the number of MSS/GCS and parenting of MGWs (i.e. MGWs controlled by MSS/GCS). Determine the number of calls between nodes from the end-to-end traffic matrices between MGWs and the information about which MSS/GCS controls which MGW. Determine signalling between MSSs/GCSs. Determine amount of signalling between MSS/GCS and controlled MGWs. Determine the architecture for the MSS/GCS interconnections. Route the signalling traffic. Ensure that the network element processor load and signalling transfer load is not exceeded. If no modifications are needed, from the routed traffic determine the bandwidth requirements in the backbone links. In the following paragraphs, single issues affecting the planning process are addressed. The approach is to show all the options when planning a 3GPP release 4 circuit core network with solutions from the most generic to the most detailed, bearing in mind that each practical case will have a unique combination of the presented scenarios and it should be carefully considered how to combine all those issues. Number of Signalling Points and Sites Dimensioning of the MSS/GCS needed in the network is based at first on the subscriber number (as each MSS has a limited VLR capacity) and BHCA (as each MSS/GCS has a limited processing capacity). 3GPP Release 4 Circuit Core Network The number of MSSs is calculated by determining coverage areas based on the subscriber distribution and traffic profile. Each coverage area should contain a number of estimated subscribers that: fits into the VLR capacity of the element (that should not be fully utilised to allow user mobility); generates total traffic in terms of BHCA (as well as other processing capacity constraints, e.g. SMS) within the processing capacity of the MSS. The coverage areas of MGWs and MSSs are not in a fixed relation: one physical MGW can be logically divided into several virtual MGWs under the control of different MSSs, thus allowing a great degree of flexibility. It has to be noticed that one RNC can be connected to several virtual 