Fibre to the Cabinet INTER. INTERCONNECT COMMUNICATIONS A Telcordia Technologies Company. Steve Morgan Senior Consultant, InterConnect Communications

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1 Fibre to the Cabinet The Solution to Superfast Broadband or a Convenient Stopgap? INTERCONNECT COMMUNICATIONS A Telcordia Technologies Company INT INTERCONNECT COMMUNICATIONS A Telcordia Technologies Company INTER Steve Morgan Senior Consultant, InterConnect Communications

2 Written and published by: InterConnect Communications Ltd Merlin House Station Road Chepstow Monmouthshire NP16 5PB United Kingdom Telephone: +44 (0) Facsimile: +44 (0) Internet: Design and layout: Copyright : InterConnect Communications Ltd InterConnect Communications Ltd 2011 Image on front page: PhotoDisc TM / Getty Images All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, mechanical, photocopying, recording or otherwise, without the prior permission, in writing, of InterConnect Communications Ltd. Note: This document is intended only as a discussion of selected issues relating to the subject matter. It is neither a definitive statement nor a legal document, nor does it purport to suggest any detailed commercial strategy. For this reason, readers are advised to liaise with the appropriate authorities and, if necessary, seek suitable legal and/or technical advice prior to making business decisions. Whilst InterConnect Communications Ltd has exercised every care in the preparation of this document, no responsibility can be accepted for any omissions or errors contained herein. ii

3 Synopsis Despite the global trend towards the upgrading of core network infrastructure through the deployment of Next Generation Networks (NGNs), in the majority of countries, legacy access networks constructed from copper cables remain in place. In order to deliver broadband services to end users.over these copper access networks, Digital Subscriber Loop (DSL) technologies are used. These, however, suffer from inherent technical characteristics which limit the bandwidth that can be delivered over all but relatively short copper loops. The deployment of NGN technologies that make relatively high bandwidths available at the local exchange has served to emphasise the limitations of copper access networks and has highlighted the need for a viable alternative architecture. Some countries have decided to replace low performance access network infrastructure by deploying large scale Fibre to the Building (FTTB) networks having the capability to deliver very high end user bandwidths. In some of these cases, however, many end users live in multi-dwelling buildings which are relatively easy and cost effective to serve using FTTB networks, and countries with different demographics will experience different degrees of difficulty in deploying FTTB cost effectively. The obvious solution is to upgrade the copper access network infrastructure; so-called Next Generation Access (NGA). Current NGA architectures use two basic network configurations; FTTB and FTTC (Fibre to the Cabinet). FTTC is currently considered by many network operators to be the most feasible cost effective option that meets existing bandwidth requirements. As these requirements continue to rise, however, the question must be asked as to just how future proof FTTC deployments may be for many user communities, and whether its lesser cost compared with FTTB deployment is a worthwhile trade-off against the inevitable shortfall in performance. 1

4 Background A national telecommunications network has two basic elements; an access network that connects end users to the nearest network node (usually the local exchange), and a core network that connects all network nodes locally and nationally. Around the world, network operators are upgrading their core networks by deploying Next Generation Networks (NGNs) which will replace old legacy multi-platform networks with a single network platform based upon Internet Protocol (IP). NGN architectures and their associated technologies provide a platform that has the ability to transport a growing variety of enhanced, high bandwidth, high performance services from content and service providers to end users. NGN deployments are, however, exclusively core network upgrades which do not impact on network infrastructure connecting end users to the core network, i.e. the access network. This means that NGN infrastructure ends at the local exchange. In most cases, delivery of enhanced, high bandwidth services carried by the NGN to end users relies on the capabilities of the existing copper access network. In the majority of countries, legacy access networks constructed from copper cables remain in place and Digital Subscriber Loop (DSL) technologies are used to deliver broadband services to end users. Copper networks have inherent technical characteristics which limit the bandwidth that can be delivered to end users using DSL technologies. These limitations effectively impede efficient end-to-end delivery of enhanced services across NGN and access network infrastructures. If anything, the deployment of NGN technologies that make relatively high bandwidths available at the local exchange has served to emphasise the limitations of copper access networks and has highlighted the need for a viable alternative architecture. A number of countries have taken the decision to replace low performance access network infrastructure by deploying large scale Fibre to the Building (FTTB) networks having the capability to deliver very high end user bandwidths, up to and exceeding 100 Mbps. These countries include South Korea and Japan in South East Asia but also European countries such as Sweden. It should be noted, however, that in South Korea and Japan significant numbers of users live in multidwelling buildings which are relatively easy and cost effective to serve using FTTB networks. Countries with different demographics will experience different degrees of difficulty in deploying FTTB cost effectively compared to other network architectures. The obvious solution would be replace, or at least to upgrade, the copper access network infrastructure. The various alternative architectures being deployed are collectively referred to as Next Generation Access (NGA). Current NGA 2

5 architectures use two basic network configurations; Fibre to the Cabinet (FTTC) and Fibre to the Building (FTTB) 1. NGA deployments are being implemented in a number of countries and FTTC is currently considered by many network operators to be the most feasible cost effective option that meets existing bandwidth requirements. This paper will discuss the proposition that, where copper legacy networks need to be upgraded, FTTC should be regarded as a stopgap rather than a solution to the need for the deployment of an effective and viable NGA. In addition, new technologies being developed to increase delivered bandwidths on FTTC networks are also examined along with their relative attributes. What Access Networks do we have now? Why do existing Access Networks need to be upgraded? Most current generation access networks, often referred to as legacy access networks, have been constructed and deployed over long periods of time for the primary purpose of providing voice and other narrowband services. Consequently, most use cables with copper conductors although in many countries optic fibre cables have also been installed. These aremainly intended to provide digital business services, but residential fibre networks are also being installed, albeit in relatively limited numbers. With the exception of countries such as Japan and South Korea where large scale, all optic fibre access networks have been deployed, copper cables remain the primary transmission medium in access networks and now carry a range of end user services from analogue narrowband voice to digital broadband. However, it is worth noting that the technical and operational specifications of copper cables, which are still being installed in many access networks, continue to be based on the requirements for transmission of narrowband analogue voice services. The access network carries and delivers all end user services. Of these, the service that has experienced the most significant growth over the last decade is Internet access, and the most efficient medium for accessing the Internet is to use digital services. As the format of Internet sites and the content they make available have become more sophisticated, the transfer of data between the provider and the end user has required ever increasing bandwidths to support efficient access. Over the last 10 years available bandwidth has grown at a rate of 50% per annum to a current average maximum of around 30 Mbps. Broadband services need to deliver bandwidths that allow fast and efficient delivery of services and applications and 1 Also known as Fibre to the Home (FTTH) or Fibre to the Premises (FTTP) 3

6 allow them to operate to their optimum functionality. Demand for bandwidth is forecast to continue, driven by developments in Internet services and content, and the capability of copper networks to support demand for increased bandwidth is reaching its limit. This is because DSL technologies are used to deliver broadband services on copper access network cables but technical characteristics inherent in copper cables impose limitations on the maximum bandwidth that DSL can deliver to end users. The most significant factor is the cumulative build-up of signal loss, or attenuation, over the length of a cable. Attenuation increases with signal frequency and DSL technologies use high frequency signals to deliver high bandwidths. Table 1 (below) illustrates the performance of DSL technologies relative to cable length using copper pairs with conductor diameter of 0.4mm and in reasonable condition: Technology Transmission No. of Pairs Maximum Bandwidth SDSL Symmetric DSL HDSL High Speed DSL ADSL Asymmetric DSL ADSL 2 Asymmetric DSL ADSL 2+ Asymmetric DSL Upstream (End user to DSLAM) Downstream (DSLAM to end user) Symmetric 1 to 3 2 Mbps 2 Mbps Symmetric 1 2 Mbps 2 Mbps Asymmetric kbps 8 Mbps Asymmetric kbps 12 Mbps Asymmetric Mbps 25 Mbps VDSL Very High Speed DSL VDSL2 Symmetric 1 52 Mbps 52 Mbps Asymmetric 1 16Mbps 52 Mbps Symmetric Mbps 100 Mbps Asymmetric 1 16 Mbps 100 Mbps Table 1 - Comparison of Various xdsl Technologies by Maximum Bandwidth Capability These performance figures do not take into account the effect of local conditions in the external distribution network which will reduce the actual delivered bandwidths.as can be seen from the graph in Figure 1 (overleaf), the practical effect is that delivered bandwidth deteriorates with cable length. ADSL technologies have maximum bandwidths that range from 8 Mbps to 24 Mbps which are maintained over various cable lengths from 2.4 Km to 0.9 Km. VDSL and VDSL2 technologies can be used to provide bandwidths up to a 4

7 Figure 1 - Theoretical Performance of Various xdsl Technologies Showing Differential Deterioration of Speed Over Cable Length maximum of 52Mbps and 100Mbps respectively, but only over very short copper connections around 300 metres. A point to note is that at a cable distance of around 2.5 Km the maximum delivered bandwidth is limited to around 8 Mbps regardless of which DSL technology is used. In practice the bandwidth at this point will be less than 8 Mbps. The reality is that existing copper access network infrastructure cannot sustain anticipated increases in bandwidth due to the technical operational limitations inherent in the ability of copper cables to support the delivery of end user broadband services. What is Superfast Broadband? Superfast broadband is defined by Ofcom as broadband services that deliver bandwidths up to 10 times the level of today s broadband services. Broadband Delivery UK (BDUK), part of the UK Government s Department of Culture, Media and Sport, responsible for supporting the delivery of broadband in the UK particularly to not and slow spots within the UK, made the statement that: Superfast is a question of volume throughput; Today s broadband has an average potential throughput of around 6Mbps; Superfast has a potential throughput of over 20Mbps with no upper limit. The implication of both these definitions is that copper access networks cannot support delivery of superfast broadband and 5

8 that network infrastructure must be upgraded or replaced with new, better performing infrastructure. This new infrastructure has been given the name Next Generation Access (NGA) and utilises fibre optic cable for part or all of the new network along with associated technologies to provide high bandwidth connectivity in the access network to all end users. What is a Next Generation Access network? What is Fibre to the Cabinet? The EC Draft Recommendation on Regulated Access to Next Generation Access (NGA) Networks contains the following description: NGAs are access networks which have been substantially upgraded either wholly or in part, using existing local access infrastructures and technologies and/or using new optical fibre infrastructures, and which are capable of delivering broadband access services with bandwidths significantly above those currently widely available. The most significant requirement of the EC Draft Recommendation is for an NGA network to be constructed to support the delivery of broadband services with bandwidths significantly higher than those supported by current legacy copper access networks. It would be reasonable for an NGA network to also be able to accommodate future increases in bandwidth for a reasonable period of time, a feature that is often referred to as being future proof. This essentially means that an NGA network should not need significant upgrading, for example work involving extensive replacement of installed infrastructure, at least until the network reaches the end of its operational life. Although forecasts vary as to the extent and timing of any increased demand for bandwidth it would be reasonable to expect a future proof network to be in operation for 5 to 7 years. Current NGA networks use optical fibre cables and associated technologies to construct part, or all, of the network infrastructure in order to deliver high bandwidth broadband services. NGA networks are based upon two basic network architectures, Fibre to the Cabinet (FTTC) and Fibre to the Building (FTTB), sometimes referred to as Fibre to the Home (FTTH). Transmission systems used on optical fibre cables are digital and are capable of supporting very high bandwidths up to the Gigabit range and above. Fibre to the Cabinet (FTTC) is a hybrid optical fibre/copper pair network architecture that uses existing local access infrastructure and technologies and new network build where necessary. A basic FTTC network configuration is shown in Figure 2 (overleaf). Cable Television (CATV) networks based upon FTTC architecture have been in service for some time in many 6

9 Primary Crossconnection Point (PCP) DSLAM / MSAN Housed in Roadside Cabinet - Requires mains power and battery back-up Tie Cable Splicing Point Copper Distribution Cable to End User Connections Short Copper Cable End User Connections One pair per end user Local Network Node Site Optic Fibre Feeder Cable one fibre pair per DSLAM Fibre Flexibility Rack Optic Network Line Termination and Transmission Equipment Figure 2 - FTTC Basic Network Configuration countries and have the capability to deliver television, voice and broadband services. FTTC networks are sometimes referred to as deep-fibre network architectures because their deployment involves extending access to the core network on backhaul connectivity using optical fibre cables deep into the access network. The fibre cable provides high capacity backhaul connectivity to Digital Subscriber Loop Access Multiplexer (DSLAM) or Multi Service Access Node (MSAN) equipment housed in roadside cabinets. This is done in order to access relatively short copper end user connections that can support high bandwidths close to the maximum capabilities of the DSL technologies used to provide broadband services. FTTC networks utilise existing copper end user connections and this provides a significant saving in deployment costs. BT is currently deploying FTTC NGA networks across the UK and a number of other European operators are also implementing similar network topologies. The driver for deployment of FTTC as opposed to FTTB networks is principally cost based. FTTC networks are much cheaper to install than FTTB and also have some operational advantages. FTTH rollout involves the installation of fibres and associated technology up to the customer s premises, completely replacing the existing copper cables. 7

10 A study carried out for the Broadband Stakeholder Group on the costs of deploying fibre-based next generation infrastructure in the UK 2 produced a comparison that FTTB would cost 2856 per premise passed, whereas a FTTC solution would cost 591 on average nationally. On a purely financial basis, therefore, FTTC appears to offer the best option for deployment of NGA. That said, the copper connections in a FTTC network have the same technical characteristics and performance limitations as a legacy copper network in that bandwidth deteriorates along the cable length and there is a finite maximum delivered bandwidth that can be supported. Even though the copper connections used from the cabinet are relatively short, their lengths will vary and prevent delivery of services with a uniform defined performance. Based upon potential performance, deploying FTTC as an NGA solution could be considered to be a gamble on the maximum delivered bandwidth being sufficient to meet demand, ideally for the foreseeable future or at least until the costs of installed infrastructure are fully depreciated and migration to FTTB becomes viable. If the growth in demand for bandwidth continues at its current rate, it is only a matter of time before it exceeds the maximum delivered bandwidth capable of being supported by FTTC networks. Migration from FTTC to FTTB will be a complex and potentially expensive exercise. So, is Fibre to the Cabinet a Next Generation Access Solution or a Stopgap? The purpose of this paper is to address the question of whether FTTC networks offer a viable solution to the need to deploy NGA networks or a stopgap that will serve to bridge the gap between the migration of legacy access networks to NGA. The definition of an NGA network is central to deciding whether deploying FTTC networks is really a solution or a stopgap measure. It would be reasonable to accept that the critical requirement for any NGA is for it to be, as far as is possible, future proof. First, we have to accept the basic assumption that demand for bandwidth will continue to grow to meet the requirements of developing services and applications, at least for the foreseeable future. It is a fact that over the past 10 years available bandwidth has increased by around 50% per year and this trend shows every sign of continuing. We also have to recognise the fact that, because end user connections are on copper cables, FTTC networks have a finite limit on the maximum bandwidth that can be delivered, around 60 Mbps on average. 2 The costs of deploying fibre-based next-generation broadband Infrastructure, 8 September 2008 available on-line from download/gid,1036/ 8

11 Given these two factors, at the current rate of growth, sometime within the next seven years typical bandwidths required to support developments in services and applications will exceed the capabilities of FTTC. So, what does future proof actually mean? It would be reasonable to assume that a network solution that is regarded to be future proof will not need to be substantially materially altered or upgraded at least for the short to medium term future which, considering the characteristics of the technologies and equipment used in an NGA, would be 3 to 5 years or at least the operational life of the network equipment. Given the facts and assumptions so far, does Fibre to the Cabinet fall within the defined requirements of an NGA solution? FTTC certainly meets the requirement for an NGA network to support bandwidths significantly greater than those currently available. It does not, however, meet requirements for being future proof when compared with FTTB networks. It is clear that FTTC networks have a limited operational lifespan which is dependent upon the growth in demand for bandwidth not exceeding the capabilities of network infrastructure. However, future demand is difficult to forecast, and FTTC infrastructure may be future proof for some, depending on the bandwidth they and their neighbours require. To mitigate the limitations of current FTTC network architectures and to extend the operational life of network deployments, new technology options are being developed that have the potential to significantly increase bandwidth on the copper connections of FTTC networks. Whilst these solutions do increase the bandwidth that FTTC networks can support and deliver, they raise operational issues that have the potential to negate the advantages they offer. Despite these technology options, FTTC is likely to be a once only deployment, which cannot be upgraded in itself to offer significantly higher bandwidths. The need for FTTB may be an inevitable follow-on if demand for faster speeds than FTTC can support become widespread. However, there is a danger that, having incurred the costs of investment in FTTC, there will be little incentive for network operators to migrate end users to FTTB when demand for bandwidth exceeds network capabilities. In this case, would FTTB deployment now be a more suitable solution despite the high cost? Alternative investment models may well be an answer. It is becoming apparent that business models used for NGA networks need to regard NGA from the perspective of a utility, such as water or electricity, in order to make a compelling case for deployment. The large initial capital expenditure will require a longer payback period to absorb the relatively low service charges which users expect to pay from the current highly competitive broadband market. This view tends 9

12 to be supported by evidence from countries where NGA deployments have already taken place, such as South Korea and Japan, which suggests that high bandwidth broadband services are readily available for affordable prices. However, it is difficult to estimate what end users will be prepared to pay for truly high bandwidth, and this in turn affects return on investment calculations. As a result of uncertain levels of revenue which will impact investment decisions, a single view on the deployment of FTTB or FTTC may not be reached for some time. For some areas with very poor DSL access at present, FTTC may be their best solution for many years, whereas others may aspire to FTTB and work to achieve it sooner. The practical result may be a patchwork of deployments over time depending on elements such as new build schemes which may implement fibre from their inception, competition from existing networks (such as CATV) and the ability or willingness of local bodies to find investment or partners to support a FTTB rollout. FTTC may well offer a solution for the bandwidth requirements of some areas for the foreseeable future, but will become less relevant as developments in applications and services require networks that can support broadband with ever increasing bandwidths to deliver them. If, or more probably when, these services become commonplace, the discussion regarding fibre to everywhere and who will pay for it will continue. 10

13 The Author InterConnect Communications Steve Morgan is a Senior Consultant with InterConnect s Commercial Services team, specialising in access, interconnection and network planning issues. Steve has worked on a wide variety of projects involving the planning and operations of telecommunications networks, including the provision of xdsl technologies, network and customer infrastructure strategic and detailed planning, technical due diligence assessments, strategic deployment and management of operator-independent open access networks. Steve has also advised clients on issues relating to the impact of telecommunications on economic regeneration, the development of processes and procedures, network planning/ operational performance and Quality of Service, Local Loop Unbundling network operation including collocation/distant location issues, and technical and operational issues around the deployment of open access Fibre to the Cabinet (FTTC) and Fibre to the Home (FTTH) Next Generation Access networks. Steve is also a regular presenter at InterConnect s Regulatory, Interconnection and NGN Master Classes. Steve may be contacted on or ed at stevemorgan@icc-uk.com InterConnect Communications is a wholly-owned subsidiary of Telcordia Technologies Inc., based in the United Kingdom, and a leading provider of consultancy services on Next Generation Networks, Next Generation Access and broadband strategy development issues. InterConnect has been working on broadband and wider ICT strategy over the last 10 years. In that time, we have prepared strategies, developed business cases and evaluated programmes for many of the UK s Regional Development Authorities and devolved administrations as well as for a number of UK sub regions, counties and cities. We are also currently developing the national broadband strategy for a Middle Eastern government. Our team offers a unique combination of economic, market, technical and regulatory expertise and this enables us to advise on all the key areas of broadband implementation including: Development of a high level strategic plan for broadband delivery; Review network architectures and model deployment options; Undertake commercial and financial market testing and analysis; Review the funding options available for deployment including private capital and state funding; Manage the full network procurement process, including the development of RFP documents and the evaluation of responses. For more details of InterConnect s Broadband Strategy Development services, please visit or us at ict-development@icc-uk.com 11

14 Merlin House, Station Road, Chepstow, Monmouthshire, NP16 5PB. United Kingdom INTERCONNECT COMMUNICATIONS A Telcordia Technologies Company Telephone: +44 (0) Facsimile: +44 (0) Internet: INTERCONNECT COMMUN A Telcordia Technolog