How LTE helped improve white space access

18 Oct

Regulators are inherently conservative beasts. It is very hard for them to be otherwise – the mix of external inspection and the likelihood of adverse publicity if they get things wrong bias them towards caution. So when they set access rules for new technologies they always take a conservative approach to ensure that the existing users do not suffer interference even if this causes additional costs or other penalties for the new entrant. That’s why you very rarely hear of cases of interference other than malicious or accidental transmissions.

In the UK this bias was resulting in rules for white space access that threatened to be so conservative that availability and power levels would be too low to allow for most commercial deployments of technologies like Weightless. Ofcom promised to review limits over time – but the problem is that if they are set too low initially there are no deployments and hence no evidence on which to base any future review.

Then along came the deployment of LTE at 800MHz. This deployment had the possibility of causing interference to TV viewers who were in some cases in adjacent bands to the LTE transmission. Modelling by Ofcom and by the broadcasters suggested that around 2-3 million homes could be affected. Because Ofcom could not change the access rules for LTE (they are set in the 3GPP standards) they decided to require a new body called at800 to be established to supply filters to viewers and take other mitigation approaches that might be needed.

Early deployments seemed to be going much better than expected. So much so that the number of affected homes has been revised downwards rapidly. There are no official predictions, but it looks likely that it will be more like 20,000-30,000 than 2-3 million – two orders of magnitude less. Ofcom, sensibly, asked themselves if LTE interference was proving to be much lower than expected, might not the same be true of white space devices – after all the interference is very analogous. As a result, their latest consultation has much less conservative access rules than might otherwise have been expected. This is clearly very good news for white space access and commendable adaptability from Ofcom. Thank you LTE! Other regulators take note.



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