Improvements in radio positioning systems

摘要

The invention provides a method of estimating the time offsets between signals transmitted by plural transmitters of a communications network and received by a receiver attached to a terminal. In the method a section of a representation of the signals from the plural transmitters received by the receiver at the terminal (a "terminal section") is created as are a first section of a representation of the signal transmitted by a first of said transmitters and a second section of a representation of the signal transmitted by a second of said transmitters. Each of the first and second sections overlaps in time with the terminal section. Using the first section, the second section and a set of signal parameters, including initial estimates of the time offsets between the first section and the terminal section and between the second section and the terminal section, a model of a section of a representation of the composite signal received by the receiver from the first and second transmitters is created. Thereafter, the model is compared with the terminal section and the set of signal parameters including the time offset estimates is refined to minimise the difference between the model and the terminal section. The time offsets in the refined parameter set used to minimise the difference between said model and the terminal section, are adopted as the estimated time offsets between the first section and the terminal section and between the second section and the terminal section. <IMAGE>