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Rajeev Gupta
Vice President, Engineering

Rajeev Gupta is Vice President of Engineering at Kineto Wireless, where he is responsible for core and client software products. Earlier, he was responsible for defining the convergence architecture for WiFi and GSM cellular, and driving the standardization of Kineto's technology in the UMA forum, which was successfully completed in Sept. 2004. Prior to Kineto, Mr. Gupta was Vice-President of Software at Pico Communications, where he led the development of system software for enterprise-grade Bluetooth and 802.11 Access Points. view full bio
UMA and IMS
You sometimes see UMA and IMS positioned as competitive technologies. Are they truly in conflict with one another? No, UMA and IMS are not conflicting technologies, but are instead complimentary technologies. UMA enables transparent delivery of IMS services over Wi-Fi, and IMS services run seamlessly on UMA handsets.

Like GSM/GPRS/EDGE and UMTS/HSPA, UMA is, in effect, a radio access technology and completely agnostic to the services which run over it. Alternatively, IMS is famously agnostic to the underlying radio access technology. Therefore, in the same way UMTS/HSPA networks transport and provide seamless mobility for IMS services, UMA transports and provides seamless mobility for IMS services.
But SIP is widely accepted as the call control technology for IMS, why doesn't UMA use SIP?
SIP is a control/service layer protocol used for setting up sessions (voice calls, video calls, audio streams) over pre-existing IP links. UMA is an access layer technology used to establish secure, managed links over the Internet between mobile handsets and a mobile core network. Once the UMA access link is in place, SIP can be used to establish sessions.

Saying SIP should replace UMA is a bit like saying SIP should replace GPRS, EDGE or UMTS. Like GPRS, EDGE, or UMTS, UMA is a mobile access layer technology, over which SIP-based services run transparently. Fundamentally, UMA and SIP are at different layers in the network, and are responsible for performing different, complementary functions.

As an access layer technology, UMA also ensures mobility and session continuity between Wi-Fi/broadband networks and GSM/UMTS networks. UMA enables SIP-based services running on a handsets to move seamlessly between the two access networks today.
When a mobile operator ultimately moves to IMS for their basic telephony services, does UMA still have a role?
Absolutely. The fundamental principles which compel operators to deploy UMA today for GSM/UMTS circuit-based telephony service (e.g. providing low cost, high performance mobile services in home) still apply with IMS-based telephony service.

Once operator's find it technically and economically feasible to deliver IMS-based telephony services over their macro radio networks (e.g. potentially with deployment of HSPA+), they still need UMA to enable seamless delivery of those service to handsets over Wi-Fi, as well as enable the seamless handover of active IMS-based telephony services between the macro network and Wi-Fi in subscriber homes and offices.