When Might Cable, Telcos Devote 100% of Bandwidth to High Speed Access?

Tier-one U.S. cable TV companies and telcos face interesting access bandwidth challenges as demand for high speed access requires more capacity, while linear video also competes for that bandwidth.

Eventually, one might surmise that nearly all bandwidth on the access networks could be devoted to Internet access, that occurring when the linear TV business has become so challenged by on-demand delivery that virtually all entertainment video is delivered using streaming, rather than dedicated linear bandwidth.

The transition is the issue. U.S. cable TV operators, still the leading providers of linear programming, are steadily allocating more bandwidth for high speed access, in an incremental way that makes more efficient use of available bandwidth on hybrid networks.

Verizon, where it has FiOS deployed, reserves 870 MHz of bandwidth for linear video, but does so using a separate optical wavelength from that used to deliver high speed access and voice services. That means, as a practical matter, that linear video does not compete with bandwidth required to deliver high speed access.

In other words, linear TV and high speed access are not in a “zero sum” situation where more bandwidth for high speed access must come from bandwidth used to deliver video.

AT&T, on the other hand, uses an access technique similar that of the cable TV operators, where all services are delivered over a single physical medium, with bandwidth shared between all applications.

Like the cable TV operators, AT&T (except where it is deploying fiber to the home), has to make “zero sum” decisions about allocation of its access bandwidth. More bandwidth for high speed access must be created or taken from video bandwidth.

Should AT&T succeed in buying DirecTV, one potential future development, aside from the ability to compete for nearly 100 percent of the linear video business, nationwide, is to reclaim nearly 100 percent of access bandwidth to deliver high speed access services, as video might be delivered using DirecTV. That might not happen right away, as regulators require a transition period where AT&T is barred from switching existing U-verse video customers to DirecTV.

Cable TV operators switched from a mix of analog and digital TV signals to “all digital,” in part, to free up bandwidth for high speed access.

AT&T might eventually be able to act in the same way to reclaim bandwidth, by shifting all linear video to the separate satellite network.

Cable operators might someday shift even more bandwidth, if streaming delivery becomes the norm. That would be a radical step, and would be contemplated only at the point operators concluded they would be no worse off, in terms of revenue, by switching to streaming delivery on an all-IP network, and abandoning linear formats.

Cable operators do not seem to anywhere close to that point, yet. But they already foresee the possibility. The DOCSIS framework aims for 10 Gbps downstream, one Gbps upstream. It is hard to see how that could happen unless virtually all bandwidth were devoted to high speed access.

In that regard, Broadcom has announced gigabit speeds on hybrid fiber coax networks using its new DOCSIS 3.1 cable modem system-on-a-chip capability.

The new chip relies on use of two OFDM 196 MHz downstream channels and two 96 MHz OFDM-A upstream channels. Modern HFC networks feature something up to 948 MHz of total downstream bandwidth.

So two 196-MHz OFDM channels would represent consumption of about 392 MHz of downstream bandwidth, or about 40 percent of total available downstream bandwidth on an HFC network operating up to 1002 MHz in a standard frequency plan.


The objective, eventually, is support for 10 Gbps downstream and 1 Gbps upstream. But that likely would occur only after the linear video subscription model has run its course, and been abandoned for streaming access.
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