UAG Applications
The UAG fits into FMC “underlay” networks as an element in a number of different network architectures. These architectures have been defined within various standards bodies and industry associations. The principle underlying all of the architectures, and driving the requirement for the UAG, is that a generic IP network—often the public Internet—is used to connect underlay network elements such as femtocells or dual-mode devices to the operator’s core network. Beyond this basic similarity, there are four architectural differences depending on the specific application.
UAG as a Femtocell Access Gateway
In a femtocell architecture, femtocells provide 2G or 3G wireless access towards existing clients, and then send the data via a secure tunnel over the IP backhaul network to the UAG and into the operator’s network.
Figure 1: Airvana UAG as a Femtocell Access Gateway
UAG in a CDMA Wireless Network (PDIF)
The main standards development organization for CDMA networks, 3GPP2, has defined an architecture for inter-worked WLAN deployments (dual-mode devices, such as cellular and Wi-Fi) as shown in Figure 2. Access to the operator network is mediated by an element known as the Packet Data Interworking Function (PDIF). The Airvana UAG is a 3GPP2-compliant PDIF.
Figure 2: Airvana UAG as a PDIF
UAG in a GSM/UMTS Wireless Network (TTG and PDG)
The main standards development organization for GSM/UMTS networks, 3GPP, has also defined an architecture for inter-worked WLAN deployments. However, as shown in Figures 3 and 4, there are two variants of this architecture. In one variant, the UAG fills the role of a Tunnel Terminating Gateway (TTG), which forwards all traffic directly to the Gateway GPRS Support Node (GGSN). In the other variant, the UAG fills the role of a Packet Data Gateway (PDG), which, like the PDIF described in item 2, interfaces directly to the operator’s core network. The UAG is both a 3GPP-compliant TTG as well as a 3GPP-compliant PDG.
Figure 3: Airvana UAG as a TTG
Figure 4: Airvana UAG as a PDG
UAG in a UMA/GAN Architecture (UNC or GANC)
An alternative method for interfacing to a GSM/UMTS network is known as Unlicensed Mobile Access (UMA) or, in the terminology adopted by 3GPP, Generic Access Network (GAN). In this architecture, shown in Figure 5, access from the IP network is mediated by an element known as a UMA Network Controller (UNC) or GAN Controller (GANC). This controller has, as one of its elements, a security gateway. The UAG is a UMA/GAN-compliant security gateway.
Figure 5: Airvana UAG as a UNC or GANC
