DISTINGUISHING AND COMMUNICATING BETWEEN WHITE SPACE DEVICES TRANSMITTING ATSC-COMPATIBLE SIGNALS

• US 20110164186A1
• Filed: 01/05/2010
• Published: 07/07/2011
• Est. Priority Date: 01/05/2010
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Raveendran, Vijayalakshimi, Bergan, Charles A., Zhang, Wenyi, Sadek, Ahmed K., Shellhammer, Stephen J., Jain, Avinash, Aryan, Babak
• Granted Patent: US 8,749,714 B2
• Time in Patent Office: Days
• US Class Current: 348/724
• CPC Class Codes: H04H 20/30 by a single channel
• CPC Class Codes: H04H 20/33 by plural channels
• CPC Class Codes: H04H 60/07 characterised by processes or methods for the generation
• CPC Class Codes: H04L 5/005 of common pilots, i.e. pilots destined for multiple users or terminals
• CPC Class Codes: H04L 5/0062 Avoidance of ingress interference, e.g. ham radio channels
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks

Abstract

White space signals are differentiated from licensed ATSC signals through modification of a waveform of the white space signal. White space signals may be modified by shifting the ATSC-compatible waveform so that the pilot frequency of the white space signal is at a location outside of the frequency range associated with the pilot frequency in a licensed ATSC signal or embedding a watermark signal into said ATSC-like white space signals. White space device transmitters generate the signals with these modifications and white space receivers are equipped to detect whether a pilot exists in the standard licensed pilot frequencies. Based on these differences, white space devices can better operate without interfering with licensed ATSC transmission. Additionally, the modification techniques may be used to embed data in the white space signal that may be used to communicate connection data or networking data to other white space devices.

Claims

1. A method to differentiate an Advanced Television Systems Committee (ATSC)-like white space signal from a licensed ATSC signal, said method comprising:

modifying a waveform of said ATSC-like white space signal, wherein said modifying comprises one of;

shifting said ATSC-like signal so that a frequency of a pilot signal of said ATSC-like signal is shifted outside of at least one frequency range associated with said licensed ATSC signal; and

embedding a watermark signal into said ATSC-like white space signal; and

transmitting said modified waveform.

2. The method of claim 1 wherein said shifting said ATSC-like signal comprises one of:

shifting said ATSC-like signal to shift said frequency of said pilot signal to a middle frequency of a safe frequency range outside of said at least one frequency range;

sweeping said ATSC-like signal to sweep said frequency of said pilot signal between a set of selected frequencies within said safe frequency range; and

varying said ATSC-like signal over time to shift said frequency of said pilot signal over said time between said set of selected frequencies within said safe frequency range.

3. The method of claim 1 further comprising:

quieting a transmitter during sensing operations.

4. The method of claim 2 further comprising:

embedding communication data in said modified waveform, said communication data directed to at least another white space device.

5. The method of claim 4 wherein said embedding comprises one of:

modulating said watermark signal within said modified waveform; and

sweeping said ATSC-like signal such that said frequency of said pilot signal is swept through said selected frequencies at a rate decodable as said communication data.

6. A white space device comprising:

a processor;

a modulator/demodulator (modem) coupled to said processor;

an Advanced Television Systems Committee (ATSC) signal detector coupled to said processor;

a transceiver coupled to said processor;

an antenna array coupled to said transceiver;

a memory coupled to said processor; and

a white space signal generator module stored in said memory, wherein when executed by said processor, said executing white space signal generator configures said white space device;

to modify a waveform of white space signals, wherein said modified waveform includes one of;

a pilot signal frequency shifted outside of at least one frequency range associated with a licensed ATSC signals; and

a watermark signal embedded into said white space signals;

wherein said transceiver transmits said modified waveform over said antenna array.

7. The white space device of claim 6 wherein said modified waveform results in said shifted pilot signal frequency being one of:

shifted to a middle frequency of a safe frequency range outside of said at least one frequency range;

swept to selected frequencies within said safe frequency range; and

varied with time between a set of selected frequencies within said safe frequency range.

8. The white space device of claim 6 further comprising:

a white space information modulation logic module stored on said memory, wherein, when executed by said processor, said executing white space information modulation logic module configures said white space device;

to embed communication data in said modified waveform, said communication data directed to at least another white space device.

9. A computer-readable medium including program code stored thereon, comprising:

program code to modify a waveform of a white space signal, wherein said program code to modify comprises one of;

program code to shift said white space signal so that a frequency of a pilot signal of said white space signal is shifted outside of at least one frequency range associated with a licensed Advanced Television Systems Committee (ATSC) signal; and

program code to embed a watermark signal into the white space signal; and

program code to transmit said modified waveform.

10. The computer-readable medium of claim 9 wherein said shifting said white space signal frequency comprises one of:

shifting said white space signal to shift said frequency of said pilot signal to a middle frequency of a safe frequency range outside of said at least one frequency range;

sweeping said white space signal to sweep said frequency of said pilot signal between a set of selected frequencies within said safe frequency range; and

varying said white space signal over time to shift said frequency of said pilot signal over said time within said safe frequency range.

11. The computer-readable medium of claim 9 further comprising:

quieting a transmitter during sensing operations.

12. The computer-readable medium of claim 10 further comprising:

embedding communication data in said modified waveform, said communication data directed to at least another white space device.

13. The computer-readable medium of claim 12 wherein said embedding comprises one of:

modulating said watermark signal within said modified waveform; and

sweeping said white space signal such that said frequency of said pilot signal is swept through said selected frequencies at a rate decodable as said communication data.

14. A system to differentiate an Advanced Television Systems Committee (ATSC)-like white space signal from a licensed ATSC signal, said system comprising:

means for modifying a waveform of said ATSC-like white space signal, wherein said means for modifying comprises one of;

means for shifting said ATSC-like signal so that a frequency of a pilot signal of said ATSC-like signal is shifted outside of at least one frequency range associated with said licensed ATSC signal; and

means for embedding a watermark signal into said ATSC-like white space signal; and

means for transmitting said modified waveform.

15. The system of claim 14 wherein said means for shifting said ATSC-like signal frequency comprises one of:

means for shifting said ATSC-like signal to shift said frequency of said pilot signal to a middle frequency of a safe frequency range outside of said at least one frequency range;

means for sweeping said ATSC-like signal to sweep said frequency of said pilot signal between a set of selected frequencies within said safe frequency range; and

means for varying said ATSC-like signal over time to shift said frequency of said pilot signal over said time between said set of selected frequencies within said safe frequency range.

16. The system of claim 15 further comprising:

means for embedding communication data in said modified waveform, said communication data directed to at least another white space device.

17. A method for distinguishing between a white space signal and an licensed Advanced Television Systems Committee (ATSC) signal, said method comprising:

detecting a modified waveform in an ATSC-compatible signal, wherein said modification comprises one of;

a pilot signal frequency outside at least one frequency range associated with said licensed ATSC signal;

a watermark signal embedded into said ATSC-compatible signal, wherein said watermark signal is indicative of said white space signal; and

at least one quiet period within said ATSC-compatible signal; and

in response to detecting said modified waveform, determining said ATSC-compatible signal is said white space signal.

18. The method of claim 17, wherein said detecting said at least one quiet period comprises:

analyzing a signal power of said ATSC-compatible signal;

responsive to said signal power exceeding a predetermined threshold;

measuring a signal strength of said ATSC-compatible signal;

detecting at least one drop in signal strength over said measurement;

comparing said at least one drop to a quiet time period; and

responsive to said at least one drop matching said quiet time period within an error window, determining said ATSC-compatible signal is said white space signal;

responsive to said signal power failing to exceed said predetermined threshold;

calculating a power spectral density (PSD) of said ATSC-compatible signal;

detecting a pilot signal of said ATSC-compatible signal in said PSD;

identifying at least one pilot drop of said pilot signal in said PSD;

comparing said at least one pilot drop to said quite time period; and

responsive to said at least one drop matching said quiet time period within said error window, determining said ATSC-compatible signal is said white space signal.

19. A white space device comprising:

a processor;

a modulator/demodulator (modem) coupled to said processor;

an Advanced Television Systems Committee (ATSC) signal detector coupled to said processor;

a transceiver coupled to said processor;

an antenna array coupled to said transceiver;

a memory coupled to said processor; and

a signal analyzer module stored in said memory, wherein when executed by said processor, said executing signal analyzer module configures said white space device;

to detect a modified waveform in an ATSC-compatible signal, wherein a modification in said modified waveform comprises one of;

a pilot signal frequency outside at least one frequency range associated with a licensed ATSC signal;

a watermark signal embedded into said ATSC-compatible signal, wherein said watermark signal is indicative of a white space signal; and

at least one quiet period within said ATSC-compatible signal; and

to determine said ATSC-compatible signal is said white space signal in response to detection of said modified waveform.

20. The white space device of claim 19 wherein when detecting said at least one quite period, said executing signal analyzer module further configures said white space device:

to analyze a signal power of said ATSC-compatible signal;

responsive to said signal power exceeding a predetermined threshold;

to measure a signal strength of said ATSC-compatible signal;

to detect at least one drop in signal strength over said measurement;

to compare said at least one drop to a quiet time period; and

to determine said ATSC-compatible signal is said white space signal responsive to said at least one drop matching said quiet time period within an error window;

responsive to said signal power failing to exceed said predetermined threshold;

to calculate a power spectral density (PSD) of said ATSC-compatible signal;

to detect a pilot signal of said ATSC-compatible signal in said PSD;

to identify at least one pilot drop of said pilot signal in said PSD;

to compare said at least one pilot drop to said quite time period; and

to determine said ATSC-compatible signal is said white space signal responsive to said at least one drop matching said quiet time period within said error window.

21. A computer-readable medium including program code stored thereon, comprising:

program code to detect a modified waveform in an Advanced Television Systems Committee (ATSC)-compatible signal, wherein said modification comprises one of;

a pilot signal frequency outside at least one frequency range associated with a licensed ATSC signal;

a watermark signal embedded into said ATSC-compatible signal, wherein said watermark signal is indicative of a white space signal; and

at least one quiet period within said ATSC-compatible signal; and

program code, executable in response to detecting said modified waveform, to determine said ATSC-compatible signal is said white space signal.

22. The computer-readable medium of claim 21, wherein said program code to detect said at least one quiet period comprises:

program code to analyzing a signal power of said Advanced Television Systems Committee (ATSC)-compatible signal;

program code, executable responsive to said signal power exceeding a predetermined threshold;

to measure a signal strength of said ATSC-compatible signal;

to detect at least one drop in signal strength over said measurement;

to compare said at least one drop to a quiet time period; and

program code, executable responsive to said at least one drop matching said quiet time period within an error window, to determine said ATSC-compatible signal is said white space signal;

program code, executable responsive to said signal power failing to exceed said predetermined threshold;

to calculate a power spectral density (PSD) of said ATSC-compatible signal;

to detect a pilot signal of said ATSC-compatible signal in said PSD;

to identify at least one pilot drop of said pilot signal in said PSD;

to compare said at least one pilot drop to said quite time period; and

program code, executable responsive to said at least one drop matching said quiet time period within said error window, to determine said ATSC-compatible signal is said white space signal.

23. A system for distinguishing between a white space signal and a licensed Advanced Television Systems Committee (ATSC) signal, said system comprising:

means for detecting a modified waveform in an ATSC-compatible signal, wherein said modification comprises one of;

a pilot signal frequency outside at least one frequency range associated with said licensed ATSC signal;

a watermark signal embedded into said ATSC-compatible signal, wherein said watermark signal is indicative of said white space signal; and

at least one quiet period within said ATSC-compatible signal; and

means, executable in response to detecting said modified waveform, for determining said ATSC-compatible signal is said white space signal.

24. A method for establishing communication between at least two white space devices, said method comprising:

receiving a white space signal at a first white space device;

detecting modulation of a watermark signal embedded in said white space signal;

demodulating said watermark signal into communication data; and

establishing communication with a second white space device based on said communication data.

25. The method of claim 24 wherein said watermark signal is one of:

a pseudo noise (PN) sequence; and

a set of embedded tones.

26. A method for establishing communication between at least two white space devices, said method comprising:

receiving an Advanced Television Systems Committee (ATSC)-like white space signal at a first white space device;

searching for two tones embedded in said ATSC-like white space signal;

detecting an active one of said two tones;

decoding said ATSC-like white space signal into a prefix free code based on said detected active one of said two tones; and

establishing communication with a second white space device using said prefix free code.