•Notícia

A team of researchers of the Signal Processing and Communications Group of the Universitat Politècnica de Catalunya (UPC)-Barcelona Tech, headed by Prof. Josep Vidal, is coordinating the European Freedom project, which is aimed at designing technological solutions that make it possible to extend mobile telephony coverage inside buildings and offer high-speed data transmission services at a low cost. The project focuses on increasing the capacity of telecommunication networks, cutting energy consumption, and delivering both economic and social benefits.
The smartphone boom in recent years has increased congestion on cellular networks in urban environments because it allows users to have multiple applications open at the same time (e-mail, internet, etc.). These applications generate more data traffic and therefore consume more radio spectrum resources. If data consumption continues to grow at the current rate, it is predicted that networks will collapse completely at some point in the next three years.

Spain ranks third in Europe in terms of the number of smartphone users (9.9 million), behind top-ranking Italy (15 million), and the United Kingdom (11 million). The other countries in the top five are Germany (8.4 million) and France (7 million). The UK market leads in growth of smartphone adoption over the last year (with an increase of 70% according to comScore, a digital marketing intelligence firm).

In this context, telecommunications operators have no choice but to look for technological solutions that will enable them to tackle the looming threat of collapse. One solution is to increase the number of base transceiver stations. However, this response has a number of drawbacks: it is not widely accepted by society and has a high economic cost.

Neither does it solve the problem of coverage inside buildings, where delivery of internet services over cellular networks can be too slow to meet the expectations of current users, even when voice coverage is good. In fact, most data traffic over wireless telephony networks occurs in domestic and office environments, where coverage is even more reduced.
Over the last ten years, a reduction in the size of the area assigned to base transceiver stations (cell sites) has helped increase the transmission rate for wireless systems, but no further reduction is possible, particularly in urban environments. Femtocells are small low-cost cellular base stations with a short range (coverage of 30 to 50 meters). They are installed in domestic and office environments and connect standard cell phones to the network of a mobile operator via an IP link (using the connection to an ADSL or fiber-optic network). According to experts, femtocells represent an important advance when it comes to improving coverage and providing high-speed data services at a reasonable cost. Moreover, femtocells operate at low radio power levels (about 20 mW, five times less than an ADSL WiFi router).

These mini base stations are wireless devices that share the licensed wireless spectrum used for conventional mobile telephony services. Femtocells are expected to be deployed on a massive scale in the medium term, around 2012-2013.

Some operators are already experimenting with the implementation of mini base stations and femtocells inside buildings, but not on a massive scale. The devices are not yet as efficient as they could be, and many technical hurdles need to be overcome before they can deliver real advantages for the network.

The massive deployment of mini base stations and femtocells depends on efficient handling of mutual interference between the two types of network. One of the challenges for the Freedom project (which is funded under the European Union’s 7th Framework Program and has a budget of €3.45 million) is to work out how to organize data transmission for indoor mini base stations and conventional outdoor cell sites within the common radio spectrum and determine what part of the underutilized spectrum will be reused.

Researchers are also studying the business model that can be built around the new technology.
Transmission via small base stations and femtocells benefits both consumers and telecommunications operators. The systems improve coverage inside buildings, with data rates equivalent to a complete sector of the 3G network and very low transmission power. This extends the life of existing telephone batteries without the need to introduce additional WiFi devices.

Users could also benefit if telcos opt to apply special rates for calls to cell phones within the zone covered by a femtocell. There are also plans to offer services based on the proximity of cell phones to the mini base station, including, for example, SMS notification services or activation of home automation devices. Using mini base stations instead of DECT phones (cordless systems) or WiFi will allow business users to have a single telephone and contact list.

For telephone operators, in areas where the density of users is high and the density of cell sites is proportionately low, short-range stations and femtocells are a way to reduce congestion when there is a peak in demand by offloading some traffic to the conventional cell site via an ADSL connection.

This approach also reduces the cost of operating a conventional cell site because part of the expense, particularly the cost of transmission output power, is paid by users.

The Freedom project is coordinated by the UPC-Barcelona Tech and involves a consortium of eight university and business partners. The other members of the consortium are Università di Roma La Sapienza, the Czech Technical University, the French Atomic Energy Commission, and the companies Dune S.L.R. (Italy), Telkom (Indonesia), Sequans (France), and Siradel (France).