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The Rural Challenge

By Lesley Hansen, Marketing Director EMEA, Net to Net Technologies Ltd

The lack of deployments in rural areas show just how hard formulating the business case can be. The issues however are not substantially different to those experienced in urban deployments. A key factor to the urban business case is the number of potential customers to be found in an area and determining what Revenue Per User (RPU) they will be willing to pay and can afford. This has resulted in urban areas in DSL Access Multiplexer (DSLAM) vendors focussing on cramming as many customer ports as possible into a DSLAM and setting high contention ratios (up to 50:1) to reduce the cost per user of the expensive backhaul connections and network switches. These DSLAMs were designed to be housed in the Central Office Exchanges in typically clean and air-conditioned facilities with relatively easy access.

In rural areas the issue is the same but the design philosophy is different. Rural areas do not provide enough potential customers to allow this kind of playoff of numbers against bandwidth costs, and the large capacity DSLAMs designed for urban central offices will be too expensive when shared between low port numbers. So a new philosophy is needed.

Low port count DSLAMs from 6 to 24 for example have been designed to be environmentally hardened to allow them to be housed in harsh rural conditions and to provide a variety of inexpensive backhaul connections that can be scaled down to suit infrastructures where fibre is too expensive or not available. Backhaul connectivity is able to run over copper or fibre for basic Ethernet or Fast Ethernet solutions or using existing WAN links (E1 or E3) taking advantage of the typically available SDH infrastructure. Products need to be low maintenance, easy to deploy and able to be monitored and managed remotely since visits to the rural Point of Presence (POP) are likely to be expensive and irregular. AC and DC units able to accommodate whatever power option is available locally are needed and these need to be low power consumption units to work within the limited power supply capacity that is likely at the rural exchange.

Most Operators (Incumbent as well as Competitive) have tended to avoid DSL deployments in rural areas since the high CAPEx and OpEx for DSL technology has meant it is extremely difficult to build a business case for DSL deployment for low volumes of users. For the most part the Operators have deployed very large DSLAMs to get the best rate of return on the high number of ports (ie. users) able to be connected. More recently innovative companies have developed new smaller and more flexible DSLAMs that don’t have the dependency of large capacity expensive ATM backhaul links thereby making the business case more feasible - particularly for business users where value added services over IP can provide incremental revenue rapidly after service rollout.

Even with these new products available the Incumbent typically has an issue with handling the rural area because their organizations are often monolithic systems that rollout a standard package of hardware to large volumes of connections (residential up until now, ignoring the business community in most cases) and therefore they do not possess the flexibility or individual local initiatives to be able to handle the complexities of rural deployment.

For the smaller and more flexible Competitive Operator or Local Service Provider who is not restricted by these issues of size the Incumbent’s reluctance to move into rural areas provides a clear opportunity. Price points in these areas where alternatives are not available are likely to be higher and churn is not an issue since the competition is limited. However, Competitive Carriers need to choose their markets carefully and consider how to serve them most efficiently, balancing a cost effective solution against the quality required to attract those customers with the potentially highest RPU.

Issues to Consider when Building the Rural Business Case :

Rate vs Reach

The distance limitations of DSL are also an issue to be considered and are particularly significant in rural deployments where copper ducts may not be direct from end user to exchange and where the volume of copper lines available may be lower.

Cascading DSLAMs with a remote unit in a local street cabinet or at a centralized site area such as the local hall or school and then multiplexed back over a second link such as a Wireless or Radio link, or if greater distance is required over a WAN link (E1) to the local POP, is one potential solution to this issue.  Loop bonding of multiple DSL copper links or E1 circuits can provide solutions to extend the rate in longer reach deployments. In this solution the pairs are bonded together using inverse multiplexing techniques to double, triple or even quadruple the bandwidth available. This solution is ideally suited to markets such as Germany, UK and Scandinavia where copper is already heavily deployed and bandwidth costs using traditional E1 and E3 circuits are high.

Service Type to be Provided

ADSL has been the technology of choice for residential applications where the need is to deliver more bandwidth to the end user but limit the amount of bandwidth coming back up into the network infrastructure. The Net to Net ADSL Mini and Micro DSLAMs will interoperate with any industry standard ADSL or G.Lite modem over the local loop while still preserving the benefits of a packet based architecture. Simultaneous voice and data support allows Providers to take advantage of line sharing agreements and further reduces the cost of deploying residential DSL services. ADSL is an ideal voice and data solution for residential use, supporting data and POTS or ISDN voice services over a single copper pair. By maintaining lifeline POTS, the voice connection is never terminated in the event of power loss. ADSL provides the high-speed downstream bandwidth required to deliver IP video from the Street Cabinet.

DSLAMs that support the highest rates possible using ADSL (ADSL S=1/2) can provide up to 10.5 Mbps downstream at distances up to 10,000 feet from the Central Office or Remote Terminal/Street Cabinet. This high-speed bandwidth allows Providers to deliver the “Triple Play” of IP services: voice, video, and data, which some Operators are looking at very closely as a means of increasing the RPU value significantly.

SHDSL provides high-speed, symmetrical bandwidth (ie in both directions) that is typically required by the small business user, SOHO or telecommuter. Using Customer Premise modems that support loop bonding it is possible to bond 2, 3 or 4 copper loops together to increase total bandwidth to as high as 9.2Mbps at distances up to 12,000ft/3600m. More importantly, loop bonding allows for higher speeds at greater distances for end users further away from the rural POP or Street Cabinet. With up to four DSL lines and IP QoS included on a small fixed port DSLAM, the Provider is able to deliver additional service options and revenue opportunities for the business user that make use of the higher upstream bandwidth of symmetrical DSL. The other spin off benefit is that of having some resilience should any of the copper pairs be terminated at any time, providing very high levels of uptime which is as important to the rural business community as it is those located within towns and cities.

Controlling the Backhaul Costs

Once the DSLAMs have been multiplexed back to the local POP then either a direct fibre link, or wireless, radio or even a copper backhaul needs to be provided from the local POP to the core network. Typically in DSL deployments this link has been an OC-3 or more recently a Gigabit Ethernet port. This means that with an ATM based DSLAM architecture this connection is either 155Mbps and therefore a large costly pipe, or it involves a conversion of the traffic from ATM cell formats to Ethernet frame formats, a conversion that is expensive in terms of power consumption at the unit as well as the hardware costs and the unit size, all important considerations in a rural deployment.

Therefore using a native Ethernet IP architecture in the DSLAM and backhauling on 10/100Mbps or GigE copper or fibre, or into a wireless or radio backhaul using native Ethernet without having to go through a cell to frame conversion with the related overheads, makes a lot of sense.

An efficient alternative is the ability to backhaul using multiple E1 Leased lines, as practically every rural POP has plenty of these connecting them to other facilities. Net to Net’s ability to transmit Ethernet frames over several E1s provides a very beneficial means by which low cost DSL connectivity can be achieved economically and efficiently.

Fixed Technology Solutions

DSL and Fixed Wireless are natural partners in a rural deployment since both address the issues of low cost bandwidth deployment in low-density areas.  Technologies are available for Fixed Wireless that offer from 500Kbps to 6Mbps over distances up to 35km. Not all Fixed Wireless spectrum is licensed, bands in the region of 2.5GHz and 5GHz are unlicensed and available for Fixed Wireless communications. Fixed Wireless can be considered as a Local Access solution backhauled on SHDSL or as a Backhaul solution for DSL services with a link from the Central Office to the repeater station.

For more information : please contact:  Lesley Hansen:  lhansen@nettonet.com

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