UK's Broadband Local Loop Lengths
Posted: 01st Nov, 2005 By: MarkJ
Point-Topic has published a new report into the reality of higher speed unbundled (LLU) UK broadband ADSL2+ services, which points out why many will never get the speed advertised (line length):
The bandwidth which DSL technologies can deliver over a telephone line falls off sharply with distance. For example, ADSL2+ can deliver its maximum of 24Mb only within 300 metres of the telephone exchange. Bandwidth continues to fall with distance dropping to 8Mb at most by 3000 metres (roughly 10,000 feet).
So far as we know BT has not published the actual numbers for the distribution of its local loop length, but it has provided enough information for Point Topic to reverse-engineer this graph and to create a model which estimates the actual length of each end-users line as a function of their linear distance from the telephone exchange. It shows, for example, that only 5% of end users have local loops of 1200 metres or less, 45% have 3km or less, and 85% are within 5km.
Figure 1: Distribution of telephone line (local loop) length in the UK
The distances over which DSL speeds are available are not very clearly defined in practice. DSL services will still work with worse signal-to-noise conditions than the design standards assume. BT has successfully used this extra latitude to extend broadband service to much more of the country than originally seemed possible, giving the much quoted 99.6% coverage of the UK.
Despite these uncertainties the conclusion is that ADSL2+ high-speed services will be unavailable to a large percentage of the population unless and until there is some major investment in extending fibre deeper into BTs access network.
None of this is new to those familiar with the technology, yet Point-Topic has also provided a clever, if rough, tool to check every postcode in the UK and it's related line-length (must be registered with them):
http://www.point-topic.com/home/bbus/
The bandwidth which DSL technologies can deliver over a telephone line falls off sharply with distance. For example, ADSL2+ can deliver its maximum of 24Mb only within 300 metres of the telephone exchange. Bandwidth continues to fall with distance dropping to 8Mb at most by 3000 metres (roughly 10,000 feet).
So far as we know BT has not published the actual numbers for the distribution of its local loop length, but it has provided enough information for Point Topic to reverse-engineer this graph and to create a model which estimates the actual length of each end-users line as a function of their linear distance from the telephone exchange. It shows, for example, that only 5% of end users have local loops of 1200 metres or less, 45% have 3km or less, and 85% are within 5km.
Figure 1: Distribution of telephone line (local loop) length in the UK
The distances over which DSL speeds are available are not very clearly defined in practice. DSL services will still work with worse signal-to-noise conditions than the design standards assume. BT has successfully used this extra latitude to extend broadband service to much more of the country than originally seemed possible, giving the much quoted 99.6% coverage of the UK.
Despite these uncertainties the conclusion is that ADSL2+ high-speed services will be unavailable to a large percentage of the population unless and until there is some major investment in extending fibre deeper into BTs access network.
None of this is new to those familiar with the technology, yet Point-Topic has also provided a clever, if rough, tool to check every postcode in the UK and it's related line-length (must be registered with them):
http://www.point-topic.com/home/bbus/
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