Getting local...and personal
The value of our cable networks and services is increasingly judged by the degree to which they are localized and personalized. Subsequently, a critical component of any full-scale video service is the local channels. Although cable operators have known this for some time, satellite providers have only recently realized the importance of local channels and have moved to offer them as a part of their total package.
But localization does not stop at the city or municipality. More and more subscribers are interested in access to video services that are specific to the community in which they live. In many cases, these channels provide additional security measures (the most obvious and widely deployed is the front-gate or front-door camera). But in many locations, these security channels are augmented with channels that provide localized conveniences or services, such as a community events calendar or a message board.
Figure 1: Analog community channel insertion.
Local analog channels are modulated and combined with the analog cable feed
entering the community, a process requiring agile modulators for each channel.
The notch filter filters out three analog channels, replacing them with internal channels.
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 community-based video services. By incorporating these community video services into the cable line-up, operators position themselves as true full-service providers.
With more Americans living in apartments, condominiums and close-knit communities, the ability to offer a fully integrated video service that includes the community-channels is a competitive differentiator that cable operators should continue to exploit in order to maintain and grow the MDU subscriber base. New emerging competitors in the video services arena are actively targeting new and existing MDU contracts to convert large numbers of subscribers en masse. As cable operators are currently the leading providers offering this highly localized community programming, they are well-positioned to grow these differentiated services going forward.
Historically, the method for enabling these local channels was to switch in the analog community channel(s) in the place of alternate analog services. In some locations, operators have pre-designated which analog services will be replaced, while in others, it is based on a negotiation with the community for which the program is being substituted. But in nearly all cases, the inserted community channels are analog. Now that 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 community.
Chief among these benefits is the bandwidth efficiency of digital programming. By converting an MDU with two local channels to all-digital, operators can use one QAM channel with two programs instead of using two analog channels with one analog program each, thereby reclaiming an entire 6 MHz channel. For communities with more than two channels, the impact on bandwidth efficiency is even more substantial.
Secondly, by converting the community channels to digital, the operator can deploy the latest all-digital set-top boxes, providing a significant cost savings on a per set-top basis. Lastly, the all-digital network gives the operator more flexibility to either add additional channels within the community without adding bandwidth, or deploy advanced bandwidth management tools such as switched digital video.The community premise equipment
There are two primary concerns for adding the community channels to the digital tier: the functionality of the equipment deployed at the community, and the management of bandwidth and channel maps at the headend.
The community premise equipment (ComPE) must be able to perform and function similar to a small regional headend, a micro-headend, if you will. It must be agile and work in concert with a channel deletion filter notching out the QAM channel that will be used for the community video channels. It must also be able to encode the analog video into a standards-compliant MPEG-2 format. The ComPE must support Dolby Digital AC-3 audio encoding, to support legacy set-top boxes. In communities with multiple channels or services, the ComPE must be able to multiplex those services together and then modulate them for either 64 or 256 QAM environments. The ComPE must then be able to upconvert that QAM channel to the right frequency. It is worth noting that systems that are 750 MHz or smaller can distribute these services above the normal plant spectrum for the short runs within the community or building. The viability of this approach will be highly specific to the actual community and installation environment. Apart from these active elements of the solution, operators will need to deploy splitters/combiners to split off the HFC service and recombine the community QAM channel with the rest of the line-up.
Figure 2: Digital community channel insertion.
The single ComPE device encodes, multiplexes, modulates and
upconverts the local channels for the community.
The bulk of the technical requirements for the ComPE solution are derived from the technical environment described above. There exist, however, a number of operational requirements that have significant impact on the ComPE solution design.
As the installation locations are scattered (distributed) outside the plant or headend, the devices must be very simple to install. They must come equipped with default configurations that work "out-of-the-box" and are easily adaptable. Once the systems are installed and operational, there must be standards-based support for remote monitoring and management.
As subscriber demand for more security cameras and other community-based video grows, cable operators will want to leverage the deployed base of ComPE solutions. The ComPE solution should be scalable; it must be able to add channels without adding significant complexity or space.
Lastly, but perhaps most importantly, although the technical functionality for the ComPE solution is similar to a micro-headend, the environment is not. The distributed nature of the application requires a high degree of fault tolerance. Unlike a headend, there is no trained technician in the next room who can jump up to address service disruption. In an effort to better understand the new root causes of service disruption, Cox has recently conducted a study on the core elements of network resiliency. The results of this study are both interesting and surprisingly obvious–the least resilient part of the network is the cables and connectors. What this means for the ComPE solution is that full system integration is vital to the overall fault resiliency of the application. A multitude of cables and connectors works against the desire for fault tolerance.
There must be a way to secure the ComPE solution such that untrained, clumsy or even malicious people are not given the opportunity to modify or disrupt community services. The ComPE solution must also be robust enough to tolerate temperature extremes and environmental hazards such as excessive dust. As the installation environment will in many cases not be equipped with robust or redundant cooling systems, the solution must be capable of not only alerting the administrator to internal temperature status, but of taking protective action.Bandwidth & channel management
The other necessary component of a community 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 installation of the ComPE solution is simply adding a QAM channel into 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 communities served by that headend to add their video services according to the pre-defined set of parameters. Channel map strategies will vary based on the specifics of the system into which the ComPE solution is being deployed. In some systems, the channel map can be specific to the set-top box, while in others, it will be specific to the hub or node. The operational impact of establishing a channel map per set-top box may be too complex to manage, no matter the potential of the system. It is expected that more generic channel mapping schemes will be the norm as systems are initially deployed. In some instances, the cable operator may elect to establish a group of channels as "Leased Access" channels. This approach enables a QAM for programming such as infomercials or long-form advertising outside of the community and substitution of that content inside of the community. In all cases, channel provisioning and mapping will need to be thought through in advance of the deployment.
Setting up a QAM and then substituting that QAM inside of the community is a generic approach for dealing with bandwidth allocation and channel mapping. The example given above (infomercial QAM) is one method to enable this application. However, QAM substitution is not necessarily limited to infomercial QAMs. The key to this approach is that one QAM channel is treated as the ubiquitous community channel QAM; each community loading its localized services into the one pre-determined QAM channel and channel map.Advanced solutions for community channel insertion
For systems supporting MDU contracts with multiple channels per location, the digitization of community channels provides an opportunity to reclaim some of the analog bandwidth previously used for these analog community channels. But for systems supporting MDU contracts with just one community channel per location, there is little-to-no immediate bandwidth savings, as the digital channel would still occupy an entire (but mostly empty) QAM channel. In this case, a primary benefit of digital simulcasting is in providing a smooth transition to an all-digital line-up.
In order to extend the bandwidth efficiency of the application to single and multichannel communities, a more capable bandwidth management scheme is required. The most beneficial solutions for community channel insertion will be those that do not require an entire QAM, but are capable of taking in either a partially occupied QAM channel and inserting into the available bandwidth, or taking a fully occupied QAM channel and substituting one or more community channels rather than substituting the whole QAM. A solution capable of this would enable operators to measure the community channel bandwidth in megabits, rather than megahertz. Not only does this approach provide bandwidth savings for both single and multichannel community support, but it provides a scalable method to grow community-based video services as required to add or maintain existing MDU service contracts in the face of new competitive pressure.
Of course, this optimal approach creates new requirements for the ComPE solution. In order to support this advanced program substitution model, the ComPE solution must be capable of tuning to the appropriate QAM channel, demodulating the signal and performing the drop/add multiplexing function. Adding a further layer of complexity, the solution must be capable of performing these per-program functions on encrypted multiplexes as many of the QAM channels distributed to the community are secured by conditional access schemes. Finally, to apply this advanced solution, the ComPE must take into account the possibility or likelihood that the other services in the "drop/add" QAM are important to the subscriber base, and that any failure of the ComPE solution must not cause them to be disrupted.
In conclusion, video service providers have a unique opportunity to meet the demand for more localized and personalized video services, while winning and maintaining valuable MDU and community service contracts.