Standards: the femtocell goes public

GSM/3G Vision - 28 September 2007

The arrival of femtocells in the consumer market is getting ever closer. And where femtocells are, UMA - the acronym for unlicensed (or, in some formations, universal) mobile access - will not be far behind. That at least is the belief of some companies enabling the indoor base station revolution. UMA technology is the 3GPP global standard for fixed-mobile convergence. It's also seen by Kineto Wireless, a supplier of UMA technology, as the leading if not de facto standard linking femtocells to the mobile core network over the public internet. But how did UMA find itself in the enviable position of being, arguably, a key enabler of a whole new infrastructure market?

Steven Shaw, AVP marketing of Kineto Wireless, offers a brief history. When UMA was moved into the 3GPP in April 2005, he points out that it was actually called GAN, or Generic Access Network, a reasonable description because UMA is indeed a generic way to take services the mobile operator already has (such as voice, SMS, MMS and ringtones), package them up and tunnel them over the broadband network. Just to clarify the point, Shaw adds: "UMA isn't a service; UMA is a technology for taking existing services and sending them over the internet. Think of UMA," he suggests, "as a way to make the public internet another radio access network (RAN), just like GSM, 3G, HSPA, or 4G."

How, then, does UMA work in a femtocell environment, where there are, it is hoped, going to be hundreds of thousands of devices deployed in consumers' homes? For a UMA-enabled femtocell deployment, the UMA client would reside in the femtocell itself.

Subscribers would use existing 3G handsets, which would talk to the femtocell. But, says Shaw, "the way the femtocell communicates back to the mobile core network is through a secure UMA tunnel, nearly identical to the way dual-mode phones do it".

UMA is not the only game in town. But the other options available today (Iu-B or SIP), in Kineto's view, face significant challenges. Shaw summarises them as follows: "Basically Iu-B was never designed to run on the public internet; it has no security and the timing is very tight. Also, while it sounds like a standard, Iu-b is actually 'enhanced' by each RAN vendor (Siemens, Nokia, Alcatel, Ericsson) to be closed so that, as an operator, you must buy Ericsson radios - node-bs - to communicate with an Ericsson RNC." He continues: "For SIP, there are several challenges. First, there is no message specification. Just saying "SIP" doesn't make it a standard. Someone needs to define what SIP messages are sent when and with what payloads. That work is just beginning. But, more importantly, most mobile operators don't have SIP infrastructure. Therefore, the business case immediately becomes burdened. The case for femtocells is costly enough without driving the investment in a full SIP core network."

Which leads to the inevitable question: Will UMA become a de facto standard? Yes, says Shaw, for two reasons. First, he argues, it's already 90 per cent of what's required for a complete femtocell standard. He continues: "It will definitely be easier to rally the industry around something that's 90 per cent done rather than starting from scratch (as with SIP). But second, because it's already 90 per cent of what's required, operators are going to see that UMA actually offers them the fastest path to market. Because UMA has been 'proven' in the field, through deployments, it already addresses what's required to be actually installed in the network."

He sums up: "From the day the spec was completed until it was fully proven out took nearly two years for UMA. UMA has a huge head start versus any other approach. That head start translates directly into time to market."

Confident talk. However, even with the linking problem apparently solved there are a number of issues still to be sorted out relating to femtocell deployment. Shaw's assessment of these will appear in next issue's feature on network management.

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