System and method for recognizing zero-amplitude symbols in a QAM signal and digital receiver incorporating the same

• US 20030016768A1
• Filed: 07/19/2001
• Published: 01/23/2003
• Est. Priority Date: 07/19/2001
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Guardian Corp. (Broadcom, Inc.)
• Inventors: Wang, Zhenyu, Huang, Gang, Liang, Min
• Granted Patent: US 7,349,486 B2
• Time in Patent Office: Days
• US Class Current: 375/340
• CPC Class Codes: H04L 25/061 providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset removal of dc offset in coupling arrangements H04L25/029, H04L25/0296

Abstract

A system for, and method of, recognizing zero-amplitude symbols in a quadrature amplitude modulated (QAM) signal and a digital receiver incorporating the system or the method. In one embodiment, the system includes: (1) an amplitude detector that extracts a candidate symbol from the signal and locates the candidate symbol relative to a constellation of symbols and (2) a zero-amplitude symbol interpreter, associated with the amplitude detector, that recognizes the candidate symbol as being a zero-amplitude symbol when the candidate symbol is closer to an origin of the constellation than to symbols proximate thereto.

Claims

1. A system for recognizing zero-amplitude symbols in a quadrature amplitude modulated (QAM) signal, comprising:

an amplitude detector that extracts a candidate symbol from said signal and locates said candidate symbol relative to a constellation of symbols; and

a zero-amplitude symbol interpreter, associated with said amplitude detector, that recognizes said candidate symbol as being a zero-amplitude symbol when said candidate symbol is closer to an origin of said constellation than to symbols proximate thereto.

2. The system as recited in claim 1 wherein said zero-amplitude symbol constitutes an end-of-file symbol according to a Home Phoneline Networking Alliance standard.

3. The system as recited in claim 1 wherein a plurality of said zero-amplitude symbols separate subframes according to a Home Phoneline Networking Alliance standard.

4. The system as recited in claim 1 wherein said symbols proximate said origin number four in quantity.

5. The system as recited in claim 1 wherein said symbols proximate said origin are located at relative amplitudes of:

1, 1,

1, −

1,

−

1, 1, and

−

1, −

1.

6. The system as recited in claim 1 wherein said constellation is arranged on a Cartesian plane.

7. The system as recited in claim 1 wherein said zero-amplitude symbol interpreter is free of a slicer table.

8. A method of recognizing zero-amplitude symbols in a quadrature amplitude modulated (QAM) signal, comprising:

extracting a candidate symbol from said signal;

locating said candidate symbol relative to a constellation of symbols; and

recognizing said candidate symbol as being a zero-amplitude symbol when said candidate symbol is closer to an origin of said constellation than to symbols proximate thereto.

9. The method as recited in claim 8 wherein said zero-amplitude symbol constitutes an end-of-file symbol according to a Home Phoneline Networking Alliance standard.

10. The method as recited in claim 8 wherein a plurality of said zero-amplitude symbols separate subframes according to a Home Phoneline Networking Alliance standard.

11. The method as recited in claim 8 wherein said symbols proximate said origin number four in quantity.

12. The method as recited in claim 8 wherein said symbols proximate said origin are located at relative amplitudes of:

1, 1,

1, −

1,

−

1, 1, and

−

1, −

1.

13. The method as recited in claim 8 wherein said constellation is arranged on a Cartesian plane.

14. The method as recited in claim 8 wherein said zero-amplitude symbol interpreter is free of a slicer table.

16. The receiver as recited in claim 15 wherein said zero-amplitude symbol constitutes an end-of-file symbol according to a Home Phoneline Networking Alliance standard.

17. The receiver as recited in claim 15 wherein a plurality of said zero-amplitude symbols separate subframes according to a Home Phoneline Networking Alliance standard.

18. The receiver as recited in claim 15 wherein said symbols proximate said origin number four in quantity.

19. The receiver as recited in claim 15 wherein said symbols proximate said origin are located at relative amplitudes of:

1, 1,

1, −

1,

−

1, 1, and

−

1, −

1.

20. The receiver as recited in claim 15 wherein said constellation is arranged on a Cartesian plane.

21. The receiver as recited in claim 15 wherein said slicer employs a slicer table to interpret said nonzero symbols, but said zero-amplitude symbol interpreter is free of said slicer table.

15. A digital receiver, comprising:

a digital-to-analog (D/A) converter that converts a received quadrature amplitude modulated (QAM) signal in digital form to analog form;

a demodulator, coupled to said D/A converter, that demodulates said QAM signal;

an equalizer, coupled to said demodulator, that equalizes said QAM signal;

a slicer, coupled to said equalizer, that recognizes nonzero-and zero-amplitude symbols in said QAM signal, said slicer having a system for recognizing said zero-amplitude symbols, including;

an amplitude detector that extracts a candidate symbol from said signal and locates said candidate symbol relative to a constellation of symbols, and

a zero-amplitude symbol interpreter, associated with said amplitude detector, that recognizes said candidate symbol as being a zero-amplitude symbol when said candidate symbol is closer to an origin of said constellation than to symbols proximate thereto; and

a decoder, coupled to said slicer, that decodes said nonzero- and zero-amplitude symbols to yield data.