Indoor and outdoor geolocation and time of arrival estimation using wireless signals
A method for estimating a time of arrival of a signal transmitted over a wireless channel, includes receiving the signal by a receiving device; correlating the received signal with a filtered code sequence to create a correlation output, identifying in the correlation output, an observation window associated with a main lobe in the correlation output; and processing the observation window to determine a time of arrival of a first path component in the received signal. The filtered code sequence is formed by incorporating a time of arrival matched filter (TOA-MF) inside predetermined shaped code sequence. The TOA-MF is matched to the predetermined shaped code sequence and is based upon a power delay profile of the wireless channel. The predetermined shaped code sequence is a convolution of a predetermined shaping sequence and a predetermined code sequence.
1. A method for estimating a time of arrival of a signal transmitted over a wireless channel, the method comprising:
receiving the signal by a receiving device;
correlating the received signal with a filtered code sequence to create a correlation output, wherein the filtered code sequence is formed by incorporating a time of arrival matched filter (TOA-MF) inside a predetermined shaped code sequence, wherein the TOA-MF is matched to the predetermined shaped code sequence and is based upon a power delay profile of the wireless channel, wherein the predetermined shaped code sequence is a convolution of a predetermined shaping sequence and a predetermined code sequence;
identifying in the correlation output, an observation window associated with a main lobe in the correlation output;
processing the observation window to determine a time of arrival of a first path component in the received signal.
2. The method of claim 1 wherein the TOA-MF is configured such that the correlation output has reduced early sidelobes due to multipath and a steepened rising edge of a main lobe compared to a hypothetical correlation output using an unfiltered shaped code sequence.
3. The method of claim 1 wherein the TOA-MF is configured such that the correlation output has increased SINR compared to a hypothetical correlation output using an unfiltered shaped code sequence.
4. The method of claim 1 wherein the filtered code sequence is precomputed and stored by the receiving device.
5. The method of claim 1 wherein the filtered code sequence is computed by the receiver.
6. The method of claim 1 wherein the shaping sequence is a square wave or binary offset carrier (BOC) waveform.
7. The method of claim 1 wherein the power delay profile is an expected power delay profile of the wireless channel.
8. The method of claim 1 wherein the power delay profile is a measured power delay profile of the wireless channel.
9. The method of claim 1 wherein the code sequence is a PRN code sequence, CDMA code sequence, GNSS code sequence, or GPS L 1 code sequence.
10. The method of claim 1 wherein identifying an observation window associated with a main lobe comprises identifying a rising edge in the correlation output.
11. The method of claim 1 wherein identifying an observation window associated with a main lobe comprises identifying a falling edge in the correlation output.
12. The method of claim 1 further comprising correlating the observation window with correlator sequences that reduce the effect of colored noise after a hypothetical first path component.
13. The method of claim 12 wherein the correlator sequences correspond to different time shifts of the hypothetical first path component.
14. A method for estimating a time of arrival of a signal transmitted over a wireless channel, the method comprising:
receiving the signal by a receiving device;
correlating the received signal with a filtered code sequence to create a correlation output, wherein the filtered code sequence is formed by incorporating a time of arrival matched filter (TOA-MF) inside a predetermined shaped code sequence, wherein the TOA-MF is matched to the predetermined shaped code sequence and is based upon a power delay profile of the wireless channel, wherein the predetermined shaped code sequence is a convolution of a predetermined shaping sequence and a predetermined code sequence;
identifying in the correlation output, an observation window associated with a main lobe in the correlation output;
processing the observation window to determine a time of arrival of a first path component in the received signal;
wherein the TOA-MF is configured such that the correlation output has reduced early sidelobes due to multipath and a steepened rising edge of a main lobe compared to a hypothetical correlation output using an unfiltered shaped code sequence.
15. A method for estimating a time of arrival of a signal transmitted over a wireless channel, the method comprising:
receiving the signal by a receiving device;
correlating the received signal with a filtered code sequence to create a correlation output, wherein the filtered code sequence is formed by incorporating a time of arrival matched filter (TOA-MF) inside a predetermined shaped code sequence, wherein the TOA-MF is matched to the predetermined shaped code sequence and is based upon a power delay profile of the wireless channel, wherein the predetermined shaped code sequence is a convolution of a predetermined shaping sequence and a predetermined code sequence;
identifying in the correlation output, an observation window associated with a main lobe in the correlation output;
processing the observation window to determine a time of arrival of a first path component in the received signal;
wherein the TOA-MF is configured such that the correlation output has increased SINR compared to a hypothetical correlation output using an unfiltered shaped code sequence.