1. A system for determining the location of a mobile radio station relative to radio base stations, comprising

2. Apparatus for estimating the time of arrival of a radio signal transmitted between a fixed radio station and a mobile radio station comprising

3. A system for determining the location of a mobile radio station relative to radio base stations, comprising a mobile radio station equipped to transmit a signal, a plurality of radio base stations, each equipped to receive the signal transmitted by the mobile radio station and having means for estimating the time of arrival of the received signal, and means for computing the location of the mobile radio station from the estimated time of arrival of the signal received at each radio base station; wherein the means for estimating the time of arrival comprises the apparatus of claim 2.

4. A system as claimed in claim 1, characterised in that the means for making the first estimate of time of arrival comprises means (

### 14) for multiplying a Fast Fourier Transform of a received signal by a Fast Fourier Transform of a replica of a transmitted signal and determining an Inverse Fast Fourier Transform of the resulting product.

5. A system as claimed in claim 1, characterised in that the means for making the second estimate of time of arrival comprises means (

### 16) for performing the time domain correlation of a received signal with a replica of a transmitted signal.

6. A method of determining the location of a mobile radio station relative to radio base stations, comprising

7. A method of determining the location of a mobile radio station relative to radio base stations, comprising

8. A method as claimed in claim 6, characterised in that the first stage of estimation comprises multiplying (

### 14) a Fast Fourier Transform of a received signal by a Fast Fourier Transform of a replica of a transmitted signal and determining an Inverse Fast Fourier Transform of the resulting product.

9. A method as claimed in claim 6, characterised in that the second stage of estimation comprises performing a time domain correlation (

### 16) of a received signal with a replica of a transmitted signal.

10. Apparatus as claimed in claim 2, characterised in that the first means for making a first estimate of time of arrival comprises means for multiplying a Fast Fourier Transform of a received signal by a Fast Fourier Transform of a replica of a transmitted signal and determining an Inverse Fast Fourier Transform of the resulting product.

11. Apparatus for estimating the time of arrival of a radio signal transmitted between a fixed radio station and a mobile radio station comprising

12. Apparatus sa claimed in claim 11, characterised in that the means for performing the time domain correlation comprises an NCO.

13. A system as claimed in claim 3, characterised in that the means for making the first estimate of time of arrival comprises means for multiplying a Fast Fourier Transform of a received signal by a Fast Fourier Transform of a replica of a transmitted signal and determining an Inverse Fast Fourier Transform of the resulting product.

14. A system for determining the location of a mobile radio station relative to radio base stations, comprising

15. A method as claimed in claim 7, characterised in that the first stage of estimation comprises multiplying a Fast Fourier Transform of a received signal by a Fast Fourier Transform of a replica of a transmitted signal and determining an Inverse Fast Fourier Transform of the resulting product.

16. A method of determining the location of a mobile radio station relative to radio base stations, comprising

17. The apparatus of claim 2, wherein the second means uses a time domain calculation.

18. The system of claim 1, wherein the first means uses a frequency domain calculation.

19. The system of claim 18, wherein the second means uses a time domain calculation.

20. The method of claim 6, wherein the first stage uses a frequency domain calculation.

21. The method of claim 18, wherein the second stage uses a time domain calculation.

22. The method of claim 7, wherein the second stage uses a time domain calculation.