Managing Cable TV Migration to IP Part 1 Advanced Digital Cable Leadership Series Series Introduction: Analyzing Cable Market IP Distribution Drivers and Network Tech Challenges Migration Strategies Part 2: Preparing to Implement IP Cable TV Services
Contents List of Figures... 3 Introduction... 4 Distribution Network Migration Options... 5 Hybrid MPEG/IP... 6 Advanced Digital Cable Services over DOCSIS... 8 DOCSIS 3.0 CMTS Advantages... 9 CMTS Bypass Advantages... 11 Factoring CCAP into Migration Strategies... 11 Keys to Creating an Optimal Migration Strategy... 13 The Media Gateway Advantage... 13 The Timing Advantage... 16 Addressing Transition Bandwidth Requirements... 17 Key Factors Impacting Capacity for IP Video... 17 IP Tools for Conserving Bandwidth... 19 Multicasting and Switched Linear IP... 19 Statistical Multiplexing and Adaptive Streaming... 20 Conclusion... 21 References... 22 Acronym List... 23 2 ARRIS 2011. All rights reserved. August 16, 2011
List of Figures Figure 1: DOCSIS 3.0 CMTS... 5 Figure 2: CMTS Bypass... 5 Figure 3: Gateway... 5 Figure 4: Two Phase IP Transition... 6 Figure 5: Single Phase IP Transition... 6 Figure 6: IP over DOCSIS... 8 Figure 7: Statistical Gains of Channel Bonding... 9 Figure 8: Channel and Processor Efficiency Gain... 10 Figure 9: Converged Cable Access Platform... 12 Figure 10: Single Phase IP Transition... 13 Figure 11: Two Phase IP Transition... 13 Figure 12: Cost Relationship of Today's MPEG/DVB Deployment vs. a Hybrid/Video Gateway Deployment... 14 Figure 13: Advanced Digital Cable Benefits... 15 Figure 14: Sample Bandwidth Requirements During Transition... 18 Figure 15: Bandwidth Savings Associated with Multicast Delivery... 20 3 ARRIS 2011. All rights reserved. August 16, 2011
Introduction As discussed in Part 1 of this series, cable operators long-term success depends on their ability to respond to changing market conditions by delivering entertainment services over converged IP infrastructures. The question is, how do they reach that goal in a way that keeps pace with market requirements without causing unnecessary disruptions to operations or spending more than necessary at any point in the transition? Given the market uncertainties with respect to both consumers and competitors, not to mention the complexities attending so many interrelated technical issues, there are no easy answers to that question. Each MSO will come to its own conclusions based on analysis of local market conditions and how myriad network and operational factors impact the pros and cons of any given course of action. The purpose here is to describe various iterations of the most commonly discussed migration strategies and certain technological developments that should be taken into account as those strategies are weighed, including advances in CMTSs (cable modem termination systems); the capabilities of new media gateways; the emergence of CCAP (Converged Cable Access Platform) technology; and bandwidth-management options associated with multiple factors, including MPEG-4 H.264 compression, IP multicasting, statistical multiplexing, adaptive streaming and much else. Beyond the network transport aspects of migration to IP there are a variety of factors pertaining to service migration that come into play as well. Questions concerning how content is managed, encoded, formatted, protected and distributed across the network and within customer premises all must be taken into account in the formulation of migration strategies. Part 3 of this series, Systems, Processes, and Components, Essential to Meeting New Service Goals, provides background on how these issues feed into the strategic planning process. This part of the series will focus on how MSOs can manage their migrations toward IP Video deployments in the distribution network. 4 ARRIS 2011. All rights reserved. August 16, 2011
Distribution Network Migration Options Today, many MSOs are making some portion of their premium content available to subscribers for time-shifted, on-demand viewing on PCs and other IP-enabled devices. These TV Everywhere services are delivered on an unmanaged or off-net basis over broadband access links, in contrast to traditional cable TV services, which are delivered with the full quality assurance and protection enabled through managed or on-net network operations. The full-service capabilities envisioned with migration of cable TV to IP are by definition the province of managed network operations. There are three major areas of the network to be considered in the transition: Figure 1: DOCSIS 3.0 CMTS The IP-over-HFC distribution network In instances where operators begin simulcasting cable TV services in IP for distribution to any household, there are two near-term avenues under consideration. The first involves use of advanced DOCSIS 3.0-enabled CMTSs depicted in Figure 1. The second utilizes techniques that allow the IP video flow to bypass the CMTS as shown in Figure 2. In the medium to long term CCAP and PON architectures must be considered. IP content access in the home This may start with introduction of a Hybrid MPEG/IP mode of managed IP content delivery, which entails distribution of all content over legacy MPEG/DVB channels to the home. As shown in Figure 3, a hybrid MPEG/IP home premises gateway encapsulates linear and ondemand programming into IP packets for distribution over the home network to IP-enabled set-tops and other devices. An alternative method is to access simulcast IP content via the data connection (cable modem) in the home through the use of IP STBs or video player clients running on smart devices. Content origination and management This will be addressed in the ARRIS Leadership Series on Managing Cable TV Migration to IP Part 3: Systems Processes and Components Essential to Meeting New Service Goals. Figure 2: CMTS Bypass Figure 3: Gateway 5 ARRIS 2011. All rights reserved. August 16, 2011
Operators may take a phased approach to introduce Advanced Digital Cable Services. An example of one such phased approach is to leverage the existing MPEG/DVB delivery system through the use of the Hybrid MPEG/IP premises gateway, or Media Gateway (MG) as a first step. Figure 4: Two Phase IP Transition In the second phase, operators may implement Advanced Digital Cable Services over DOCSIS 3.0 bonded channels to households equipped with hybrid MPEG/IP devices or all IP media gateways while continuing to deliver MPEG/DVB services to households with legacy set-tops. At some point, these households, too, will be converted to gateway-based service reception, completing the transition to all-ip operations. This Two phased migration is depicted in Figure 4. Other operators may use a single step approach and go directly to all IP delivery for newly installed or upgraded customers while existing customers remain on the analog and MPEG/DVB STB system as shown in Figure 5. Figure 5: Single Phase IP Transition Hybrid MPEG/IP The appeal of the Hybrid MPEG/IP mode of IP migration is that it allows MSOs to incrementally introduce IP-based service to some households while continuing to serve the rest of the market in the traditional manner. For as long as Hybrid MPEG/IP remains the sole means of content distribution for both traditional and all- IP households, this approach avoids the need to allocate bandwidth for simulcasting of premium content in all-ip mode over DOCSIS. The strategy enables a cap-and-grow approach to building the IP customer base by allowing operators to deploy Hybrid MPEG/IP gateways and IP set-tops in all new subscribers homes. This also creates an opportunity to offer new service tiers that provide a revenue-generating justification for upgrading existing subscribers to Hybrid MPEG/IP CPE. For example, the IP-encapsulating gateway used in conjunction with low-cost IP set-tops is a cost-effective alternative to legacy solutions when it comes to providing whole-home DVR and managed network services. 6 ARRIS 2011. All rights reserved. August 16, 2011
However, there are drawbacks to taking the Hybrid MPEG/IP route, which could prove decisive in some situations. One key issue has to do with the fact that this approach is not conducive to fully exploiting IP technology to create new types of services or to bring IP-based interactivity and advertising features into the operational framework. For example, operating in an all-ip managed network mode end to end allows operators to blend over-the-top and premium programming and application components however they choose from a single point of application and service management. While it s possible to present MPEG/DVB content and IP-delivered OTT content options on an integrated navigation interface, the Hybrid MPEG/IP approach doesn t allow full integration of applications across both modes of distribution. Where advanced advertising and interactive applications are concerned, operators may find the benefits of pursuing these agendas on an all- IP foundation are such that they would be better off going directly to all-ip rather than building advanced advertising and applications on the platforms that have been designed for use with traditional digital set-tops. The question of how the industry will coordinate the implementation of advanced advertising with the transition to IP remains an unsettled issue, but it looms as a major consideration as MSOs weigh their IP migration strategies. Hybrid MPEG/IP also adds more costs to media gateways in comparison to gateways deployed with the pure IP-over-DOCSIS approach. For example, the MPEG transport streams delivered to the gateway require use of cable cards or DVB simulcrypt for CAS-based content. There are also potentially higher costs associated with the IP encapsulation process and other processing functions, such as transcoding, that will be required to support distribution of content to PCs, tablets and handheld devices. The cost disparities between gateways suited for use in the Hybrid MPEG/IP mode versus pure IP gateways are highly variable depending, in part, on where formatting and transcoding functionalities reside in the IP-over- DOCSIS architecture. MSOs must also take into account the fact that, for whatever period of time they use Hybrid MPEG/IP as a transition mode in lieu of cutting over to IP-over-DOCSIS, they will be delaying realization of the CAPEX/OPEX benefits that accrue with conversion to a fully converged IP infrastructure. A discussion of valuations to be accorded such benefits can be found in Part 6 of this series, The Business Case Analysis for Cable IP Migration. 7 ARRIS 2011. All rights reserved. August 16, 2011
Advanced Digital Cable Services over DOCSIS One question that has generated much debate is whether IP Video over DOCSIS can be implemented cost effectively using the traditional CMTS-based architecture. Some participants argue that costs of adding sufficient downstream capacity to accommodate delivery of all TV content in IP mode are too high. Some suggest the best approach is to use the CMTS to process off-net broadband in the traditional manner but to bypass the CMTS in the distribution of the cable operators, managed IP Video content. Others suggest a wholesale replacement of the DOCSIS and HFC infrastructure with a Passive Optical Network (PON) may be required. However, these arguments fail to take into account the immense improvements achieved with a new generation of CMTSs, especially the DOCSIS 3.0 CMTS. Nor does this view recognize the fact that distinctions between how off-net broadband and premium IP content with regard to control plane, data format and data rates are beginning to blur. Moreover, the CMTS bypass strategy relies on use of proprietary solutions, which eliminates the multiplevendor advantages of a standards-based platform. Further, the PON approach would significantly delay market launch and require an end-to-end overhaul of the operators networks and operations. For these reasons the end game for most MSOs, regardless of their path, will be all-ip delivery of premium content over DOCSIS as pictured in Figure 6. By leveraging the field-hardened, robust capabilities of the DOCSIS platform in combination with channel-bonding enabled by DOCSIS 3.0, operators can tap into the vast range of video-optimized functionalities that are now part of the IP protocol stack to create the next-generation multi-device premium services that are essential to sustaining competitive leadership in the years ahead. Figure 6: IP over DOCSIS But several issues and technological developments must be addressed to everyone s satisfaction if operators are to confidently move to Advanced Digital Cable Services over DOCSIS. Once it s clear to decision makers that they can make the transition without sacrificing any of the performance attributes of the legacy MPEG/DVB architecture, they can judge various transition strategies based on what works best from a cost/benefit standpoint. 8 ARRIS 2011. All rights reserved. August 16, 2011
In the discussion that follows, references to CMTS apply to both the I-CMTS and the M-CMTS options enabled by DOCSIS 3.0 specifications. Subsequently, the discussion will touch on some of the benefits that are unique to alternatives to a DOCSIS 3.0 CMTS, specifically the CMTS bypass architecture, CCAP technology, which represents an elegant evolutionary step to the CMTS. DOCSIS 3.0 CMTS Advantages Critically, rapid gains in processing capacity and density stemming from Moore s Law have vastly altered the CMTS cost analysis over the past two to three years. Three years ago the most advanced CMTS configuration supported fewer than 100 downstream DOCSIS channels; today the channel count per chassis numbers in the hundreds. Equally important, today s most advanced CMTS architectures do away with the fixed ratio of downstream to upstream channels in the RF (QAM) modules to allow operators to flexibly allocate directional channels as conditions require. The combination of higher processing capacity and flexible allocation of downstream and upstream channels increases the downstream channel capacity per CMTS chassis many fold with commensurate decreases in the downstream perchannel costs in comparison to legacy CMTSs. As shown in Figure 7, one of the greatest benefits transmitting IP Video over DOCSIS 3.0 architectures is the greater bandwidth savings to be realized through use of channel bonding. Statistical multiplexing can be applied in conjunction with variable bit rate formatting of content across all streams within a given channel or bonded cluster of channels, which can t be done in an architecture that cannot flexibly spread IP content across a group of QAM channels. Figure 7 depicts the statistical gain of channel bonding. The CMTS also supports dynamic activation of service flows and multicast streams to achieve the same types of efficiencies that are accomplished with switched digital video (SDV) in the MPEG/DVB realm. Figure 7: Statistical Gains of Channel Bonding Intrinsic to all DOCSIS 3.0 CMTSs are quality-of-service mechanisms that manage and adjust bandwidth for specific service flows, ensuring that third-party IP video content can be safely multiplexed into the mix of MSO-managed IP video streams. This is essential to the MSO s ability to include select OTT content as part of a blended IP subscription service mix. Bypassing the CMTS eliminates this benefit. 9 ARRIS 2011. All rights reserved. August 16, 2011
Figure 8: Channel and Processor Efficiency Gain For example, in some CMTS models, refinements in how processing resources are allocated depending on the type of IP traffic being transmitted have significantly reduced the CPU requirements for handling IP video content, as pictured in Figure 8. DOCSIS processes used to compile individual Ethernet packets into a single DOCSIS frame, so as to increase the bit rate ratio of payload to MAC headers, can be avoided with video flows, owing to the fact that video packets are sufficiently long to achieve the desired ratios without packing. Innovative software techniques are also used to eliminate repetitive DOCSIS processes on individual packets, such as source authentication in video streams, from TV programming networks and other trusted sources. Another CMTS feature, which contributes to maximizing bandwidth efficiency, is dynamic load balancing between channels associated with HSD and those associated with the IP video tier. In instances when higher-than-necessary bandwidth allocations occur on some channels and less-than-satisfactory allocations on others, most CMTS models can activate load-balancing algorithms to re-configure the channel loading, thereby assuring sustained quality-of-experience on the video flows. There are great operational efficiencies to be realized as well, starting with the fact that the CMTS architecture simplifies creation of a single backplane infrastructure that supports both on-net and off-net IP video services. Traffic engineering complexities are greatly reduced with the unified IP infrastructure, allowing the entire spectrum for all services to be dedicated to DOCSIS without the need to build out dedicated capacity for each traffic type. Finally, the full use of the trusted, field-hardened CMTS architecture for an IP-over-DOCSIS strategy is essential to realizing the CAPEX/OPEX benefits that come with operating over a converged HSD and video network. 10 ARRIS 2011. All rights reserved. August 16, 2011
CMTS Bypass Considerations In the CMTS bypass approach, an application server works in conjunction with edgeqams equipped with special software that applies DOCSIS MAC (media access control) frames to the managed IP video streams so that the streams can be delivered through DOCSIS modems equipped with proprietary client-based software to end users. Modem provisioning and upstream functions are still handled by the accompanying CMTS. The resulting benefit of implementing the above functionality in a network previously equipped with the edge intelligence required to support SDV is a network now equipped to treat the IP video as another data plane at the edge. Thus, CMTS bypass could be viewed as an alternative implementation of a modular CMTS minus the benefits of channel bonding and a unifed control plane. Factoring CCAP into Migration Strategies The discussion so far has focused on the merits of migration strategies in the context of existing technology options. However, there is a new option on the horizon, namely, CCAP, which adds a new perspective that could well lead operators to different strategic paths than they otherwise might take. The CCAP Converged Cable Access Platform conceived by Comcast and Time Warner now under development industry wide through CableLabs efforts is an extremely high-density advanced processing device that combines the functionalities of the DOCSIS 3.0 CMTS, broadcast and narrowcast QAMs, signal combining and splitting, and electrical-to-optical conversion, in a single chassis at the headend. Industry architects anticipate CCAP will enable a 200 percent increase in QAM capacity with one half the space required, along with a 50 percent reduction or more in power consumption. The technology takes advantage of the fact that ever more video content is delivered to the headend in IP mode. There s not only an increasing volume of narrowcast content coming in over Ethernet links; there s also greater reliance on IP transport for delivering broadcast content from central headends to regional headends. By switching all this IP content prior to its conversion to RF, CCAP can dynamically change the proportionate service allocations to QAMs without incurring the costs and complexities of redirecting RF resources as required by the current architecture. Rather than having to manually decouple and rewire headend components with every change in bandwidth allocation to various service groups, operators can simply input software commands to alter how much bandwidth is allocated to traditional MPEG/DVB versus DOCSIS-based IP transport. Specifically, as operators transition subscribers and services from MPEG/DVB to IP Video over DOCSIS they simply reprovision the video QAM to DOCSIS. 11 ARRIS 2011. All rights reserved. August 16, 2011
Because the CCAP design relies on direct digital synthesis techniques that can be accommodated on existing field programmable gateway arrays (FPGAs), the industry will not have to await fabrication of new silicon to proceed with development of the platform. While many details remain to be worked out, the core hardware design is well enough understood to allow manufacturers to proceed with development of CCAP-compliant implementations. Figure 9: Converged Cable Access Platform With CCAP on the horizon, operators have greater freedom to migrate to IP video transport to the home at whatever pace and with whatever modes of delivery Hybrid MPEG/IP or full IP TV over DOCSIS is best suited to their legacy circumstances. With IP TV over DOCSIS as the ultimate goal, it s clear that an MSO that anticipates use of CCAP technology may be less inclined to invest in CMTS bypass architectures. 12 ARRIS 2011. All rights reserved. August 16, 2011
Keys to Creating an Optimal Migration Strategy As mentioned, migration strategies can be grouped into two categories: the single phase approach, where operators go directly from traditional MPEG/DVB delivery to Advanced Digital Cable Services over DOCSIS as shown in Figure 10, the two phase approach, where operators implement the Hybrid MPEG/IP strategy prior to introducing pure IP delivery of premium TV content shown in Figure 11. Operators who have freed up bandwidth with elimination of analog channels or have expanded their bandwidth capacity at higher spectrum levels above 860 MHz are more likely than others to take the two-phase approach because they have adequate spectrum to support full simulcast of all cable TV content in IP mode. Operators would continue to serve legacy set-tops in the traditional way while continually converting households to all IP Video gateways over a period of years with the goal of eventually eliminating the legacy footprint. Figure 10: Single Phase IP Transition Figure 11: Two Phase IP Transition Presently a far greater proportion of MSOs worldwide are contemplating the threephase transition, primarily due to limited bandwidth availability for simulcasting the existing line up. This transition strategy allows operators to displace legacy MPEG/DVB hardware at whatever pace they choose while laying the groundwork operationally for the shift to all IP. There are other key advantages to this approach, including the following. The Media Gateway Advantage First and foremost, introduction of a Hybrid MPEG/IP Gateway capable of encapsulating MPEG/DVB content in IP packets for distribution to all devices in the home provides a means by which operators can begin to eliminate the most costly element in their capital budgets, namely, the set-top box. On average, supplying set-tops to customers accounts for up to 75 percent of MSOs annual network capital spending. 13 ARRIS 2011. All rights reserved. August 16, 2011
Operators can use gateways as the foundation for introducing whole-home DVR and managed network services, possibly charging a premium that helps cover the costs of the gateways. Whether or not they charge more, operators will find that the gateway saves costs of implementing whole-home DVR by allowing use of low-cost IP set-tops as well as connected TVs in lieu of set-tops. The gateway architecture saves the operator capital and operational cost on a per house basis for multiple service deployments by consolidating the CPE for video, data, voice and home data distribution into a single managed device. In addition, the MSO can offer the subscriber whole home DVR in a very efficient way. Figure 12 depicts the relative cost relationship of today s MPEG/DVB deployment vs. a hybrid/video gateway deployment on a per home basis. Figure 12: Cost Relationship of Today's MPEG/DVB Deployment vs. a Hybrid/Video Gateway Deployment Operationally the gateway limits the ingress noise from the home to a single point, and it eliminates the need for the network to communicate with more than one device. This greatly improves the signal delivery quality throughout the network and reduces maintenance cost and service calls. The Hybrid MPEG/IP Gateway allows operators to deliver premium content to all IPenabled devices by leveraging built-in standards compliant interfaces such as MoCA (Multimedia over Coax Alliance), DLNA (Digital Living Network Alliance) and DTCP (Digital Transmission Content Protection). This further reduces the operators expense by allowing the elimination of video players when a Smart TV or gaming system is connected directly to the gateway. Satisfying consumer demand for multi-device service in the near term will contribute to subscriber retention and the ability to draw new subscribers without waiting to develop an all-ip delivery and control infrastructure. 14 ARRIS 2011. All rights reserved. August 16, 2011
While the Hybrid MPEG/IP Gateway approach doesn t support back office and distribution network integration between managed and off-net IP content it does allow operators to introduce subscriber facing IP-based widgets for applications like weather, traffic, news and caller ID. It also makes it possible to display OTT service options through a unified User Interface (UI) that can be branded by the MSO. Figure 13 presents a simplified view of the advanced digital cable implementation with gateway architecture. Figure 13: Advanced Digital Cable Benefits 15 ARRIS 2011. All rights reserved. August 16, 2011
The Timing Advantage Moreover, because the gateway supports DOCSIS 3.0 connections, operators will be able to establish a foundation for building on-net Advanced Digital Cable Services capabilities. They could start with over-the-top components delivered over DOCSIS, such as on-demand TV Everywhere types of service and managed OTT components from aggregators of long-form online video. They may later decide to deploy new premium or niche channels over DOCSIS. As discussed in Part 3 of this series, Processes and Components Essential to Meeting New Service Goals, there are many technical processes that must be put in place on the content control backplane to govern ingestion, provisioning and other OSS interfaces, quality-of-service assurance, formatting, transcoding, digital rights management and CDN (content delivery network) operations. All of this represents a fairly steep learning curve for the MSO staff. Having the opportunity to incrementally work with these functions to orchestrate managed IP TV service before a cutover to delivering everything in IP will be immensely helpful to making sure everything works as it should for cable premium TV service. Specifically, the phased approach allows the operator to test the technology, the architecture, their operations and maintenance systems on a limited set of services to a limited set of subscribers. This confines the risk to their primary revenue stream vs a whole sale cutover. This three-phase approach to launching all-ip TV service also maps well to the projected timeframe for availability of the CCAP products and, by coincidence, the microprocessors that enable content delivery over a larger bandwidth range on the gateway. These higher density DOCSIS 3.0 chips are slated for commercial production by late 2012 and will allow gateways to support all the bandwidth that will be required for Advanced Digital Cable Services operations. 16 ARRIS 2011. All rights reserved. August 16, 2011
Addressing Transition Bandwidth Requirements Unless an operator waits until every household has a hybrid MPEG/IP gateway before making the cutover, there will be some period of time once all-ip TV service delivery begins when some households on gateways receive their service entirely over IP transport and others with legacy set-tops continue getting MPEG/DVB services. For however long that period lasts, operators will need sufficient bandwidth to simulcast all TV content in both modes. Further complicating the transition, the need to serve multiple devices, with differing display resolutions and QoS parameters for each class of device, presents a more complex bandwidth management situation than operators have dealt with in the legacy TV environment. Each class of device requires a separate video stream, which means operators will have to determine where in the network they want to position processing-intensive transcoders that can turn a master HD stream into multiple streams with different resolutions and possibly different encryption schemes. Key Factors Impacting Capacity for IP Video Bandwidth will be conserved to the greatest extent if the transcoding takes place at the gateway. In this model, only one stream per program is delivered to the home to the Gateway. The gateway then transcodes that content into the proper format based on the client s request. There are also solutions that will allow transcoding to be performed in the network fairly close to end users so as to minimize bandwidth consumption over the primary optical distribution networks. This can be done centrally, where the tradeoff is more bandwidth consumption in exchange for lower gateway costs. The starting point for determining how best to accommodate the simulcast bandwidth requirements that come with introducing Advanced Digital Cable Services is to look at the many ways operators can go about freeing up bandwidth and maximizing efficiency. Once one is able to analyze how much bandwidth will be required for a centralized transcoding approach, it will be possible to determine whether there s enough available capacity to go this route without spending money on the physical plant. If it turns out spending will be required for such steps 17 ARRIS 2011. All rights reserved. August 16, 2011
as pushing fiber deeper or expanding RF spectrum, operators will want to weigh the costs of meeting the bandwidth needs engendered by a centralized approach to transcoding against the costs of supporting the transcoding closer to the edge or at each gateway. As operators look into these issues, it s important to note that, for however long the interim period of relying exclusively on Hybrid MPEG/IP lasts, they will buy time for freeing up more bandwidth to accommodate the implementation of Advanced Digital Cable simulcasting. As they retire analog channels and eliminate at least some of their SD channels, they will be contributing ever more channels for bonding into an Advanced Digital Cable Services distribution pipe. Implementing or expanding the use of SDV or DTAs will serve the same purpose. Figure 15 (1) depicts channel allocation of a sample transition from MPEG/DVB services to Advanced Digital Cable Services. Figure 14: Sample Bandwidth Requirements During Transition Operators will also significantly reduce the amount of bandwidth required for a given volume of broadcast and narrowcast streams with the introduction of MPEG-4 H.264 compression, which reduces the per-stream RF spectrum requirements by about 30%. MPEG-4 is a natural bandwidth-saving step to take with implementation of IP-based TV content, given the fact that all IP-enabled media gateways will be equipped with H.264 decoders. 18 ARRIS 2011. All rights reserved. August 16, 2011
IP Tools for Conserving Bandwidth There are many other tools tied to IP technology which operators will be able to use to maximize bandwidth for Advanced Digital Cable Services. While IP content from the Web is always delivered in unicast mode, operators will be able to limit the unicast consumption of bandwidth to on-demand viewing, just as they do today with VoD. When it comes to linear broadcast type services, they will be able to replicate the traditional delivery mode by employing IGMP (Internet Group Management Protocol) multicasting. Multicasting and Switched Linear IP Although IP multicast was supported by earlier versions of DOCSIS, these implementations did not provide the functionalities that are essential to making multicasting useful for delivering premium content. DOCSIS 3.0 adds the necessary enhancements. One of these features is support for multicasting over bonded channels. Additionally, there are new security mechanisms that afford the CMTS much greater control over access authorization for each device by defining the interfaces on the CPE side that are targeted for any given multicast session. These new multicasting capabilities also provide a means of validating the multicast source, which is a vital protection against denial-of-service virus attacks. It s also important to note that, where DOCSIS 3.0 security is concerned, the standard requires use of the AES (Advanced Encryption Standard) 128-bit encryption mode on all encrypted multicast and unicast content. Another major feature included in DOCSIS 3.0 was support for IPv6-based Multicast. IP multicast can be used in several different ways for linear programming. One method is analogous to broadcast video where several IP Multicast streams carrying linear video programming are statically configured to be always available in every DOCSIS Service Group. A second method is similar to the Switched Digital Video model where only those linear program streams that are being actively viewed are available in a given DOCSIS Service Group. These two methods may be used together to optimize the configuration. Figure 16 represents calculations showing that the bandwidth savings accrued with the use of multicast IP video in comparison to nailed-up multicast channels increases as the ratio of selectable programs in the multicast group increases in proportion to the number of active users. Applying typical peak-hour usage patterns of customer channel change data, it was found that in an instance where 250 selectable programs would be offered to about 500 active viewers, only about 200 programs would be delivered at any one time, representing a bandwidth savings of about 20 percent. If 1,000 selectable programs were offered to the same number of active viewers, only about 350 would be transmitted, resulting in a bandwidth savings of 65 percent. (2) 19 ARRIS 2011. All rights reserved. August 16, 2011
Figure 15: Bandwidth Savings Associated with Multicast Delivery Statistical Multiplexing and Adaptive Streaming Two other significant modes of reducing bandwidth consumed by IP Video operations should be noted. In the case of linear multicast programming, operators will want to use variable bit rate encoding in conjunction with statistical multiplexing over bonded channels to maximize bandwidth savings. By combining all HSD, voice and TV services over the spectrum allocated to a set of bonded channels, operators gain greater bandwidth efficiencies than can be achieved with statistical multiplexing of MPEG streams separately from DOCSIS channels. The greater the number of bonded channels, the greater the bandwidth savings will be. The other approach to saving bandwidth, adaptive streaming (AS), occurs with unicast programming. It should be noted that, as an alternative to AS, unicast programming can be Variable Bit Rate (VBR) encoded and statistically multiplexed with other IP streams. But AS offers a more bandwidth-efficient approach by adjusting bit rates to maintain uninterrupted viewing on all streams within a given spectrum space during peak congestion periods. 20 ARRIS 2011. All rights reserved. August 16, 2011
This allows operators to support far more unicast streams on a given channel or set of bonded channels than would be possible if allocations were pegged to what could be accommodated operating at fixed bit rates during peak congestion. Operators may even want to use AS on the high-resolution streams targeted to the TV, provided they set data rate parameters to prevent any noticeable deterioration in the quality of experience. (A further discussion of AS modes and issues can be found in Part 3 of this series.) For further reading on bandwidth saving please reference Architectural Alternative to Help Circumvent the Simulcast Roadblock of IP Video deployments, Tom Cloonan, ARRIS NCTA 2011 proceeding Conclusion There s no getting around the fact that planning the transition to Advanced Digital Cable Services is a major undertaking touching on every aspect of TV service operations and support systems. But it s also clear that a cost-effective, highly advantageous path can be plotted to all-ip that allows operators to drive new revenues and increase subscriber satisfaction through implementation of IP-based distribution in the home early on. With clear understanding of all the options and the significant technological advances affecting CMTSs, CPE and all points in between, operators can devise a migration strategy that precisely suits their budgets and their customers needs. Their ability to tap trusted sources for reliable, objective insight on technology issues will be essential to achieving optimal results. 21 ARRIS 2011. All rights reserved. August 16, 2011
References (1) Data model created by ARRIS engineers using typical North American Channel Assignments. (2) Data model created by ARRIS engineers utilizing data gathered from a top 10 North American MSOs. (3) CableLabs : http://www.cablelabs.com/ (4) Wikipedia: www.wikipedia.org 22 ARRIS 2011. All rights reserved. August 16, 2011
Acronym List Adaptive Streaming AES Adaptive Streaming a process that adjusts the quality of a video based on changing network conditions to ensure the best possible viewer experience. Advanced Encryption Standard a symmetric-key encryption standard. Bonded Channels A technology introduced in DOCSIS 3.0 allowing multiple RF channels to be combined to provide higher throughput. CAPEX Cap and Grow CAS CCAP CDN CM CMTS CMTS Bypass CPE Capital Expenditure. A strategy that can be adopted by Cable MSOs so that they effectively introduce new technology while retaining the older installed base of equipment. Conditional Access System a system using both scrambling and encryption to prevent unauthorized reception of services by those not paying for the service. Converged Cable Access Platform The Converged Cable Access Platform (CCAP) integrates the functions of broadcast and narrowcast quadrature amplitude modulators (QAMs), as well as DOCSIS 3.0 downstream and upstream interfaces. It also includes the option to support passive optical network (PON) termination equipment in the same chassis. Content Delivery Network a collection of computers that cache data at various points in a networks for delivery to end users. Cable Modem connects a computer or local network to broadband Internet service through the same cable that supplies cable television service. Cable Modem Termination System a DOCSIS network device that manages and communicates with many Cable Modems. One of several methods of introducing IP video into the cable system. It utilizes proprietary management systems and stand alone QAMs to bypass the CMTS for IP video transmission. Customer Premises Equipment Communications equipment that resides in the customer's premises. 23 ARRIS 2011. All rights reserved. August 16, 2011
DOCSIS DOCSIS 3.0 DLNA DTA DTCP DVR Data Over Cable Service Interface Specification an international telecommunications standard that permits the transmission of internet protocol communications transfer over an existing Cable TV (CATV) system. Version 3 of the DOCSIS specification introduced Channel Bonding, IPv6 Support, IP Sec changes and other new features. Digital Living Network Alliance a standard used by manufacturers of consumer electronics to allow entertainment devices within the home to share their content with each other across a home network. Digital Terminal Adaptor a low-cost set-top box deployed by cable companies that provides digital service from the cable to analog TVs or digital TVs. Digital Transmission Content Protection a digital rights management (DRM) technology that aims to restrict "digital home" technologies including DVD players and televisions by encrypting interconnections between devices. Digital Video Recorder a system or device that records video on a hard disk. EQAM E-MTA A class of IP edge network devices that enables delivery of a wide variety of multimedia. Supports delivery of Video on Demand, Digital Broadcast, Switched Digital Video Services, and DOCSIS downstream data using the Modular Cable Modem Termination (M-CMTS) architecture. Embedded-Multimedia Terminal Adapter a device that combines a DOCSIS cable modem and analog telephone adapter. Gateway A device that converts one protocol or format to another. FPGA Field Programmable Gate Array an integrated circuit designed for configuration by the customer or designer after manufacturing. HFC HSD Hybrid Fiber Coaxial a communications access network constructed from the economical use of optical fiber and electrical coaxial cable technologies. High Speed Data a subscriber service offering for access to the internet at speeds faster than previously offered with dial up modems. 24 ARRIS 2011. All rights reserved. August 16, 2011
Hybrid MPEG/IP A combination of traditional broadcast TV services and video delivered over either managed IP networks or the public Internet. I-CMTS IGMP IP IP Multicasting IPTV IP STB Integrated CMTS all DOCSIS 3.0 features, including separate US and DS modules, in a single high-availability CMTS chassis. Internet Group Management Protocol a communications protocol used by hosts and adjacent routers on IP networks to establish multicast group memberships. Internet Protocol the packet data protocol used for routing and carrying messages across the Internet and similar networks. A method of sending Internet Protocol (IP) datagrams to a group of interested receivers in a single transmission. It is often employed for streaming media applications on the Internet and private networks. Internet Protocol Television television and/or video signals that are delivered to subscribers or viewers using internet protocol, the technology that is also used to access the internet. Internet Protocol Set Top Box in this context, a low cost device used to receive TV signals over an IP network and deliver them to a consumer display or recording device. M-CMTS Media Gateway MoCA MPEG MPEG-4 Modular CMTS all DOCSIS 3.0 features delivered via multiple chassis (CMTS Core, Universal Edge QAM, DTI server, and Edge Resource Manager) to enable QAM sharing for IP and MPEG services. A translation device or service that converts digital media streams between disparate networks. Multimedia over Coax Alliance MoCA is a standard using the existing coax cabling in the home for connecting devices such as TV decoder (set-top-box), PVR, home gateways, wireless access point, game consoles, etc. Moving Picture Experts Group the name of a family of standards used for coding audio-visual information (e.g., movies, video, music) in a digital compressed format. A newer version of the MPEG standards. 25 ARRIS 2011. All rights reserved. August 16, 2011
MPEG TS MSO MPEG Transport Stream (TS) a standard format for transmission and storage of audio, video, and data, and is used in broadcast systems such as DVB and ATSC. Multi Systems Operator cable service providers with multiple locations and services. NCTA National Cable Television Association the principal trade association for the U.S. cable TV industry, representing cable operators serving more than 90 percent of the nation s cable households and more than 200 cable program networks, as well as equipment suppliers and providers of other services to the cable industry. OPEX OTT Operating Expenditure. Over-The-Top a general term for service used over a network that is not offered by that network operator. These services ride on top of the service already received and don't require any business or technology affiliations with the network operator. QAM QoS Quadrature Amplitude Modulation - both an analog and a digital modulation scheme used to convey two analog message signals, or two digital bit streams, for transmission of the information between two points. Quality of Service the ability to provide different priority to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow. RF Radio Frequency a rate of oscillation in the range of about 3 khz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents, which carry radio signals. SDV Smart TV Switched Digital Video a telecommunications industry term for a network scheme for distributing digital video via a cable. Switched video sends the digital video in a more efficient manner so that additional uses may be made of the freed up bandwidth. Smart TV also sometimes referred to as "Connected TV" or "Hybrid TV", is the phrase used to describe the current trend of integration of the internet and Web 2.0 features into modern television sets and set-top boxes, as well as the technological convergence between computers and these television sets / set-top boxes. 26 ARRIS 2011. All rights reserved. August 16, 2011
Statistical Multiplexing Statistical Multiplexing a type of communication link sharing, very similar to Dynamic Bandwidth Allocation (DBA). In statistical multiplexing, a communication channel is divided into an arbitrary number of variable bit-rate digital channels or data streams. The link sharing is adapted to the instantaneous traffic demands of the data streams that are transferred over each channel. TV Everywhere TV Everywhere a verification system that allows television service providers to authenticate that those who wish to use their IPTV video on demand internet television services are actually paying customers, for instance of cable television. VBR VoD Variable Bit Rate An encoding method that has an efficient use of bandwidth by using a constantly changing bit rate during the encoding process. Video on Demand a service that allows viewers to select and watch programs or films without the need for a schedule. (3) (4) The capabilities, system requirements and/or compatibility with third-party products described herein are subject to change without notice. ARRIS and the ARRIS logo are trademarks of ARRIS Group, Inc. Other trademarks and trade names may be used in this document to refer to either the entities claiming the marks and the names of their products. ARRIS disclaims proprietary interest in the marks and names of others. Copyright 2011 ARRIS Group, Inc. All rights reserved. Reproduction in any manner whatsoever without the express written permission of ARRIS Group, Inc. is strictly forbidden. For more information, contact ARRIS. 27 ARRIS 2011. All rights reserved. August 16, 2011