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If Rube Goldberg were an economist, he would have had no trouble relating to the information networking world in which we live today. Cable competes with satellite by introducing triple-play services; telcos, feeling the threat, respond with video, initially via alliances with some satellite enterprises; satellite responds with massive HDTV channels, and so forth. The game is afoot, and telcos are responding with aggressive upgrades to their access infrastructure to provision competitive service bundles.

Much of the attention by competitors will be squarely focused on the box, or more precisely, the boxes. The average household in the U.S. has 2.6 television sets, up from 1.4 sets in 1970. It is a widely held assumption that high definition (HD) sets will cause that average number to rise--perhaps to 3 or more. HD sets are undergoing a rapid reduction in price, and are projected to begin an aggressive rate of expansion, growing to about 60 million homes by 2008. In 2008, there are likely to be more than 33 million households with personal video recorders (PVRs).

Also expanding are the number of picture-in-picture sets, the number of small portable video display devices, and a host of other consumer electronics that could be on the receiving end of a flow of Internet protocol-based video channels. These devices will likely not replace older vintage sets, but rather will add to the average number of video devices per home.

These statistics are significant for telephone carriers seeking to offer bundles of voice, data and video services since the IP-TV services that many of them will offer will require bandwidth for each channel consumed at any given time. And yet, they are the wrong statistics for this discussion in that they address average bandwidth usage or the average number of TVs per home.

This would indeed be an odd perspective for network engineers accustomed to planning for peak-hour voice usage on Mother’s Day, where over twice the “normal” busy hour calls are made. Why would video network engineers implement an access plant that could only meet the needs of half of the potential pool of subscribers?

While many telephone carriers have decided to implement fiber-to-the-premises (FTTP) to accommodate this demand, several which are seeking to offer bundled services at the lowest cost possible are implementing fiber-to-the-node (FTTN) infrastructures. They will deliver these services using fiber to some point in a neighborhood, but from there, use the existing copper telephone wire and offer these services via DSL to the home or business. Unfortunately, this will generally limit them to fewer than 24 Mb/s in most cases--certainly less than the 100 Mb/s they could make available with a FTTP infrastructure.

This bandwidth will be insufficient to address the demand discussed above. (Actually, the 24 Mb/s assumes laboratory conditions; actual field results will likely be substantially less.) In addition to the absence of “peak” planning, the logic behind a “24 Mb/s is plenty for triple play” philosophy is further vulnerable to the degree that initial deployments will be in higher-end communities where “average” is usually higher than “average.”

Arise the white knight for the “24Mb/s is plenty for triple play” philosophy--otherwise known as MPEG-4 pt 10 or Windows Media 9. And although the knight is powerful, two HDTV streams, a few standard-definition TVs and a PVR can soon overpower even the might of next-generation compression. The use of more aggressive compression parameters to sustain the overly-taxed 24 Mb/s infrastructure will not sit well with content owners who might witness their HD quality assets diminished or with consumers who expect visually stunning results to appear on their newly purchased and expensive HDTV sets. While it might be argued that two HDTVs in today’s home would be excessive (although evidence at the local Best Buy suggests otherwise), it would be hard to argue that such would not be the case in the coming five or so years. Generally, access plant is deployed with something more than five years of useful life expectancy.

Fortunately, there is an option for carriers who find themselves in this access quandary.

The first step is to confront the new realities in the core network. With the availability of service quality options for Ethernet traffic, most network providers have embraced core Ethernet switching. Legacy ATM switching imposes a high non-payload bandwidth tax on IP/Ethernet-originated traffic. In addition, the manual provisioning of each entry and egress port required with ATM adds far more operations cost than the self-discovery provisioning supported by Ethernet. Retaining an ATM infrastructure is a liability.

Implementing VDSL modulation over the copper plant is the second part of the solution; it enables carriers to migrate to an end-to-end Ethernet solution and significantly reduce their operating expenses. It also provides more efficient bandwidth in terms of payload-throughput. VDSL2 enables a carrier to offer far greater amounts of bandwidth within short distances--up to 100 Mb/s when the node is within 500 feet of a premises. This is an ideal means for serving multiple dwelling units (MDUs) or multiple tenant units (MTUs) where copper currently resides in the risers.

A third part of the solution is the deployment of nodes that can economically, efficiently and modularly evolve from copper to fiber as demand requires. At an aggregation node, an Ethernet aggregation switch can accommodate both VDSL-based line cards with copper interfaces, as well as Ethernet switched optical network (ESON) line cards with fiber interfaces. Thus, with a point-to-point, switched Ethernet topology, a carrier can insert VDSL line cards--each serving eight subscribers over copper, while other ESON line cards can be inserted into the same chassis in order to provide up to 100 Mb/s service over fiber to each of eight other subscribers. These ESON ports could be associated with subscribers who have a sufficient number of consumer electronics such that they require the added bandwidth. Or perhaps they are part of a new build, up to 40 kilometers away from the node, and thus are most effectively served from that node by fiber.

The decision to deploy FTTN or FTTP topologies in the near term will be dependent on a litany of factors that will vary from carrier to carrier. The likely reality is that in the longer term, universal FTTP will be required--even with the most aggressive compression algorithms. Thus, the decision framework is not FTTN vs. FTTP, but rather FTTP vs. FTTN that can economically and efficiently evolve to FTTP. The above proposal offers a strategy for those carriers implementing FTTN in the near term to support that evolution.

Gary Feldman is Vice President of Marketing and Business Strategy, Amedia Networks Inc.

Visit Amedia Networks online.