Method and apparatus for joint equalization and decoding of multidimensional codes transmitted over multiple symbol durations

• US 20030115541A1
• Filed: 12/18/2001
• Published: 06/19/2003
• Est. Priority Date: 12/18/2001
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Azadet, Kameran, Haratsch, Erich Franz
• Granted Patent: US 8,095,857 B2
• Time in Patent Office: Days
• US Class Current: 714/796
• CPC Class Codes: H03M 13/256 with trellis coding, e.g. with convolutional codes and TCM
• CPC Class Codes: H03M 13/39 Sequence estimation, i.e. using statistical methods for the reconstruction of the original codes
• CPC Class Codes: H03M 13/3961 Arrangements of methods for branch or transition metric calculation
• CPC Class Codes: H03M 13/4107 implementing add, compare, select [ACS] operations
• CPC Class Codes: H03M 13/6331 Error control coding in combination with equalisation
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference
• CPC Class Codes: H04L 25/03305 Joint sequence estimation and interference removal joint detection of several desired signals H04L25/03331

Abstract

A method and apparatus are disclosed for performing joint equalization and decoding of multidimensional codes transmitted over multiple symbol durations. An RSSE scheme is disclosed that cancels the intrasymbol interference caused by other symbol components within the same multidimensional code symbol. The disclosed RSSE technique for multidimensional codes applies where the number of trellis code dimensions exceeds the number of channels. The disclosed RSSE decoder computes the intersymbol interference caused by previously decoded multidimensional code symbols and subtracts the intersymbol interference from the received signal. In addition, a branch metrics unit compensates for the intrasymbol interference caused by other symbol components within the same multidimensional code symbol. The disclosed RSSE decoder for 4D-TCM includes 2D branch metric units (2D-BMU) that calculate the 2D branch metrics for the two wire pairs based on the received 2D signals. The 2D-BMUs compensate for intrasymbol interference caused by other symbol components within the same multidimensional code symbol. In addition, the decision feedback unit (DFU) in the RSSE decoder processes the survivor symbols from the survivor memory unit (SMU) to calculate the intersymbol interference estimates for all code states and channels, which are used by the 2D-BMUs to calculate the 2D branch metrics.

Claims

1. A method for decoding a multidimensional code, said method comprising the steps of:

compensating for intersymbol interference caused by previously decoded multidimensional code symbols; and

compensating for intrasymbol interference caused by symbol components within the same multidimensional code symbol.

2. The method of claim 1, wherein a minimum decodable number of symbols is transmitted over more than one symbol interval.

3. The method of claim 1, wherein said multidimensional code includes a number of trellis code dimensions that exceeds a number of available channels.

4. The method of claim 1, further comprising the steps of:

calculating intersymbol interference estimates based on said previously decoded multidimensional code symbols;

calculating intrasymbol interference estimates based on possible data symbol values; and

calculating branch metrics based on a received signal and said intersymbol interference and intrasymbol interference estimates.

5. The method of claim 1, further comprising the step of calculating a one-dimensional branch metric for an initial symbol duration of a multiple one-dimensional symbol duration sequence, wherein said initial symbol duration is not affected by intrasymbol interference.

6. The method of claim 1, further comprising the step of calculating a one-dimensional branch metric for subsequent symbol durations of a multiple one-dimensional symbol duration sequence, wherein said subsequent symbol durations are affected by intrasymbol interference.

7. The method of claim 1, further comprising the step of calculating a two-dimensional branch metric based on said one-dimensional branch metrics.

8. The method of claim 7, further comprising the step of combining said two-dimensional branch metrics to calculate four dimensional branch metrics corresponding to the transitions in the trellis diagram for a 4D-TCM.

9. The method of claim 1, further comprising the step of determining a best surviving path into a trellis state.

10. The method of claim 1, wherein said multidimensional code is 4D-TCM.

11. A reduced state sequence estimation decoder for a multidimensional code, comprising:

at least one branch metric unit that calculates branch metrics for a received signal based on intersymbol interference and intrasymbol interference estimates, said at least one branch metric unit compensating for intrasymbol interference caused by symbol components within the same multidimensional code symbol; and

a decision feedback unit that processes survivor symbols to calculate the intersymbol interference estimates for different code states of said multidimensional code and channels used to transmit said multidimensional code.

12. The reduced state sequence estimation decoder of claim 11, wherein a minimum decodable number of symbols is transmitted over more than one symbol interval.

13. The reduced state sequence estimation decoder of claim 11, wherein said multidimensional code includes a number of trellis code dimensions that exceeds a number of available channels.

14. The reduced state sequence estimation decoder of claim 11, wherein said at least one branch metric unit is further configured to:

calculate intrasymbol interference free estimates based on possible data symbol values; and

calculate branch metrics based on a received signal and said intersymbol interference and intrasymbol interference estimates.

15. The reduced state sequence estimation decoder of claim 11, wherein said at least one branch metric unit is further configured to calculate a one-dimensional branch metric for an initial symbol duration of a multiple one-dimensional symbol duration sequence, wherein said initial symbol duration is not affected by intrasymbol interference.

16. The reduced state sequence estimation decoder of claim 11, wherein said at least one branch metric unit is further configured to calculate a one-dimensional branch metric for subsequent symbol durations of a multiple one-dimensional symbol duration sequence, wherein said subsequent symbol durations are affected by intrasymbol interference.

17. The reduced state sequence estimation decoder of claim 11, further comprising a two-dimensional branch metric unit to calculate a two-dimensional branch metric based on said one-dimensional branch metrics.

18. The reduced state sequence estimation decoder of claim 17, further comprising a four-dimensional branch metric unit to combine said two-dimensional branch metrics to calculate four dimensional branch metrics corresponding to the transitions in the trellis diagram for a 4D-TCM.

19. The reduced state sequence estimation decoder of claim 11, further comprising an add-compare-select unit to determine a best surviving path into a trellis state.

20. The reduced state sequence estimation decoder of claim 11, wherein said multidimensional code is 4D-TCM.

21. A system for decoding a multidimensional code, said system comprising:

means for compensating for intersymbol interference caused by previously decoded multidimensional code symbols; and

means for compensating for intrasymbol interference caused by symbol components within the same multidimensional code symbol.