1. A method for identifying a source location of an electromagnetic signal having a known waveform, comprising:
positioning a plurality of monitoring stations at different spaced apart geographic locations;
receiving a signal at each of said plurality of monitoring stations from a common source having a source location;
periodically synchronously generating at each monitoring station a replica waveform having a characteristic shape and duration that conforms to said known waveform;
using an autocorrelation process at each of said plurality of monitoring stations to determine a time offset between an occurrence of said known waveform in said signal and an occurrence of said replica waveform at each said monitoring station;
communicating said time offset from each of said plurality of monitoring stations to a central processor; and
identifying the source location of the electromagnetic signal having the known waveform, by the central processor, by use of said time offset from each of said plurality of monitoring stations.
2. The method according to claim 1, further comprising calculating at said central processor a position of said source location using said time offset communicated from each of said plurality of monitoring stations.
3. The method according to claim 2, further comprising calculating at said central processor a time difference of arrival of said signal at each monitoring station based on a difference in said time offsets.
4. The method according to claim 1, further comprising selecting said replica waveform to have a shape and duration that conforms to a waveform produced by a lightning strike.
5. The method according to claim 4, further comprising selecting said replica waveform to have a characteristic shape and duration corresponding to a waveform produced by a cloud-to-ground type lightning strike.
6. The method according to claim 4, further comprising selecting said replica waveform to have a characteristic shape and duration corresponding to a waveform produced by a cloud-to-cloud type lightning strike.
7. The method according to claim 1, further comprising selecting said replica waveform exclusive of a noise component to improve a signal to noise ratio of an autocorrelation result.
8. The method according to claim 1, further comprising assigning a time stamp to each occurrence of said replica waveform.
9. The method according to claim 7, further comprising assigning a common time stamp to said replica waveform at each of said monitoring stations.
10. The method according to claim 1, further comprising synchronizing said generating step at each said monitoring station by using a GPS timing signal.
11. A system for identifying a source location of an electromagnetic signal having a known waveform, comprising:
a plurality of monitoring stations positioned at different spaced apart geographic locations;
radio receiving means provided at each of said plurality of monitoring stations for receiving and demodulating a radio frequency signal from a common source having a source location;
replica generating means provided at each of said plurality of monitoring stations and configured for periodically synchronously generating at each monitoring stations a replica waveform having a characteristic shape and duration that conforms to said known waveform;
an autocorrelation processor provided at each of said plurality of monitoring stations configured for performing an autocorrelation process at each of said plurality of monitoring stations to determine a time offset between an occurrence of said known waveform in said signal, and an occurrence of said replica waveform at each of said monitoring station; and
communication means at each of said plurality of monitoring stations configured for communicating said time offset from each of said plurality of monitoring stations to a central processor, the central processor configured to identify the source location of the electromagnetic signal having the known waveform by use of the time offset.
12. The system according to claim 11, further comprising position calculating means for calculating at said central processor a position of said source location using said time offset communicated from each of said plurality of monitoring stations.
13. The system according to claim 12, wherein said position calculating means calculates a time difference of arrival of said signal at each monitoring station based on a difference in said time offsets.
14. The system according to claim 11, wherein said replica waveform has a shape and duration that conforms to a waveform produced by a lightning strike.
15. The system according to claim 14, wherein said replica waveform has a characteristic shape and duration corresponding to a waveform produced by a cloud-to-ground type lightning strike.
16. The system according to claim 14, wherein said replica waveform has a characteristic shape and duration corresponding to a waveform produced by a cloud-to-cloud type lightning strike.
17. The system according to claim 11, wherein said replica waveform is exclusive of a noise component to improve a signal to noise ratio of an autocorrelation result.
18. The system according to claim 11, further comprising a time stamp generator at each monitoring station configured for assigning a time stamp to each occurrence of said replica waveform.
19. The system according to claim 17, wherein each said time stamp generator is configured to assign a common time stamp to said replica waveform at each of said monitoring stations.
20. The system according to claim 11, further comprising a time synchronization sub-system in each of said monitoring stations configured for synchronizing said time stamp generated by each of said time stamp generators.
21. The system according to claim 11, wherein said time synchronization sub-system is responsive to a GPS timing signal.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of advertising to a remote unit belonging to a user group of remote units, the method comprising:
identifying, by the remote unit, a context associated with a communication sent to or received by the remote unit belonging to the user group of remote units;
determining, on a server, whether the identified context is associated with one or more advertisements by querying correlation data to identify advertisements having context that correlates to the identified context; and
when the identified context is associated with one or more advertisements, transmitting, by the server, the one or more advertisements to at least one remote unit belonging to the user group
wherein transmitting the one or more advertisements comprises transmitting the one or more advertisements to at least one remote unit belonging to the user group that did not send or receive a communication containing the identified context.
2. The method of claim 1 wherein before determining whether the identified context is associated with one or more advertisements, the method comprises:
determining, by the server, whether the identified context is contained in a context index;
when the identified context is not contained in the context index, determining, by the server, whether the identified context is contained in a candidate list; and
when the identified context is not contained in the candidate list, adding, by the server, the identified context to the candidate list.
3. A method of managing contexts in a communication system, the method comprising:
determining, by a server, how frequently a selected context is identified; and
when identification of the selected context is increasing:
determining, by the server, whether frequency of use of the context is equal to a first threshold; and
when frequency of use of the context is equal to the first threshold:
adding, by the server, the selected context to a context index; and
linking, by the server, the selected context to one or more contexts already in the context index.
4. The method of claim 3 further comprising:
determining, by the server, whether frequency of use of the context is equal to a second threshold; and
when frequency of use of the context is equal to the second threshold, alerting, by the server, an advertiser of a new context trend.