4.6 Unlicensed Mobile Access and Generic Access Network

Unlicensed Mobile Access (UMA) is another approach to improving in-house coverage and offloading cellular traffic from the macro network to DSL or cable IP connections. The big difference to femtocells, however, is that UMA does not require any special network equipment on the user side. Instead, the mobile device is equipped with a Wi-Fi interface that it uses to communicate with a standard Wi-Fi access point. Furthermore, UMA simulates 2.5G GSM/GPRS connections through the Internet while femtocells tunnel B3G UMTS/HSPA or CDMA/EvDO traffic through the Internet.

4.6.1 Technical Background

UMA is a 3GPP standard and defined in [37] and is referred to in the standards as Generic Access Network (GAN). The principle of UMA/GAN is simple: it replaces the GSM radio technology on the lower protocol layers with Wireless LAN. A call is then tunnelled via a Wi-Fi Access Point connected to a DSL/cable modem via the Internet to a gateway node. The gateway then connects to the mobile switching center for voice calls and SMS and to the Serving GPRS Support Node for packet data. The gateway between the Internet and the network of the mobile operator is called a GAN Network Controller (GANC), as shown in Figure 4.31.