FEATURE CABLE NETWORKS
Cable
Competition from fibre-to- the-home networks is putting cable operators under pressure. Robert Roe investigates the options available to cable operators wishing to upgrade their networks
@fibresystemsmag |
www.fibre-systems.com
conundrum C
able operators are used to having the upper hand when it comes to delivering entertainment services to consumers. But as demand for
high-speed broadband surges and telecom operators expand into Internet protocol television (IPTV), cable operators must invest in their networks or face losing subscribers to other service providers. With an increasing number of telecom
operators moving towards gigabit services and fibre-to-the-home (FTTH), cable operators are now facing an even greater challenge: should they upgrade their networks in order to compete more effectively with FTTH operators or should they become FTTH operators? One of Google Fiber’s objectives has been to
accelerate wireline broadband investment by creating competition, says Julie Kunstler, principal analyst, intelligent networks and components, at market research firm Ovum. And it’s certainly been successful in that respect. ‘We are seeing a flurry of activity by first- and second-tier equipment vendors as cable operators adopt access solutions to support one gigabit for residential subscribers and 10G for business services,’ she said.
Cable operators are having a very hard look at becoming fibre providers
Upgrade choices Te previous upgrade from pure coaxial cable to hybrid fibre coaxial (HFC) systems in the 1990s was carried out by introducing optical fibre into the main distribution routes of the network. Tis upgrade can be viewed as the equivalent of fibre to the cabinet (FTTC) for telecom operators – it pushes fibre deeper into the access network and shortens the length of coaxial cable so that the throughput of the network can be increased. Tis architecture, in combination with the DOCSIS (Data Cable Over System Interface Specification) operating system, gave cable operators ample capacity for television and broadband services – until the gigabit obsession started to take hold. Te cable industry has several paths to gigabit broadband, explained Dan Rice, vice president,
16 FIBRE SYSTEMS Issue 7 • Spring 2015
access network technologies at CableLabs, the non-profit research and development consortium for the cable industry. Depending on the current configuration of the network, some of these would be minor changes, while others could be considerably more disruptive. Rice points out that the current generation
DOCSIS 3.0 technology that most cable operators have already deployed can, in theory, deliver gigabit broadband downstream. Based on cable, modem capability of bonding 32 channels in the downstream direction yields total capacity of about 1.6 Gb/s (including overheads), which would allow for downstream gigabit services – albeit only for smaller cable customer groups. (Typically, a single optical node in the HFC network will serve anywhere between 250 and 2000 subscribers via coaxial cable.) He conceded that DOCSIS 3.0 technology is
more restricted in the upstream direction. With the amount of upstream spectrum typically available in Europe, a capacity of 160 Mb/s would enable upstream services in the 100 Mb/s range for smaller cable groups. However, bandwidth consumption has historically been quite asymmetric, he says, while the next major generation of DOCSIS technology will enable gigabit capacity upstream. Released in October 2013 but not yet widely
deployed, DOCSIS 3.1 is designed to support speeds up to 10 Gb/s downstream, to enable sustained 1 Gb/s services to consumers. Te technology could also enable 1 Gb/s service in the upstream direction if the cable operator chooses to dedicate the frequency spectrum resources on the coaxial part of the network. ‘Te network operator has many options to
scale speed and capacity based on how they choose to deploy DOCSIS 3.1 technology,’ Rice said. ‘Operators will be able to increase performance over time, as needed, by simply changing the configuration. For example, if an operator choses to expand the use of spectrum for IP broadband using equipment built to the
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