Wide area positioning system
Systems and methods are described for determining position of a receiver. The positioning system comprises a transmitter network including transmitters that broadcast positioning signals. The positioning system comprises a remote receiver that acquires and tracks the positioning signals and/or satellite signals. The satellite signals are signals of a satellite-based positioning system. A first mode of the remote receiver uses terminal-based positioning in which the remote receiver computes a position using the positioning signals and/or the satellite signals. The positioning system comprises a server coupled to the remote receiver. A second operating mode of the remote receiver comprises network-based positioning in which the server computes a position of the remote receiver from the positioning signals and/or satellite signals, where the remote receiver receives and transfers to the server the positioning signals and/or satellite signals.
1. A method for transmitting positioning signals that are used by a receiver to compute an estimated position of the receiver, the method comprising:
transmitting, from each transmitter in a set of transmitters of a transmitter network, a positioning signal that includes a pseudo random number (PRN) sequence;
determining a timing correction at each of the transmitters in the set of transmitters; and
providing the timing corrections to the receiver,
wherein the set of transmitters are synchronized using a timing reference.
2. The method of claim 1 , wherein the method comprises:
selecting a first PRN sequence to include in a first positioning signal,
wherein the first PRN sequence is selected instead of another PRN sequence when suppression of side-lobes relative to a peak of an autocorrelation function of the first PRN sequence is more than suppression of other side-lobes relative to another peak of an autocorrelation function of the other PRN sequence.
3. The method of claim 1 , wherein each transmitter in the set of transmitters transmits a different positioning signal in a different time slot than other transmitters in the set of transmitters.
4. The method of claim 1 , wherein each transmitter in the set of transmitters transmits a different positioning signal that includes a different PRN sequence, and wherein the different positioning signals are transmitted in the same time slot.
5. The method of claim 4 , wherein a carrier signal of each transmitter in the set of transmitters is offset in frequency from the carrier signals of the other transmitters in the set of transmitters.
6. The method of claim 1 , wherein the method further comprises:
transmitting assistance data from each of the transmitters in the set of transmitters,
wherein the assistance data comprises at least one of network time at a rising edge of a pulse of a waveform, network time at a falling edge of a pulse of a waveform, geocode data of the transmitters in the set of transmitters, geocode data of transmitters adjacent to the transmitters in the set of transmitters, index of a sequence used by at least one transmitter in proximity of the transmitters in the set of transmitters, clock timing corrections for at least one transmitter in the set of transmitters, local atmospheric corrections, a relationship of network timing to GNSS time, or an indication of local environment to aid the receiver in pseudorange resolution.
7. The method of claim 1 , wherein the method comprises:
transmitting a timing difference between transmissions from different transmitters in the set of transmitters.
8. The method of claim 1 , wherein the method comprises:
receiving, at a reference receiver, a signal waveform from each of the transmitters in a set of transmitters; and
time-tagging pseudorange measurements for each of the transmitters in the set of transmitters using the signal waveform received from that transmitter.
9. The method of claim 8 , wherein the method comprises:
receiving differential corrections from the reference receiver; and
using the differential corrections to generate timing difference corrections for the set of transmitters.
10. The method of claim 1 , wherein the method comprises:
generating timing difference corrections using a timing correction and pseudorange measurements corresponding to each of the transmitters in the set of transmitters.
11. The method of claim 10 , wherein the method comprises:
applying the timing difference corrections to the positioning signals.
12. The method of claim 1 , wherein the method comprises:
using time transfer with a GNSS satellite in common view of the set of transmitters to generate timing difference corrections for the set of transmitters.
13. The method of claim 1 , wherein the method comprises:
using a different GNSS receiver as a local time reference for each of the transmitters in the set of transmitters; and
deriving, at each of the different GNSS receivers, a timing pulse aligned to GNSS time using at least one common GNSS satellite.
14. The method of claim 1 , wherein each of the transmitters in the set of transmitters transmits an offset relative to GNSS time.
15. The method of claim 1 , wherein the positioning signals include timing synchronization and correction information.
16. The method of claim 1 , wherein each of the transmitters in the set of transmitters transmits a data stream of embedded assistance data associated with a GNSS system.
17. The method of claim 1 ,
wherein the set of transmitters are positioned so that positioning signals can be received from at least three transmitters in the set of transmitters at different locations in the transmitter network such that a geometric dilution of precision for each of the different locations is less than a predetermined threshold,
wherein the different locations include an edge of the transmitter network and other locations,
wherein each transmitter in the set of transmitters is at a position determined by minimizing a function that is a volume integration of a square of geometric dilution of precision over a coverage volume,
wherein the volume integration is with respect to possible coordinates of a location of the receiver within the transmitter network, and
wherein the minimizing of the function is with respect to n transmitter position coordinates in a given coverage area in the coverage volume.
18. The method of claim 17 , wherein the function is weighted according to performance quality of a coverage region.
19. One or more non-transitory computer-readable media embodying program instructions that, when executed by one or more processors, cause the one or more processors to implement a method for transmitting positioning signals that are used by a receiver to compute an estimated position of the receiver, the method comprising:
transmitting, from each transmitter in a set of transmitters of a transmitter network, a positioning signal that includes a pseudo random number (PRN) sequence;
determining a timing correction at each of the transmitters in the set of transmitters; and
providing the timing corrections to the receiver,
wherein the set of transmitters are synchronized using a timing reference.
20. The non-transitory computer-readable media of claim 19 , wherein the method comprises:
selecting a first PRN sequence to include in a first positioning signal,
wherein the first PRN sequence is selected instead of another PRN sequence when suppression of side-lobes relative to a peak of an autocorrelation function of the first PRN sequence is more than suppression of the other side-lobes relative to another peak of an autocorrelation function of the other PRN sequence.
21. The non-transitory computer-readable media of claim 19 , wherein each transmitter in the set of transmitters transmits a different positioning signal in a different time slot than other transmitters in the set of transmitters.
22. The non-transitory computer-readable media of claim 19 , wherein each transmitter in the set of transmitters transmits a different positioning signal that includes a different PRN sequence, and wherein the different positioning signals are transmitted in the same time slot.
23. The non-transitory computer-readable media of claim 22 , wherein a carrier signal of each transmitter in the set of transmitters is offset in frequency from the carrier signals of the other transmitters in the set of transmitters.
24. The non-transitory computer-readable media of claim 19 , wherein the method further comprises:
transmitting assistance data from each of the transmitters in the set of transmitters,
wherein the assistance data comprises at least one of network time at a rising edge of a pulse of a waveform, network time at a falling edge of a pulse of a waveform, geocode data of the transmitters in the set of transmitters, geocode data of transmitters adjacent to the transmitters in the set of transmitters, index of a sequence used by at least one transmitter in proximity of the transmitters in the set of transmitters, clock timing corrections for at least one transmitter in the set of transmitters, local atmospheric corrections, a relationship of network timing to GNSS time, or an indication of local environment to aid the receiver in pseudorange resolution.
25. The non-transitory computer-readable media of claim 19 , wherein the method comprises:
transmitting a timing difference between transmissions from different transmitters in the set of transmitters.
26. The non-transitory computer-readable media of claim 19 , wherein the method comprises:
receiving, at a reference receiver, a signal waveform from each of the transmitters in a set of transmitters; and
time-tagging pseudorange measurements for each of the transmitters in the set of transmitters using the signal waveform received from that transmitter.
27. The non-transitory computer-readable media of claim 26 , wherein the method comprises:
receiving differential corrections from the reference receiver; and
using the differential corrections to generate timing difference corrections for the set of transmitters.
28. The non-transitory computer-readable media of claim 19 , wherein the method comprises:
generating timing difference corrections using a timing correction and pseudorange measurements corresponding to each of the transmitters in the set of transmitters.
29. The non-transitory computer-readable media of claim 28 , wherein the method comprises:
applying the timing difference corrections to the positioning signals.
30. The non-transitory computer-readable media of claim 19 , wherein the method comprises:
using time transfer with a GNSS satellite in common view of the set of transmitters to generate timing difference corrections for the set of transmitters.
31. The non-transitory computer-readable media of claim 19 , wherein the method comprises:
using a different GNSS receiver as a local time reference for each of the transmitters in the set of transmitters; and
deriving, at each of the different GNSS receivers, a timing pulse aligned to GNSS time using at least one common GNSS satellite.
32. The non-transitory computer-readable media of claim 19 wherein each of the transmitters in the set of transmitters transmits an offset relative to GNSS time.
33. The non-transitory computer-readable media of claim 19 , wherein the positioning signals include timing synchronization and correction information.
34. The non-transitory computer-readable media of claim 19 , wherein each of the transmitters in the set of transmitters transmits a data stream of embedded assistance data associated with a GNSS system.
35. The non-transitory computer-readable media of claim 19 ,
wherein the set of transmitters are positioned so that positioning signals can be received from at least three transmitters in the set of transmitters at different locations in the transmitter network such that a geometric dilution of precision for each of the different locations is less than a predetermined threshold,
wherein the different locations include an edge of the transmitter network and other locations,
wherein each transmitter in the set of transmitters is at a position determined by minimizing a function that is a volume integration of a square of geometric dilution of precision over a coverage volume,
wherein the volume integration is with respect to possible coordinates of a location of the receiver within the transmitter network, and
wherein the minimizing of the function is with respect to n transmitter position coordinates in a given coverage area in the coverage volume.
36. The non-transitory computer-readable media of claim 35 , wherein the function is weighted according to performance quality of a coverage region.
37. A transmitter network for transmitting positioning signals that are used by a receiver to compute an estimated position of the receiver, the transmitter network comprising:
a set of transmitters,
wherein the set of transmitters are synchronized using a timing reference, and
wherein each transmitter in the set of transmitters is configured to:
transmit a positioning signal that includes a pseudo random number (PRN) sequence;
determine a timing correction at each of the transmitters in the set of transmitters; and
provide the timing corrections to the receiver.