 in Erlangs. Determine the architecture for MGW interconnections. Route the traffic in Erlangs. Ensure that the network element processing load and interface capacity are not exceeded. If no modifications are needed, from the routed traffic determine the bandwidth requirements in the backbone links. Number of MGWs, Site Locations and Coverage Areas The MGW location and coverage area are important factors affecting the total number of MGWs required for a network. MGW Site Location The location of an MGW site depends on several factors. Some of the factors are: location of the RNC and BSC; total traffic from the MGW coverage area (both RNC and BSC traffic); subscriber distribution; call profiles; location of the point of interconnection with the PSTN/PLMN; transmission availability and cost. Though the MGW does not contain a subscriber database, it is necessary to consider the required traffic handling capacity to determine the required number of subscribers. The required capacity depends on traffic generated by subscribers in the MGW coverage area. The coverage area of an MGW may be considered as the area served by the RNCs/BSCs parented to a given MGW. The number of MGWs with radio access interfaces (Iu or A interfaces) can be determined by: (a) the total traffic generated by the RNC/BSC in the MGW coverage area in terms of the BHCA; (b) total interfaces required to carry traffic from the coverage (RNC/BSC) area; call processing capacity of the MGW, while depends on the amount of resources required to handle a given type of call (i.e. UE-UE, UE-MS, MS-MS, UE-PSTN, MS-PSTN, etc.). The number of MGWs dedicated to external interconnects (i.e. other PLMNs and PSTNs) is determined (a) the total traffic of the interconnect in terms of the BHCA; (b) the location of the POI location and size; Core Network Planning and Optimisation Backbone Figure 4.12 MGW distributed architecture (c) the number calculated from the routing of the end-to-end traffic matrices; (d) the call processing capacity of MGW, which depends on the am