Broadband Regenerators on copper lines providing ADSL

I can't see that this has been posted anywhere here but apologies if it has. Sounds like an interesting idea on potentially increasing speeds where the ADSL signal is poor at the cabinet - anyone have any more info?

Original Article is here and is an OpenReach briefing.

GEN057/12 Network Rearrangements for ADSL

05/07/2012 For Information

This briefing on network rearrangement is for all ADSL Communications Providers.

The purpose of this briefing is to raise awareness of a potential network rearrangement option for ADSL in BDUK funded County led projects

As part of Openreach's Network programme and our ongoing operations we have been trialling some network rearrangements, including the installation of Broadband Regenerators on copper lines providing ADSL. These Regenerators can be placed in or near a cabinet and are powered by new equipment in the Exchange. The ADSL signal is 'cleaned' and 'amplified'. Early indications from the technical trials are positive with some increases in ADSL speeds - although they do require additional network investment.

As part of its portfolio Openreach already offers a range of Network Rearrangements services which can be requested by CPs. Following commencement of the initial technical trials we wish to advise interested CPs that we would like to hear from any CPs who might wish to participate in a CP trial. The Broadband Regenerator may be an option in the future (subject to trial) available to all those who are involved in proposals connected with areas for intervention under BDUK County led rural broadband programme. Any proposals for Broadband Regenerators would need to be evaluated and costed on an individual case by case basis (including feasibility, survey, plan and build). These would then be charged back to the bidding CP on a per project basis.

Yes looked very deeply into this. Got a cheap source who offered free units for testing and documentation specs etc pushed up to the engineering boffins but was told we could not apply it to the network due to the ANFP frequency plans. The day after we announced fttc roll-out anyway. Would have been very interesting - closest thing BT have developed is BET - which uses an adsl to shdsl converter at the exchange (so llu equipment etc can be connected without more investment by isps) then an shdsl regenerator at the pcp to provide 1 meg (limited due to anfp) on any line length (2meg with bonded pairs). I believe it uses a openreach NTU and delivers adsl to your router. Although I have never seen it in action.
- BT ENGINEER

Although I have never seen it in action.

Trust me, don't bother. Single pair gets you 750Kbps and two pairs 1500.

BIG pain to fit, and worse still to fault.

Only plus is, if you can't get diddly, it's better than nowt.

This is different to BET and has been used abroad, but not in the UK due to the ANFP, it still may not be in the ANFP, trials are often used to build a real data set to figure out if the rules can be changed.

Not new - has been around for a few years in various forms. One of my teams installed some in a few (non-UK) remote locations. They were fine and provided a good robust service.

However, in one location, it had to be removed (until a line re-routed) as the repeater caused massive interference/cross talk issues with other users who had their termination points close (in line length terms) to where the repeater was.

For that customer - money was no object (almost).

I'm not seeing why this wouldn't fit the ANFP - you can do ADSL at a street cab in part B of the ANFP (as well as VDSL) which is conceptually the same - a remote injection point.

Is ADSL at a street cabinet acceptable where there are already ADSL circuits passing through?

Take a cabinet several km from the exchange with an attenuation of maybe 65 or 70 dB at that point and a premises just a few metres away - Local Customer (LOC) An ADSL regenerator is installed for a remote customer (REM) several km further away.

LOC has a signal running at maybe -55dBm (20dBm with 75 dB attenuation) - at the cabinet REM's signal is generated at +20dBm. There will be cross talk and it could very well be significant, causing several dB reduction in SNR/margin and possibly loss of service for LOC.

Similarly, REMs upstream will arrive at the cabinet with a high attenuation, LOC will be generating a fairly strong upstream signal, again 50, 60, 70 dB higher - the cross talk from that could kill REMs upstream.

Is ADSL at a street cabinet acceptable where there are already ADSL circuits passing through?

It's not excluded by the ANFP.

There is a power mask, and there are different masks for different D-side line lengths. Some early sub loop unbundling (Trilogy Telecom, RIP) was ADSL at the street cab.

I'm no expert, the power mask is at http://www.niccstandards.org.uk/files/current/ND1602... (part C applies). The exchange mask (part A) is -36.5 dBm/Hz up to 1 MHz, the cabinet mask at 400 kHz starts at -43 dBm/Hz for ultra short D-side lines rising to -85 on long lines.

So compared to the exchange based DSLAM on a very long line one at the PCP is attenuated by about 50 dB (at 400 MHz, as an example) which I think addresses the issue you raise.

http://www.niccstandards.org.uk/publications/llu_spe...