OPEN MIC - Solving the DOCSIS 3.0 Upstream Challenge

Sat, 07/31/2010 - 8:20pm
Wim Mostert, Director of Product Management for Optical Transport Solutions at Aurora Networks

Digital return is the answer.

For all of its success so far in deploying next-generation DOCSIS 3.0 technology to systems serving millions of homes and businesses, the cable industry has one big hurdle remaining: The return path.

Wim MostertAs CED reported during The Cable Show 2010, upstream capacity remains a nagging problem. With broadband Internet access a critical competitive differentiator between cable operators and telcos, the need to future-proof the upstream path with technologies such as digital return takes on a greater priority.

The cable industry is dedicating extensive time and resources to implementing DOCSIS 3.0 technology, which uses channel bonding both in the upstream and the downstream to create much faster Internet connections. While downstream channel bonding is easily achievable, the demands placed on the upstream with channel bonding are more significant.

To solve the upstream challenge while avoiding extensive capital expenditures and reducing operating costs, cable operators are evolving their existing networks with digital return technology.

Digital return enables a cable operator’s push to deliver faster upstream data speeds to consumers and businesses, supplying up to 100 Mbps in that direction. When these upstream speeds are sold along with even faster downstream speeds – up to 150 Mbps – cable operators have an appealing highspeed data proposition that satisfies customer demand.

These speeds compare extremely favorably with overall average advertised cable modem speeds of 25 Mbps downstream and nearly 3 Mbps upstream, according to the Organisation for Economic Co-operation and Development (OECD). Also, industry statistics state that cable’s present broadband services deliver speeds of at least 10 Mbps – or faster – to consumers today. Compare these speeds with advertised DSL speeds topping out at 14 Mbps downstream, according to OECD data, and it is plain to see that cable is ahead in “the need for speed” game today and is positioning itself to maintain future leadership, as well.

How well is cable positioning itself? Cable supports speeds that exceed goals of the Federal Communications Commission’s aggressive National Broadband Plan, which envisions 100 million U.S. households with access to download speeds of at least 100 Mbps and upload speeds of at least 50 Mbps within the next 10 years.

Effective DOCSIS 3.0 implementation to achieve these needed higher speeds requires channel bonding in the upstream, together with 64 QAM modulation, resulting in significantly higher reverse link performance requirements. CMTS cost is another consideration: Higher aggregation requirements are driven by a need to limit the deployment cost of D3 systems to just the replacement cost of a DOCSIS 2.0 system, deferring the service enhancement cost until it is needed to offset competitive threats or is driven by higher capacity demand (revenue increase).

Many existing analog optical links will not be able to support the increased performance requirements. The links will have to be upgraded, or replaced, with analog links of much higher performance, and typically much higher cost. This still does not guarantee support for future services, and certainly does not provide significant benefits to network operating practices.

Alternatively, collector nodes that remotely aggregate the receive side of these installed analog links and then transport the aggregated traffic over a muchhigher-quality reverse link to the remote headend can be deployed. These nodes significantly reduce the reach required to transport the reverse signals over the existing links, thus preserving the analog reverse transmitters already deployed.

However, the most cost-effective and future-proof solution to resolve the reverse link upgrade issue is probably the complete replacement of the reverse analog links with digital links. The RF performance of the digital link is independent of distance and RF level. This technology supports all of the requirements for the increased performance. The digital reverse technology also simplifies the design, alignment and maintenance of the optical reverse path while providing additional network management, and ultimately revenuegeneration capabilities.

Cable operators with an HFC platform built on digital return technology ensure current and future DOCSIS 3.0 deployments and other broadband upgrades are supported with ease and without costly and time-consuming changes to infrastructure.

DOCSIS 3.0 technology gives cable operators a game-changing platform to deliver high-speed data services to residential and commercial customers. For operators that want to successfully pursue broadband subscribers, digital return technology supports all of the requirements for the increased performance both today and for the future, solving the upstream challenge.

Next month, thePlatform’s Marty Roberts, vice president of sales and marketing, will write about lessons learned from TV Everywhere.



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