Feature Stories - Broadband, a gig per second for all!
Up to now 1 Gb/s networks have been limited to countries like Sweden that enjoy very advanced telecoms infrastructure. But the research carried out by EU-funded scientists will make it easier for other countries to set up their own high-speed networks. The extra speed is required for emerging data applications and it will deliver such services as super high-definition TV, video on demand, next-generation gaming as well as remote medical diagnostics and elderly care. 'Services like local and global storage area networks, high-definition video-conferencing and grid computing will need high-speed networks,' explains Dr Mikhail Popov, coordinator of the 'Architectures for flexible photonic home and access' (ALPHA) project. 'Some applications like online interactive medical diagnostics do not tolerate data compression, so you need raw speed to make these services work properly. Ultimately, it might require more than 1 Gb/s for each user with a very high quality of service,' he continues. ALPHA was a highly ambitious 39-month project that tackled high-speed network bottlenecks in the access network — which delivers broadband to the front door — and in building networks for the home and office. The scientists in the project sought to define new network models and standards to deliver blistering speeds at the lowest possible cost and with the most logical upgrade path. The work included test beds and validations to demonstrate that the ALPHA proposals can cope with massively rising bandwidth requirements. 'Beyond the high bandwidth requirements, the solution should also provide foundations for easy deployment and maintenance, affordable scalability as well as for easy quality-of-service provisioning in the network,' notes Dr Popov. ALPHA was a major undertaking, with 17 partners and a total budget over €16 million (around two-thirds coming from the European Commission). It addressed both future access and in-building networks for the home and office, and researched special infrastructure to support a heterogeneous environment of converged wired and wireless technologies. Huge field This is a huge field. There are dozens of technologies and enabling systems all along the broadband pipe, from core and metro area networks to in-home outlets. Each enabling technology has several potentially contending technical solutions, each with their advantages and disadvantages. And those solutions are all evolving rapidly. Take active and passive optical networks (AON and PON), for example, which are the physical heart of ALPHA's work. AONs use electrically powered switching to manage signal distribution, while PONs use optical splitters. PONs are efficient and reliable due to a simple passive-only fibre infrastructure in the field, but they have a lower range than AONs and it can be difficult to isolate the location of a failure in a PONs network. Data transmissions can also slow down during peak load, because bandwidth is not dedicated to individual subscribers, but split among a number of them. AONs rely on ethernet technology, which makes interoperability among vendors easier to achieve. Subscribers can select hardware that delivers an appropriate data transmission rate and scale up as needed without having to restructure the network. But AON deployment can be more costly than PONs. Then there is the optical fibre itself, with a choice between glass single-mode, glass multi-mode and plastic, each with its own advantages. There are routers, switches, multiplexers, amplifiers and dozens of elements that handle bandwidth from the backbone to end-user. And there are distinct networks all with their own constraints and demands. The telecoms backbone connects to the metro area network (MAN), which in turn splits into local access networks (LAN) that connect to the home or office. Then LANs connect individual devices within buildings. What's more all the work has to meet European and international standards and norms. And there are several standards bodies for broadband to consider, including the IEEE and the International Telecommunications Union. Despite these challenges, ALPHA achieved its objectives, defining, integrating and validating the wide range of technologies required to make ultra-high-speed broadband for access networks and home domains a reality. Indeed, it is impossible to go into all the work undertaken by the project in this article. Perplexing multiplexing But one very good example is the team's work with multiplexing, the technique used to broadcast several streams of data over a single line. Multiplexing will be a key factor in any future network because it uses physical wires in the most efficient way. Wavelength division multiplexing (WDM) works by using light at different wavelengths, or colours, to create separate streams and so enlarge the capacity of a line. WDM is considered the technology of the future, but it is too expensive at current prices. Time division multiplexing (TDM) is more affordable, since it is performed by electronics. It splits data streams over time, with each stream broadcast in a particular time slot. So, the ALPHA team developed a hybrid WDM/TDM multiplexing system, delivering 10 Gb/s over a passive optical network. This ALPHA technology supports access networks, which supply broadband connections to the home or office. The ALPHA solution even supports radio-over-fibre, a technology for handling the support of mobile broadband in wired networks. The multiplexer system is a key crossover technology that will let networks evolve cost-effectively. It both enhances what is available now and paves the way for next-generation broadband. But that is only one small part of ALPHA's work. the team achieved a world first by recording speeds of 20 Gb/s in real time with a novel modem that used optical orthogonal frequency division multiplexing (OOFMD), which creates multiple streams of data by modulating tone. It is a useful and popular transmission method because it can handle difficult channel conditions, like fading and interference. The consortium worked on universal plug 'n' play quality of service (UPnP QoS) and generalised multi-protocol label switching (GMPLS), which add service guarantees to both the home and access networks. The project also developed a low-cost gigabit modem for home networks that works with plastic optical fibres, a crucial bit of technology that would let users download a DVD quality movie in just 60 seconds! Right now those speeds are only available in a few places around the world, but thanks to the architecture and transmission solutions developed by ALPHA it will be a lot easier for other networks to upgrade. In all, the project has had a remarkable impact, with its work leading to 9 patent applications, 77 journal peer-reviewed journal publications and over 200 conference contributions. The team also contributed significantly to standardisation efforts. The ALPHA project received funding from the EU's Seventh Framework Programme for research into information and communications technology (ICT), the 'Network of the future' Theme. Useful links: - 'Architectures for flexible photonic home and access' project - ALPHA Project data record on CORDIS Related articles: - Europe in full throttle for e-services economy - Europe in the right MODE for future internet - Putting mobile internet under one roof - Competitiveness Council pushes research agenda