The transmission of a Cellular Radio Access network is an important component for mobile communication networks. In some parts of the world especially in wide rural areas or in far away remote areas, operators face the difficulties to develop services and/or deploy networks due to the lack of or cost of fast and reliable backhaul transport resources. However, according to statistical data, many calls in a mobile communication network, especially in the above-mentioned areas, are local calls. That is, these calls are generated and terminated by users served by the same BTS or the same BTS cluster or the same BSC. For local calls, if local switch (voice data in user plane is looped in a BTS or a BSC) is performed, then transmission resource of the Abis and/or A interface could be saved. To avoid impacts to the support of various kinds of supplementary services (e.g., Multiparty Call, Explicit Call Transfer, etc.), and the support of Lawful Interception procedures, not only the BSS, but also the MSC-S needs to be involved in the establishment/release of the local switch. Furthermore, in order to perform local switching, the BSS needs to correlate the two legs of the call, i.e. it needs to know who is talking to whom. This information needs to be provided by the MSC-S. A solution for Local Call Local Switching may have major impacts on the core network regarding allocation of resources on the MGW, potential procedures for MGW removal/insertion, binding into supplementary service control within the core network (e.g. MPTY), Lawful Intercept procedures within the Core Network, Handover procedures, interaction with MSC-S pooling, etc. It is thus necessary to perform an analysis of different solutions in order to determine the core network impacts.

The present document provides a study into the Core Network impacts for providing a solution for Local Call Local Switching. The document analyses and evaluates different solutions to determine the benefits provided compared to the identified impacts. Specific considerations are given to the following areas:-

• Sending of correlation information between the two legs of the call to the BSS
• Triggering to enable/release Local Call Local Switch (e.g. based on activation of Supplementary Services, etc.)
• Support of existing Supplementary Services
• Support of existing Lawful Intercept functionality
• Impacts to the user plane handling on the A-interface
• Impacts to the MSC-S - MGW Interface (Mc Interface)
• Impacts to the MSC-S - MSC-S Interface (Nc Interface)

The solution(s) considered for local call local switch should keep the core network impacts to a minimum, e.g. the impacts on the nodal functions, existing call flows, call establishment and call release. The contents of this report when stable shall determine the modifications to existing core network specifications.

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.

• References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.