Published: 7 June, 2010
Femtocells are starting to gain real operator momentum - just this month, AT&T has extended availability round the US, and Vodafone has gone live in Spain, adding to its UK and French roll-outs. Most of these deployments still focus mainly on improved in-home coverage, but carriers are looking for a wider range of functionality and applications in future, and the femtocell platform is expanding rapidly. The latest evidence - enhancements from the main femto silicon provider, picoChip, that support up to 400 smartphones at once in always-on mode, and address the problem of smartphone 'chattiness'.
This is done using the company's 'smartSignalling' technology, now included in the picoXcell system-on-chip platform for femtos or available as a firmware upgrade. This "employs a collection of techniques to increase the effective signaling capacity within a cell and reduce the signaling required by each handset", according to the vendor.
The UK-based firm says its PC3x3 series of chips, which underpin picoXcell, can already support 64 users, taking the architecture beyond the home device and into the realms of enterprise of even outdoor metro access points. As VP of marketing Rupert Baines puts it: "That is a pretty big femto - intended for metrozone or a bigger enterprise. It is past pico and creeping up on micro."
The latest additions, though, make that scale usable in the real world, by dealing with the particular issues of smartphone behavior, particularly the constant signalling and 'checking in' that always-on handsets do when using applications like social networking or push email. This is an issue that has been highlighted in recent months by many companies, perhaps most vocally by Nokia Siemens, which points out that a 'signalling storm' can have as destructive an effect on a network as high volumes of data traffic. picoChip agrees, and claims to have addressed the issue, in so doing increasing network efficiency and extending handset battery life.
The updated picoChip architecture enables a femtocell that can support 64 users in active conversation or web browsing, and 400 phones engaged in general network signalling or 'chatter'. The chip designer hopes this will enhance the operator business case by proving femtos are usable for large scale deployments, including outdoor metrozones. This could significantly expand the clear but somewhat limited business case that exists when the femto is confined to the living room, and address some hot cellco issues such as offload from the macro network, and building efficient 'hotzones' for urban areas of heavy and unpredictable usage.
The main tactics used by smartSignalling are to support special handset 'sleep' modes, such as Cell_PCH, which require fewer signaling messages to 'wake up'; additional specialized channels for signaling information via Common E-DCH and Enhanced Cell_FACH functionality, which allows many devices to share a base station efficiently.
ABI Research analyst Aditya Kaul wrote in a blog post: "Compared to Wi-Fi offload this gives femtocells an edge for sure, as Wi-Fi is primarily meant to offload capacity and not signaling traffic. With collapsed RNCs, femtos are able to take most of the signaling traffic off the operator core network."