Unlicensed Mobile Access (UMA) technology is the 3GPP standard for Cellular/Wi-Fi convergence. UMA enables mobile operators to deliver their existing services, whether based on circuit, packet, Session Initiation Protocol or IP Multimedia Subsystem (IMS), over unlicensed spectrum technologies, including Bluetooth and 802.11. Users will be able to roam between cellular networks and public and private unlicensed wireless networks using dual-mode mobile handsets.
The UMA specification defines a new network element - the UMA Network Controller - as well as protocols that provide for the secure transport of GSM and General Packet Radio Service signals over IP. Known as TS 43.318 in the 3GPP standards body, the specification has been approved for inclusion into 3GPP Release 6.
Unlicensed Mobile Access (UMA) brings cost and performance advantages to mobile services and offers four benefits: discounts for services delivered over the IP network, minimal impact to enterprise IT support staff or additional capital equipment, increased mobile performance, and seamless, high-quality in-building coverage.
How does it work?
- A mobile subscriber with a UMA-enabled, dual-mode handset moves within range of an unlicensed wireless network to which the handset is allowed to connect.
- Upon connecting, the handset contacts the UMA Network Controller (UNC) over the broadband IP access network to be authenticated and authorized to access GSM voice and GPRS data services via the unlicensed wireless network.
- If approved, the subscriber's current location information stored in the core network is updated, and from that point on all mobile voice and data traffic is routed to the handset via the Unlicensed Mobile Access Network (UMAN) rather than the cellular radio access network (RAN).
- Roaming: When a UMA-enabled subscriber moves outside the range of an unlicensed wireless network to which they are connected, the UNC and handset facilitate roaming back to the licensed outdoor network. This roaming process is completely transparent to the subscriber.
- Handover: If a subscriber is on an active GSM voice call or GPRS data session when they come within range (or out of range) of an unlicensed wireless network, that voice call or data session can automatically handover between access networks with no discernable service interruption. Handovers are completely transparent to the subscriber.
UMA is independent of underlying unlicensed spectrum technology. It is a simple and effective technology that enables mobile operators to roll out the solution in the short term, but mobile operators and manufacturers need to develop a clear transition path to a SIP-based architecture (Session Initiation Protocol), which will make it easier to extend the service to other wireless technologies, like CDMA, EV-DO, WiMAX or FLASH-OFDM, and to include advanced IMS-based services.
UMA-based solutions will likely be available from mobile operators in North America and Western Europe by mid-2006.
