DOCSIS 3.0, while not entirely here yet, is definitely up and coming. Canadian cable operator Videotron has deployed channel-bonded high-speed Internet service on a substantial scale.

According to a Leger Marketing survey, 71.7 percent of people in Quebec – the province where Videotron primarily operates – use the Internet, and 59.3 percent have high-speed connections. Videotron has a few competitors in the Quebec market, the largest being Bell Canada, the incumbent telco for the province.

Until Feb. 6, Videotron offered different residential high-speed Internet packages: Basic Internet, High-Speed Internet, Extreme High-Speed Internet, and Extreme-Plus High Speed Internet that delivers 20 Mbps. Videotron’s traditional DOCSIS 1.x/2.0-based Internet packages are summarized in Table 1. But on Feb. 6, Videotron launched Internet service based on channel bonding as defined in CableLabs’ DOCSIS 3.0. The service followed on Videotron’s launch of the pre-DOCSIS 3.0 technology on Feb. 1, 2007, where it demonstrated data rates of 100 Mbps. For the service launch, Videotron introduced two "Ultimate" branded tiers of high-speed Internet service. See Table 2. High-speed trials To prepare for the rollout of "Ultimate" services, the company first ran a trial with 150 Videotron subscribers. Twenty business customers and 130 residential customers were selected for the trial, which started in December 2006, and various speeds were tested.

While there was no technological hurdle to offering 100 Mbps (or higher) services, a decision was made to offer 30 Mbps and 50 Mbps in initial deployments so that Videotron could price the "Ultimate" services at $64.95 and $79.95 (for the 30 Mbps and 50 Mbps services respectively). This allowed Videotron to drive rapid adoption in order to both grow the installed base as well as provide a better experience for existing high-speed Internet subscribers.

Videotron found during the trial that there are numerous bottlenecks in the Internet and in the home – including limited speeds on Internet servers, 802.11g wireless routers that peaked at 54 Mbps, un-optimized transmission control protocol (TCP) stacks, and older computers with limited central processing unit (CPU) or network interface card (NIC) capabilities – that may prevent users from realizing the highest bit rates. These bottlenecks are typically uncovered only after subscribers move to higher throughput services, and Videotron makes recommendations to its subscribers on how to maximize the performance of their high-speed connections in order to achieve the peak bit rates advertised for each tier.

To date, subscriber reaction to the new high-speed services, also known by the  French TVG (tres grande vitesse) label, has been overwhelmingly positive. Technology Videotron’s 30 Mbps and 50 Mbps services are deployed using Cisco Systems’ uBR10012 cable modem termination systems (CMTSs) and Scientific Atlanta DPC2505 Wideband cable modems.

Traditional DOCSIS 1.x and DOCSIS 2.0 modems make use of a single 6 MHz downstream channel on the cable plant. Using 256-QAM (quadrature amplitude modulation), the maximum attainable bit rate is about 38.8 Mbps – and that is shared with other subscribers in the same service group. The DOCSIS 3.0 channel bonding technology allows multiple 6 MHz channels to be grouped together and used like a single virtual channel. Euro-DOCSIS similarly allows the bonding of multiple 8 MHz channels.

On the CMTS, a new shared port adapter (SPA) is connected via Gigabit Ethernet to an edge QAM modulator, which can support up to 24 DOCSIS QAM channels.

The "Ultimate" service also requires a cable modem that understands channel bonding at the customer premises. Traditional cable modems only have a single tuner and only support a single channel. A modem supporting channel bonding, by contrast, has multiple tuners. Videotron is using a modem that provides data rates up to 100 Mbps or more. As a result, Videotron will be able to offer new high-speed services with data rates even higher than 50 Mbps in the future – without having to swap out existing equipment.

Current products deployed are capable of supporting a subset of the DOCSIS 3.0 specifications: namely downstream channel bonding and Internet protocol version 6 (IPv6). Full DOCSIS 3.0 support will mean adding enhanced multicast support, upstream channel bonding, and AES encryption functionality. Challenges Because DOCSIS 3.0 downstream channel bonding uses the same modulation techniques as traditional DOCSIS, there is no specific engineering requirement to increase carrier-to-noise ratio (CNR) or do other plant cleanup. That said, many cable operators are still in the process of migrating to 64-QAM in the upstream – as a first step in increasing upstream throughput prior to moving to DOCSIS 3.0 upstream channel bonding. For example, moving from 16-QAM to 64-QAM can increase upstream capacity from a usable 18 Mbps to 27 Mbps on a 6.4 MHz upstream channel.

Freeing up sufficient spectrum on the RF plant to offer downstream channel bonding does remain a significant challenge. Prior to offering the new "Ultimate" speed services, Videotron allocated one 6 MHz frequency for DOCSIS services. To support its "Ultimate" tiers, Videotron now requires three different 6 MHz frequencies; one of those continues to provide traditional DOCSIS services to the bulk of the customer base – those receiving services of up to 20 Mbps. The two additional channels are used for the "Ultimate" tier customers.

Cable operators have many options for making additional spectrum available, including changing downstream modulation from 64-QAM to 256-QAM, re-optimizing video QAM channels using grooming and transrating, performing node splits, implementing switched digital video (SDV) to increase the efficiency of digital video spectrum, reclaiming analog spectrum, and upgrading the outside plant.

Through the addition of two new DOCSIS channels, a significant advantage for Videotron is that many customers who consume significant capacity migrate to the "Ultimate" tier and thereby reduce congestion on the channel reserved for "traditional" DOCSIS customers. Performance is thereby improved for all customers. Planning for 3.0 The cable modems rolled out in Videotron’s "Ultimate" tier are not "full DOCSIS 3.0" devices. One major difference is that they are three-channel devices, whereas DOCSIS 3.0 requires a minimum of four channels for both the upstream and downstream directions.

Full DOCSIS 3.0 modems should be available later this year, and Videotron plans to transition to a fully DOCSIS 3.0 compliant modem to support future services that require DOCSIS 3.0 features such as AES encryption and enhanced multicast.

Later this year, Videotron also plans to implement DOCSIS Timing Interface (DTI) synchronization between the CMTS and a DTI-enabled edge QAM modulator. Having DTI in the architecture enables Videotron to migrate to the modular CMTS (M-CMTS) architecture. The M-CMTS architecture increases CMTS scalability by offloading QAM processing, while at the same time reducing cost. The move to an M-CMTS architecture also enables "QAM sharing" – where edge QAM modulators can be shared between video on demand (VOD), SDV, and high-speed data. QAM sharing, if desired by the cable operator, allows capacity to be used more efficiently since throughput typically peaks at different times for each of the services. Taking leadership By offering high-speed Internet services based on DOCSIS 3.0 downstream channel bonding, Videotron has placed itself in a leadership position – and in the process enabled a whole host of new service possibilities that can leverage the new capacity. At the same time, Videotron now has a smooth migration path to a full set of future services that will incorporate additional DOCSIS 3.0 features such as upstream channel bonding, enhanced multicast, and IPv6.

In addition, higher speeds will serve Videotron’s subscribers by improving the quality of experience, reducing wait times, and maintaining high performance even as multiple household members and applications vie for the same high-speed capacity to the home.

Videotron’s launch is just the beginning of the new DOCSIS 3.0 era.

Derek Pangia is director of Internet services for Videotron. Dave Brown is cable solutions manager for Cisco. Reach him at davebr@cisco.com. Sidebar: Videotron Synopsis Videotron, a wholly owned subsidiary of Quebecor Media, is an integrated communications company engaged in cable TV, interactive multimedia development, Internet access services, cable telephony and wireless telephone service. Videotron offers its illico (VOD) interactive TV system and its broadband network, which supports high-speed cable Internet access, analog and digital cable TV, and other services such as telephony. As of Dec. 31, Videotron was serving 1,638,000 cable TV customers in Québec, including 768,000 illico subscribers. Videotron got its start in the cable business in 1964 in Montreal, and through the next two decades continued to grow and acquire new cable assets throughout Quebec.

Media conglomerate Quebecor acquired Videotron in 2000. Today Videotron is a technologically advanced cable operator/telecommunications company offering a full suite of "quadruple play" services – including video, digital voice, high-speed Internet, and mobile phone services – to both residential and business customers.

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