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topology

IS-826 Topology

IS-826 is an interim specification for a method of implementing prepaid billing for CDMA/TDMA systems using WIN (Wireless Intelligent Network) principles. TCAP/IS-826 messaging allows the Tri-plex Platform to get call control information without inbound and outbound or loop around circuits. With IS-826, Tri-plex and the MSC communicate by means of a Point Code (PC) and Sub-System Number (SSN) and messages directed via TCAP to an application. Rather than being physically in the call path, the MSC uses messages to allow the Tri-plex Platform to do call control. For example, the MSC would send a message to the Tri-plex Platform asking us if a MIN had a valid balance. The platform would respond with a message, and the MSC would set up the call. When the call is over, the MSC informs the Tri-plex Platform and the account is decremented.

In an IS-826 installation, loop-around trunks are not necessary. However, additional trunks are needed for in-band services such as announcements. These additional trunks can be arranged to operate as release link, operator, or regular configuration.

ISUP Topology

In an ISUP installation, the Tri-plex Platform offers a network topology that minimizes the number of voice paths that have to be connected to the platform. This topology is called Adaptive Roll Forward (ARF) and is a way to control a call without the need for the voice circuit to be routed to the Tri-plex Platform for the entire duration of the call. ARF requires the voice path only while announcements are made at the beginning of the call, rather than for the entire call. Nevertheless, calls can be fully controlled.

For call control purposes, each call uses two trunks, one that connects the call out of the switch and the other that connects back to the same switch. This looparound serves no purpose except for the creation of out-of-band signaling that can be intercepted by the Tri-plex Platform. The platform can then use these signaling messages to acquire the information it needs. Additional trunks are needed for in-band services such as announcements.