 MSC is dependent upon the regulatory regime To produce a general method of linking BTS to BSC, a mixture of under which the PCN is being operated. For example, some coun- the star and ring methods should be used, as in Figure 48.5. To allow tries might consider the MSC to be an adjunct to the ISDN/PSTN control of capacity, it has been proposed that Digital Cross Connect whereas in the UK, PCN operators are seen as independent net- (DCX) equipment is used to re-route traffic when necessary. works. For this reason MSC's are situated in locations which TO MSC achieve both on-net and off-net traffic routeing optimisation. BSC/BTS CROSS CONNECT 48.6.3.2 BTS - BSC - MSC connection optimisation Notwithstanding the connection methods suggested above, it is necessary to ensure that location updating and handovers are opti- mised. This is achieved by parenting, and parenting BTS on BSC and BSC on MSC based upon predicted or measured traffic flows. BSC/BTS BSC/BTS BSC/BTS CROSS CROSS CROSS For example, one would not have a location area boundary through CONNECT CONNECT CONNECT the centre of Oxford Street or Times Square, nor would one have 2 BTS's in these areas parented on different BSC's. 48.6.3.3 MSC-MSC routes Figure 48.5 Star BTS's within a ring of cross connects Standard telecommunication practices are used to develop routeing and BSC's rules for inter-MSC routes and to ensure a reasonable grade of service. Mobility 48/7 48.6.4 Numbering 48.6.4.4 Global title One of the important considerations when developing the network This is S number conforming to CCITT recommendation E.214 and routeing strategy for both customer traffic and signalling informa- is utilised to route MAP SCCP information to appropriate nodes. tion, is to develop a detailed numbering plan. Numbering plays an important part in PCN's, and the PCN com- panies are pressing for the introduction of a ten digit numbering 48.6.4.5 Point codes scheme which will ensure that sufficient numbers are available, for both the proposed and future telecommunications