Spectrum Assurance analysis of BT Openreach VDSL
The Radio Society of Great Britain (‘RSGB’) have made complaints to Ofcom and BT Openreach on behalf of its members, predominantly radio licensed amateurs, stating that the deployment of very-high-bit-rate digital subscriber line (VDSL) technology by BT Openreach has resulted in interference to radio reception.
Following a meeting with representatives from the RSGB, Ofcom and BT Openreach, it was agreed that surveys would be conducted to assess the effects of VDSL on amateur radio reception.
Ofcom Spectrum Engineering Officers carried out surveys at three locations, where RSGB members had experienced problems associated with VDSL deployment and where BT Openreach had previously visited.
The methodology involved a physical examination of the affected station and tests using calibrated apparatus. The overall conclusion was that there was no evidence that emissions from BT Openreach VDSL drop wires was causing harmful interference to the amateur radio reception.
Following the publication on the first report published in May 2017 Ofcom carried out further technical surveys focusing on the effects of electromagnetic emissions from Openreach cables carrying VDSL (Very high bit rate Digital Subscriber Line) services. This survey was commissioned to assess the efficacy of corrective measures achieved by Openreach intended to ameliorate any impact on radio reception. Representatives from the Radio Society of Great Britain (RSGB) have attributed VDSL emissions as interfering with radio amateur’s reception of high frequency (‘HF’) wireless telegraphy. VDSL facilitates high speed internet access to many of the 30 million households and business using the existing ‘copper’ infrastructure.
The RSGB nominated six affected stations operated by their members for the purpose of this survey. Representatives from their EMC Committee acted as observers. The methodology involved surveys before and after Openreach carried out remedial activities. Ofcom restricted second visits to the sites where Openreach discovered anomalies in their VDSL installations.
Ofcom tests indicate that wires used for VDSL emit an electromagnetic disturbance at levels capable of affecting HF radio reception. The degree of effect is contingent on several factors, the most significant being the proximity of the receiver antenna, other factors include the relative strength of the wanted signal, the local ambient ‘noise’, atmospheric conditions and the engineering of the VDSL installation. In this survey, Openreach found anomalies in two of the complaints they investigated, in one, remediation showed some benefit and the other, the outcome was at best inconclusive.
Openreach have stated that VDSL emissions can be affected by inadequacies in their customers in home wiring, a matter beyond their control.
Against the backdrop of an estimated 25 million VDSL installations, the overall the impact of VDSL remains extremely small. Over the past five years Ofcom has received an average of six complaints a year.