January 1, 2008

Business Services:
Video Gives MSOs an Edge

By John Hartung

Cable operators are focused on winning commercial accounts by offering voice and high-speed Internet services, yet they sometimes neglect the one service they do so well - video. By expanding edge or enterprise services by adding local, customized digital video services, cable operators can gain a competitive advantage over the telcos while recognizing both bandwidth and cost savings.

To capitalize on this opportunity and seamlessly insert business or community-based video into the digital channel lineup, the operator will need to deploy digital conversion equipment at the edge of the network. This equipment for edge service expansion will include technologies and architectures that cable engineering teams are familiar with and have at their disposal. By combining MPEG encoding, quadrature amplitude modulation (QAM) deletion and insertion devices, and digital set-top boxes, cable operators can quickly put together a customized and unique enterprise video solution.

This article explores the business, technical and cost benefits of offering all-digital video services to the business customers, as well as the competitive advantages of converting local analog channels to digital and inserting them at the customer premises. It discusses the equipment, architecture and unique technical challenges of deploying a full digital-enterprise package that will win the highly valued business customer.

Business services

Business services represent a large potential market for cable network operators, and it is estimated that these services represent a $120 billion market that is primarily served by telcos today. Cable operators have attempted to grab some of this market because of its high growth rate relative to the single-digit growth of residential video services, and also to increase their markets as telcos begin to take away portions of their video market. While telcos have a firm hold on large business customers, the small and medium size enterprises (SMEs) present an available market to cable. Cable operators represent a stable, well-known local provider who can give more attention to the SMEs than the telcos; however, cable operators must differentiate their products to reduce churn.

Business services today consist mainly of local and long distance telephone and high-speed data, and are being provided by cable operators using the same HFC network used to deliver video. These networks provide cost-effective transport because they are already located close to the businesses to be served. While telcos are struggling to figure out how to deploy video over their networks, video is already ubiquitously available in the cable network. Video is an important service for the commercial, education, healthcare and hospitality markets and also provides informational services for the business, education and government markets.

Figure 1 shows the components of a modern cable HFC network using digital distribution in the core and access networks as shown in red.

Data, voice and video services are consolidated in the operator’s network and delivered over coaxial cable in the last mile access network to the enterprise (gray box). Both digital and analog video are delivered over a common coaxial cable.

Figure 2 shows the bandwidth allocation in a typical 870 MHz access network.

Many system operators are now in the final stages of converting their analog video tier to digital and are simultaneously distributing both formats for compatibility with analog receivers. This simulcast conversion, along with an increasing amount of high definition (HD) content, is constraining the bandwidth available for additional services such as locally generated video. This can be remedied by recovering the analog bandwidth using digital-capable set-top boxes for all displays within the enterprise. Using digital-only boxes also provides a cost advantage, as shown later. However, use of digital-only boxes requires all locally inserted services to be delivered in the digital tier.

FIGURE 1: Modern HFC network

FIGURE 2

Localized video

The value of our cable networks and services is increasingly judged by the degree to which those networks and services are localized and personalized. Subsequently, a critical component of any full-scale video service is the local channels. But localization does not stop at the city or municipality. More and more customers are interested in access to video services that are specific to the enterprise in which other business services are provided. In many cases, these channels provide additional security measures, but in many locations, these security channels are augmented with channels that provide localized informational and training services, such as an enterprise events calendar, company-wide communication or training video.

Just as cable led the way in providing local affiliate channels on the network, cable is equally well-positioned to lead the way in offering new tiers of highly localized enterprise-based video services. By incorporating these enterprise video services into the cable lineup, operators position themselves as true full-service providers and thereby deepen the relationship with the customer base.

Historically, the method for enabling these local channels was to switch in the analog enterprise channel(s) in place of alternate analog services as shown in Figure 3. In this implementation, a pre-determined 6 MHz channel in the incoming cable service is removed using a 6 MHz band elimination filter (Ch. 7 in the example). The local baseband video from a camera or other analog video source is modulated into the Ch. 7 band and coupled into the cable feed that is distributed within the enterprise. This channel can then be displayed on a TV set having a cable tuner or using an analog set-top box. Each additional local channel requires an additional 6 MHz band and the elimination of a network channel.

In some locations, operators have predesignated which analog services will be replaced, while in others it is based on a negotiation with the enterprise for which program is being substituted. But in nearly all cases, the inserted enterprise channels are analog.

FIGURE 3

Benefits of digital

Now that many operators have moved forward with digital conversion and digital simulcast projects, an opportunity exists to extend the benefits of the all-digital network into the enterprise. Chief among these benefits is the bandwidth efficiency of digital programming. Digitally encoding the local channels enables the carriage of multiple channels within a single 6 MHz band, thereby allowing bandwidth reclamation for other services. Additional bandwidth savings can be achieved by multiplexing the local channels with existing network channels within a 6 MHz slot. Figures 4 and 5, respectively, show these configurations.

In Figure 4, an empty 6 MHz band is provided for the carriage of local video services. The local services are encoded using MPEG-2 encoders at about 3.8 Mbps, providing high-quality video. These four video services are then multiplexed using MPEG-2 transport into a multiple program transport stream with the necessary program information and modulated to an intermediate frequency using a QAM modulator. The resulting modulated signal is then upconverted into the allocated 6 MHz channel, which has been left empty by the cable operator for this use, and then sent on to the enterprise cable network. This method allows up to approximately 10 local channels within a 6 MHz band using 256-QAM. The local channels can then be received by either a TV set having a QAM tuner or by a digital-capable set-top box.

Figure 5 shows the addition of local video channels within an existing multi-program transport stream. In this case, the 6 MHz band carrying the multiplex is removed from the network feed using a band elimination filter similar to the analog case. However, for digital systems there are more stringent requirements on the band elimination filter in order to avoid interference in the adjacent digital channels. This band is also downconverted, demodulated and demultiplexed so that predetermined channels within the multiplex can be dropped and replaced by the local video channels that have been digitized. Finally, the modified multiplex is modulated and upconverted so that it can be reinserted into the eliminated band in the enterprise feed. As in the previous case, the local channels and remaining network channels in the multiplex can be received by either a TV set having a QAM tuner or a digital set-top box. Both encrypted and unencrypted network channels can be handled by the drop/add multiplexer. An alternate approach would be to provide a network feed with enough unused transport stream capacity to support the addition of local channels without requiring the elimination of network channels.

Beyond bandwidth efficiency, there are two other advantages in converting the enterprise-channels to digital. The first is that the operator can deploy the latest all-digital set-top boxes, providing a significant cost savings on a per set-top basis over provisioning set-tops capable of receiving both analog and digital services. Second, the all-digital network gives the operator more flexibility to either add additional channels within the enterprise without adding bandwidth or to deploy advanced bandwidth management tools such as switched digital video (SDV).

FIGURE 4

FIGURE 5

Challenges

There are two primary concerns for adding the enterprise channels to the digital tier: the functionality and management of the equipment deployed at the enterprise and the allocation of access bandwidth and channel maps at the headend.

As described earlier, the digital local insertion equipment must provide most of the functionality of a small regional headend. These functions include encoding the local analog content in a standards-compliant MPEG-2 format that also conforms to the unique requirements of the many types of set-top boxes deployed. For example, in Motorola equipment, there are additional requirements on the encoded video format (Quad Byte Alignment) and audio encoding standard (AC-3) that are not required by other set-top boxes. The equipment must also multiplex the added channels into network feeds for maximum efficiency and modulate the resulting signal using either 64- or 256-QAM as required. Finally, the resulting signal must be upconverted to the appropriate 6 MHz analog channel and inserted without affecting the adjacent channels delivered from the headend.

Deletion and insertion of 6 MHz channels in digital systems is a relatively new application that cannot be accomplished using standard analog band elimination filters. Figure 6 shows the 6 MHz signal spectrum for an analog video channel and a digital QAM channel that might be carrying video, data, or voice over Internet protocol (VoIP) services.

The red template shows the notched frequency range for a standard 6 MHz analog video band elimination filter. For analog video channels, the filter has minimum effect on the signal spectrum; however, for QAM channels the same filter introduces unacceptable group delay at the edges of the adjacent channels. This results in an increase in the effective noise in the signal constellation as measured by modulation error ratio (MER) and results in an increased error rate and loss of signal if additional noise is present. Figure 7 shows a correctly designed filter for elimination of QAM channels. This filter provides the required 40 dB of rejection for the eliminated band and 35 dB of rejection at the signal’s Nyquist frequency. This tenth order filter reduces the MER by about 2 dB, but maintains a 2.5 dB margin over the 35 dB MER required to achieve a 10-13 bit error rate (BER) after equalization and forward error correction (FEC).

In some cases additional efficiency can be achieved in 750 MHz systems by modulating the added channels in the unused portion of the spectrum up to 870 MHz because of the short cable runs within the enterprise.

Because of the remote location of the insertion equipment, it is important that it be remotely managed from the headend to avoid costly truck rolls and that it provide failover to the network feed. The implementation of simple network management protocol (SNMP) allows the integration of the insertion equipment into headend network management systems through DOCSIS modem interfaces for control and signaling of error conditions. Automatic RF bypass is essential to preserve network services in the event of equipment or power failure. These features allow the network operator to provide a managed service that minimally affects the customer when network changes or failures occur.

The other necessary component of enterprise video service is the allocation and management of the bandwidth and channel maps from the video headend. There are multiple ways to address this need. The following provides some examples and suggestions of best practice.

If the insertion equipment is simply adding a QAM channel to an available part of the spectrum, the bandwidth management approach is rather straightforward. Operators will assign the QAM channel for this purpose and then designate a channel map that enables the enterprise served by that headend to add the video services according to the predefined set of parameters. In a Motorola system, the channel map can be specific to the set-top box, enabling the operator to activate those channels only for set-tops that are within the enterprise. In a Scientific Atlanta (Cisco) system, operators can either establish a “package” of services to which the enterprise is granted access or can create a generic channel map for “leased access” channels. This approach enables a QAM channel for programming outside of the enterprise and substitution of that content inside the enterprise.

Setting up a QAM channel and then substituting that QAM channel inside the enterprise is a generic approach for dealing with bandwidth allocation and channel mapping. The example given earlier is one method to enable this application. The key to this approach is that one QAM channel is treated as the ubiquitous enterprise QAM channel, each enterprise loading localized services into the one predetermined QAM channel and channel map.

FIGURE 6: Channel deletion using standard analog band elimination filters

FIGURE 7: Proper filter performance for elimination of QAM channels

Cost benefits

Deploying digital insertion equipment at the enterprise for distribution of local video enables more efficient use of the available access bandwidth and an overall reduction in the cost of delivering those services. The following deployment model illustrates the savings possible. Take for example an enterprise having 500 set-top boxes and a requirement to distribute eight channels of local video. Analog distribution requires the use of analog/digital set-top boxes that cost between $50 and $100 more than digital-only set-top boxes. If we assume a difference of $65, for example, a cost of $2,000 per channel for digital insertion equipment, and neglect the cost of analog insertion equipment, the digital system costs $16,500 less. In this model, a break-even is reached at about 250 set-tops, although this does not include the value of the access bandwidth reclaimed in the digital system.

Conclusion

Business services represent a large potential market for cable operators, and they are well-positioned to provide these services. This is in large part because of the ubiquitous reach and digital conversion of their networks, allowing them to efficiently provide video, voice and data services. The unique advantage they have, though, is in their ability to provide video services. By providing localized video specific to the enterprises they are serving, they can gain a large advantage over their telco competitors. These services can now be delivered in a cost-effective fashion through the deployment of integrated mini-headends at the enterprise premises.

John Hartung is CTO of EGT. Reach him at john@egtinc.com.