How far does FTTC reach?

In general, FTTC (VDSL) will extend the reach of broadband, because it effectively shortens the length of the connection by the distance between the street cabinet and the exchange (by at least 3km in Ewhurst). However, this does not help those a very long way from their cabinet or connected directly to an exchange. Nor does it remedy any deficiencies in the line between the cabinet and the property. In many cases, it is the quality of the copper and/or aluminium connection to the cabinet which has the greatest impact on broadband performance. Therefore, there is no straightforward answer to this question.

If we use Mark Heath’s VDSL2 graph (here), then superfast downstream connection speeds of 24 Mbps or more can theoretically be achieved on line lengths of up to 1.2 km, and from around 1.6 km performance is identical to ADSL2 (N.B. Mark says “the graph is very much based on a good quality copper line”). More realistic performance estimates from ThinkBroadband can be found here. With ADSL services, the relevant line length is all the way from the (Cranleigh) exchange, but with FTTC it is the distance from the cabinet which matters. My line length is recorded as 6.6 km (from the exchange), and engineers have told me that this includes sections of old, corroded aluminium cable, poor joints and failing insulation. Therefore, I was probably lucky to achieve around 1.7 Mbps after optimising the ADSL connection with Walter’s help. My speed estimate for FTTC (obtained here) was 4.6 Mbps. The line length from my cabinet should be about 2 km if it follows a reasonably direct route, which could give me up to 16 Mbps from FTTC using Mark’s graph. We assume that the large difference is due to the poor quality of the cables and joints, and possibly some external interference from power cables. In reality I achieved 5 Mbps download sync, two months after VDSL installation in December 2012. This deteriorated to under 4 Mbps then increased to 5.6 Mbps following a line repair and ISP intervention.

Anyone much more than 1km from their street cabinet in Ewhurst should consider themselves furtunate to achieve the “superfast” broadband minimum of 24Mbps using FTTC, depending on line quality and cable route. Those with lines up to 1.5 km may reach the SCC target minimum of 15 Mbps. Beyond that, speeds achieved so far here in Ewhurst seem to drop off much more rapidly than expected, and are highly variable.

Openreach provide the following guidelines from national results: Premises up to 200 metres from cabinets get 50+ Mbps; those up to 500 metres achieve between 25 and 40 Mbps; up to 900 metres they achieve from 15 – 25 Mbps; the minimum 2 Mbps service reaches out to 1.2 miles.

Learn more at the following links.

BT FTTC speed against distance from the cabinet

Detailed analysis of the potential for FTTC

Real world results in Ewhurst

Discussion on aluminium v copper

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2 Responses to How far does FTTC reach?

  1. Walter says:

    To get BT’s received wisdom you can try the BT retail and wholesale fibre checkers:-

    http://www.productsandservices.bt.com/consumerProducts/displayTopic.do?topicId=25795

    and

    https://www.btwholesale.com/includes/adsl/main.html

    For long or poorly performing lines the retail checker will not offer a fibre option whereas the wholesale one will give a rather silly answer of 100 Kbps upstream and Downstream. These values are usually significantly below those currently obtained from ADSL@ connections all the way from Cranleigh. Quite clearly nobody should attempt such a connection until a more accurate estimate is provided.

  2. Walter says:

    I have just realised that my post above is now out of date. Using an example on cabinet 6 on Parkhouse Green, all upper Barhatch Lan, Horseblock Hollow and western Warren subscribers do not see any mention of FTTC (i.e. VDSL2 FTTC services) being available in cabinet 6. However those that are closer, where BT estimate there might be such a service available, are told that Cabinet 6 has actually got FTTC available.

    Telephone Number 01483277xxx on Exchange CRANLEIGH is served by Cabinet 6

    WBC FTTC Up to 36.1 Up to 6.1 – Available
    WBC ADSL 2+ Up to 6 – 4 to 8 Available
    WBC ADSL 2+ Annex M Up to 6 Up to 1 4 to 8 Available
    ADSL Max Up to 5 – 3.5 to 7.5 Available
    WBC Fixed Rate 2 – – Available
    Fixed Rate 2 – – Available

    I am not aware of any solution for all the Cabinet 6 properties (which is at least 36 probably with maybe a total of around 50 lines) without FTTC available. This was raised with BT before any of the Ewhurst cabinets were enabled but we only received some warm but wooly words.

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