Broadcom today announced a chip for cable modems that can power gigabit-per-second Internet service, and Comcast said it will use the chips to boost speeds this year.

Broadcom's cable modem system-on-a-chip relies on DOCSIS 3.1, a faster version of the Data Over Cable Service Interface Specification. "DOCSIS 3.1 is a critical technology for Comcast to provide even faster, more reliable data speeds and features such as IP video to our subscribers' homes by harnessing more spectrum in the downstream," Comcast Executive VP Tony Werner was quoted as saying in the Broadcom press release. "By more effectively using our cable plant to grow our total throughput, we expect to offer our customers more than 1 Gigabit speeds in their homes in 2015 and beyond."

Gigabit service is generally available only from fiber providers. Comcast's fastest residential service today is 505Mbps downstream and 100Mbps upstream, but even that relies on fiber instead of cable, just as Comcast's business offerings do. At a June 2013 industry conference, Comcast CEO Brian Roberts demonstrated a 3Gbps DOCSIS 3.1 connection.

As we explained in a December 2013 story, DOCSIS 3.1 will support higher data throughput a lot more efficiently than DOCSIS 3.0. This will help cable's download speeds compete against fiber-to-the-premises, but isn't likely to match the symmetrical upload and download speeds offered by many fiber services.

Broadcom said its "BCM3390 cable modem SoC delivers video content with a nearly 50 percent increased efficiency on existing spectrum allocations and allows for the delivery and use of a new range of content and services. The single device supports high-speed data rates exceeding 1Gbps. The BCM93390 modem reference design with integrated Wi-Fi provides up to 2 Gigabit speeds in the home, providing a path for cable operators to transition to all-IP video."

DOCSIS 3.1 "enables higher-order modulations in existing hybrid fiber-coaxial (HFC) networks without changes to the existing cable plant," Broadcom further explained. "The combination of low-density parity check-based Forward Error Correction (FEC) and Orthogonal Frequency Division Multiplexing (OFDM) technology in DOCSIS 3.1 allow operators to more efficiently install more data in the existing spectrum."

The BCM3390 is being sampled to manufacturers for rollout later this year.

We asked Comcast what its gigabit service will cost and what the upload speeds will be, but the company said "that will come at a later date TBD." A Comcast spokesperson pointed to a CableLabs announcement that says, "DOCSIS 3.1 modems are designed to co-exist with older versions enabling incremental deployment based on market demand." That "flexible migration strategy" is the key point for Comcast. "When we roll this out, we’ll be able to leverage our existing plant and infrastructure to introduce this capability at scale," Comcast said.