This report has been written to serve the needs of managers, investors and technical people who require a solid, independent introduction to Last Mile broadband technologies. Last Mile access networks – the millions of separate connections between the carrier’s core network and the homes, factories, farms and offices of its customers – are arguably the greatest challenge in telecommunications today. They require huge investments and must last for decades with minimal maintenance, while at the same time providing an increasing range of voice, video, Internet and private networking services.
Firstly we discuss the traditional (POTS - Plain Old Telephone Service) and ISDN (Integrated Digital Services Network) uses of twisted pair copper telephone lines. We then discuss the highest performing technology, Fibre to the Premises, including elegant Passive Optical Networks (PONs) – where a single fibre is split to provide >100MB/s services to dozens of homes.
Despite the superiority of pure fibre networks, the majority of broadband services in the foreseeable future are likely to be provided with ADSL or VDSL (Asymmetrical and Very High Rate Digital Subscriber Line). We explore the history of these technologies, the characteristics of their latest versions (ADSL2+ and VDSL2) and the practical problems of implementing VDSL2 Fibre to the Curb (FttC, also known as Fibre to the Node) with its complex switching, modulation and power requirements in thousands of widely distributed cabinets.
Hybrid Fibre Coax Cable (HFC) networks are the other main broadband last mile technology. We discuss the history of HFC, its forthcoming DOCSIS 3.0 standard and HFC’s emerging Switched Digital Video architecture. Finally, we discuss Free Space Optical technologies, which have unique advantages for links within urban areas with direct line-of-sight paths.
Carriers, service providers and regulators face many challenges understanding the various last mile technologies, in terms of their principles, applicability to particular urban and rural areas and their capacity to provide a variety of services. Since the technical characteristics of all last mile technologies favour a single network with a single owner, regulators need a great deal of technical insight to craft arrangements which favour competitive access whilst encouraging the large investments necessary to build these networks.
The report provides vital information to enable readers to answer many important questions, such as:
- The cost and performance differences between an ADSL2 network based on existing exchange buildings and a VDSL2/FTTC network with new fibre and nodes located within 200 metres of customers’ premises.
- The impact on exchange and core network architectures of converting the existing twisted pair copper infrastructure to VDSL2.
- The capacity of ADSL2, VDSL2, HFC and FTTP to support fully digital video delivery, for multiple streams of standard and high definition television.
- The ability of both HFC and Passive Optical Networks to carry a hundred or so RF channels of analogue and digitally modulated video.
- The benefits and challenges of replacing HFC’s analogue and distributive digital video channels with Switched Digital Video.
The companion volume to this report is available and includes information on long distance telecommunications technologies and the switching and carriage technologies for voice and data communications: 2006 Telecoms Infrastructure Technologies Handbook - Volume 2 - Long Distance & Data