BLIND IDENTIFICATION OF ADVANCED MODULATION AND CODING MODES

• US 20070206638A1
• Filed: 02/07/2007
• Published: 09/06/2007
• Est. Priority Date: 02/08/2006
• Status: Active Grant

• Current Assignee: DIRECTV, LLC (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Santoru, Joseph, Maitra, Shamik, Lai, Dennis, Zhou, Guangcai, Chen, Ernest
• Granted Patent: US 7,715,786 B2
• Time in Patent Office: Days
• US Class Current: 370/476
• CPC Class Codes: H04L 1/0046 Code rate detection or code type detection H04L1/0038 takes precedence; detection of the data rate H04L25/0262; for packet format H04L1/0091
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 25/03866 using scrambling
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation
• CPC Class Codes: H04L 7/04 Speed or phase control by synchronisation signals H04L7/0075 takes precedence
• 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 21/2389 Multiplex stream processing, e.g. multiplex stream encrypting
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 21/434 Disassembling of a multiplex stream, e.g. demultiplexing audio and video streams, extraction of additional data from a video stream; Remultiplexing of multiplex streams; Extraction or processing of SI; Disassembling of packetised elementary stream demultiplexing of data packets for data networks, e.g. RTP/UDP H04L65/00
• 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
• CPC Class Codes: H04N 21/4385 Multiplex stream processing, e.g. multiplex stream decrypting
• CPC Class Codes: H04N 21/6143 involving transmission via a satellite
• CPC Class Codes: H04N 7/20 Adaptations for transmission via a GHz frequency band, e.g. via satellite

Abstract

Methods and apparatuses for acquiring and demodulating a data stream transmitted in a communication system. A method in accordance with the present invention comprises finding a boundary of a physical layer frame (PLFrame) in the data stream, finding a first 26 bits of a Unique Word (UW) associated with the data stream, finding a scrambling code utilizing the UW, and using a decoding procedure to determine a modulation type and code rate used for desired signals within the data stream.

Claims

1. A method for acquiring and demodulating a data stream transmitted in a communication system, comprising:

finding a boundary of a physical layer frame (PLFrame) in the data stream;

finding a first 26 bits of a Unique Word (UW) associated with the data stream;

finding a scrambling code utilizing the UW; and

using a decoding procedure to determine a modulation type and code rate used for desired signals within the data stream.

2. The method of claim 1, wherein the data stream is a downlink signal from a satellite.

3. The method of claim 2, wherein the scrambling code further comprises a Gold code used to scramble a payload portion of the data stream.

4. The method of claim 3, wherein finding the boundary of the PLFrame further comprises finding a coarse boundary of the PLFrame.

5. The method of claim 4, wherein finding the boundary of the PLFrame further comprises finding a Start Of Frame (SOF) of the PLFrame.

6. The method of claim 5, wherein finding the SOF comprises normalizing a conjugate product of a last symbol of a physical layer header and a first symbol of the physical layer header.

7. The method of claim 6, wherein finding the first 26 bits of the UW comprises normalizing the first 26 symbols of the data stream after the SOF such that a first symbol has a known phase.

8. The method of claim 7, wherein finding a scrambling code comprises looking up the scrambling code associated with the UW.

9. An apparatus for acquiring and demodulating a data stream transmitted in a communication system, comprising:

a demodulator for finding a boundary of a physical layer frame in the data stream and for finding a first 26 bits of a unique word associated with the data stream;

a descrambler, coupled to the demodulator, for finding a scrambling code utilizing the unique word; and

a decoder, coupled to the descrambler, for determining a modulation type and code rate used for desired signals within the data stream and for decoding the data stream.

10. The apparatus of claim 9, wherein the data stream is a downlink signal from a satellite.

11. The apparatus of claim 10, wherein the scrambling code further comprises a Gold code used to scramble a payload portion of the data stream.

12. The apparatus of claim 11, wherein finding the boundary of the physical layer frame further comprises finding a coarse boundary of the physical layer frame.

13. The apparatus of claim 12, wherein finding the boundary of the physical layer frame further comprises finding a start-of-frame of the physical layer frame.

14. The apparatus of claim 13, wherein finding the start-of-frame comprises normalizing a conjugate product of a last symbol of a physical layer header and a first symbol of the physical layer header.

15. The apparatus of claim 14, wherein finding the first 26 bits of the unique word comprises normalizing the first 26 symbols of the data stream after the start-of-frame such that a first symbol has a known phase.

16. The apparatus of claim 15, wherein finding a scrambling code comprises looking up the scrambling code associated with the unique word.

17. A system for transmitting and receiving a data stream, comprising:

a transmitter, the transmitter further comprising;

an encoder, the encoder accepting the data stream and generating an encoded version of the data stream including a physical layer header and a payload portion;

a scrambler, coupled to the encoder, for accepting the encoded version of the data stream and creating a scrambled version of the data stream; and

a modulator, coupled to the encoder, for modulating the scrambled version of the data stream onto a carrier; and

a receiver, the receiver further comprising;

a demodulator for finding a boundary of a physical layer frame in the scrambled version of the data stream and for finding a first 26 bits of a unique word associated with the scrambled version of the data stream;

a descrambler, coupled to the demodulator, for applying a scrambling code to the scrambled version of the data stream utilizing the unique word to re-create the encoded version of the data stream; and

a decoder, coupled to the descrambler, for decoding the encoded version of the data stream using a modulation type and code rate that extracts desired signals within the data stream.

18. The system of claim 17, wherein scrambling the encoded version of the data stream scrambles only the payload portion of the encoded version of the data stream.

19. The system of claim 18, wherein the data stream is a downlink signal from a satellite.

20. The system of claim 19, wherein the scrambling code further comprises a Gold code used to scramble a payload portion of the data stream.