Hierarchical 8PSK performance

• US 7,577,213 B2
• Filed: 07/21/2008
• Issued: 08/18/2009
• Est. Priority Date: 07/01/2002
• Status: Expired due to Term

• Current Assignee: DIRECTV, LLC (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Santoru, Joseph, Chen, Ernest C.
• Primary Examiner(s): Ahn; Sam K
• Application Number:
  US12/176,533
• Publication Number:
  US 20080298505A1
• Time in Patent Office: 393 Days
• Field of Search: 375/216, 375/262, 375/279, 375/316, 375/324, 375/329, 375/331, 375/333, 370/207, 714/786, 348/638, 348/725, 348/726
• US Class Current: 375/316
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 1/208 involving signal re-encoding
• CPC Class Codes: H04L 2001/0098 Unequal error protection
• CPC Class Codes: H04L 27/183 Multiresolution systems

Abstract

A method and receiver systems for demodulating and decoding a hierarchically modulated signal, e.g. an 8PSK signal, are disclosed. An exemplary method includes demodulating and processing (502) the hierarchically modulated signal (202) to produce symbols (212) from the first modulation at the first hierarchical level, applying information (504) from a plurality of the symbols from the first modulation at the first hierarchical level in subtracting (214) from the demodulated hierarchically modulated signal to obtain the second modulation at the second hierarchical level and processing (506) the second modulation at the second hierarchical level to produce second symbols (222) from the demodulated second signal. The hierarchically modulated signal comprises a non-uniform 8PSK signal. Applying the information from the plurality of the symbols from the first modulation can be achieved by applying the symbols after error correction. A decision-directed demodulation of the first modulation can also be used to further improve performance.

Claims

1. A method for demodulating and decoding a hierarchically modulated signal having a first modulation at a first hierarchical level and a second modulation at a second hierarchical level, comprising the steps of:

demodulating and processing the hierarchically modulated signal to produce symbols from the first modulation at the first hierarchical level;

applying information from a plurality of the symbols from the first modulation at the first hierarchical level in subtracting from the demodulated hierarchically modulated signal to obtain the second modulation at the second hierarchical level; and

processing the second modulation at the second hierarchical level to produce second symbols from the second modulation at the second hierarchical level;

wherein the hierarchically modulated signal is non-coherent and processing the second modulation at the second hierarchical level to produce second symbols further includes demodulating the second modulation at the second hierarchical level.

2. The method of claim 1, wherein applying information from the plurality of the symbols from the first modulation at the first hierarchical level comprises applying the symbols from the first modulation at the first hierarchical level after error correction.

3. The method of claim 2, wherein applying information from the plurality of the symbols includes performing an error corrected demodulation on the hierarchically modulated signal.

4. The method of claim 2, wherein the error correction comprises a forward error correction process.

5. The method of claim 1, wherein processing the hierarchically modulated signal to produce symbols from the first modulation at the first hierarchical level includes a decision-directed carrier recovery process.

6. The method of claim 1, wherein the plurality of the symbols from the first modulation at the first hierarchical level are re-encoded before being subtracted from the demodulated hierarchically modulated signal.

7. A receiver system for demodulating and decoding a hierarchically modulated signal having a first modulation at a first hierarchical level and a second modulation at a second hierarchical level, comprising:

a first demodulator for demodulating the first modulation of the hierarchically modulated signal;

a symbol decoder, communicatively coupled to the first demodulator, for producing symbols from the demodulated first signal;

an error decoder, communicatively coupled to the symbol decoder, for producing an error corrected symbol stream from the symbols from the demodulated first signal;

a re-encoder for re-encoding the error corrected symbol stream;

a subtractor, communicatively coupled to the re-encoder and the first demodulator, for subtracting the re-encoded symbol stream from the first signal to produce a second signal; and

a second symbol decoder, communicatively coupled to the subtractor for producing second symbols from the second signal;

wherein the hierarchically modulated signal is non-coherent and the receiver system further comprises a second level demodulator, communicatively coupled between the subtractor and the second symbol decoder for demodulating the second signal from the subtractor and providing the demodulated second signal to the second symbol decoder.

8. The receiver system of claim 7, wherein the error decoder comprises a forward error correction decoder.

9. The receiver system of claim 7, wherein the hierarchically modulated signal comprises a non-uniform eight phase shift keyed signal.