DENVER – Upstream channel bonding – meaning far faster uploads – is coming to cable.
With DOCSIS 3.0 now passing an estimated 75 million homes in North America and set to pass another 10 million households by the end of the year, U.S. and Canadian cable operators have been steadily offering higher downstream data speeds to broadband subscribers. Thanks to the wideband spec’s channel-bonding capabilities, at least six North American MSOs offer peak downstream speeds of at least 100 Mbps today, including Videotron and Shaw Communications.
Upstream data speeds have lagged behind, though, due to a lack of upstream channel-bonding. As a result, no cable operator comes close to matching Verizon Communications’ top upstream speeds of 35 Mbps.
But now that may soon change. In the wake of positive results from recent field trials of upstream channel-bonding, a senior Comcast technology executive thinks this feature will be “production-ready” for the giant MSO by the end of March.
Speaking at a Light Reading conference on cable next-gen broadband strategies in Denver last week, Chris Bastian, senior director of network architecture for Comcast, said the MSO has already completed an upstream channel-bonding field trial with one of its cable modem termination system (CMTS) vendors. Plus, he said, the MSO will wind up a second trial with another equipment supplier by the end of March.
Bastian declined to name the sites of the two trials or the vendors involved. But, with the new capabilities in place, he said Comcast will be able to turn on upstream channel-bonding in these markets whenever it’s ready. He declined to say when that might be, noting that it was up to the company’s business unit to decide.
So far, Comcast has been trying out upstream channel bonding on its "Extreme" DOCSIS 3.0 tiers, which cap upstream speeds at 10 Mbps. With the aid of upstream channel bonding, Comcast will be able to hike those speeds significantly. At last year’s Light Reading conference, for instance, Bastian said the company’s lab trials were producing "sustained" upstream speeds of 75 Mbps.
Comcast won’t say how much speed it will add once it launches upstream channel bonding. But the technology will certainly give it a new weapon against such prime rivals as Verizon, which already offers a FiOS Internet tier featuring the 35 Mbps upstream rates.
Bastian noted that a technique known as “partial service mode” has worked as expected with bonded upstream channels. With this technique, even if one channel has to be taken out of service temporarily due to high noise levels, the cable modem can continue operating normally using the unaffected upstream channels. Although the modem’s peak speeds are lower, Bastian said, the device remains in operation.
Even as MSOs like Comcast seek to boost upstream and downstream speeds further for high-end broadband users with DOCSIS 3.0, they’re also looking to use the wideband spec to create a fat pipe for the delivery of IP video. Knowing this, equipment vendors are now developing a lineup of new hybrid IP set-tops and gateways, most of them equipped with embedded DOCSIS 3.0 modems that can act as conduits for IP-based video services.
CableLabs’ director of DOCSIS Specifications Matt Schmitt addressed the industry’s IP video ambitions at last week’s conference. Speaking on the same panel as Bastian, Schmitt said CableLabs has been crafting ways to improve how IP multicast works in the DOCSIS 3.0 environment. Using IP multicasting, cable operators can send one IP video stream to multiple locations, much as they now do with switched digital video (SDV) technology.
Schmitt explained that IP multicast can help MSOs conserve the amount of bandwidth they dedicate to linear IP video. So, if a customer in a particular service group is tuned to a channel on the MSO’s linear IP video lineup, the cable operator can create that multicast stream. If any other customers in that group also tune into the channel, that stream can then be sent to them as well, eliminating the need for the operator to set up a separate one.
Schmitt said CableLabs has redesigned that capability in DOCSIS 3.0 by moving control from the cable modem to the network and the CMTS. CableLabs has also introduced two additional features – multicast QoS and multicast authorization/encryption.
Alan Breznick is a Toronto-based senior analyst at Heavy Reading, part of the Light Reading Communications Network.
