Backbone Transport

Throughout the past two decades, cable operators have purchased and sold cable TV systems in an effort to strategically consolidate their properties to achieve economies of scale, operational efficiencies, reduced cost, and reduced time to market for launching new services.

In many cases, various forms of optical networking technologies have been deployed to combine closely located properties, specifically headends, into a single operating entity. This has resulted in the birth of regional systems, a grouping of geographically similar individual cable systems, formerly separate operating entities, into a regional division. As evidenced by this year’s "SCTE system of the year" winners, all four were actually regional "divisions" representing a regional grouping of smaller cable system entities.

But this is not the case with all operators. Some still rely on "leased" circuits, either in the form of synchronous optical network (SONET) or Ethernet, to provide Internet protocol (IP) data capacity and connectivity to connect geographically remote systems to a central location for processing of high-speed data and voice traffic.

Circuit costs with carriers can be exorbitantly expensive in many parts of the country. For cable ops taking this approach, growing their high-speed data and voice over IP (VoIP) subscriber bases, the cost of leased circuit capacity can drastically reduce per subscriber profitability. Basically, the operator starts becoming a victim of its own success. AS DOCSIS 3.0 emerges with greatly improved data rates, the throughput requirement continues to grow at a rapid pace. In addition, a real need exists to offer improved and expanded high definition (HD) and standard definition (SD) digital video services from central locations, both to improve return on investment (ROI) through economy of scale, and also to compete with direct broadcast satellite (DBS) and telco offerings. Video is by far the most throughput-intensive service for transport over optical networks. Many operators today are now seeing their backbone throughput requirements double every six to 12 months.

Operators continuing to rely on leased backbone circuit capacity are left with a difficult capital decision: whether to construct their own optical backbone between systems. Doing so allows for the elimination of circuit costs, reduction of Internet/voice peering costs, and the ability to provide cost effective HDTV/SDTV/on-demand advanced services from centralized, regional locations. This does not include new commercial services revenue that was simply not achievable with the leased backbone approach.

On the technology front, the cable community has now fully embraced IP, Gigabit Ethernet (GigE) and dense wavelength division multiplexing (DWDM) transport mechanisms for the delivery of high-speed data, voice over IP, and now advanced digital video services. In an effort to reduce subscriber set-top box equipment costs and provide a more competitive cable video service offering, cable operators are deploying new video technologies to enable the "all digital" delivery of broadcast and narrowcast video services. These allow cable operators to converge all broadcast and narrowcast video services onto the same IP/GigE transport infrastructures used for high-speed data and voice services. Significant infrastructure investments have been made by many cable operators in the areas of IP routing, DOCSIS, digital video headend processing, and 1/10/40 GigE/DWDM transport to support these services in a converged, reliable and affordable manner.

As with many larger tier 1 operators, both Mediacom and Suddenlink West Texas have witnessed these exact business and technology issues in the past 5 years. Both decided to build their own DWDM backbone transport networks.
Build, trade, lease The first job in building a transport network is the acquisition of fiber-optic assets between the locations to be interconnected. This can be both adventurous and difficult, but creativity can bring surprise results in this area.

"Build it yourself" is always a solution, but usually only feasible for shorter interconnects.

To address the longer interconnects, one should identify potential partners with fiber assets in the areas of interest, including competitive local exchange carriers (CLECs), utilities, wholesale carriers and neighboring cable ops. Potential partners that are hungry can be willing to long-term lease portions of their fiber bundles at a fraction of the cost to build, usually in the $1,000-$2,000/fiber/mile range for a 20-year term with upfront payment. Those less hungry are often amenable to fiber swaps that benefit both parties, assuming business strategies are fairly non-competitive.

In either case, and especially with a hungry partner, it’s important to protect the acquired fiber from bankruptcy or acquisition with an indefeasible right of use (IRU) contract that includes rights to maintain the fiber should the contracted partner not be able to. Payment terms can usually be negotiated as an upfront lump sum or spread over the course of the contract should budgetary constraints require it.

To be successful at acquiring fiber through a partner, it’s important to avoid the sales channel initially and begin the communication with a senior level business development contact.

Once the fiber assets have been acquired, it is highly recommended to have the performance of the fiber qualified before deploying high data rate, multi-wavelength DWDM transport networks. This is described as "fiber characterization." Fiber characterization To achieve greater network throughput over longer distances, optical network products are being engineered that increase the amount of information that can be sent along a single fiber using two methods:

• Higher signal throughput (e.g., 10/40 GigE, OC-192/768)
• Increased number of signals/wavelengths used over a single fiber

As higher speed signals are sent over longer distances, the characteristics of the optical fiber being used becomes much more critical than for low speed signals over shorter distances. A number of phenomena work to undermine a fiber’s ability to support high capacity, long-range transmission.

As systems evolve from 10 Gbps through 40 Gbps and beyond, acceptable bit error rates (BERs) become smaller, and test measurements, analysis and engineering adjustments become more critical. Today, many cable operators are planning for the future. Although only eight, 16, or 32 DWDM wavelengths might be required near-term, ensuring that newly installed transmission system has the ability to carry 40, 80, or 160 wavelengths can avoid the costs of installing additional fiber when demand rises.

For these reasons, it is highly recommended that the existing characteristics of an installed fiber plant be evaluated against a strict set of specifications such as Telcordia and EIA/TIA before designing and installing new DWDM and/or 10 Gbps equipment into a network. These specifications are designed to ensure optimum, reliable network operation when using the latest high-performance equipment.

It is recommended that the following parameters be tested and characterized.

• Splice/connector loss and reflection
• Optical attenuation
• Optical return loss
• Chromatic dispersion
• Polarization mode dispersion
• C and L band attenuation profile

Some vendors offer fiber characterization services to assist a service provider with the implementation of a multi-wavelength and/or 10/40 Gbps system. In addition to performing the measurements mentioned, fault location and corrective actions are performed in order to bring non-compliant fiber components up to industry standards. A comprehensive report detailing how a customer’s network measures up to these standards is produced, and recommendations for improvements and optimization, if required, are made. Layer 1 and DWDM Over the past five years, many cable operators have deployed unified digital optical transport networks with DWDM as the underlying and enabling layer 1 optical transport technology. Because of DWDM’s bit rate and protocol independent nature, cable operators have used it as a "unifying underlay" for both their time division multiplexing (TDM) and 1/10/40 GigE systems. (See Figure 1.) DWDM transport networks reduce fiber requirements by unlocking the embedded capacity of existing fiber infrastructures while also providing forecast tolerance for the transport network. With DWDM, cable operators have achieved operational efficiencies and savings while also positioning themselves for future revenue-generating services and emerging low-cost transport protocols.

In addition, significant technology advancements are occurring in the areas of intelligent optical DWDM line systems and DWDM pluggable optics. Some of these technologies include reconfigurable optical add/drop multiplexers (ROADMs), intelligent throughput management via L1/L2/L3 control mechanisms such as G.MPLS, as well as pluggable DWDM optics such as XENPAK, XFP, SFP, and GBIC that enable "transponder-less" DWDM deployments.

These advancements will provide increased flexibility, reduced operational complexity and lower equipment cost through the reduction of DWDM transport network components. The upshot Both Mediacom and Suddenlink West Texas were in the same position prior to building their backbone networks. (See sidebars.) Each faced highly increased leased throughput costs without a clear path for significantly improving per subscriber profitability, as well as the need to add advanced service offerings. The business case for a transport backbone build was favorable for both companies.

In an effort to reduce customer churn, as well as increase subscriber service penetration/satisfaction and ultimately revenues, the cable backbone transport network is evolving into a self-owned and operated, highly reliable, intelligent, converged IP/1/10/40 GigE/DWDM network for the delivery of triple-play video, voice, and data services between multiple inter-connected systems. These network changes are allowing cable operators to reduce the time to market of new services, reduce network capital costs, reduce network complexity and operational expenses, and most importantly, increase both revenue and profit. Self-owned and operated backbone transport networks allow cable operators to effectively compete and maintain their leadership positions in the broadband services market for both residential and commercial customers.

Greg Euker is director, IP and transport, for Mediacom Communications. Reach him at [email protected]. Omar Sandoval is director of engineering, Suddenlink Communications West Division. Reach him at [email protected]. Christopher Skarica is CTO of Huawei Technologies North American Cable MSO Team. Reach him at [email protected]. Sidebar 1: Mediacom OneNet In 2003, Mediacom launched the build-out of the OneNet, an 11-state DWDM optical network located in the midwest and southeast regions of the United States, used to connect all of the company’s strategic headends and systems.

With subscriber and organic growth causing a 70 percent year over year increase in high-speed data capacity needs, circuit lease costs continued to compound. Mediacom, then with roughly 100,000 subscribers, was experiencing a $4.50/sub monthly cost for transport alone, with very little offset to the cost of capacity in moving to larger circuits. These rising costs provided a strong business case for building collocations with the company’s Internet service provider (ISP) and a backbone that could transport the majority of the subscriber base to those collocations.

Today, Mediacom has 85 percent of its subscriber base connected to its OneNet backbone, reducing monthly transport costs for those systems to pennies per subscriber, having only collocation charges to account for. Of course, a backbone presents new recurring costs such as hardware maintenance and network operations center (NOC)/network support, but they pale in comparison to the cost of leased transport. With more than 729,000 high-speed data subs at the end of Q3 2008, the estimated savings of building rather than leasing for high-speed data service alone is more than $25 million annually.

Although Mediacom’s backbone was justified by high-speed data alone, the company’s video, phone and enterprise networks service offerings have also reaped many benefits.

For video, an IP multicast network was built in 2005 using existing infrastructure. Centralizing a majority of its video distribution has allowed Mediacom to launch HD channels at a lower cost per sub though a reduction in the number of satellite receivers and encoders necessary. Local broadcaster feeds can be encoded at the studios and distributed via the backbone, delivering the highest quality signals possible. VOD content management as well as command and control functions have been consolidated into regional divisions.

Phone transport has benefited with very similar savings per sub as high-speed data. Enterprise networks, with a vastly improved reach for fiber-based service offerings, has grown from less than $500,000 annual revenue into a real bottom line contributor. Sidebar 2: Suddenlink West Texas Suddenlink’s completion of a 957-mile fiber ring in west Texas in 2008 is another point in the trend toward building vs. leasing optical assets. It also marked the maiden deployment of Chinese telecom equipment provider Huawei in U.S. cable.

The six-month long construction was aimed at enabling an expansion of video and other services for the operator’s customers in 14 regional west Texas systems. It was constructed with both newly built and leased dark fiber assets using advanced multi-wavelength, 10 Gbps DWDM technology as the converged optical transport mechanism for all voice, video and data services. It is now being used to carry multiple IP/GigE and OC-48 client signals via 10 Gbps DWDM wavelengths. (See Figure 2.) The case for Suddenlink’s building vs. leasing decision had three pieces: distances and the regional fiber market, headend economics, and carrier sales opportunities.

With spans between the region’s five major cities – Amarillo, Lubbock, Midland, San Angelo and Abilene – ranging between 120 and 180 miles and lease providers being few and far between, Suddenlink was looking at long deployment timelines and high circuit costs for continuing to go the leased route. As for headends, the centralization of expensive video processing equipment as well as reduced mean time to repair (MTTR) for advanced SDTV/HDTV/on-demand digital video services drove that business decision.

This major investment has opened the doors to new and better services for Suddenlink West Texas markets and has given them the ability to introduce these services much faster. It has also reduced the overall cost of servicing each existing subscriber.

With an aggressive focus on delivering more HD services to Suddenlink customers, the interconnect enabled Suddenlink to decrease its cost by funding one location instead of funding eight headends to deploy the HD channels. With Suddenlink’s recent HD additions and more in the future, savings can easily start moving into the millions. By implementing in one location, Suddenlink estimates it could see savings of more than 80 percent. The same would be true for introducing digital simulcast to Suddenlink West Texas expanded basic line up as well as doing ad insertion from one central location.

Suddenlink’s build also opened up significant opportunities to market carrier and commercial services, with the ability to deliver services to customers all over the Suddenlink West Texas footprint.

Examples of greatly improved services are the small communities of Post and Tulia, which are fed via linear amplitude modulated (AM) optical spurs from a headend on the backbone network. These very small communities now see big-city benefits since they have been retrofitted and connected to the backbone. The HFC plant retrofit has increased plant upper frequency limits in these towns to 750 MHz and 860 MHz, respectively. The fiber connectivity provides Post and Tulia access to improved high-speed data, all advanced video services (including digital simulcast and video on demand, VOD), as well as telephone service, which was not previously cost effective in the days of the leased circuit backbone.

Towns of 1,500 people now have access to the same services as cities of 100,000. Additionally, Suddenlink can now offer commercial high-speed services to an advanced, wider reaching, geographical footprint. Early commercial high-speed demand has been tremendous, and the ability to offer these high margin services will no doubt improve the net income and profitability of the region significantly.