The world of communications is ever growing. One only has to look at Apple’s AppStore reports from fall 2009, to get the picture: 2 billion apps have been downloaded by over 5 million iPhone and iPod Touch consumers in little over 1 year. Today there are 350 million Facebook users -- more than the total population of the U.S., according to current data from the social networking site -- and the number keeps growing. These are only 2 small examples of the consumer’s insatiable demand for communications and communications-related applications. Already traffic on the Internet exceeds 400 exabytes daily on a global basis for videos, social media, audiovisual content, and electronic literature access.

The migration to the digital world has occurred over the past decade as service providers have transitioned from a pure pipeline service offering to a service offering that includes voice, video, data, and mobile network elements. Service providers continue to examine ways to modernize and upgrade their wireline, wireless, and broadcasting infrastructures to support our rapidly increasing digital economy. Indeed, service providers are uniquely challenged to keep up with the explosion of traffic that is invading their networks. That said, though the current network is reliable, it has become strained.

Fiber optic connections are the ideal solution for providing bandwidth, but deploying an all-fiber solution is not always possible for a variety of reasons. As a result, many service providers are looking for alternatives to fiber that both deliver the bandwidth needed cost-effectively and within a short time to market.

One of the most innovative solutions on the market, the outside plant (OSP) digital subscriber line access multiplexer (DSLAM), combines the bandwidth carrying capacity of fiber with existing copper facility connections to the customer resulting in a cost-effective delivery solution optimized to meet both of these objectives.

The Network Evolution
The evolution of the network cannot, and does not, stop at voice, video, data, and mobile networking. Carriers worldwide are teaming up with content providers, financing local productions and producing independent content with the ultimate goal of moving beyond the pipe and becoming total solutions providers. Because network services continue to grow, despite downturns in the economy, service providers must likewise grow their networks to support the growth in technologies such as IPTV/IP Video, Video-on-demand, video telephony, broadcast TV, online gaming, and music downloads. The delivery of these services requires digital, packet-based, high-bandwidth networks, which is imperative to the survival of today’s service providers.

With technology driving the need for more bandwidth, carriers must consider the business case for deploying these services. Fiber is a likely solution to increase speed and extend the reach of bandwidth to the customer. However, it is widely known and accepted that extending fiber to every customer is cost-prohibitive for most service providers. Conversely, copper connectivity is readily available to virtually every subscriber worldwide. Solutions that extend Fiber-to-the-Node (FTTN) and allow for high-bandwidth network services to overlay or use the existing copper infrastructure are a natural compromise to support these high-bandwidth services.

Most service providers already have a limited number of fiber routes in their wire centers. Rather than extend the fiber plant all the way to the customer premises, which is not cost-effective from either an infrastructure or time to market perspective, many service providers are turning to solutions such as FTTN.

FTTN is an ideal compromise that leverages existing copper infrastructure while deploying high-bandwidth services to the end-user or business customer. Fiber extends the reach to the node, allowing for shorter loop lengths and higher bandwidth utilizing existing copper to the premises. With technologies, such as Bonded ADSL2+ and VDSL2, customers do not have to compromise performance and bandwidth -- all in support of the evolving network and infrastructure.

However, not all FTTN solutions are created equal. To achieve the desired loop length to all customers, many nodes must be deployed in the network. This can be costly and introduce delays in deployment. In addition, traditional FTTN solution deployments often include a separate cabinet containing a non-environmentally hardened DSLAM. This can make for a time and cost-intensive deployment.

Other factors also increase the cost of traditional FTTN deployments:

• Land and Site Preparation. Land must be purchased or leased and prepared for the installation. A concrete pad is required along with trenching and conduits for access. Power is required at the site prior to the cabinet installation.

• Cabinet and Installation. The traditional deployment requires a cabinet, which houses the DSLAM, with an environmentally hardened enclosure with power supplies, cooling systems, and cable management. These cabinets are not aesthetically pleasing and the noise produced from the cabinet as well as ease-of-access must be considered especially when deployed in residential areas. A crane is required to place the cabinet on the previously laid concrete pad during installation. This solution can cost up to $35,000 and take up to 45 days to install.

An Ideal Solution
The OSP DSLAM is the ideal solution for service providers looking to evolve their network and keep up with the growing demand for advanced communications services. With an OSP DSLAM, service providers are able to lower total cost of ownership and time to market because it is a completely self-contained, environmentally hardened, sealed enclosure that eliminates the cost, land considerations, and need for a separate cabinet to be installed for FTTN applications. (See Figure 1.)

Figure 1. Deployment costs cabinet-based solution vs. OSP FTTN DSLAM.

A sealed DSLAM represents an innovative approach to the successful deployment of (FTTN) architectures. Recognizing the technological and economic barriers of traditional cabinet-based DSL deployments, some manufacturers have designed standalone, weatherproof FTTN OSP DSLAMs to eliminate the need for expensive cabinet enclosures, heat exchangers and site construction, which account for a large portion of the total deployment cost.

While cabinet-based solutions are well accepted, they are not always the right solution. Advocates of these solutions focus their arguments around lower electronics costs, but tend to ignore the impact of other associated deployment costs, which significantly impact total cost of ownership. OSP FTTN DSLAMs present a unique alternative to cabinet-based systems. While base costs (per port) may be marginally higher in some cases, the cost savings achieved through the elimination of expensive infrastructure elements such as cabinets, concrete pads and labor more than make up the difference, resulting in a total cost savings of more than two-thirds and an exponential decrease in time to market.

As service providers continue to address the deployment of next-generation services, OSP DSLAMs will play a key role in shortening copper loops to enable service delivery. Because these platforms are robust enough to go anywhere in the outside plant -- giving service providers unmatched flexibility to deploy broadband services, they allow service providers to economically provide both legacy and next-generation services while providing a migration path toward the converged network architecture of the near future.

About the Author
Kevin Morgan is Director of Product Marketing, Carrier Networks Division, ADTRAN. He has more than 23 years experience in advanced technologies and fiber optic systems. For more information, email tammie.dodson@adtran.com or visit www.adtran.com.

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