Measuring signal quality

1. A method of determining a signal quality parameter for a signal received by a device operating in a wireless communications network, wherein the device receives a signal comprising a plurality of physical channels, said method including:

determining two signal parameters, on the basis of measurements made on at least one of said plurality of physical channels;

determining a calibration parameter indicative of variations common to the signal parameters; and

determining the signal quality parameter on the basis of said two signal parameters and said calibration parameter,

wherein said two parameters are an interference signal code power (ISCP) and a received signal code power (RSCP),

wherein said calibration parameter is the RSCP determined from a different channel of said plurality of physical channels to said two signal parameters, and

in said step of determining the signal quality parameter, dividing both the RSCP and the ISCP by the calibration parameter to remove most of the common variation, smoothing the ISCP, and calculating the signal quality parameter by using the following expression:

S

⁢

⁢

I

⁢

⁢

R

=

R

⁢

⁢

S

⁢

⁢

C

⁢

⁢

P

t

C

t

Smoothed_ISCP

t

where SIR is the signal quality parameter, Smoothed ISCP t is the smoothed ISCP, and C t is the calibration parameter.

2. A method of determining a signal quality parameter as claimed in claim 1 wherein the method includes:

measuring the RSCP and the ISCP on one of said plurality of physical channels.

3. A method of determining a signal quality parameter as claimed in claim 1 wherein the method includes:

measuring the RSCP on one of said plurality of physical channels and measuring the ISCP on a second one of said plurality of physical channels.

4. A method of determining a signal quality parameter as claimed in claim 1 , wherein the calibration parameter is determined on the basis of a measurement of the RSCP on a channel of said plurality of channels which is not used for the measurement of the RSCP and the ISCP.

5. A method of determining a signal quality parameter as claimed claim 1 , which is used to determine the signal to interference ratio (SIR) of a downlink of a wideband CDMA network.

6. A method of determining a signal quality parameter as claimed in claim 4 , which further includes:

measuring the ISCP from a dedicated physical channel (DPCH);

measuring the RSCP from the DPCH; and

determining said calibration parameter from a measurement on a common pilot channel (CPICH) of the downlink.

7. A method of determining a signal quality parameter as claimed in claim 6 , wherein the calibration parameter is the RSCP measured from the CPICH.

8. A mobile terminal configured to receive a signal comprising a plurality of physical channels from a wireless communications network, said mobile terminal being further configured to determine a signal quality parameter for the received signal using the method as recited in claim 1 .

9. A method of determining a signal quality parameter as claimed in claim 2 , wherein the calibration parameter is determined on the basis of a measurement of the RSCP on a channel of said plurality of channels which is not used for the measurement of the RSCP and the ISCP.

10. A method of determining a signal quality parameter as claimed in claim 3 , wherein the calibration parameter is determined on the basis of a measurement of the RSCP on a channel of said plurality of channels which is not used for the measurement of the RSCP and the ISCP.

11. A method of determining a signal quality parameter as claimed in claim 2 , which is used to determine the signal to interference ratio (SIR) of a downlink of a wideband CDMA network.

12. A method of determining a signal quality parameter as claimed in claim 3 , which is used to determine the signal to interference ratio (SIR) of a downlink of a wideband CDMA network.

13. A method of determining a signal quality parameter as claimed in claim 4 , which is used to determine the signal to interference ratio (SIR) of a downlink of a wideband CDMA network.

14. A mobile terminal configured to receive a signal comprising a plurality of physical channels from a wireless communications network, said mobile terminal being further configured to determine a signal quality parameter for the received signal using the method as recited in claim 2 .

15. A mobile terminal configured to receive a signal comprising a plurality of physical channels from a wireless communications network, said mobile terminal being further configured to determine a signal quality parameter for the received signal using the method as recited in claim 3 .

16. A mobile terminal configured to receive a signal comprising a plurality of physical channels from a wireless communications network, said mobile terminal being further configured to determine a signal quality parameter for the received signal using the method as recited in claim 4 .

17. A mobile terminal configured to receive a signal comprising a plurality of physical channels from a wireless communications network, said mobile terminal being further configured to determine a signal quality parameter for the received signal using the method as recited in claim 5 .

18. A mobile terminal configured to receive a signal comprising a plurality of physical channels from a wireless communications network, said mobile terminal being further configured to determine a signal quality parameter for the received signal using the method as recited in claim 6 .

19. A mobile terminal configured to receive a signal comprising a plurality of physical channels from a wireless communications network, said mobile terminal being further configured to determine a signal quality parameter for the received signal using the method as recited in claim 7 .