Big bandwidth VDSL networks held backDavid MannersHigh hopes for VDSL may be scuppered by a raft of issues - legal, technological, lack of standardisation and cost.
While many industry analysts have been bullish about the prospects for VDSL because it offers telecommunications operators the chance to provide the 'triple play' of voice, Internet and video services, telecoms firms have pointed out that, as things stand, it is illegal to install VDSL on the UK telecoms network.
Under the Radiocommunications Agency's MPT1570 rules governing RFI, it is forbidden to attach devices to the network which operate at frequencies higher than 1.5MHz. VDSL operates at higher frequencies than 1.5MHz.
"It is perverse that telecoms circuits are singled out in this way," said Hugh Saunders, group regulatory affairs and technical director at Kingston Communications. While the Radiocomms Agency looks at amending MPT1570, technological advances in compression technology could overwhelm VDSL.
"I can see video being delivered over ADSL in the not too distant future," said Saunders, while Lesley Hansen of US DSL provider Net to Net Technologies, said: "We're working with iMagic in Canada, nCube in the UK and i3Micro in Finland and the consensus is that, within 18 months, compression technologies will halve the bandwidth needed for video-on-demand from 3.5Mbit/s to 1.75Mbit/s."
VDSL's prospects are also being hit by a split among suppliers pushing competing standards. There is the discrete multitone (DMT) standard supported by Alcatel, Globespan-Virata, Ikanos, STMicroelectronics and Zarlink Semiconductor and there is the quadrature amplitude modulation (QAM) standard being pushed by US firm Broadcom and Infineon Technologies of Germany.
Finally, VDSL is hampered by the high cost of pushing fibre access closer to the curb because of VDSL's relatively short reach.