One question that the team have been asked a lot during the project is “what technology will be used, and why?” Frustratingly, it has not been possible to answer this question until very recently, due to the nature of the government funding rules. The RCBF funding application, in order to ensure completely fair competition, does not allow a project to define in advance what technology is to be used. Instead, the proposal has to be made in terms of defined performance requirements, and then any company can propose any technical solution that meets the requirements. So, we created a specification that was built up from real user requirements, and also incorporated the guidance for Next Generation Access as defined by Broadband Delivery UK (BDUK). The BDUK guidelines set a minimum download speed of 24 Mbit/s in order for a service to qualify as “superfast” and thus to be eligible for funding. This specification could have been met by a number of different technologies – including Fibre to the Premises (FTTP), Fibre to the Cabinet (FTTC), and Wireless. Each of these have advantages and disadvantages, but the project team is very happy that the procurement process identified Gigaclear’s FTTP solution as the best overall value, since it is also the belief of the team that an FTTP approach is the best long-term sustainable solution.
In a Fibre-to-the-Premises network, all the connections are fiber optic, right into each subscriber’s home or business. Because the performance of fiber optic cable does not degrade with distance (well not the sort of distances we are talking about in West Oxfordshire, anyway) this means that every premise gets exactly the same performance. The fibres themselves can carry much higher data rates than are required today, so the expensive part of the network (getting the fibres in the ground and connected into the homes) will have a very long service life – at least 25 years, and potentially much longer. Over the years it will be possible to upgrade the services that run over those fibres, so the network can keep pace with technology. Software can be used to control the actual data rate delivered to an individual subscriber, which allows a range of different data rates to be offered – important for affordability. If a subscriber on a low-cost tariff wants to upgrade to a higher speed connection later, this does not require any change in any of the equipment, just a software change. Another benefit of the Gigaclear FTTP network is that it is “symmetrical” – you get the same speed uploading data as you do downloading. Older technologies like ADSL were designed to have a lot of download bandwidth at the expense of upload speed in the era when the internet was just about looking at web pages. The assumption is that you only have mouse clicks and keystrokes going upsteam (a tiny amount of data) and lots of page data and images coming back downstream. Today however, for services like video calling on Skype or Facetime, videoconferencing, uploading video clips to YouTube, on-line gaming, or moving large files around when working from home (for example PowerPoint presentations), exactly the same speed is needed in both directions.
In contrast, a Fibre-to-the-Cabinet approach (for example BT’s Infinity product) only uses a fibre optic connection from the telephone exchange to the street cabinet – the big green boxes by the side of the road where all the telephone wires are terminated. In an FTTC network the street cabinets are upgraded from just being a connection point for wires into a “mini exchange” so that they contain active equipment. The existing copper telephone wires are then used to connect from the street cabinet to each house, typically using a technology called VDSL which is a faster version of conventional ADSL broadband. This works quite well in towns and cities where the houses are close to the street cabinets, but the catch is that once a house is more than about 500 metres from the street cabinet the speed falls off rapidly. By about 750 metres it is typically not possible to achieve superfast speeds at all. VDSL is also not symmetrical, so the upload speed is slower still than the download speed, which is the only number that vendors typically quote. Critically, it is dependent on the condition of the old telephone cables to each house, which our experience in Northmoor with ADSL suggests is not at all good. The overall effect is that for rural networks where distances of over a kilometre between premises are typical, FTTC can get very difficult to deploy. Either a very large number of new and expensive cabinets have to be installed, or subscribers will get wide differences in performance. Also, because the condition of the old copper wires is essentially unknown, it is not possible to predict the performance accurately in advance.
Wireless networks can be very cost-effective to deploy, mainly because they do not require the civil engineering expense of digging trenches for fibre or copper cables. However it is difficult to achieve the same performance as a wired network (fibre or copper) due to limitations of the spectrum available – it has to fit around the broadcasters, the mobile phone operators, the emergency services etc. Generally trade-offs have to be made between data rates and latency (delay) which can cause problems for gaming or video calling. Also, upgrading a wireless system in the future typically requires the replacement of almost everything, so there are some risks over how long it can be expected to cope with future demands. The technology available today can just about meet our current needs, but not more. Finally in a conservation area like Northmoor there are issues around attaching an antenna to every house with line-of-sight to a transmitter tower of some sort, with the attendent potential for problems in obtaining planning permission.