Method for calculating a location of a remote Unit utilizing observed time difference (OTD) and real time difference (RTD) measurements.

Abstract

Base stations (101, 103, and 105) transmit, and a remote unit (117) receives a radio frequency (RF) location signal. The remote unit (117) then computes an observed-time-difference (OTD) for each base station at particular time t1. Observed differences in received signal times, and are reported to a Mobile Location Center (MLC) (111). Additionally, a Real-Time-Difference receiver (115) receives an RF signal from two or more base stations. The Real Time Differences between the base stations (101, 103, and 105) are computed at a second time. These differences are also reported to the MLC (111). The MLC (111) computes an estimated RTD for the time period t.sub.1 via standard curve fitting algorithms, or simple interpolating algorithms. A corrected Time Difference of Arrival (TDOA) as determined by the remote unit (117) is computed based on the OTD measurements and the estimated RTD measurements.

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