Time difference of arrival multilateration method for mobile positioning
A method for location determination in a wireless communications system solves a minimization problem using estimated time-of-arrivals (TOAs) of reference signals [ 108, 110, 112 ] received by a receiving node [ 100 ] from transmitting nodes [ 102, 104, 106 ] and predetermined locations of the transmitting nodes, to produce an estimate of unknown receiving node location and/or an estimate of an unknown time of transmission (t) of the reference signals. The minimization problem is defined in terms of a theoretical system model of time-of-arrivals (TOAs), linearized globally as a function of the unknown receiving node location, the unknown time of transmission (t) of the reference signals, and an additional intermediate variable (u) that defines a non-linear quadratic constraint over position coordinates of the unknown receiving node location and the time of transmission (t) of the reference signals, wherein the minimization problem optimizes the additional intermediate variable (u). The method may also be implemented with the roles of transmitters and receivers interchanged.
1. In a wireless communications system comprising a receiving node and transmitting nodes, wherein the receiving node receives reference signals from the transmitting nodes, a method for location determination comprising:
estimating time-dependent doppler effect errors in timing of the received reference signals;
determining a time-dependent receiving node clock drift model from the estimated doppler effect errors;
correcting TOA measurements of the reference signals using the receiving node clock drift model evaluated at a selected time;
determining by TOT multilateration a receiving node location at the selected time using the corrected TOA measurements.
2. The method of claim 1 wherein the receiving node estimates the doppler effect errors, determines the receiving node clock drift model, and corrects the TOA measurements.
3. The method of claim 1 wherein one or more of the transmitting nodes estimates the doppler effect errors, determines the receiving node clock drift model, and corrects the TOA measurements.
4. The method of claim 1 further comprising reporting from the receiving node to a location server the TOA measurements of reference signals received from one or more reference cells.
5. The method of claim 4 further comprising reporting from the receiving node to a location server the estimated time-dependent doppler effect errors.
6. The method of claim 4 further comprising reporting from the receiving node to a location server clock corrections from the receiving node clock drift model.
7. The method of claim 1 wherein the TOA measurements of the reference signals are regenerated from RSTD measurements.
8. The method of claim 1 wherein the time-dependent receiving node clock drift model is further determined from accumulated intermittent clock corrections.