System and method to enhance ranging resolution for localization of a LoRa sensor or device

1. A method of identifying when a message is received at a control station from at least one device in a network having a plurality of devices, said method comprising the steps of:

receiving at the control station a low bandwidth signal from at least one device;

obtaining a coarse timestamp estimate of when said low bandwidth signal is received by correlating with a pre-programmed signal template and detecting where the correlation is above a preselected value;

generating a higher resolution correlation estimate by phase shifting the pre-programmed signal template and repeating the correlation; and

applying a curve fitting function about the higher resolution correlation estimate to obtain an accurate timestamp when the message was received.

2. The method of claim 1 wherein the curve fitting function comprises an nth order polynomial fit.

3. The method of claim 1 wherein the curve fitting function comprises a Gaussian fit or Poisson fit or linear fit function.

4. The method of claim 1 wherein the curve fitting function generates coefficients to determine a peak of said signal.

5. The method of claim 1 wherein the pre-programmed signal template comprises a reference signal generated or a mathematically modelled signal template.

6. The method of claim 1 wherein the step phase shifting uses a phase shifted reference signal or plurality of phase shifted reference signals to generate the higher resolution correlation.

7. The method of claim 1 wherein the step of phase shifting the pre-programmed signal template and repeating the correlation generates additional points proximate to a correlation peak.

8. The method of claim 1 wherein the step of generating a higher resolution correlation estimate comprises a further step of generating a high resolution correlation curve by using a plurality of phase shifted pre-programmed signal templates.

9. The method of claim 1 wherein the network is a Low Power Wide Area Internet-of-Things (IoT) wireless sensor network.

10. The method of claim 1 comprising using a timestamp of one or more reference devices where a location is known to provide an accurate reference timestamp at a control station, and synchronising the timestamp reference between multiple control stations that receive the low bandwidth signal.

11. The method of claim 1 comprising timestamping two reference signals from at least one reference device received at the control station which have arrived before and after the received message to provide a first reference signal with a known timestamp and a second reference signal with a known timestamp to allow an interpolation of the timestamp of the received message between the two signals.

12. A system of identifying when a message is received at a control station from at least one device in a network having a plurality of devices, comprising:

a receiver at the control station to receive a low bandwidth signal from at least one device;

wherein the control station is configured to:

obtain a coarse timestamp estimate of said low bandwidth signal by correlating with a pre-programmed signal template and detecting where the correlation is above a preselected value;

generate a higher resolution correlation estimate by phase shifting the pre-programmed signal template and repeating the correlation; and

apply a curve fitting function about the higher resolution correlation estimate to obtain an accurate timestamp when the message was received.

13. The system of claim 12 wherein the pre-programmed signal template comprises a reference signal generated or a mathematically modelled signal template.

14. The system of claim 12 wherein the control station is configured to use a phase shifted reference signal or plurality of phase shifted signals to generate a higher resolution correlation.

15. The system of claim 12 wherein the control station is configured for phase shifting the pre-programmed signal template and repeating the correlation to generate additional points proximate to a correlation peak.

16. The system of claim 12 wherein the control station is further configured to generate a high resolution correlation curve by using a plurality of phase shifted pre-programmed signal templates.

17. The system of claim 12 wherein the network is a Low Power Wide Area Internet-of-Things (IoT) wireless sensor network.