BROADBAND DEMODULATOR FOR MODIFIED DOWNSTREAM WAVEFORM

• US 20090022086A1
• Filed: 07/16/2008
• Published: 01/22/2009
• Est. Priority Date: 10/03/2006
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Dankberg, Mark D., Thesling, William H.
• Granted Patent: US 8,259,640 B2
• Time in Patent Office: Days
• US Class Current: 370/316
• CPC Class Codes: H04B 7/18582 Arrangements for data linking, i.e. for data framing, for error recovery, for multiple access

Abstract

Systems, devices, processors, and methods are described for the transmission and reception of broadband signals between a gateway and subscriber terminals via satellite. In one set of embodiments, a wireless signal is generated and transmitted including a series of frames including a physical layer header and payload. A sub-channel identifier may be included in the physical layer header to identify the sub-channel for the payload, and allow for various novel filtering techniques at the subscriber terminal. The frames may be generated to be of substantially equal duration. Novel subscriber terminal configurations are described to leverage this formatting.

Claims

1. A terminal to receive a wireless signal from a satellite, the terminal comprising:

a receiver unit configured to receive the wireless signal transmitted via the satellite;

a header processing unit, communicatively coupled with the receiver unit, and configured to;

receive a digitized stream comprising a physical layer signal representative of the received wireless signal, the digitized stream including a plurality of physical layer headers spaced substantially equidistant in time and each associated with a respective physical layer payload;

analyze the digitized stream to detect a first header identifier identifying a first physical layer header portion of the digitized stream;

demodulate and decode the first physical layer header portion to identify a first sub-channel identifier for an associated first physical layer payload;

determine a search location in the digitized stream for a second header identifier detection analysis; and

omit an identifier detection analysis in the digitized stream at one or more known header identifier locations between the first physical layer header portion and the search location, based at least in part on the first sub-channel identifier; and

a filter unit, communicatively coupled with the header detection unit, and configured to exclude from demodulation or decoding one or more physical layer payloads in the digitized stream associated with the omitted identifier detection analysis locations.

2. The terminal of claim 1, wherein the filter unit is further configured to determine whether the first sub-channel identifier is an identifier associated with a physical layer payload to be filtered from demodulation and decoding.

3. The terminal of claim 2, wherein the filter unit is further configured to:

identify the physical layer payload associated with the first sub-channel identifier as data to be filtered to prevent demodulation and decoding; and

filter the digitized stream to exclude the identified physical layer payload from demodulation or decoding.

4. The terminal of claim 2, wherein the filter unit is further configured to:

identify the physical layer payload associated with the first sub-channel identifier as data to be forwarded for demodulation and decoding; and

forward the identified physical layer payload.

5. The terminal of claim 4, further comprising:

a demodulation unit configured to receive and demodulate the forwarded physical layer payload associated with the second header; and

a decoder unit configured to decode the demodulated physical layer payload,

wherein the demodulation and decoder units are each configured to demodulate and decode only a subset of the plurality of physical layer payloads in the digitized stream.

6. The terminal of claim 2, wherein the filter unit is further configured to:

store one or more sub-channel identifiers indicating whether a physical layer payload is to be demodulated and decoded; and

determine whether the first sub-channel identifier is the identifier associated with physical layer payload to be filtered by accessing the stored sub-channel identifiers.

7. The terminal of claim 1, wherein,

the plurality of physical layer headers spaced substantially equidistant in time each include one of a plurality of sub-channel identifiers;

and

each one of at least a subset of the sub-channel identifiers recur at a regular interval in time in the digitized stream.

8. The terminal of claim 1, wherein the header processing unit is configured to determine the search location in the digitized stream for the second header identifier detection based at least in part on the regular interval.

9. The terminal of claim 1, wherein,

the plurality of physical layer headers spaced substantially equidistant in time each include one of a plurality of sub-channel identifiers;

and

each one of at least a subset of the sub-channel identifiers do not recur at a regular interval in time.

10. The terminal of claim 1, wherein the header processing unit is configured to omit the identifier detection analysis in known header identifier locations based at least in part on a minimum interval between same sub-channel identifiers.

11. The terminal of claim 1, wherein the header processing unit is configured to determine the search location for the second header identifier detection analysis based at least in part on the first sub-channel identifier.

12. The terminal of claim 1, wherein the header processing unit is further configured to:

receive data identifying modified spacing between the plurality of physical layer headers; and

change spacing in time between each header identifier detection analysis to account for the modified spacing.

13. The terminal of claim 1, wherein,

the received wireless signal comprises a modified digital video broadcasting signal on a single carrier;

the header identifier comprises a start of frame (SOF) pattern; and

the header portion comprises a modified physical layer signaling (PLS) code including sub-channel identifier information and an indication of a dynamically assigned modulation and coding format.

14. A processor for processing a digitized representation of a wireless signal received from a satellite, the processor comprising:

a header processing unit configured to;

receive a digitized stream comprising a physical layer signal representative of the received wireless signal, the digitized stream including a plurality of physical layer headers spaced substantially equidistant in time and each associated with a respective physical layer payload;

analyze the digitized stream to detect a first header identifier identifying a first physical layer header portion of the digitized stream;

demodulate and decode the first physical layer header portion to identify a first sub-channel identifier for an associated first physical layer payload;

determine one or more subsequent headers having different sub-channel identifiers from the first sub-channel identifier, the determination based at least in part on the first sub-channel identifier; and

omit a header identifier detection analysis at known header identifier locations for the determined one or more subsequent headers; and

a filter unit, communicatively coupled with the header detection unit, and configured to exclude from demodulation or decoding one or more physical layer payloads in the digitized stream associated with the determined one or more subsequent headers.

15. A satellite communications system comprising:

a gateway configured to transmit a wireless signal sent to a satellite for retransmission to a terminal;

the satellite, communicatively coupled with the terminal and the gateway, and configured to receive the wireless signal from the gateway and retransmit the received signal to the terminal; and

the terminal comprising;

a receiver unit configured to receive the wireless signal transmitted via the satellite;

a header processing unit configured to;

receive a digitized stream comprising a physical layer signal representative of the received signal, the digitized stream including a plurality of physical layer headers spaced substantially equidistant in time and each associated with a respective physical layer payload;

analyze the digitized stream to detect a first header identifier identifying a first physical layer header portion of the digitized stream;

demodulate and decode the first physical layer header portion to identify a first sub-channel identifier for an associated first physical layer payload;

determine, based at least in part on the first sub-channel identifier, one or more subsequent header identifier locations in the digitized stream that have different sub-channel identifiers from the first sub-channel identifier; and

omit an identifier detection analysis at the determined one or more header identifier locations; and

a filter unit communicatively coupled with the header detection unit, and configured to exclude from demodulation or decoding a physical layer payload located in the digitized stream and associated with the different sub-channel identifiers.

16. A method of processing a digital representation of a wireless signal received from a satellite, the method comprising:

detecting a first header identifier identifying a physical layer header portion of a digitized stream, the digitized stream comprising a physical layer signal representative of the received wireless signal from the satellite;

demodulating and decoding the first physical layer header portion to identify a first sub-channel identifier associated with a first physical layer payload;

identifying the first physical layer payload as a portion of the digitized stream to be demodulated and decoded based at least in part on the first sub-channel identifier;

identifying, based at least in part on the first sub-channel identifier, other physical layer payloads of the digitized stream associated with different sub-channel identifiers from the first sub-channel identifier; and

filtering the digitized stream to prevent demodulation or decoding of the identified other physical layer payloads associated with the different sub-channel identifiers.

17. The method of claim 16, further comprising:

determining whether the first sub-channel identifier is an identifier associated with a physical layer payload to be filtered from demodulation and decoding.

18. The method of claim 16, further comprising:

demodulating and decoding a second physical layer header portion of the digitized stream to identify a second sub-channel identifier associated with a second physical layer payload;

identifying the physical layer payload associated with the second sub-channel identifier as data to be filtered to prevent demodulation and decoding; and

filtering the digitized stream to exclude from demodulation or decoding the identified physical layer payload associated with the second sub-channel identifier.

19. The method of claim 16, wherein,

the digitized stream includes a plurality of physical layer headers spaced substantially equidistant in time, wherein each of at least a subset of the physical layer headers include one of a plurality of sub-channel identifiers;

and

each one of at least a subset of the plurality of sub-channel identifiers recur at a regular interval in time in the digitized stream.

20. The method of claim 19, further comprising:

determining a search location in the digitized stream for a second header identifier detection analysis based at least in part on the regular interval.

21. The method of claim 19, further comprising:

omitting a header identifier detection analysis for known physical layer header portions based at least in part on the regular interval.

22. The method of claim 16, further comprising:

omitting a header identifier detection analysis based at least in part on a minimum interval between same sub-channel identifiers.

23. The method of claim 16, further comprising:

determining a search location in the digitized stream for a second header identifier detection analysis based at least in part on the first sub-channel identifier.

24. The method of claim 16, further comprising:

receiving data identifying modified spacing between the plurality of physical layer headers; and

changing spacing in time between each header identifier detection analysis to account for the modified spacing.

25. A terminal to receive a wireless signal from a satellite, the terminal comprising:

a receiver unit configured to receive the wireless signal transmitted via the satellite;

a header processing unit, communicatively coupled with the receiver unit, and configured to;

receive a digitized stream comprising a physical layer signal representative of the received wireless signal;

demodulate and decode a first header portion of the digitized stream to thereby identify a first sub-channel identifier for a first physical layer payload associated with the first header portion; and

identify, based on the first sub-channel identifier, other physical layer headers of the digitized stream associated with different sub-channel identifiers from the first sub-channel identifier; and

a filter unit, communicatively coupled with the header detection unit and receiver unit, and configured to exclude from demodulation or decoding each physical layer payload associated with the identified different sub-channel identifiers.