IP Signaling Forwarding

The IP signaling forwarding feature enables the UMG8900 to route signaling over IP. In an all-IP network, the base station controller (BSC) or radio network controller (RNC) communicates with the media gateway controller (MGC) by means of a dedicated signaling network or the UMG8900. When serving as a router, the UMG8900 can forward packets directly without processing them. For example, after IP transport is enabled on the A interface or Iu interface, the UMG8900, when serving as a router, is able to route signaling over IP and forward packets between the BSC (or RNC) and the MGC.

The signaling routing function must be used together with the Address Resolution Protocol (ARP) agent function if the two remote IP addresses, which are configured on the UMG8900 for signaling routing, are in the same network segment.

Application Scenario

In different networking modes of Code Division Multiple Access (CDMA), signaling routing is implemented on the A interface between the UMG8900 and the BSC, the Iu interface between UMG8900 and the RNC, and the Mc interface between the UMG8900 and the MGC.

• WCDMA/TD-CDMA networking mode 1: IP transport used between the UMG8900 and the RNC
• WCDMA/TD-CDMA networking mode 2: IP signaling over E1 (IPoE1) transport used between the UMG8900 and the BSC

Figure 1 WCDMA/TD-CDMA networking mode 1

In this networking mode, IP-enabled Iu interface is used on the RNC side. The UMG8900 routes signaling over the IP-enabled Iu interface and forwards packets from the RNC to the MGC. The packet forwarding path is as follows: RNC->UMG8900->Router->MGC.

Figure 2 WCDMA/TD-CDMA networking mode 2

In this networking mode, IPoE1-enabled A interface is used on the BSC side. The UMG8900 routes signaling over the PoE1-enabled A interface and forwards packets from the BSC to the MGC. The packet forwarding path is as follows: BSC->UMG8900->Router->MGC.

Implementation Principle

The UMG8900 connects to the BSC or RNC over the A interface or Iu interface and connects to the MGC over the Mc interface. It serves as a router to transmit signaling between the BSC (or RNC) and the MGC.

After the UMG8900 receives a packet from the BSC or RNC, it resolves the packet. If the packet does not need to be processed, the UMG8900 forwards the packet to the MGC. The red dotted line in Figure 3 indicates the path on which the UMG8900 directly forwards packets from the BSC or RNC to the MGC. To implement signaling routing over IP, the UMG8900 performs the following operations:

• Identifying the packets to be forwarded
• Forwarding packets in two directions
• Tracing forwarded packets

Identifying the Packets to Be Forwarded

1. The UMG8900 resolves a received packet and checks the source and destination IP addresses in the packet.
2. If both IP addresses are not the internal IP addresses of the UMG8900, the UMG8900 searches the configured signaling routing data and determines whether the destination IP address is a remote IP address already configured for signaling routing.
3. If the destination IP address is a configured remote IP address, the UMG8900 starts the signaling routing procedure; if the destination IP address is not a configured remote IP address, the UMG8900 starts a different procedure.

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