START OF FRAME CORRELATION FOR PHYSICAL LAYER HEADER SYNCHRONIZATION

• US 20100150053A1
• Filed: 06/17/2009
• Published: 06/17/2010
• Est. Priority Date: 12/17/2008
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Thesling, William H., Becker, Donald W., Nimon, Matthew D.
• Granted Patent: US 8,300,571 B2
• Time in Patent Office: Days
• US Class Current: 370/316
• CPC Class Codes: H04B 7/18504 Aircraft used as relay or high altitude atmospheric platform
• CPC Class Codes: H04L 7/0016 correction of synchronization errors

Abstract

Systems, devices, processors, and methods are described which may be used for the reception of a wireless broadband signal at a user terminal from a gateway via a satellite. A wireless signal may include a series of physical layer frames, each frame including a physical layer header and payload. The received signal is digitized and processed using various novel physical layer headers and related techniques to synchronize the physical layer frames and recover data from physical layer headers for purposes of demodulation and decoding.

Claims

1. A terminal to identify a start of frame location for a received wireless signal, the terminal comprising:

a receiver module configured to receive a wireless signal transmitted via a satellite;

an A/D module, communicatively coupled with the receiver module, and configured to process the received wireless signal to generate a digitized stream of symbols comprising a physical layer signal; and

a correlator module, communicatively coupled with the A/D module, and configured to;

calculate a plurality of correlation values over a period for the digitized stream, each of the correlation values comprising a correlation between different portions of the digitized stream of symbols; and

utilize the plurality of correlation values to locate one or more correlation peaks and thereby identify the start of frame location.

2. The terminal of claim 1, wherein the different portions of the digitized stream comprise adjacent code blocks.

3. The terminal of claim 1, wherein the start of frame location is identified by locating a plurality of correlation peaks.

4. The terminal of claim 1, wherein the start of frame location is identified by correlating a first half and a second half of a Walsh code block, for each of three adjacent Walsh code blocks.

5. The terminal of claim 1, wherein the correlation peaks correspond to a physical layer header including signaling information.

6. The terminal of claim 1, wherein the period comprises a duration of the frame.

7. The terminal of claim 1, wherein the correlator module is further configured to:

calculate a plurality of correlation values over a subsequent period for the digitized stream, each of the correlation values comprising a correlation between different portions of the digitized stream of symbols over the subsequent period; and

utilize the plurality of correlation values for the subsequent period to verify the start of frame location.

8. The terminal of claim 1, wherein the correlator module is further configured to:

calculate a plurality of correlation values over a subsequent, second period for the digitized stream, each of the correlation values comprising a correlation between different portions of the digitized stream of symbols over the subsequent, second period;

utilize the plurality of correlation values for the subsequent frame to identify a second, different start of frame location;

calculate a plurality of correlation values over a subsequent, third period for the digitized stream, each of the correlation values comprising a correlation between different portions of the digitized stream of symbols over a third period subsequent to the second period; and

utilize the plurality of correlation values for the third period to verify the second start of frame location.

9. A method of identifying a start of frame location, the method comprising:

receiving a wireless signal;

processing the received wireless signal to generate a digitized stream of symbols comprising a physical layer signal representative of the received wireless signal;

calculating, using a correlator module, a plurality of correlation values over a period for the digitized stream, each of the correlation values comprising a correlation between different portions of the digitized stream of symbols; and

utilizing the plurality of correlation values to locate one or more correlation peaks and thereby identify the start of frame location.

10. The method of claim 9, further comprising:

correlating adjacent code blocks for each of a plurality of different sections of the period, wherein the correlations for the adjacent code blocks are used to calculate the plurality of correlation values.

11. The method of claim 9, wherein utilizing the plurality of correlation values to locate one or more correlation peaks comprises:

locating a plurality of correlation peaks corresponding to the start of frame location.

12. The method of claim 9, further comprising:

setting a minimum threshold for the one or more correlation peaks to verify the start of frame location.

13. The method of claim 9, further comprising:

decoding a physical layer header to identify modulation and coding information, wherein the correlation peaks correspond to a code block comprising the physical layer header.

14. The method of claim 9, further comprising:

calculating a plurality of correlation values over a subsequent period for the digitized stream, each of the correlation values comprising a correlation between different portions of the digitized stream of symbols over the subsequent period; and

utilizing the plurality of correlation values for the subsequent period to verify the start of frame location.

15. A system for transmitting a wireless signal, the system comprising:

a gateway configured to;

generate a code block comprising a physical layer header identifying signaling information, wherein the code block includes one or more sub-blocks comprising symmetrical elements formatted to be useable by a receiving terminal to identify the start of a frame; and

transmit the physical layer header and a set of data appended thereto as a wireless signal; and

a terminal, in wireless communication with the gateway via satellite, and configured to;

receive the transmitted wireless signal and generate a digitized stream of symbols representative of the wireless signal;

calculate a plurality of correlation values over a period for the digitized stream, each of the correlation values comprising a correlation between different portions of the digitized stream of symbols; and

utilize the plurality of correlation values to locate one or more correlation peaks and thereby identify the one or more sub-blocks.

16. The system of claim 15, wherein,

the gateway is further configured to generate three adjacent Walsh code blocks corresponding to the start of frame location, wherein a first half and a second half of each Walsh code block is substantially symmetrical, wherein the Walsh code blocks include signaling information;

and

the terminal is further configured to identify the start of frame by locating a plurality of correlation peaks corresponding to the symmetry of each Walsh code block.

17. A gateway to generate a wireless signal, the gateway comprising:

a receiver module configured to receive a set of data to be transmitted via a satellite destined for a user terminal;

an adaptive coding and modulation module, communicatively coupled with the receiver module, and configured to dynamically assign a modulation and coding format for the set of data based on link conditions for the user terminal;

an encoder module, communicatively coupled with the adaptive coding and modulation module, and configured to generate a code block comprising a physical layer header identifying the assigned modulation and coding format, wherein the code block includes one or more sub-blocks comprising symmetrical elements formatted to be useable by a receiving user terminal to identify a start of frame; and

a transmitter module, communicatively coupled with the encoder module, and configured to transmit the physical layer header and the set of data appended thereto, the set of data transmitted according to the assigned modulation and coding format.

18. The gateway of claim 17, wherein the code block comprises a plurality of the sub-blocks.

19. The gateway of claim 18, wherein each of the sub-blocks comprises a Walsh code block, wherein a first half of each respective Walsh code block is substantially symmetrical to a second half of each respective Walsh code block.

20. The gateway of claim 19, wherein the code block comprises three sub-blocks, wherein two of the sub-blocks include signaling information and the third sub-block includes parity information.