The importance of access technologies for the provision of super-fast broadband services means access networks are now being regarded as the first mile, not the last. Steve Powell of Viatel looks at how this is unfolding in the UK market

 

For a long time most of the attention regarding super-fast broadband was placed on Next Generation Networks (NGN). In the last couple of years the industry has begun to recognise the significance of the access network, a change in perspective that has been reflected by the evolution of technical terminology.

Once known as the last mile, the crucial role the access network plays in delivering high-speed services means it is now more commonly known as the first mile. Last year's Carter Report and the recent General Election has seen the technology receive significant attention in the mainstream media in the United Kingdom. However, this coverage is often too vague and simplistic in both its explanation of Next Generation Access (NGA) technology and the timeframe predictions for deployment. In addition, at present, NGA technologies have only been deployed in a limited number of locations and there is no consensus on the best way to extend this across the country. All of this has led to uncertainty and confusion about what these solutions mean for businesses.

NGA refers to the replacement of existing access networks with super-fast access technologies and represents the connection from the local serving exchange to the location of the subscriber (a home or business premises). Due to the previous focus on core networks, operators made the majority of infrastructure investments in this area, a move that has resulted in the access network being left as a bottleneck. The goal of NGA is to fix this problem by focusing investment on the first mile, and providing sufficient network capacity on a subscriber's local access circuit to enable them to benefit from any service that may be available to them from service providers, for example cloud computing for businesses.

Access services can be divided into Shared services, where the available capacity is shared between multiple users, or Dedicated services, where the bandwidth is reserved for use by only one user. When people speak about Next Generation Access they will often be talking about shared services based on Next Generation Broadband. This relates to the move from existing ADSL services (with up to 8-Mbps line speeds and the newer ADSL2+ services with up to 24-Mbps line speeds) to next-generation technologies that can deliver shared services up to 40 Mbps over copper and 100 Mbps over fibre.

For several years the higher-speed dedicated services beyond broadband have been delivered using Ethernet rather than DSL. This has mainly been via fibre but with Ethernet in the First Mile (EFM) technology, dedicated high speed symmetrical services can now be delivered over multiple copper pairs bonded together.

There are a number of different shared and dedicated access technologies already in use, and new higher speed technologies are also emerging.

Current broadband access types include first-generation ADSL (up to 8 Mbps via copper pair, speed varies by distance of the copper between the subscriber and exchange), SDSL (symmetrical DSL service, up to 2 Mbps, based on copper lines), and ADSL 2+ (up to 24 Mbps downstream and 1 Mbps upstream). Trials of super-fast NGA services began last year and rollout is set to continue throughout 2010. These services include fibre-to-the cabinet (FTTC), with services of up to 40 Mbps, and fibre-to-the-premises (FTTP), with services of up to 100 Mbps.

Whereas ADSL is run over copper lines between a telephone exchange and the subscriber, FTTC runs over the copper between the street cabinet and subscriber with fibre from the street cabinet back to the local exchange. With the much shorter copper distances involved, higher speeds can be obtained. The technology running on the copper in this case is VDSL2 (Very High Speed DSL), with fibre linking the street cabinet back to the network operator's core network.

FTTC can be purchased in enabled areas up to 40 Mbps down and, from July 2010, 15 Mbps up. Availability remains very limited, however.

To achieve the highest levels of bandwidth it will be necessary to run fibre into premises, with the higher costs this brings. FTTP runs fibre from the network provider all the way to the premises and uses Packet Optical Network (PON) technology to enable multiple users to share a single fibre. This reduces the cost of deployment compared to dedicating fibre to each premises as in the case of traditional Ethernet access services.

FTTP customer trial are planned to start in Q3 2010 with the service offering download speeds of 40 Mbps and 100 Mbps, and a choice of 2 Mbps, 10 Mbps and 15 Mbps up. Future developments are likely to see upload speeds increase.

However, availability of both current and new access services varies considerably throughout the UK. In the case of ADSL 2+, services are now being rolled out around the UK. For example as part of BT's 21CN project, ADSL 2+ services are now available to 65% of UK premises. Coverage will rise to 75% by March 2011, and then further exchanges will be enabled with completion of the rollout. Around 90% national coverage is expected by 2012.

Rollout of FTTC and FTTP is likely to be a more protracted affair. BT initially announced that it would invest £1.5 billion for the rollout of super-fast fibre broadband with coverage for 10 million premises by 2012. This goal has recently been increased with the aim now being 40% coverage by 2012 and 60% by 2015.

At the time of writing the initial greenfield trial of FTTP has taken place at Ebsfleet. In the majority of cases FTTC will be deployed because of its lower costs. However, FTTP will be used in brownfield sites for exchange direct-fed lines, and FTTC will be used wherever a premises is fed via a street cabinet.

In terms of alternatives to these technologies and what BT is doing, Virgin Media has also been rolling out Next Generation Access services. Current services provide up to 50 Mbps to about 50% of the country. Virgin Media uses a technology called DOCSIS (Data over Cable Service Interface Specification), which allows subscribers to take advantage of high-speed data services over their cable TV network, a hybrid fibre and coaxial cable network. The company has also started trialling a 200 Mbps service.

Over the last few years we have witnessed bandwidth levels increasing whilst cost per Mbps falls, and consumers and businesses can expect this to continue. As a result of this trend the access technologies used to deliver IP services are continuing to evolve.

Looking at the next two to three years the legacy services of dial-up, leased lines and first-generation ADSL/SDSL will be outmoded by Shared and Dedicated NGA services. Coverage of ADSL2+ and EFM will continue to increase while the rollout of FTTC and FTTP will accelerate in an attempt to keep up with the ever-increasing demand for faster and more reliable services.

Steve Powell is product manager for connectivity at Viatel

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