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MediaOne, a US West company and main provider of cable television entertainment services throughout metropolitan Atlanta, has embarked on a $350 million rebuild/upgrade of its Atlanta network, most of which was originally built during the late 1970s.

With the goal of creating a state-of-the-art 750 MHz hybrid fiber/coax system to provide entertainment, data, video and telephony services, MediaOne is also investing heavily in the "brains" of the network with the consolidation from 12 headends to two super headends.

MediaOne's project is an excellent example of what needs to be considered when consolidating headends to both immediately serve customers with a full complement of analog channels and also provide flexibility for future telephony, data and other digital services. Using the MediaOne headend rebuild as an example, this article will summarize some of the challenges and opportunities operators face when consolidating and rebuilding headends.

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Figure 1: Service area map for the Atlanta rebuild project. Redundant ring headend interconnect path: From the Vinings super headend to the Stone Mountain super headend.
MediaOne's history

In December 1994, MediaOne acquired most of the cable properties in the Atlanta area, which provide service to a total of 475,000 customers. These customers were served by 12 separate headends. The quality of the headends and the distribution plant varied widely and clearly could not support the ambitious plans MediaOne had for its current and future service offerings. As a result, a consolidation and rebuild of the headends, along with an extensive upgrade of 12,000 miles of plant, was undertaken.

The objective of MediaOne's rebuild was to grow its customer base by investing in its headends to improve the reliability, quality and efficiency of its operations. Ensuring future flexibility requires planning now for a future that is not completely understood, but one that will surely make the headend a more complex, critical and effective component in the delivery of programming and services.

With this scenario in mind, how does the headend contribute to improved quality, reliability and efficiency? Let's look at reliability first. Improving service reliability is the most significant reason for consolidating and rebuilding headends. There is no doubt the successful service providers of the future will need to offer their customers more than simple audio and video services. Customers will expect services like telephony, data and security. But customers will not purchase these services unless they have confidence in the service provider. Thriving as a service provider requires operators to improve the reliability of the network, and the headend is a good first place to start.

To improve reliability, headend equipment can now be monitored and backed up automatically, reducing downtime and improving customer service levels. Current headend management products monitor the combined headend output, scanning each channel constantly for key problems like loss of video or loss of modulation. If a problem is found, that channel is immediately removed and a backup channel is inserted, limiting service interruption to as little as several seconds. Without this tool, headend problems may cause interruptions that last for many minutes before a technician observes the problem or a subscriber phones customer service. Headend management tools can also control individual pieces of equipment, allowing operators to do remotely virtually anything they could do if they were standing in the headend. This feature is particularly valuable in controlling unmanned or remote headend locations.

For the MediaOne network, system monitoring and control will be handled by the Network Operations Center (NOC). Operating 24 hours a day, 7 days a week, with a staff of 15 to 20 full-time employees, the NOC will monitor all network elements from the headend all the way to the optical and power nodes. The NOC utilizes a network management system provided by Megasys and is located at a nearby business office. A redundant system is located at one of the two super headends and is connected to the nearby office location via a Sonet backbone network.

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The Vinings super headend, which is 25,500 square feet in size, will accommodate MediaOne's immediate and future needs. The building is one of two — the other is located in Stone Mountain. (All photography by Frank Zayas; photos courtesy of MediaOne.)

The Megasys network management system can manage a wide variety of network elements. As the MediaOne network grows, additional network element protocol subdrivers can be developed and installed.

Along with reliability, the quality of the signal reaching customers can be significantly improved with a headend rebuild. The combined carrier-to-noise ratio (CNR) is the specification that best measures the quality of the outgoing headend signal. Through the use of improved output convertor and vestigial sideband (SAW) filtering, premium quality modulators can improve the CNR by 3 dB to 4 dB over top-of-the-line modulators manufactured only a few years ago. Whereas older, coax-based distribution systems would have "drowned out" this improvement by the time the signal reached the customer, current HFC networks can allow this improved CNR to positively impact end-of-line performance. At a cost of $7,000 to $8,000 per channel, investment in the headend can yield some of the best performance per dollar invested.

The MediaOne headends utilize all new high performance headend electronics to take advantage of this performance opportunity.

The final reason for updating the headend is to increase operational efficiencies and lower costs. Reducing the number of headends reduces the need for skilled operators and decreases the total amount of equipment and spares required, thereby lowering operational expenses. By consolidating from 12 to two headends, and by taking advantage of a network management system, MediaOne has significantly increased its operating efficiencies and reduced its costs.

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Figure 2: MediaOne's combining system for zoning. Sixty-six common channels are combined with 28 unique channels to facilitate targeted ad insertion and local program capability.
Consolidation details

As mentioned earlier, MediaOne inherited 12 headends. These 12 independent headends were replaced by two new super headends joined by a fiber link for redundancy, as shown in Figure 1. Even a complete failure of one headend would not affect service, because the other headend serves as a backup.

Each headend is serviced by a separate antenna farm containing 4.5 meter antennas, one of which is motorized at each site. More than 200 fixed channel modulators provide 66 common and 28 custom channels to each of five zones. Plug-in frequency agile output convertors are utilized for modulator backup, and all channels are routed through patch panels for easy channel realignment and testing. In addition, a 32×32 matrix switch provides timed switching capability for special programming needs. Emergency audio and video override capability is also provided to meet the upcoming Emergency Alert System requirements.

To save floor space, all equipment is racked in 84-inch tall racks. Plenty of room is left between equipment pieces for future expansion. All RF outputs are routed to a central location to accommodate monitoring by a future headend management system.

The off-air television signals will be replaced with a point-to-point special fiber studio that feeds from the television stations back to MediaOne's two super headends. The first three stations will be on-line soon, and the balance by year-end. These links will provide MediaOne customers with near studio quality television pictures. They will also benefit the local television stations if they have power or transmitter problems because programming will continue to MediaOne customers.

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David Sharp, headend technician for MediaOne and for the Vinings super headend, makes an equipment adjustment.
The MediaOne distribution network

While this article focuses on the headends, the distribution system has also been upgraded and is an important part of the project. The new MediaOne headends feed a hybrid fiber/coax 750 MHz distribution network with 42 distribution hubs, each serving 20,000 to 30,000 homes and businesses. Each distribution hub will have a diverse routed fiber optic 1550 nanometer (nm) headend feed with protection switching. The distribution hubs will deliver signals to more than 2,000 nodes of 500 homes each via 1310 nm fiber optic transport with a fully activated return in the 5 MHz to 40 MHz bandwidth.

More than one billion feet (189,000 miles) of fiber will be deployed over the next two years. As of this writing, over 400 million fiber feet and approximately 300 of the nodes have been activated. Network powering is served by about 2,100 power units, each rated at 5,400 watts, located at the optical node. The power plant is backed up by batteries, as well as a natural gas fuel generator.

Telephony equipment

A key part of the MediaOne strategy is to offer telephony service over the new HFC network. Therefore, a telephone switch and associated transport hardware have been co-located at the super headends. The switched telephony, alternative access and multimedia/data services will be transported to and from the distribution hubs via Sonet self-healing networks. Each network ring consists of Sonet intelligent multiplexers linked together in a ring configuration. The inherent route diversity and self-healing capabilities of ring architectures allow uninterrupted services to the customer in the event of a fiber failure in the backbone ring.

Additional distribution rings provide a dual homing configuration from MediaOne headends to interexchange carriers (IXCs) and local serving offices (LSOs), as well as business customers.

The zoning concept

As described above, the super headends provide 66 common channels to all subscribers. Additionally, each headend provides 28 channels to five zones served by each headend, for a total of 140 additional channels per headend. Figure 2 depicts the channel lineup and the combining for each headend.

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A view of racks and racks of equipment provides some perspective on the sheer size of the super headend.

By zoning video distribution from a super headend, an operator can cost-effectively provide targeted programming to smaller subscriber pockets while retaining the efficiency of one headend location. Customer service is enhanced by providing truly local PEG (public, education and government) channels, and advertising revenue potential is increased many times by offering targeted audiences for both local and regional advertisers. Presently, MediaOne generates more than $30 per sub per year in advertising revenue. With the cost of digital ad insertion gear at less than $10,000 per channel, payback periods are expected to often run less than 24 months.

In summary, as product and service options available to customers continue to increase, retaining them will remain an ongoing challenge for cable operators. Meeting this challenge will require network investments to ensure reliability, quality and efficiency. The headend is becoming a more complex and critical piece of the network that can have significant impact on each of these parameters. A headend rebuild can offer the cable operator a competitive advantage, and investing in the headend can yield some of the best performance per dollar.

At the same time, headend rebuilds offer operators an opportunity to set up a zoning strategy to improve customer service and boost ad revenue.

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