Shift space-time coding for digital video broadcasting systems

1. A shift space-time coding (SSTC) system for digital broadcasting, the system comprising:

a first SSTC component, comprising:

a first channel encoder having an input receiving a high-priority bit stream and an output supplying a first channel-encoded bit stream;

a QAM symbol mapper having an input receiving the first channel-encoded bit stream and an output supplying a QAM-modulated symbol sequence; and

a first adder comprising:

a first input receiving the QAM-modulated symbol sequence;

a second input; and

an output supplying a first shift space-time-encoded symbol sequence; and

a second SSTC component, comprising:

a second channel encoder having an input receiving a low-priority bit stream and an output supplying a second channel-encoded bit stream;

an STBC encoder having an input receiving the second channel-encoded bit stream and two outputs supplying a first STBC-modulated symbol sequence to the second input of the first adder and a second STBC-modulated symbol sequence; and

a second adder, comprising:

a first input receiving the second STBC-modulated symbol sequence;

a second input receiving the QAM-modulated symbol sequence; and

an output supplying a second shift space-time-encoded symbol sequence.

2. A system as recited in claim 1 , comprising a shift space-time encoder, the shift space-time encoder including the QAM symbol mapper, the STBC encoder, and the first and second adders.

3. The system of claim 1 , wherein the high-priority bit stream is modulated using a 16-QAM constellation.

4. The system of claim 1 , wherein the low-priority bit stream is modulated using a QPSK constellation.

5. The system of claim 1 , wherein each of the two SSTC components contains both the information from the high-priority bit stream and the low-priority bit stream.

6. The system of claim 1 , wherein two bit streams are mapped into and carried by the first SSTC component and the second SSTC component simultaneously.

7. The system of claim 6 , wherein the high-priority bit stream is modulated to complex symbols without STBC encoding.

8. The system of claim 6 , wherein the low-priority bit stream is modulated to complex symbols followed by STBC encoding.

9. The system of claim 7 , wherein the high-priority bit stream is configured to be demodulated by conventional receivers.

10. The system of claim 9 , wherein the high-priority bit stream is configured to be demodulated by a QAM detector.

11. The system of claim 10 , wherein the QAM detector is backward compatible.

12. A method for providing shift space-time coding (SSTC) bit streams for digital broadcasting, the method comprising:

receiving a high-priority bit stream;

encoding the high-priority bit stream to form a first channel-encoded bit stream;

mapping the first channel-encoded bit stream into complex symbols to form a QAM-modulated symbol sequence;

receiving a low-priority bit stream;

encoding the low-priority bit stream to form a second channel-encoded bit stream;

performing STBC-encoding on the second channel-encoded bit stream to form a first STBC-modulated symbol sequence and a second STBC-modulated symbol sequence;

adding the first STBC-modulated symbol sequence to the QAM-modulated symbol sequence to form a first shift space-time-encoded symbol sequence; and

adding the QAM-modulated symbol sequence to the second STBC-modulated symbol sequence to form a second shift space-time-encoded symbol sequence.

13. The method of claim 12 , further comprising:

transforming the first shift space-time-encoded symbol sequence using inverse fast Fourier transformation;

inserting guard intervals in the transformed first shift space-time-encoded symbol sequence; and

transmitting the transformed first shift space-time-encoded symbol sequence and guard intervals over a first transmitter;

transforming the second shift space-time-encoded symbol sequence using inverse fast Fourier transformation;

inserting guard intervals in the transformed second shift space-time-encoded symbol sequence; and

transmitting the transformed second shift space-time-encoded symbol sequence and guard intervals over a second transmitter.

14. The method of claim 12 , further including modulating the high-priority bit stream using a 16-QAM constellation.

15. The method of claim 12 , further including modulating the low-priority bit stream using a QPSK constellation followed by STBC encoding.

16. The method of claim 12 , comprising inserting guard intervals in the transformed first shift space-time-encoded symbol sequence and in the transformed second shift space-time-encoded symbol sequence prior to transmission.

17. The method of claim 14 , further including configuring the high-priority bit stream to be demodulated by conventional receivers.

18. The method of claim 14 , further including configuring the high-priority bit stream to be demodulated by a QAM detector.

19. The method of claim 15 , further including configuring the low-priority bit stream to be demodulated by receivers capable of STBC decoding.