gain value.

10. The method of claim 9 where calculating the step size of the subchannel comprises:

determining an eta value from the signal to noise ratio loss value;

calculating a subchannel average input signal power value; and

dividing the eta value by the subchannel average input signal power value.

11. The method of claim 10 where generating the plurality of step sizes comprises taking a square of the subchannel equivalent gain value multiplied by the total signal to noise ratio gap multiplied by a square of the baseband equivalent noise standard deviation value multiplied by a scaling factor value, where the scaling factor value is calculated by subtracting one from two raised to an integer power, where the integer is selected from the range [2 . . . 16] inclusive.

12. The method of claim 7 further comprising approximating the plurality of step sizes as a plurality of powers of two.

13. The method of claim 7 where the plurality of step sizes are stored as integer powers of two in the lookup table.

14. The method of claim 7 where selecting the step size of the subchannel from the plurality of step sizes in the lookup table according to a received signal power while on-line comprises:

calculating a signal power accumulation;

calculating an average received signal power;

comparing the average received signal power to a plurality of threshold values stored in a lookup table;

when a threshold value of the plurality of threshold values is greater than the average received signal power value, selecting the subchannel step size associated with a chosen threshold value of the lookup table where the average received signal power is greater than or equal to the chosen threshold value and where the average received signal power is less than all threshold values in a set of a plurality of threshold values larger than the chosen threshold value;

when each threshold value of the plurality of threshold values is less than the average received signal power value, selecting a maximum subchannel step size; and

when each threshold value of the plurality of threshold values is greater than the average received signal power, selecting a minimum subchannel step size.

15. A method for implementing a frequency-domain equalizer comprising:

generating a lookup table comprising a plurality of step sizes and a plurality of threshold values;

calculating a signal power accumulation;

calculating an average received signal power; and

selecting a subchannel step size according to a decision policy.

16. The method of claim 15 where each step size of the plurality of step sizes is associated with one threshold value of the plurality of threshold values, and where each threshold value of the plurality of threshold values is associated with a single step size of the plurality of step sizes.

17. The method of claim 15 where the decision policy comprises:

comparing the average received signal power to the plurality of threshold values;

when a threshold value of the plurality of threshold values is greater than the average received signal power value, selecting the subchannel step size associated with a chosen threshold value of the lookup table where the average received signal power is greater than or equal to the chosen threshold value and where the average received signal power is less than all threshold values in a set of a plurality of threshold values larger than the chosen threshold value;

when each threshold value of the plurality of threshold values is less than the average received signal power value, selecting a maximum subchannel step size; and

when each threshold value of the plurality of threshold values is greater than the average received signal power, selecting a minimum subchannel step size.

18. The method of claim 15 where each step size of the plurality of step sizes is approximated by an integer power of two.