Scrambling code selection

A method, for use in a basestation forming part of a group of basestations within a cellular communications network, for selecting an identifying code for use in identifying transmissions from the basestation, the method comprising:

• receiving from a management node a first list of identifying codes and a second list of identifying codes, wherein the identifying codes of the first list can appear in neighbour cell lists of basestations outside said group, and wherein the identifying codes of the second list can not appear in neighbour cell lists of basestations outside said group;
• determining whether it is necessary to be able to perform cell reselection between the basestation and basestations outside said group;
• if it is determined that it is necessary to be able to perform cell reselection between the basestation and basestations outside said group, selecting an identifying code from the first list of identifying codes;
• and
• if it is determined that it is not necessary to be able to perform cell reselection between the basestation and basestations outside said group, selecting an identifying code from the first list of identifying codes or from the second list of identifying codes.

A method of allocating identifying codes to basestations forming part of a group of basestations within a cellular communications network, the method comprising, in each basestation within the group:

• selecting an identifying code in a manner that attempts where possible to avoid selecting the same identifying code as a neighbour,
• and the method further comprising, in at least one basestation within the group:
• determining that a clash has occurred if any neighbour basestation has selected the same identifying code as said at least one basestation, and
• if a clash has occurred, determining whether the clash can be resolved by said basestation or by another basestation in said group.

A basestation, for use in a cellular communications network, being configured to:

• receive from a management node a first list of identifying codes and a second list of identifying codes, wherein the identifying codes of the first list can appear in neighbour cell lists of basestations outside said group, and wherein the identifying codes of the second list cannot appear in neighbour cell lists of basestations outside said group;
• determine whether there is at least one identifying code either in the first list of identifying codes or the second list of identifying codes that is not used by any other basestation in said group;
• and
• if there is at least one identifying code in the first list of identifying codes and at least one identifying code in the second list of identifying codes that are not used by any other basestation in said group, select an identifying code from the first list of identifying codes in preference to an identifying code from the second list of identifying codes.

A basestation, for use in a cellular communications network, the basestation being configured to:

• receive from a management node a first list of identifying codes and a second list of identifying codes, wherein the identifying codes of the first list can appear in neighbour cell lists of basestations outside said group, and wherein the identifying codes of the second list can not appear in neighbour cell lists of basestations outside said group;
• determine whether it is necessary to be able to perform cell reselection between the basestation and basestations outside said group;
• if it is determined that it is necessary to be able to perform cell reselection between the basestation and basestations outside said group, select an identifying code from the first list of identifying codes;
• and
• if it is determined that it is not necessary to be able to perform cell reselection between the basestation and basestations outside said group, select an identifying code from the first list of identifying codes or from the second list of identifying codes.

A system comprising a group of basestations within a cellular communications network, wherein each basestation within the group:

• selects an identifying code in a manner that attempts where possible to avoid selecting the same identifying code as a neighbour,
• and, at least one basestation within the group:
• determines that a clash has occurred if any neighbour basestation has selected the same identifying code as said at least one basestation, and
• if a clash has occurred, determines whether the clash can be resolved by said basestation or by another basestation in said group.