Sunday, January 4, 2015

Femtocells (MicroBTS) in support of Emergency Communications

I raised a question with several on-line interest groups: Disaster Management India and Researchers and Disaster Management Professionals and Research. It was intended to understand the real value of the Femtocell (also referred to as Picocell or Microcell) technology in emergency communications. Has there been a significant uptake of the Femtocell technology in emergency communications?

The technology has been around for about ten years. It was developed for commercial wireless telecom carriers to extend their coverage in locations where construction of a full size mobile tower is not warranted or economically justifiable. They are low power, short range (< 100m), and serve between 1-5 simultaneous connections. Ones made for small business or farm use can control up to about 100 users. However, they typically aren't big enough as currently sold to support a major emergency operation [1].

A small deployment, in a disaster affected area, could serve the public in small batches allowing them to reach their loved one. The Federal Communication Commission of USA has discussed the use of Femtocells as a Public Safety Tech. US telcom operator AT&T supports some mini systems that they use for their own emergency deployments and also offer to emergency management teams. The suitcase size,  bigger than Femtocells, AT&T solutions can support 500-1500 users simultaneously. Depending on the bandwidth available they do a decent job, at least with voice.

Image from EMF Explained Series:
Femtocells are Micro Base Transceiver System (Micro BTS). The mobile phone connects to a small local Femtocell device about the size of your WiFi modem as if it would to a regular GSM/WCDMA cellular tower. That device then provides voice and data to your cell phone where it otherwise wouldn't be able to pick up a signal out of the air. Cost of the device is under $100. David Kebo Houngninou explains the technicalities and architecture of setting up a cost-effective Femtocell access point.

Pasquale Pace and Valeria Loscri published on the architecture of OpenBTS as another step forward towards establishing cost-effective Micro BTS solutions. Range Networks has primarily customized the openBTS platform for a Network in a box kind of offering. They have a handful of implementations in various parts of the world: Antarctica, Indonesia, and Zambia. Folks at Daes and Orangee have discussed their practical experience of implementing a OpenBTS-enabled Microcell.

Extreme arid terrain:
In the wake of a disaster, like an earthquake that may take out the towers and cables, it may take the telcos, at least, 48 hours to restore those BTS. The earthquake may cause landslides that may block the roads for Cells on Wheels  (COWs) to reach the cellular dark area. Some areas can be unmotorable in  terrain with high mountains, deep valleys, rocky ground, and swampy lands. A Mobile Emergency Operation Centre (MEOC), similar to the DUNE2014 project with LTE broadband capable of transmitting video data, can be setup at a distance. Then the MEOC can extend the LTE internet connection to serve the Public at a distant location by linking them to a Femtocell.

Of cause there are legalities with frequency reuse by an unlicensed service provider. There must be roaming agreements between providers to use the same frequencies in the same area; i.e. multi-carrier compatibility to allow for a femtocell to communicate with handsets from different carriers. It doesn't affect or matter who's at the other end of the line. Government agencies have the authority to overpower those licensing barriers. A Micro BTS setup by a Government emergency service can certainly override those licensing issues. Another option is to offer a set of emergency frequency bands that any authorized service operator can use to operationalize a Micro BTS in the time of an emergency.

The back-haul can simply be a broadband (internet) link to pipe the cellular signal. For example, a VSAT connection can serve as back-haul in a cellular dark area caused by a disaster . However, one must be cautious of the latency that comes along with satellites back-haul. Moreover, it has to have some form of authentication to interface and establish routing of the call in both directions. Establishing a satellite link in between would likely fail because of latency and technical routing problems. Mobile phones require specific performance characteristics that are not one size fits all that can be accommodated by one system.

While Femtocells have certain challenges with operationalizing that are mainly due to policy and regulatory issues, it still is a promising technology for serving the gaps of filling the dark cellular coverage holes in support of crisis response and management.


My gratitude to the following people (listed in alphabetical order) for their contribution to the discussion that resulted in this blog

[1] Disaster Researchers and Disaster Management Professionals, LinkedIn Group. "Femtocells, who uses them?", consulted on the web:

[2] Disaster Management India, LinkedIn group. "Femtocells, who uses them?", consulted on the web: