Comcast plans to introduce the world’s first DOCSIS 3.1-powered gigabit Internet service to residential and business customers in Atlanta and Nashville in early 2016, with Chicago, Detroit, and Miami to follow in the second half of the year.
Keep in mind that the Concast deployments are "whole city" deployments, not "neighborhoods." Every location will get gigabit capability, not just locations in selected neighborhoods.
The new technology will, for the first time, make it possible for Xfinity and Comcast Business Internet customers to receive gigabit speeds over existing hybrid fiber coax networks already installed to support current service, and will not require a fiber upgrade.
Last year, Comcast launched its residential fiber-based multi-gigabit service--Gigabit Pro--in metropolitan Atlanta, making it the first market to receive the company’s 2-gigabit symmetrical service.
Chicago, Detroit, Miami, Nashville, and several other markets were added over the following months, and Gigabit Pro is now available to 18 million homes across Comcast’s national footprint.
Gigabit Pro does require installation of a direct to location fiber connection, unlike DOCSIS 3.1.
Comcast also has increased Internet speeds for residential customers 16 times in the last 14 years, at rates equivalent to Moore’s Law, Comcast has said.