Method for receiving multicarrier digital signals

• US 6,330,293 B1
• Filed: 07/02/1998
• Issued: 12/11/2001
• Est. Priority Date: 07/28/1997
• Status: Expired due to Term

• Current Assignee: Deutsche Thomson-Brandt Gmbh (Vantiva SA)
• Original Assignee: Deutshe Thomson-Brandt GmbH
• Inventors: Laabs, Jürgen, Klausberger, Wolfgang, Klank, Otto
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US09/110,085
• Time in Patent Office: 1,258 Days
• Field of Search: 325/343, 325/344, 325/365, 325/368, 370/509, 370/510, 370/512, 370/203, 370/210, 708/404, 708/422
• US Class Current: 375/344
• CPC Class Codes: H04H 20/72 of terrestrial networks
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2665 Fine synchronisation, e.g. by positioning the FFT window
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002

Abstract

Coarse symbol synchronization is carried out during reception, for tuning, the signal being correlated in the time domain with various copies of itself which are shifted in time and correspond to the possible transmission modes. The present mode, the present guard interval and a sampling window are derived from this.

Claims

1. A receiver for multicarrier digital signals which are arranged in temporal-spectral frames and contain data symbols having a guard interval and a wanted symbol length Tu and reference information, and which may be transmitted in various transmission modes comprising:

a cascade connected multiplier and transformation circuitry for processing the multicarrier digital signals,

an oscillator coupled to provide a signal of controlled frequency to said miltiplier;

coarse time synchronization circuitry for tuning during reception or for checking for conformity of received signals, by correlating the multicarrier digital signals in the time domain with the multicarrier digital signals shifted in time by various values of Tu corresponding to ones of possible transmission modes, a present transmission mode and a sampling window being determined from a position and magnitudes of maxima of correlation values, and a present guard interval being determined from intervals between maxima of the correlation values, said sampling window having a length corresponding to Tu, being set for transformation circuitry and subsequent signal evaluation;

coarse AFC circuitry responsive to signal output from said transformation circuitry, for performing coarse AFC of said controlled frequency applied to said multiplier with the aid of information items relating to a present symbol, which information items are taken from output signal provided by the transformation circuitry and which are correlated in the coarse AFC circuitry with a defined data layout, the form of correlation being chosen in accordance with the present mode;

evaluation means for qualitative evaluation of results of the coarse time synchronization circuitry and correlation results from the coarse AFC circuitry for determining conformity and reception quality of the multicarrier digital signals.

2. The receiver according to claim 1, wherein the information items include continuous pilot signals, scattered pilot cells and TPS pilot cells and, wherein continuous pilot signals of the present symbol provided at the output of the transformation circuitry are applied to the coarse AFC circuitry, for correlation in the coarse AFC circuitry with the defined data layout.

3. The receiver according to claim 1, including frame and sampling clock synchronization means, for performing fine time synchronization by evaluation of a synchronization sequence of TPS pilot cells provided from an output of the transformation circuitry, in order to determine frame position and positions of scattered pilot cells in a frame an error between a nominal value and the center of a pulse response obtained with the aid of the scattered pilot cells being evaluated in order to adjust a sampling clock.

4. A method for receiving multicarrier digital signals which are arranged in temporal-spectral frames containing data symbols having a guard internal, a wanted symbol length Tu, and reference information, and which may be transmitted in various transmission modes, comprising the steps of:

receiving said multicarrier digital signals;

coarsely synchronizing said multicarrier digital signals received signals;

correlating said multicarrier digital signals in the time domain with a plurality of reference signals each having a different symbol length Tu corresponding to respective possible transmission modes to generate correlation values;

determining the maxima of produced correlation values and a current transmission mode therefrom;

determining a sampling window from the current transmission mode;

selecting a signal processing mode corresponding to the current transmission mode and processing said multicarrier digital signals;

applying processed said multicarrier digital signals to a coarse AFC circuit for providing a frequency error signal and for frequency correcting coarse synchronization, said coarse AFC circuit correlating processed said multicarrier digital signals with a defined data layout chosen in accordance with the current transmission signal mode.

5. The method according to claim 4 further including:

checking coarse AFC detection at predetermined intervals after positioning of the sampling window or achieving a frequency error which is less than a threshold value; and

,

restarting the coarse synchronization if the frequency error is greater than said threshold value on more than one occasion.

6. The method set forth in claim 4, further including:

repeating the step of correlating said multicarrier digital signals and determining the current transmission mode if correlation result maxima are less than a threshold value.

7. The method set forth in claim 4, further including:

averaging and filtering a plurality of correlation results generated by the coarse AFC circuit, and using averaged and filtered correlation results to provide frequency correction.

8. The method set forth in claim 4, wherein the coarse AFC circuit provides a plurality of correlation values and generates a frequency error from said plurality of correlation values associated with a group of correlation maximum.

9. The method set forth in claim 4, further including:

evaluating signal quality from results of coarse AFC correlation; and

determining whether further synchronizing search processes be initiated or signal be decoded.

10. The method set forth in claim 4, further including:

changing from coarse synchronization to fine synchronization if said frequency error signal is less than a defined first threshold.

11. The method set forth in claim 4, wherein the reference information in received said multicarrier digital signals includes continuous pilot signals, scattered pilot cells and transmission parameter signaling carriers (TPS), and wherein the coarse AFC circuit correlates processed continuous pilot cells with said defined data layout.

12. The method set forth in claim 11, further including:

extracting from processed said multicarrier digital signals, TPS signals and scattered pilot cells;

determining the position of a frame and of the scattered pilot cells using a correlation with said TPS signals, by a distance value between a desired value and the current center of a pulse response calculated with the aid of said scattered pilot cells;

adjusting a sampling clock using said distance value.

13. The method according to claim 12, wherein the scattered pilot cells are temporally interpolated in order to obtain said pulse response.

14. The method according to claim 12, further including:

determining the distance value more than once;

combining these results in order to form a final distance value.