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June 2008 | Volume 11/ Number 6
Packet Voice Over Wireless

FMC and Femtocells

We can clarify the femtocell versus WiFi Fixed-Mobile Convergence (News - Alert) (FMC) issue by recognizing that carrier/consumer FMC is very different from enterprise FMC.

The primary goal of carrier/consumer FMC is to offload the cellular network and to improve coverage. The primary goal of enterprise FMC is to treat the mobile phone as a combination of enterprise network client like a laptop computer, and PBX (News - Alert) extension phone, allowing the enterprise to maintain control of the phone number and least cost routing.

Femtocell technology doesn’t work at all for the enterprise flavor of FMC, which depends on WiFi (News - Alert), but it is well suited to carrier/consumer FMC.

The main carrier technology for FMC is UMA (Unlicensed Mobile Access, also known as GAN for Generic Access Network). UMA uses the Internet as a backhaul and WiFi access points (APs) as miniature cell towers. Substituting femtocells for WiFi APs is a good idea in this context as far as the carrier is concerned. Femtocells (News - Alert) help to retain customers not only by improving residential coverage, but because the femtocell is normally tied to a particular carrier. Femtocells benefit customers because they work with any mobile phone, not just dual-mode (WiFi plus cellular) phones, and their spectrum is licensed, so there is less potential for interference. However, Femtocells cost more than WiFi APs and they may require careful installation so they don’t interfere with local cell towers.

Carriers have traditionally seen WiFi access by phones as a challenge to their control over services on the phone. This may be changing with the success of the iPhone (News - Alert), the recent commitment by Verizon to allow third party devices on their network and the Google-instigated open access requirement for the recently auctioned 700MHz spectrum. But up to now, the WiFi in UMA phones has been locked for UMA use only, and not usable for LAN data access. So with femtocells you get exactly the same benefits as with a UMA dual-mode phone, but without the additional cost of a WiFi radio in the handset.

So UMA and femtocells make sense in the residential market. But thanks to the iPhone, a strong market force exists for all smart phones to include WiFi radios, and because they are warming to the idea of opening up their networks, the carriers no longer resist this force.

This leads to the interesting appearance of residential gateways from vendors like Netgear (News - Alert) that have both femtocells and WiFi built in. Using the femtocell, consumers can benefit from improved coverage on their cellular calls on any phone, but if they happen to have a smart phone with WiFi they can use the WiFi connection for open network access outside their mobile carrier’s billing domain. IT

Michael Stanford (News - Alert) has been an entrepreneur and strategist in Voice-over-IP for over a decade.

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