GSM calls 'spoil mobile TV'

Many TV-enabled mobile phones are vulnerable to interference from GSM calls - causing poor reception that could slow down adoption of the technology, a company claims.

GSM operates at the edge of the spectrum used by DVB-H, the mobile version of the DVB-T signal used for Freeview terrestrial TV. In a mobile handset the GSM power amplifier sits close to the DVD-H module and when it kicks into operation can reduce the sensitivity of the TV receiver by a factor of up to five, according to silicon-tuner specialist Microtune.

“This means that a subscriber can be watching mobile TV and if an SMS is received or the handset polls the network, the TV signal can break up or the signal can be lost,” said Microtune’s handheld marketing manager Phil Spruce in a white paper.

He said in London this week that even GSM signals from other phone users, or mobile phone masts, can cause interference if the TV viewer is close enough.

“Imagine, when you are on a railway platform, how many people will be using a mobile phone nearby,” he said. “You could be there watching a football match and the picture goes fuzzy as a goal is being scored.”

Naturally, Microtune claims to have the answer. It offers a technology called Cleartune, which emerged out of its work on set-top-boxes, TV sets, and in-car TV.

“Cleartune is doing something very difficult and we hold the patents. Other companies would find it very hard to do the same thing,” he said.

Spruce said the issue affects operators as well as users, because more DVB-H masts are needed when receiver sensitivity is low. The problem is exacerbated because there is no standard way of ensuring that different makes of DVB-H receivers will work globally.

DVB-H, which has been trialled in the UK, is expected to be the dominant mobile TV technology worldwide, though it faces competition from DAB-based TV here and in Germany.

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