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BROADBAND SERVICES - A fibre-rich diet
In telecommunications, as in many other industries, success usually comes from careful 
planning. Danny Berko and Ron Levin explain that planning now for the deployment of effective and proven deep fibre platforms will help meet the demands of the future wave of IPTV and other new customer services
The rapid growth of new broadband services such as IPTV will soon stretch the local loop or access network to its limits in terms of bandwidth delivery capability. Even existing Internet services are becoming thirstier for higher download speeds as they cram their site pages with customer-compelling pictures and graphical content.
Additionally, a growing customer segment - SOHOs and home workers - is looking for higher upload speeds to support their needs to send ever larger files to central office locations and facilitate increasing numbers of peer-to-peer sessions. Many telcos and LLU operators have sought successfully to address these demands by exploiting the latest advances in Digital Subscriber Loop technology - xDSL - to carry these higher speeds over a predominantly copper local loop network originally designed to carry analogue voice services.
Much has been achieved in this respect and it is estimated that a large proportion of customers (over 90 per cent in Western Europe) now have access to broadband speeds of over 2 Mbit/s with some (nearer 10 per cent) enjoying 10 Mbit/s or greater.
Characteristically however, xDSL speeds reduce with copper loop delivery distance and the laws of physics are beginning to diminish further speed improvements that can be made over existing copper loops to meet further higher speed customer services. So consideration must now be given to how these distances can be reduced to meet this next wave of bandwidth demands, which look to be of the order of 25-50 Mbit/s.
This is particularly important for operators as they plan to satisfy growing demand and retain/build their revenue streams. Deeper fibre into the access network - to shorten the copper loop distances and bring the high launch speeds of xDSL sources closer to the customer - is the principal approach to tackling the situation.
This entails the deployment of robust and reliable xDSL broadband platforms at the end of the fibre in often environmentally harsh and less accessible parts of the access network, such as cabinets, building basements and underground enclosures.
The challenges for operators and their suppliers are not insignificant. Such platform investments must support a positive business case and they need to complement operators' current network convergence strategies, as well as longer-term plans for the access network as a whole.
The rewards are nevertheless significant in terms of order of magnitude improvements in bandwidth speeds (factor of 10+) and the overall potential future services that can be offered to customers and the community in general. Cable operators who have copper pairs incorporated within their coax distribution (Siamese pairs) may also find such platforms attractive in terms of the premium service potential they can offer over and above their normal cable modem services.
Why more bandwidth?
The underlying trend within the developed world continues to be for more content and associated higher delivery speed in broadband services, be it within the standard Internet services portfolio or specific new planned services such as IPTV and video streaming/conferencing services.
The limit is difficult to ascertain and is analogous to the processing speed/memory capacity trends within the PC industry. While much has been achieved in improving the transport efficiency of such services, including advanced compression and coding techniques (MPEG, etc), the net trend still translates into ever-higher bandwidth capability required of the access transport. In cumulative terms this can move anticipated customer bandwidth demand to between 25 and 50 Mbit/s.
Currently, most Western European operators appear to be looking at around the 25 Mbit/s figure, whereas in the USA, where the attention to HD TV appears to be greater - together with a demand for more simultaneous sessions - the figure approaches the 50 Mbit/s mark.
This expectation of future bandwidth growth needs to be addressed by operators if they plan to meet and stay ahead of future demand. Current deployment of xDSL technology at CO sites has achieved much in servicing the initial growth of broadband (principally Internet services) over the last decade and typically, within Western Europe, it is estimated that around 90 per cent of broadband customers connected to incumbent telcos' networks now enjoy 2 Mbit/s plus.
However, probably only around 10 per cent enjoy 10 Mbit/s or more. This is because the high launch speeds deliverable by xDSL technologies diminish with copper loop distance (or reach) from the CO, with the result that the speeds needed for future services become progressively less attainable to customers beyond 2-3 km reach.
So the distribution of customers in relation to copper distance from exchange is currently a defining factor. This distribution is not too different across Western Europe incumbent operators, although there is a noticeable difference with the USA, by nature of its demographics. With these existing copper distance distributions, it is clear that the bandwidth identified for future service growth could only be delivered to around 10-20 per cent of Western European customers at best, and even less in the USA.
Clearly, in order to capture the bulk of customers within a much wider future services bandwidth footprint, something radical needs to be done to shorten copper transport distances within the access network.
Deeper fibre provides the solution
The means to achieving the shorter copper distances needed involves the deeper penetration of fibre into the access network. As a result, operators, along with their suppliers, need to develop optimum strategies for achieving this against valid business cases.
Most operators already deploy fibre all the way to large, and to a significant proportion of small, business customers, thus removing the copper bottle-neck altogether. However, to provide a similar major fibre overbuild to the remaining bulk of customers, i.e. fibre to the premises/home (FTTP/H), is currently a prohibitively costly investment for most operators.
Business cases are beginning to emerge for FTTP/H deployment in new build (greenfield) scenarios, but these barely amount to more than 1-2 per cent per annum of an operator's total network. Therefore, in order to address the future bandwidth challenge effectively, lower partial fibre investment solutions need to be considered. Normally referred to as ‘deep fibre' platforms, they involve deploying fibre from the CO to appropriate points deeper in the access network, terminating on xDSL platforms which then connect with the remaining (shorter) copper distribution pairs.
As a consequence, the higher launch speeds of xDSL can be exploited to provide the much greater bandwidth anticipated to meet future needs. The main governing factors determining the points in the access network where such fibre terminates are the location of appropriate and accessible copper cross-connection points where the fibre/copper transition can practically take place and the fibre count necessary to achieve an economic customer footprint deployment.
The deployment scenarios adopted by most operators are either fibre to the node (FTTN), normally coincident with the first primary cross-connect point (PCP-external cabinet), or deeper to the curb (FTTC), normally coincident with a secondary cross-connect (SCP) or street distribution point (DP).
In the case of conurbations made up of large blocks of flats or multi-dwelling units (MDUs) a fibre to the basement/building (FTTB) deployment may also be appropriate. In each case, this shortening of the copper loop enables the much higher xDSL launch speeds to be delivered to a significantly larger proportion of the population, typically 25-50 Mbit/s+.
This has been improved upon further with the latest VDSL2 chipsets (potential speeds up to 100 Mbit/s). The VDSL2 ETSI standard has been optimised for deployment at such points close to the customer and has the advantage that it can be configured to both symmetric as well as asymmetric delivery capability. Additionally, both Ethernet over DSL - Ethernet First Mile (EFN) - and traditional ATM over DSL are configurable with this standard.
Proven deep fibre deployments
Major operators around the world are now deploying deep fibre solutions either in trials or actual deployments in major segments of their networks. This is enabling them to prove the technology, develop the experience and create the processes and procedures necessary to build this necessary high-capacity access infrastructure that their customers and future service opportunities will demand.
The key for platform suppliers is to be at the forefront of many of these deployments and be able to share and understand operator needs and requirements while being able to demonstrate the capabilities of the underlying technology.
A major recent example of deep fibre platform deployment has been Deutsche Telekom's High Speed Interface (HSI) project where high-speed services are being rolled out in ten major cities in Germany and several thousand deep fibre platforms are being deployed delivering bandwidths of between 25 Mbit/s and 50 Mbit/s.
Examples of UG platforms are already in widespread deployment around the world, including Kingston Communications in the UK.
The thirst for more customer bandwidth is beginning to grow and will soon outstrip the capabilities of operators to deliver potential future services using only CO-based DSLAM architectures, particularly if a broad customer service footprint is to be maintained.
Enriching the access network with more fibre by the deployment of appropriate deep fibre platforms will address this need successfully. Such platforms are becoming available and are proving themselves to be economic deployment solutions now, which have the capability to accommodate future needs.
The key to successful deployments depends on a thorough understanding of the access network, its distributive characteristics, the harshness of its environment and the associated principal factors that will drive service improvements and OPEX reductions. This needs to be accompanied by full cognisance of the complementary service delivery management aspects required in the backhaul network.
Leading suppliers are now working closely with operators to ensure that a partnership approach is achieved in meeting new customer demands and potential revenue growth. In telecommunications, as with many other industries, success usually only comes when careful planning meets with opportunity.
Planning now for the deployment of effective and proven deep fibre platforms will ensure that the opportunities of this future wave of IPTV and new customer services can be grasped by operators successfully and with confidence.
Danny Berko, Director is Product Marketing, and Ron Levin, Director, Product Marketing, Broadband Access Division, ECI Telecom.
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