Granted Patent B2

US 8,345,734 · App. 12/377,976 · Granted Jan 1, 2013

Abstract

Claims (44)

1. A method for estimating a symbol time error in a broadband transmission system, comprising:

determining a timing error signal of an input-signal of a discrete Fourier-transformation block in a data symbol stream on the basis of intersymbol correlation using a predetermined period in each received symbol;

selecting as the predetermined period a number of samples of different useful data parts of a symbol;

determining a time error value (ε) based on the intersymbol correlation of the selected samples of the different useful data parts of the symbol;

wherein before performing the discrete Fourier-transformation of the selected number of samples:

buffering a first vector of samples of the end of a preceding symbol;

buffering a second vector of samples of the middle part of the preceding symbol;

multiplying, using element-wise complex-conjugate multiplication, the first vector with a corresponding vector from a time shifted vector of an actual symbol;

multiplying, using element-wise complex conjugate multiplication, the second vector with a corresponding vector from a time shifted vector of the actual symbol;

calculating a first averaged sum-signal of the element-wise complex-conjugate multiplied first vector;

calculating a second averaged sum-signal of the element-wise complex-conjugate multiplied second vector; and

calculating the time error value based on difference between the real part of the first averaged sum-signal and the real part of the second averaged sum-signal.

2. The method of claim 1 , further comprising:

using a preceding symbol, a succeeding symbol or an actual symbol for selecting the number of samples.

3. The method according to claim 1 , wherein the determination of the time error value (ε) comprises:

copying the selected samples as a cyclic extension preceding or succeeding in an interval of an output-signal for each symbol at a transmitter after an inverse Fourier-transformation for the cyclic extension.

4. The method according to claim 1 , wherein, a number of the selected samples on which the discrete Fourier-transformation is performed equals a length of the discrete Fourier-transformation.

5. The method according to claim 1 , further comprising,

determining a number of individual time error values (ε) by using different sample shift factors.

6. The method according to claim 5 , further comprising,

determining a combined time error value by adding the individual time error values (ε).

7. The method according to claim 1 , further comprising,

using the determined time error value (ε) to adjust timing.

8. The method according to claim 1 , further comprising,

using the determined time error value (ε) to adjust, especially to advance or retard a fast Fourier-transformation selection window.

9. The method according to claim 1 , further comprising,

using the determined time error value (ε) to increase or decrease a sample conversion rate in a sample rate converter.

10. The method according to claim 1 , further comprising,

using the determined time error value (ε) to increase or decrease a sample conversion rate in an analog-digital converter.

11. A system for estimating a symbol time error in a broadband transmission system, which receives a data symbol stream from a transmitter, comprising:

a symbol time error estimator for determining a timing error signal of a digital input-signal of a discrete Fourier-transformation block in the data symbol stream on the basis of intersymbol correlation using a predetermined period in each received symbol, wherein a number of samples of different useful data parts of a symbol are selected as the predetermined period and a time error value (ε) is determined based on the intersymbol correlation of the selected samples of the different parts of the symbol;

two units for multiplying element-wise complex-conjugate multiplication, the selected samples of a relevant symbol with buffered samples of the relevant symbol part wise;

two units for calculating a first and second averaged sum-signal of the element-wise complex-conjugate multiplied samples part wise; and

a unit for calculating a difference between the real part of the first averaged sum-signal and the real part of the second averaged sum-signal to map the time error value (ε) to a real or imaginary axis.

12. The system according to claim 11 , further comprising:

two units for selecting a number of samples of the same different useful data parts of a symbol of the digital input signal of the discrete Fourier-transformation block.

13. The system according to claim 11 , further comprising:

a buffer for storing the selected samples of the different useful data parts of the symbol.

14. The system according to claim 11 , wherein, the time error value (ε) of the time symbol error estimator is used to adjust timing.

15. The system according to claim 11 , wherein, the time error value (ε) of the symbol time error estimator is used to adjust especially to advance or retard a fast Fourier-transformation selection window.

16. The system according to claim 11 , wherein, the time error value (ε) of the symbol time error estimator is used to increase or decrease a sample conversion rate in a sample rate converter.

17. The system according to claim 11 , comprising: wherein,

the time error value (ε) of the symbol time error estimator is used to increase or decrease a sample rate in an analog-digital converter.

18. The system according to claim 11 , wherein, the time error value (ε) is averaged by means of an FIR or IIR loop filter and an output of the loop filter is used to adjust timing.

Assignments (17)