In a traditional mobile phone network, users connect to a macrocell, a cell that provides radio coverage for large areas and is served by a high-power cellular base station. While macrocells are perfect for covering 80% of the area, they fail in providing the necessary quality of service for 100% of it. With today’s lifestyles, where people rely more and more on their mobile devices, the 20% of the areas where service is problematic becomes more and more of a concern. As is the case in many fields of activity, the solution comes from delegating coverage tasks to units smaller than macrocells, ones that can be strategically placed to cover specific needs. These smaller units can add coverage in areas considered blackspots, enabling the use of mobile phones in areas like the basements of buildings, for example.

In a previous blog post, I described different kinds of small cells that address different coverage issues. In this post, I provide details on the smallest of cells, femtocells.
The term femtocell is used to identify the smallest of cellular base stations, ones that cover a very small radius, around 10 meters. These cells are being used more and more every month to provide mobile coverage in houses and small businesses around the globe. It is well established that they will play a huge role in the future of mobile coverage. They look like standard wireless routers and connect to the building’s broadband internet connection to reach the cellular provider’s network. Essentially, they are small base stations that operate in regulated frequency bands and have a limited operational range due to their low power.

Femtocells bring a lot of benefits for both users and providers:

  • Since your mobile phone is communicating with a nearby base station, the amount of power it requires to transmit is much lower than the power it would use to communicate with a macrocell that is much further away (e.g. sometimes up to 30 kilometers). This reduction in required power directly translates into a much longer battery life.
  • Femtocell coverage in your building pretty much guarantees “5-bar” service.
  • When connected to your own base station, you are freeing up bandwidth that can be used by other users who need to connect to the macrocell. Providers will usually acknowledge this by reducing your monthly fees for mobile services. It is important to note however, that the data your phone is exchanging still has to reach the core network of your mobile provider and, when using a femto base station, it does so by using your broadband internet connection. What you save in mobile service fees, you may pay in internet fees, since you’ll need to have a good broadband plan to guarantee you the required quality of service.
  • For each person connecting to a femtocell instead of a macrocell, the capacity of the macrocell is augmented and its quality of service improved.

Femtocells are the answers to many problems, but like many solutions, they bring their fair share of challenges to the table. With the growing usage of femtocells, interference becomes a concern. Interference in femtocell networks is a complex problem to solve – not only must you deal with neighbouring femtocells, most of the time you must also deal with the local macrocell. I will write about this problem in a future blog post.