print will release August 17th its Airave "femtocell," a tiny extension of their cellular network that instead of using their own tower backhaul relies on your home or office broadband network connection. Cellular networks comprise overlapping regions or cells. There are microcells for small areas, picocells for offices and buildings, and now femtocells for the home or small office.
The carrot for spending $100 on an Airave and $5 per month for the unit is that you can place unlimited domestic calls that originate through the unit for $10 per month for an individual line or $20 per month for a multi-line account (not including taxes). "Originate" is a key point: If you're placing or receiving a call outside its limited coverage and then move into its coverage area, you're charged for or have minutes counted for that call as under your normal plan. But if you place or receive a call while within its coverage, your call's minutes are under the Airave's umbrella even if you wander out.
Airave is the first mainstream deployment of femtocells, which use licensed frequencies owned by a carrier and allow a customer to use what's essentially VoIP on a cell phone. The call is handled by the femtocell, which passes it over the Internet to a Sprint gateway to proceed onto the rest of the network.
An alternate technology uses Wi-Fi or Bluetooth instead, and is called Unlicensed Mobile Access (UMA), due to using frequencies that don't require licenses. T-Mobile launched its national service, HotSpot@Home, early this year using UMA after a trial in Washington state in 2007. The service requires special handsets that have both cellular and Wi-Fi radios built in and support the UMA protocol; in contrast, Sprint's service works with any of their existing handsets. (T-Mobile also has an @Home service which is really a typical VoIP offering for 1 or 2 lines using standard phone jacks, and which costs $10 per line per month.)
T-Mobile's monthly service pricing is the same, but there's no rental fee for the device, which costs $50 after rebate, versus the $100 purchase and $60 per year for Sprint Airave. T-Mobile's handsets and base stations include extended Wi-Fi protocols that prioritize voice packets over data, and help extend the battery life of mobile devices.
Femtocells have previously been seen as too expensive to release to consumers who are paying ever less for phone service. The $5 per month fee is an attempt to recoup over a few years the cost of the device. Less cellular switching and more loyalty also help reduce marketing costs and make the device worthwhile.
The key advantage of a femtocell is that there's no chance for interference. With Wi-Fi, other networks in your vicinity--or even a nearby industrial sealer that uses microwave radiation--could disrupt phone calls, although the bandwidth needed for calls is so slight that it's unlikely. Sprint's system uses frequencies they have a license to, and which they coordinate use of among their own devices.