Power setting

1. A method of setting a downlink power for transmissions from a basestation of a cellular communications network, the cellular communications network comprising a group of such basestations, the method comprising:

determining a target value for a signal strength with which the transmissions should be received;

determining a target value for a pathloss, based on measured values for pathlosses between basestations of the group, wherein determining the target value for the pathloss comprises:

obtaining a plurality of measurements for values of pathlosses between basestations of the group; and

setting the target value for the pathloss to be equal to a value at a predetermined percentile of said plurality of measurements; and

calculating the downlink power based on the target value for the signal strength, and on the target value for the pathloss.

2. A method as claimed in claim 1 , wherein the step of obtaining a plurality of measurements for values of pathlosses between basestations of the group comprises obtaining a plurality of measurements for values of pathlosses between basestations that have a neighbour relationship to each other.

3. A method as claimed in claim 1 , wherein the step of setting the target value for the pathloss comprises setting the target value to be greater than a predetermined percentage of said plurality of measurements, and wherein the predetermined percentage is greater than 75%.

4. A method as claimed in claim 1 , comprising setting a predetermined minimum value for the target value for the pathloss, regardless of the measured values for pathlosses between basestations of the group.

5. A method as claimed in claim 1 , wherein the step of determining the target value for the signal strength with which the transmissions should be received comprises:

setting said target value based on the signal strengths with which transmissions from at least one basestation outside the group are received by at least one basestation in the group.

6. A method as claimed in claim 1 , wherein the basestation comprises a femtocell access point, and the group of basestations comprises a group of femtocell access points connected over a local area network.

7. A method of setting a downlink power for transmissions from a basestation of a cellular communications network, the cellular communications network comprising a group of such basestations, the method comprising:

determining a target value for a signal strength with which the transmissions should be received,

wherein determining the target value for the signal strength with which the transmissions should be received comprises setting said target value based on the signal strengths with which transmissions from at least one basestation outside the group are received by at least one basestation in the group;

determining a target value for a pathloss, based on measured values for pathlosses between basestations of the group;

if the basestation or a neighbour of the basestation is able to detect any signals from one or more basestation outside the group:

determining an average signal strength with which transmissions from the or each basestation outside the group are received by the basestation or the neighbour of the basestation; and

setting said target value based on said determined average signal strength; and

calculating the downlink power based on the target value for the signal strength, and on the target value for the pathloss.

8. A method as claimed in claim 7 , further comprising,

if the basestation or a neighbour of the basestation is able to detect any signals from more than one basestation outside the group:

determining for each basestation outside the group an average signal strength with which transmissions from that basestation outside the group are received by the basestation or the neighbour of the basestation;

identifying the basestation outside the group whose transmissions are received with the largest average signal strength by basestations within the group; and

setting said target value based on the signal strength with which transmissions from the identified basestation are received by basestations within the group.

9. A method as claimed in claim 7 , comprising setting a predetermined minimum value for the target value for the signal strength, regardless of the measured signal strengths with which transmissions from at least one basestation outside the group are received.

10. A method as claimed in claim 7 , wherein the basestation comprises a femtocell access point, and the or each basestation outside the group comprises a macro layer basestation.

11. A method as claimed in claim 7 , wherein the basestation comprises a femtocell access point, and the group of basestations comprises a group of femtocell access points connected over a local area network.

12. A basestation, for use in a cellular communications network comprising a group of such basestations, configured to set a downlink power for its transmissions by:

determining a target value for a signal strength with which the transmissions should be received;

determining a target value for a pathloss, based on measured values for pathlosses between basestations of the group, wherein determining the target value for the pathloss comprises:

obtaining a plurality of measurements for values of pathlosses between basestations of the group; and

setting the target value for the pathloss to be equal to a value at a predetermined percentile of said plurality of measurements; and

calculating the downlink power based on the target value for the signal strength, and on the target value for the pathloss.

13. A basestation, for use in a cellular communications network comprising a group of such basestations, configured to set a downlink power for its transmissions by:

determining a target value for a signal strength with which the transmissions should be received wherein determining the target value for the signal strength with which the transmissions should be received comprises setting said target value based on the signal strengths with which transmissions from at least one basestation outside the group are received by at least one basestation in the group;

determining a target value for a pathloss, based on measured values for pathlosses between basestations of the group;

if the basestation or a neighbour of the basestation is able to detect any signals from one or more basestation outside the group:

determining an average signal strength with which transmissions from the or each basestation outside the group are received by the basestation or the neighbour of the basestation; and

setting said target value based on said determined average signal strength; and

calculating the downlink power based on the target value for the signal strength, and on the target value for the pathloss.