Operators demand smartphones sort signalling storm

While operators spent 2009 fretting about data traffic overloading their fragile 3G networks, this year they have also been worrying about another stress on their systems, exploding signalling burdens from 'chatty' devices that constantly poll the network in applications like social networking updates.

Nokia Siemens has thrown its weight behind publicizing this issue and some vendors have already risen to the challenge, notably picoChip, which implemented a little used part of the 3GPP femtocell standard in its system-on-chip for small base stations. This allows them to support up to 400 smartphones at once in always-on mode, and "employs a collection of techniques to increase the effective signaling capacity within a cell and reduce the signaling required by each handset".

The femtocell sector has been highly operator driven, so it is no surprise that femtos have led the way on addressing the signalling storm. Now the carriers are getting more strident in their demands and are calling for device makers to get on board too, not just infrastructure firms. They have told their smartphone vendors to implement a newly standardized element of the 3GPP Release 8 set of specifications.

This is a new state transition feature, called 'fast dormancy', which sets parameters on how, and how often, a smartphone switches between being in an idle or active mode. This would keep signalling under control as well as save battery life, explains LightReading.

Fast dormancy allows the mobile device to make a query to the RNC (radio network controller) to release the connection so that it can return to the idle state faster. That means the device, not the network, is relaying the fact that the phone is going dormant, saving signaling channels.

"Handset requirements are set by the operators, so we‘re told these are the features we want," Johanna Dwyer, senior director for standards at RIM, said at the recent Mobile Broadband World conference in the UK. She added that Release 8 fast dormancy had been "requested by everybody. It‘s unusual to have a feature universally requested".

RIM will comply from the first quarter of 2011 and most other handsets are expected to adopt the standard in the same timeframe. Some have already implemented non-standard approaches to fast dormancy, but these have sometimes caused signalling to behave unpredictably. For instance, Apple included it in a firmware release last year but its fast dormancy feature often polled the network prematurely, and then had to re-establish the connection, worsening performance. Apple then updated the firmware to remove that feature.

"Fast dormancy is essential to stop phones from being in a connected data state [all the time]," Phil Twist, head of marketing for Nokia Siemens, told LightReading. "It's a big advantage for handset vendors, but chaos for networks." NSN favors its own, network-based approach.

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