The Shadowing Effect of Femtocells

What are Femtocells?

A Femtocell is the smallest type of cell used to expand cellular network connectivity within a targeted geographical area (typically a small, single location). Femtocells are used as a wireless access point that improves cellular reception inside home data traffic or office building. This device communicates with the mobile phone and converts your voice calls into voice over IP (VoIP) packets. The packets are then transmitted over a broadband connection to the mobile operator's servers.

In addition to being the smallest but smartest in the family of small cell technologies, Femtocells uses the lease amount of power; as such, they don’t offer as much of an impact when attempting to expand network connectivity. In fact, compared to other types of small cells, like picocells and microcells, femtocells offer the least amount of additional bandwidth, so they should only be deployed in specific situations. 

Femtocells are compatible with CDMA2000, WiMAX or UMTS mobile telephony technologies, using the provider's own licensed spectrum to operate. Typically, consumer-based femtocells will support only four active users, while enterprise-grade femtocells can support up to 16 active users.

 

 

AT & T's Femtocell

The Shadowing Effect

Even though Femtocell network range and capacity are relatively limited, it’s their low powered nature that often makes them the small cell geographic choice. Before deployment of a small cell network begins, the targeted space must be analyzed for certain limiting factors that might cause interference to the network signals, and the result of this analysis often limits the use of larger small cell technologies due to the potential for signal interference.

Firstly of all, for all small cell systems, there is a “shadowing effect” with the signal that must be taken into consideration when designing the small cell network. For some small cells, such as microcells, the broadcasted signal is strong enough that if placed too close to another transmitting microcell, the two signals can interfere with one another and cause signal degradation.

            This shadowing effect can cause serious problems for the targeted location if it just so happens to be filled with signal interfering obstacles. For example, let’s say your office space is arranged in such a manner that there is a combination of cubicles and smaller enclosed spaces used for meetings. These areas are separated by glass, concrete, and other building materials that can disrupt the traveling signal of the microcell.

But what’s worse is that sometimes adding additional microcells to the office will only cause the signal to degrade further, but here’s where Femtocells truly excel. Because of its tiny footprints, Femtocell designs allows for the placement of multiple antennas around the space, providing the necessary network connectivity without distracting the Femtocell network signal and simultaneously negating the effects of interfering obstacles.

In this scenario, Femtocells can be strategically placed close to and around the cubicles, as well as inside each enclosed meeting room in order to provide a stable cellular connection, and avoiding the shadow effect. 

Future Aspects

For smaller locations, or locations that feature many signal obstructing obstacles, Femtocell technology will continue to be a popular network solution. The low cost, low powered nature makes them an attractive alternative to other larger, costlier small cell solutions, especially when the need for network connectivity only covers a few individual users at any given time.

However, for the casual consumer at home, the future of Femtocells is not quite as secure. Even though Femtocell networks are small, low-powered, and easy to deploy, cellular providers are rapidly adopting the capability of offering Wi-Fi calling, which directly competes with Femtocell capabilities. Also, as popular messaging applications move more users away from traditional SMS text messaging, the need for a reliable cellular connection in the home is likely to continue to decrease in priority.