Creating neighbour cell lists
A neighbor cell list is formed, for use in a basestation of a cellular communications network. For each of a plurality of neighbor cells, a value of a first component is assigned, depending on whether or not the basestation can detect signals transmitted from said neighbor cell. A value of a second component is assigned, depending on a history of successful or unsuccessful handover attempts to said neighbor cell. The values of the first and second components are combined to form a weighting parameter, for use in determining a handover priority to be given to said neighbor cell in the neighbor cell list.
1. A method of operation of a femtocell access point in a cellular communications network, the method comprising:
receiving information about channel numbers, scrambling codes and unique cell identifiers used by femtocell access points in the network;
receiving signals broadcast by other femtocell access points in the network whose transmissions can be detected;
extracting from said received signals information relating to the channel numbers and scrambling codes used by the other femtocell access points whose transmissions can be detected;
upon detecting signals from first and second other femtocell access points that are using the same channel number and scrambling code as each other, the method further comprising:
using different timing offsets of the signals from the first and second other femtocell access points to distinguish between said signals;
extracting from said signals from the first and second other femtocell access points information relating to the unique cell identifiers used by the first and second other femtocell access points; and
including at least the first and second other femtocell access points in a neighbour cell list of said femtocell access point.
2. A method as claimed in claim 1 , comprising applying time filters around signals detected from the first and second other femtocell access points in order to distinguish between said signals.
3. A femtocell access point for a cellular communications network, the femtocell access point being configured to:
receive information about channel numbers, scrambling codes and unique cell identifiers used by femtocell access points in the network;
receive signals broadcast by other femtocell access points in the network whose transmissions can be detected;
extract from said received signals information relating to the channel numbers and scrambling codes used by the other femtocell access points whose transmissions can be detected;
upon detecting signals from first and second other femtocell access points that are using the same channel number and scrambling code as each other, the femtocell access point being further configured to:
use different timing offsets of the signals from the first and second other femtocell access points to distinguish between said signals;
extract from said signals from the first and second other femtocell access points information relating to the unique cell identifiers used by the first and second other femtocell access points; and
include at least the first and second other femtocell access points in a neighbour cell list of said femtocell access point.
4. A femtocell access point as claimed in claim 3 , the femtocell access point being further configured to apply time filters around signals detected from the first and second other femtocell access points in order to distinguish between said signals.
5. A network of femtocell access points, connected together through a local area network such that they can exchange information about their respective statuses, each being configured to:
receive information about channel numbers, scrambling codes and unique cell identifiers used by femtocell access points in the network;
receive signals broadcast by other femtocell access points in the network whose transmissions can be detected;
extract from said received signals information relating to the channel numbers and scrambling codes used by the other femtocell access points whose transmissions can be detected;
upon detecting signals from first and second other femtocell access points that are using the same channel number and scrambling code as each other, each femtocell access point being further configured to:
use different timing offsets of the signals from the first and second other femtocell access points to distinguish between said signals;
extract from said signals from the first and second other femtocell access points information relating to the unique cell identifiers used by the first and second other femtocell access points; and
include at least the first and second other femtocell access points in a neighbour cell list of said femtocell access point.
6. A network of femtocell access points as claimed in claim 5 , wherein each of the femtocell access points of the network is further configured to apply time filters around signals detected from the first and second other femtocell access points in order to distinguish between said signals.