This article originally appeared in the Sept. 2011 issue of INTERNET TELEPHONY

Wi-Fi and cellular technologies are turning out to be complementary. Cellular technology is relatively long range, and it can handle clients moving at car speeds; but it can have capacity and coverage difficulties, especially indoors, and the equipment is relatively expensive. Wi-Fi is predominantly an in-building solution; it is short range, high density, high capacity and commodity priced. Wi-Fi is ubiquitous in the devices that consume most mobile data: smartphones, tablets and laptops. Wi-Fi access points are cheap and widely deployed. Consequently, mobile data is evolving to a dual-mode solution, with Wi-Fi indoors and cellular technologies outdoors, with an overlap in large indoor spaces like airports and malls.

Femtocells (News - Alert) are low-cost self-configuring solutions to poor coverage and under capacity in cellular networks. But in the situations for which they were originally intended – residences and offices – they are too late. Wi-Fi is already there, already solving these problems. With Wi-Fi incumbent and adequate for indoor use, the economics of indoor femtocells don't add up. So femtocell providers are turning to that overlap area, repurposing their chips and technologies to deliver low-cost, self-configuring small cells to augment macro cellular networks in places like malls, airports, rural areas and urban hot zones.

This approach is being championed by Ubiquisys (News - Alert), which offers a “Self Organizing Network of small cells that don’t require radio planning and that complement the macro network’s capacity and coverage.” One of the expenses of wireless network deployment, both enterprise and cellular, is radio resource management planning: determining the most cost-effective number and layout of stationary access devices, so this “self-organizing” feature is a massive step forward. A similar capability is being touted on the Wi-Fi side by companies like Aerohive (News - Alert), with its suite of cooperative controller-less protocols that enable “automatic channel selection and power control, auto-discovery and configuration”.

The small cell approach will succeed because it is compelling economically when compared to older cellular technology solutions, but the degree of its success may be partial. In the U.S. both Verizon (News - Alert) and AT&T have announced plans to use Wi-Fi hot zones for the overlap situations.