How clean is your home?

Presents BT's experience in assessing radio frequency interference (RFI) issues encountered during the development and deployment of broadband digital subscriber line (DSL) technologies. As of the end of 2004 (at which point over 4 million DSL lines had been deployed by BT in the UK and over 100M world-wide, only a single instance of RFI caused by a DSL line has been encountered (and quickly fixed by BT) in the UK. There is no known evidence that unwanted RF emissions from DSL is a problem in other countries. However, during the same period, a large number of instances of RFI experienced by DSL lines has encountered by BT in the UK. In all cases, the causes of RFI were common domestic or suburban equipment already existing in very large numbers. Moreover, the RFI generated was severe enough in a small number of cases to cause loss of service to DSL enabled customers up to several hundred metres away. It is noted that, prior to the deployment of DSL services, spectrum regulators went to great efforts to limit DSL technology's potential to interfere with radio reception. During this time, the impression given by the radio industry was one of a generally "clean" RF environment resulting from effective regulation. However, the presentation notes that the domestic RF environment in particular has been found to be very different, far more hostile and considerably more challenging to deployment than the radio industry had led us to expect. Indeed, a portable radio receiver has proven an invaluable tool in establishing the source of the RFI that has been dealt with to date. The presentation provides an overview of the different types of interference problems that have been encountered (providing details of specific case studies) and the remedial engineering required to overcome this