Ever wondered why your DAB radio works in one corner of the room, but not in another? Sometimes, something as seemingly innocuous as a modern household appliance can wreak havoc with wireless communications. In denser urban environments this is a common problem, and one that is often hard to trace for individuals. The EBU and ITU (International Telecommunication Union) held a joint workshop in October to raise awareness of the risk of such interference into digital radio services from modern devices and LED lights.
Invisible noise
Administrations and broadcasters are seing an increase in the number of reported cases of interference to DAB(+) reception. Many of these cases can be attributed to a rising environmental "noise floor" on radio frequencies, caused by the proliferation of devices such as LED lighting systems, household appliances, and tools that use efficient and lightweight, but electromagnetically noisy, switch-mode power supplies.
At the joint EBU-ITU workshop, the participants discussed the results of measurements and tests in several countries as well as the role of administrations and Standardization Organizations in limiting this interference. After opening remarks from François Rancy, Director of the ITU Bureau of Radiocommunication (BR), and Yukihiro Nishida, Chairman of the ITU's Study Group 6, two EBU Member organizations – NRK from Norway and RTS from Switzerland – as well as European broadcast network operator Arqiva from the UK, presented their respective findings and analyses of factors causing such interference.
What can be done to limit interference?
A rising noise floor could seriously compromise service availability of current and future radiocommunication services, particularly indoors. With that in mind, the conference turned its attention to possible mitigation strategies, such as standards to improve equipment design that would help to minimize RF noise emanating from electrical devices.
It was noted that the problems experienced in particular with LED lighting systems are symptomatic for a number of deeper underlying problems. A common factor is the now near-universal use of switch-mode techniques in power supplies and AC to DC and DC to DC power converters. These tend to produce high levels of radio-frequency (RF) energy, which appears as radiated emissions across wide ranges of frequency and leakage of RF energy onto electrical mains wiring. Increasing levels of RF energy on mains wiring then causes thermal stress and rapid ageing of filter components in other connected equipment, thus creating a vicious circle of degradation and increasing RF noise. These factors are particularly evident with LED lighting systems on account of their ubiquitous use these days.
A presentation by the Norwegian spectrum regulator, and the ensuing conversation with representatives of other administrations in the audience, produced some valuable starting points to help better address these issues from a policy angle. The EBU representative to the International Special Committee on Radio Interference (CISPR) gave a remote presentation on the important role of CISPR in setting the limits of emissions that the non-radiocommunication devices should not exceed. Finally, speakers from the EBU, BBC and ITU presented the ITU-R's role in specifying the system parameters, planning parameters and protection requirements of the broadcasting systems.
All presentations and information about the programme and the speakers can be found on the ITU webpage for the Workshop on ‘Interference to DAB reception.’