Unlicensed Mobile Access (UMA)

Unlicensed Mobile Access (UMA) is a technology that connects regular unlicensed wireless networks to GSM networks. The wireless networks are currently limited to Bluetooth and 802.11, but soon others will follow. UMA defines a UMA Network Controller, UNC, which connects to the GSM mobile network using standard A/Gb connections, replacing GSM’s Base Station Controller (BSC). All GSM services are tunneled through the IP pipe, including GPRS. Of course, data transfer speeds are quite a lot faster than with cellular access (UMA Technology).
Calls and data connections feature seamless handover between cellular and UMA, as well as roaming back to cellular if UMA isn’t available. UMA enabled phones can use any standard 802.11 access point for connection, though naturally the AP must provide network access for the user. The network features multiple UNCs, one of which is a default one. The default UNC chooses another UNC for the mobile terminal if needed, based on the network topology.
The mobile terminal connects to the UNC via unlicensed wireless networks and fixed line, using point-to-point IPSec encryption. The UNC contains a security gateway (SGW), which takes care of the IPSec tunnel and IKEv2 authentication (Mobile Pipeline). The subscribers are identified by SIM credentials, and the SGW is connected to GSM’s AAA service for subscriber authentication.
Calls are transferred through IP bearers (RTP and UDP), using the same data flow as with VoIP networks. GPRS connections are carried by TCP using a lightweight UMA-RLC protocol, which is suitable for always-on broadband connections. (Mobile Pipeline). Right now, there are no phones implementing UMTS and UMA at the same time – only handoff between GSM and UMA exists. At the moment, the UNC does not support all of the UMTS services, so development still goes on (In Code 2006).

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