Interference from future mobile signals might make digital TV unwatchable for some Britons, Ofcom has said.
The telecoms watchdog is starting a research programme to find out how to help people affected when future mobile technology is switched on.
About 3% of TV-watching Britons could suffer interference from fourth-generation (4G) mobile, said Ofcom.
Filters will solve the problem for some, said Ofcom, but others may have to use other ways to get TV signals.
The problem of mobile and digital TV signals interfering with each other will arise because the chunk of spectrum reserved for 4G sits next to that used for broadcasting terrestrial digital TV signals.
The auction for the 800Mhz band is due to take place in 2012 and 4G services are expected to follow soon after. The rollout of 4G mobile will mean faster download and browsing speeds for handsets.
However, signals from base stations handling 4G services might cause interference in set-top boxes and digital televisions in homes nearby, said Ofcom in a briefing document.
Up to 3% of viewers of digital terrestrial television, about 760,000 people, might see interference if no action is taken, it warned.
In a bid to limit how many people suffer from poor picture quality, Ofcom has proposed running an education campaign to alert viewers about the possibility of interference.
Companies who buy a licence for part of the 800MHz spectrum will be expected to contribute to the costs of the education programme.
For the vast majority of affected viewers, filters will strip out the interfering signals.
However, said Ofcom, in 0.1% of cases, filters will not help and it is considering how best to handle those instances. Some viewers may have to find alternative ways to watch digital TV.
A consultation exercise which will consider ways to tackle the interference issue is being started at Ofcom and will run until 11 August.