With many countries now registering cell phone penetrations above 100%, and several reporting sizable portions of their population giving up on their fixed phone lines and going mobile-only, wireless coverage is becoming a key infrastructure of modern living and economic activities. That explains why, starting maybe this year or more likely next year, cellphone towers will start moving into living rooms and office spaces. They will have the look and shape of a standard wireless router, but will in fact be small cell phone network base stations: lower-power home versions of the antennae that we see on masts and roofs and spires all around our cities.
They're called femtocells ("femto" is the prefix denoting one million-billionth of a unit, but forget the math and just think "very small"). They are designed to piggyback on a user's broadband connection to repeat indoors the GSM and UMTS/3G mobile signal of wireless operators. Virtually every major telecom operator and manufacturer has a femtocell strategy or is developing one, while most analysts predict a very fast adoption -- and the predictions are credible, because if the technology works, it will deliver perfect cell phone performance in the home or the office, including in the basement on in that bunker-like meeting room.
And a widespread adoption would have serious impacts, from signaling the beginning of the end of traditional wireline telephony (your cell phone becomes your home phone when it is within your femtocell, and operators will adapt their tariffs accordingly) to potentially enabling all sorts of next-gen mobile-broadband services.
The obvious advantage for the user is better wireless coverage (plus new services). The advantage for the operators is a more optimized use of network resources (plus the possibility to offer truly "localized" services). But there are still many questions open.
US company Airvana is one of the largest developers of femtocell technology. I caught up with Paul Callahan, their VP of business development, to try to understand a bit more.
Paul, how does a femtocell exactly work?
A femtocell is like a Wi-Fi access point for mobile 3G; it uses a low-power integrated antenna to transmit voice and data cellular signals within a home or small office. It connects to the mobile operator’s network through a broadband internet connection.
So as a user you need to have a broadband Internet connection in order to install a femtocell?
Yes.
Will users just be able to go to the store, sign up, get a package with a hub, plug it in and go "live", pretty much like we do today with wi-fi routers? Or will it need the intervention of the telecom operator?
Femtocells operate in licensed spectrum, therefore they do require working through the mobile operator. Eventually, operators may offer femtocells in general retail outlets, but initially many operators will sell femtocells through their own retail store fronts, much the way mobile phones are offered today. Customers will go to their carrier’s retail location, purchase a femtocell, and have it activated via the point of sale system.
If the user is paying for the Internet traffic generated by his or her femtocell, can we expect very low tariffs?
This is really a business decision on the part of the mobile operator. We believe operators are likely to offer a flat-rate “home zone” calling plan that provides unlimited calling when at home for a monthly fee.
How much does the femtocell hardware cost?
We believe costs are likely to be in the $100-300 range. The actual price to subscribers will vary as a function of how the operator chooses to bundle the product along with their service plans.
You said femtocells operate on licensed spectrum: Will this lower the risk of interference?
Indeed. The whole idea of the femtocell is to be able to use your existing mobile phone, so it is designed to work on the same spectrum. This also helps guarantee the operator has better control over the interference environment. This is important because WLAN is often negatively affected by common household items such as cordless phone and microwaves. With operator control, femtocells can correct any interference without it affecting performance.
If the installation of a femtocell requires a contract with an operator, does that mean that we won't see a new Skype or Fon offer free femtocell gear to broadband users and divert customers from telecom carriers?
Yes. To offer a femtocell it will be necessary to have a license to the spectrum in which the femtocell operates. Therefore for Skype or others to offer femtocell services they will need to acquire such spectrum licenses.
How many cell phones can a femtocell support simultaneously?
This will vary based on the characteristics of the femtocell and the operator’s policy, but generally a femtocell should be able to handle at least four simultaneous conversations. This should be more than adequate for the average household.
What is the typical radius of a femtocell? Is one sufficient to cover a big house with garden?
Femtocells are being designed to cover a radius of 50-100 meters, which would cover even a fairly large house. They will also have built-in intelligence to increase or decrease transmit power so as not to interfere with other signals in the area. This "intelligent coverage" might well cover the garden; however, the range of the femtocell will be affected by the RF (radio frequencies) environment in the garden due to both the macrocell and other femtocells. The femtocell system will attempt to adjust the femtocell power to cover the garden while still maintaining a quality experience for both macrocell users and users of other femtocells.
Are femtocells exclusive to one operator? I mean: If I am a customer of operator A and I visit a friend who has a femtocell and is a customer of operator B, will I be able to tap into it with my cell phone? Or will I have to pay "femto-roaming" charges?
Typically, yes they will be exclusive to the operator. Some mobile operators may allow you to let your visiting friend to use the femtocell. Whether your friend will pay a roaming charge will be determined by the operator’s pricing policy.
Does the technology support handover (starting a call in the office and continuing it while walking on the street)?
Yes, this is another reason femtocells operate on a licensed spectrum. With operator management, macro-to-femto handoffs should be automatic and seamless, with no coverage gaps due specifically to the handoff.
Femtocells are supposed to extend the UMTS signal indoors. Does this mean they can carry IP-TV services?
Femtocells help UMTS indoors in two ways: first, they provide a strong indoor signal in comparison to macro 3G signals which often have difficulty penetrating building walls. Second, they allow the individual user or family to share the entire available spectrum, rather than sharing among perhaps 100 users on the macro network. This translates into greater capacity for bandwidth-intensive services like IP-TV.
Does this signal the arrival of an in-house competitor to Wi-Fi?
Yes and no. The European market is demanding integrated femtocell and Wi-Fi DSL routers for the home. Airvana has recently announced an agreement with Thomson, for example, to address this market requirement. Customers seem to want both mobile 3G and Wi-Fi access in the home.
Lack of standardization seems to be holding back the deployment of femtocells (although Samsung has announced it will release pre-standard products soon): what standards are missing, and when do you expect standards to be defined and agreed upon?
The key area for standardization is the connection between the femtocell and the core network. While this domain is yet to be fully standardized, there is work going on in 3GPP and 3GPP2 standards bodies and in the Femto Forum industry group to drive standards. There is also a lot of inter-vendor cooperation taking place to create viable solutions even before the standards are fully settled. For example Airvana is working closely with Nokia Siemens Networks to ensure that our HubBub femtocell interoperates fully with NSN’s Femto Network Gateway. To date, we have not encountered operators in either CDMA or UMTS markets that are slowing or hesitating to deploy femtocells because of the lack of standardization. Most say that the argument for deployment is simply too strong to wait.
When do you expect the first mass-market rollout of femtocells to happen?
Trials are already taking place now, and we are expecting rollout to take place in late 2008/early 2009, although in the end the mobile operators will determine this.
Where? (US? Europe? Asia?)
Femtocells appear to be in demand almost everywhere. There are trials currently taking place in North America, Europe and Asia.
Aside from better indoor coverage, what advantages are there for the user in installing a femtocell in his/her house or office?
The femtocell will offer better data bandwidth/performance, and lower home-zone calling tariffs. With this performance, femtocells will deliver a better multimedia experience with music, photos and live video to laptops, smartphones and feature phones.
Can you mention and describe a few of the new services that operators may be able to offer if the installed base of femtocells becomes significant?
Beyond home-zone calling plans, there are a number of services that can be envisioned; for example a number of services could be triggered off the presence information of knowing whether the user is at home or away. Parents might be notified automatically that their children have arrived home. This is just one example, but there will surely be many others once the basic technology becomes established.
One could speculate that over the long term femtocell could change the design of wireless networks: whereby they're now considered "add-ons", but because they leverage broadband connections they could play a more central role down the road. What's your take on this?
We absolutely believe femtocells will change the design of wireless networks. To date, the mobile industry has asked subscribers to move to the network-hence you see people walking out into a parking lot to get a 3G signal. With femtocells, we are bringing the network to the subscriber, which is really a dramatic shift. But femtocells won't replace the macro network. They will complement it by delivering service in specific targeted areas that the macro network cannot economically reach. Femtocells will evolve into less of a perk and more of a necessity to keep pace with the expanding service expectations.
Obviously many people will see this as moving the cellphone towers into their homes (which to a certain extent is in fact the case), and will be concerned about electromagnetic radiations. I know it's a complicated question, but how do femtocells compare with wifi routers in terms of radiations emissions?
This is an understandable concern. However, femtocells fall well within the emissions limits permitted by regulatory agencies for similar products such as wi-fi routers, baby monitors and the like. For further information, I suggest visiting the Femto Forum web site, in particular their publication “Femtocells and Health”.
UPDATE 7 April 2008 - Paul Callahan's answers to two additional questions asked by reader Mark Stosberg:
When voice data is being carried over the femtocell and out through the broadband connection, how much bandwidth will this require?
In UMTS, an AMR voice codec reduces a voice call to 12.2Kbps, not counting the overhead of the IPsec tunnel it is carried in. In CDMA, an EVRC codec reduces a voice call to about 8.5Kbps or less, not counting the overhead of the IPsec tunnel. This is a small amount of traffic relative to most broadband connections today.
Would other computer users on the broadband connection be likely to notice a drop in bandwidth while a call is active?
Again, the bandwidth required for voice is comparatively small. There would be a drop in bandwidth but in most cases we do not expect it to negatively affect the user’s experience.
Bruno Giussani is a writer, the European Director of the 
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