Multi-carrier transmission systems

• US 6,320,903 B1
• Filed: 06/07/1999
• Issued: 11/20/2001
• Est. Priority Date: 09/02/1996
• Status: Expired due to Term

• Current Assignee: STMicroelectronics NV
• Original Assignee: STMicroelectronics NV
• Inventors: Isaksson, Anders, Okvist, Goran, Ljunggren, Lis-Marie, Isaksson, Mikael, Nordstrom, Tomas, Johansson, Magnus, Isaksson, Lars-Ake, Tonvall, Harry, Bengtsson, Daniel, Olsson, Lennart, Hakansson, Siwert, Stefansson, Tomas, Wen, Ye, Ohman, Hans, Bahlenbert, Gunnar
• Primary Examiner(s): Le, Amanda T.
• Application Number:
  US09/147,744
• Time in Patent Office: 897 Days
• Field of Search: 375/229, 375/232, 375/233, 375/260, 375/266, 375/350, 708/301, 708/322, 708/323
• US Class Current: 375/232
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03522 Frequency domain
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 27/2649 Demodulators
• CPC Class Codes: H04L 27/2656 Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation

Abstract

A multi-carrier transmission system using orthogonal carriers with high order QAM constellations for the transmission of a plurality of bits per carrier and symbol. The system uses some method for the determination of an inverse channel model to be used in the equalization process. In the frequency domain, this is normally based on an estimate of the channel attenuation and phase for each carrier. A simplified method of equalization is provided which uses data at the symbol carrier input and output to adaptively estimate an inverse channel model.

Claims

1. A channel estimation and equalization system for adaptively updating frequency domain equalization parameters for an inverse channel model in a multi-carrier communications system, the channel estimation and equalization system comprising:

equalization means for equalizing parameters for the inverse channel model in the multi-carrier communications system and having an output;

detector/quantizer means for detecting and quantizing signals, said detector/quantizer means having an input connected to the output of said equalization means and an output; and

modifying means having a first input connected to the output of said equalization means and a second input connected to the output of said detector/quantizer means for modifying equalization parameters in small steps so that said equalization means converges on the inverse channel model in the multi-carrier communications system.

2. A channel estimation and equalization system, as claimed in claim 1, further comprising symbol decoder means connected to the output of said detector/quantizer means for decoding symbols to produce a decoded data stream.

3. A channel estimation and equalization system, as claimed in claim 1, further comprising variance estimation means connected to said modifying means for producing a signal indicative of a variance of interference on each carrier of the multi-carrier system.

4. A channel estimation and equalization system, as claimed in claim 3, wherein said variance means estimates a value for variance of interference on each carrier of the multi-carrier system by integrated squared deviations from a mean, in which each quantized value is used as a mean for a range of data values that are quantized.

5. A channel estimation and equalization system, as claimed in claim 4, wherein said variance means estimates a value for variance of interference on each carrier of the multi-carrier system using an algorithm defined by:

6. A channel estimation and equalization system, as claimed in claim 1, wherein said modifying means operates on an algorithm defined by:

${\mathrm{EQ}}_{k+1}={\mathrm{EQ}}_k+\frac{\mathrm{\mu <br><br>}}{{<br><br>U^k<br><br>}^2}={\mathrm{EQ}}_k·<br><br>U_k^{*}·<br><br>\left(Y_k-U_k\right)$

where U is the output of said equalizer means, Y is the output of said detector/quantizer means, and μ

is a positive constant much less than 1 to determine successive values of the equalization parameters.

7. A channel estimation and equalization system, as claimed in claim 6, wherein the expression μ

/|U_k|² in the algorithm is replaced by;

8. A channel estimation and equalization system, as claimed in claim 7, further comprising a binary priority encoder;

and wherein the algorithm portion

9. A channel estimation and equalization system, as claimed in claim 8, further comprising a barrel shifter for implementing multiplicative operations in the algorithm.

10. A channel estimation and equalization system, as claimed in claim 1, further comprising variance estimation means connected to said modifying means to produce a signal, indicative of a variance of interference on each carrier of the multi-carrier system.

11. A channel estimation and equalization system, as claimed in claim 10, wherein said modifying means operates on an algorithm defined by:

${\mathrm{EQ}}_{k+1}={\mathrm{EQ}}_k+\frac{\mathrm{\mu <br><br>}}{{<br><br>U^k<br><br>}^2}={\mathrm{EQ}}_k·<br><br>U_k^{*}·<br><br>\left(Y_k-U_k\right)$

where U is the output of said equalizer means, Y is the output of said detector/quantizer means, and μ

is a positive constant much less than 1 to determine successive values of the equalization parameters.

12. A method for adaptively updating frequency domain equalization parameters of an inverse channel model in a multi-carrier system, the method comprising:

equalizing parameters for the inverse channel model in the multi-carrier system using an equalizer;

detecting and quantizing signals using a detector/quantizer downstream from the equalizer; and

modifying equalization parameters based upon an output of the equalizer and based upon an output of the detector/quantizer so that the equalizer converges on the inverse channel model in the multi-carrier system.

13. A method, as claimed in claim 12, further comprising passing the output of the detector/quantizer to a symbol decoder to produce a decoded data stream.

14. A method, as claimed in claim 12, further comprising deriving a signal indicative of a variance of interference on each carrier of the multi-carrier system based upon the output of the detector/quantizer and the output of the equalizer.

15. A method, as claimed claims 12, wherein modifying comprises calculating successive values of equalization parameters from an algorithm defined by:

${\mathrm{EQ}}_{k+1}={\mathrm{EQ}}_k+\frac{\mathrm{\mu <br><br>}}{{<br><br>U^k<br><br>}^2}={\mathrm{EQ}}_k·<br><br>U_k^{*}·<br><br>\left(Y_k-U_k\right)$

where U is the output of said equalizer means, Y is the output of said detector/quantizer means, and μ

is a positive constant much less than 1 to determine successive values of the equalization parameters.

16. A method, as claimed in claim 15, further comprising replacing μ

/|U_k|² in the algorithm by;

17. A method, as claimed in claim 16, wherein the algorithm portion

18. A method, as claimed in claim 17, wherein implementing multiplicative operations in the algorithm is done using a barrel shifter.

19. A method, as claimed in claim 18, wherein estimating a value for variance of interference on each carrier of the multi-carrier system comprises estimating a value for variance of interference on each carrier of the multi-carrier system by integrated squared deviations from a mean, in which each quantized value is used as a mean for a range of data values that are quantized.

20. A method, as claimed in claim 19, wherein estimating a value for variance of interference on each carrier of the multi-carrier system comprises using an algorithm defined by: