Femtocells bring 3G phones in-house

Femtocells developed for UMTS mobile phone provision within buildings are one of the stars of the Mobile World Congress (MWC) in Barcelona, which finishes on Thursday. They're on offer from both established infrastructure providers and specialists. A number of vendors have now pooled their interests together in the Femto Forum. Internet giants such as Google and Cisco have also invested in the technology. A presentation by Japanese electronics manufacturer NEC, who revealed that their femtocell solution will soon be marketed in the UK by O2, makes clear both the potential for and the challenges involved in integrating the mini-cells into the UMTS mobile phone network.

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Miniature base stations – picocells – for improved in-house mobile network provision are nothing new. However, picocells need to be connected to the mobile network backbone. Femtocells, by contrast, use existing in-house public internet connections such as DSL or cable connections. Femtocells are authorised and connected to the backbone via femto gateways, either via SIP or Iu-over-IP. According to NEC, this represents a development of the Generic Access Network (GAN) - standardisation efforts are ongoing. The 3GPP standard GAN was developed for dual mode telephony and enables seamless handover of voice telephone calls which can be made in part over the mobile phone network and in part via WLAN. This procedure is known as Unlimited Mobile Access (UMA).

On top of this, Femto Access Point Management System should administer large numbers of femtocells. NEC femtocells, which are customer installable, also include a SIM card intended to prevent the use of stolen femtocells at other locations.

A further trick consists of the fact that IP traffic routed to the mobile device via the femtocell is not all routed through the mobile network backbone - this increasingly represents the bottleneck for the ravenous appetite for data which HSPA customers develop. If, for example, a user views a video on YouTube, the femto gateway ensures that the data stream is routed via the public internet - a process which NEC has christened IP breakout.

The femtocells exhibited at the MWC allow up to four simultaneous mobile phone connections, which, according to NEC, can carry both voice and data simultaneously. In collaboration with Netgear, the Japanese company also announced a router which contains both an in-built femtocell and an IEEE 802.11g WLAN base station.

(jbe)