Basestation for cellular communication system

1. A method for controlling operation of an oscillator in a basestation of a cellular communications system, the method comprising:

in said basestation, identifying at least one other basestation of the cellular communications system, and requesting a mobile device to report a first measurement of a time difference between frames transmitted from the basestation and the identified other basestation;

in said mobile device, making said first measurement, and reporting to said basestation;

in said basestation, requesting the mobile device to report a second measurement of the time difference between frames transmitted from the basestation and the identified other basestation;

in said mobile device, making said second measurement, and reporting to said basestation;

in said basestation, based on said reported first and second measurements, estimating a frequency offset between a signal generated within said basestation and a corresponding signal generated within said other basestation; and

applying a frequency control signal to said oscillator based on said estimated frequency offset.

2. A method as claimed in claim 1 , wherein the step of estimating the frequency offset comprises:

determining a difference between the reported first and second measurements;

determining from said difference, an amount of difference that accumulates in a predetermined time period; and

estimating said frequency offset therefrom.

3. A method for controlling operation of an oscillator in a basestation of a cellular communications system, the method comprising:

requesting a mobile device to report a first measurement of a System Frame Number difference, representing a time difference between frames transmitted from the basestation and another basestation;

in said mobile device, making the first measurement of the System Frame Number difference, and reporting to said basestation;

requesting the mobile device to report a second measurement of the System Frame Number difference, representing the time difference between frames transmitted from the basestation and the other basestation;

in said mobile device, making the second measurement of the System Frame Number difference, and reporting to said basestation;

based on said reported first and second measurements, estimating a frequency offset between a signal generated within said basestation and a corresponding signal generated within said other basestation; and

controlling operation of said oscillator based on said estimated frequency offset.

4. A method for controlling operation of an oscillator in a basestation of a cellular communications system, the method comprising:

in said basestation, identifying a plurality of other basestations of the cellular communications system, and requesting a mobile device to report respective first measurements of a time difference between frames transmitted from the basestation and each identified other basestation;

in said mobile device, making said first measurements, and reporting to said basestation;

in said basestation, requesting the mobile device to report a second measurement of the time difference between frames transmitted from the basestation and the identified other basestations;

in said mobile device, making said second measurements, and reporting to said basestation;

in said basestation, based on said reported first and second measurements, estimating a frequency offset between a signal generated within said basestation and a corresponding signal generated within said other basestation; and

applying a frequency control signal to said oscillator based on said estimated frequency offset.

5. A method for controlling operation of an oscillator in a basestation of a cellular communications system, the method comprising:

identifying at least one other basestation of the cellular communications system;

requesting a mobile device to report a first measurement of a time difference between frames transmitted from the basestation and the identified other basestation;

receiving said first measurement from said mobile device;

requesting the mobile device to report a second measurement of the time difference between frames transmitted from the basestation and the identified other basestation;

receiving said second measurement from said mobile device;

based on said received first and second measurements, estimating a frequency offset between a signal generated within said basestation and a corresponding signal generated within said identified other basestation; and

applying a frequency control signal to said oscillator based on said estimated frequency offset.

6. A method as claimed in claim 5 , wherein the step of estimating the frequency offset comprises:

determining a difference between the reported first and second measurements;

determining from said difference, an amount of difference that accumulates in a predetermined time period; and

estimating said frequency offset therefrom.

7. A method for controlling operation of an oscillator in a basestation of a cellular communications system, the method comprising:

requesting a mobile device to report a first measurement of a System Frame Number difference, representing a time difference between frames transmitted from the basestation and another basestation;

receiving from the mobile device the first measurement of the System Frame Number difference;

requesting the mobile device to report a second measurement of the System Frame Number difference, representing the time difference between frames transmitted from the basestation and the other basestation;

receiving from the mobile device the second measurement of the System Frame Number difference;

based on said received first and second measurements, estimating a frequency offset between a signal generated within said basestation and a corresponding signal generated within said other basestation; and

controlling operation of said oscillator based on said estimated frequency offset.

8. A method for controlling operation of an oscillator in a basestation of a cellular communications system, the method comprising:

in said basestation, identifying a plurality of other basestations of the cellular communications system, and requesting a mobile device to report respective first measurements of a time difference between frames transmitted from the basestation and each identified other basestation;

receiving from said mobile device said first measurements;

in said basestation, requesting the mobile device to report a second measurement of the time difference between frames transmitted from the basestation and the identified other basestations;

receiving from said mobile device said second measurements;

in said basestation, based on said received first and second measurements, estimating a frequency offset between a signal generated within said basestation and a corresponding signal generated within said other basestation; and

applying a frequency control signal to said oscillator based on said estimated frequency offset.

9. A method, comprising:

in a mobile device, receiving a request from a first basestation to report a first measurement representing a time difference between frames transmitted from the first basestation and a second basestation;

in said mobile device, making the first measurement, and reporting to said first basestation;

in said mobile device, receiving a request from the first basestation to report a second measurement representing the time difference between frames transmitted from the first basestation and the second basestation;

in said mobile device, making the second measurement, and reporting to said first basestation,

wherein based on said reported first and second measurements, the first basestation estimates a frequency offset between a signal generated within said first basestation and a corresponding signal generated within said second basestation, and

wherein the first basestation applies a frequency control signal to an oscillator in the basestation based on said estimated frequency offset.

10. A basestation in a cellular communications network configured to control operation of an oscillator in the basestation, the basestation comprising:

memory, and

one or more processors, the one or more processors configured to:

identify at least one other basestation of the cellular communications system, and request a mobile device to report a first measurement of a time difference between frames transmitted from the basestation and the identified other basestation;

receive from said mobile device said first measurement;

request the mobile device to report a second measurement of the time difference between frames transmitted from the basestation and the identified other basestation;

receive from said mobile device said second measurement;

based on said received first and second measurements, estimate a frequency offset between a signal generated within said basestation and a corresponding signal generated within said other basestation; and

apply a frequency control signal to said oscillator based on said estimated frequency offset.

11. A cellular wireless communications network, comprising:

one or more basestations, the one or more basestations configured to:

identify at least one other basestation of the cellular communications system, and request a mobile device to report a first measurement of a time difference between frames transmitted from the basestation and the identified other basestation;

receive from said mobile device said first measurement;

request the mobile device to report a second measurement of the time difference between frames transmitted from the basestation and the identified other basestation;

receive from said mobile device said second measurement;

based on said received first and second measurements, estimate a frequency offset between a signal generated within said basestation and a corresponding signal generated within said other basestation; and

apply a frequency control signal to said oscillator based on said estimated frequency offset; and

one or more mobile devices, the one or more mobile devices configured to:

make said first measurement, and report to said basestation;

make said second measurement, and report to said basestation.