The UK communications regulator Ofcom has outlined its plans for the completion of the transition to digital terrestrial television and they could provide more channels on Freeview.
After technical consultations, Ofcom favours an option that will provide capacity for anything up to nine additional television channels.
The details have been published in an Ofcom statement “Planning Options for Digital Switchover”.
The final overall national coverage will be similar to that currently available for analogue television. Around 375,000 UK households, about 1.5%, are unable to receive all four main public service channels from analogue broadcasts.
However, the main attraction appears to be the additional capacity for more services. It could be used for interactive services, radio, television, or high-definition broadcasts television, says Ofcom.
That is not counting the spectrum released by analogue switchoff. The additional capacity would be created by changing some of the transmission characteristics for digital terrestrial television transmission.
This is where it gets a bit technical. Ofcom says that there are advantages in adopting the “64QAM” transmission mode. This potentially allows more channels, at the expense of being less robust to noise.
When Freeview was launched, the BBC and Crown Castle multiplexes switched their signals to “16QAM” to provide a more robust signal at the comparatively low power levels used.
At the time this was seen as essential to the launch of Freeview, but the other commercial multiplexes continued to use 64QAM and consequently could fit in more services, equivalent to two or three channels per multiplex.
To compensate for any change to 64QAM, higher power levels may need to be used, and additional transmitters may be required on the south coast of England, which would need international clearance.
Another issue pondered by Ofcom was a move from a transmission standard using 2,000 sub-carrier frequencies, known as 2k, to an alternative using 8,000, known as 8k. The later allows what is known as a single frequency network to be used.
However, it could be a problem for a small minority of receivers, notably the original ITV Digital set-top boxes and certain integrated digital televisions that only support 2k. No compensation is likely to be available for anyone still using such equipment.
The current plan is digital switchover to be complete sometime around the end of 2012, although the process will take place in phases.