Blind identification of advanced modulation and coding modes

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

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

finding a Unique Word (UW) associated with the data stream; and

using the UW to select a descrambling code and 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 1 , wherein the descrambling code further comprises a Gold code.

4. The method of claim 1 , wherein finding the boundary of the physical layer frame further comprises finding a coarse boundary of the physical layer frame.

5. The method of claim 1 , wherein finding the boundary of the physical layer frame further comprises selecting a frame length used in the data stream.

6. The method of claim 1 , wherein finding the boundary is performed by finding at least one pilot block in the data stream.

7. The method of claim 1 , wherein finding the UW comprises identifying 25 differential bits of the first 26 UW bits.

8. The method of claim 7 , wherein finding the UW comprises rotating the phase of the first received bits after the physical layer frame boundary.

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 by selecting a length of the physical layer frame, and for finding a unique word associated with the data stream;

a descrambler, coupled to the demodulator, for descrambling the data stream based on the unique word; and

a decoder, coupled to the descrambler, for decoding the data stream based on the unique word.

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 descrambler uses a descrambling Gold code paired with the unique word.

12. The apparatus of claim 10 , wherein the demodulator finds the boundary of the physical layer frame by finding a coarse boundary of the physical layer frame.

13. The apparatus of claim 10 , wherein the demodulator finds the boundary of the physical layer by finding at least one pilot block in the data stream.

14. The apparatus of claim 10 , wherein the demodulator finds the unique word by identifying 25 differential bits of a first 26 symbols of the data stream after the boundary of the physical layer.

15. The apparatus of claim 10 , wherein the demodulator finds the unique word by rotating a phase of the data stream.

16. 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 unique word associated with the scrambled version of the data stream;

a descrambler, coupled to the demodulator, for applying a descrambling code to the scrambled version of the data stream, the descrambling code determined by 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 determined by the descrambling code.

17. The system of claim 16 , wherein scrambling the encoded version of the data stream scrambles only the payload portion of the encoded version of the data stream.

18. The system of claim 16 , wherein the data stream is a downlink signal from a satellite.

19. The system of claim 16 , wherein the scrambling code further comprises a Gold code.