Section: A.2 Guidance for planning
Content: From these uses, the following planning rule can be derived: If there exist places where MSs can receive signals from two cells, whether in the same PLMN or in different PLMNs, which use the same BCCH frequency, it is highly preferable that these two cells have different BSICs. Where the coverage areas of two PLMNs overlap, the rule above is respected if: 1) The PLMNs use different sets of BCCH frequencies (In particular, this is the case if no frequency is common to the two PLMNs. This usually holds for PLMNs in the same country), or 2) The PLMNS use different sets of NCCs, or 3) BSIC and BCCH frequency planning is co-ordinated. Recognizing that method 3) is more cumbersome than method 2), and that method 1) is too constraining, it is suggested that overlapping PLMNs which use a common part of the spectrum agree on different NCCs to be used in any overlapping areas. As an example, a preliminary NCC allocation for countries in the European region can be found in clause A.3 of this annex. This example can be used as a basis for bilateral agreements. However, the use of the NCCs allocated in clause A.3 is not compulsory. PLMN operators can agree on different BSIC allocation rules in border areas. The use of BSICs is not constrained in non-overlapping areas, or if ambiguities are resolved by using different sets of BCCH frequencies. If the PLMNs share one or more cells with other PLMNs, the planning rule above should be applied also when the BCCH frequency is different. The rule should be respected by using different sets of NCCs. In addition to that, the PLMN sharing one or more cells with other PLMNs should use different NCCs for shared and non-shared neighbouring cells.