The idea is to use technology to double the bandwidth available – freeing up the necessary space – but requiring us all to go out and buy a new aerial and receiver. It would work by making signals “spatially multiplexed”. This allows you to send two bitstreams on one frequency, sending the signals at different times. This means in addition to packing several channels into a bitstream, you can pack two bitstreams into one frequency. As long as the receiver can tell which one is which, it will be able to decode them into two separate bitstreams and from there decode them into the various channels.
And here’s some more science. It requires MIMO. MIMO works using two transmitters, and two receivers. The two transmitters mean the two sets of data — sent on the same frequency — will arrive at the receivers at different times. Different arrival times are what allow the receiver to differentiate between the two separate signals and subsequently decode them.
The BBC has apparently conducted a small-scale test of this technology and has found that it does double the available bandwidth. Will it be taken beyond the experimental stage? Watch this space.