Making good on its promise in January to offer 1Gbps speeds across its hybrid fibre-coaxial (HFC) network in 2015, Comcast has announced that it has installed the world's first commercial Data Over Cable Service Interface Specification (DOCSIS) 3.1 modem for a customer in Philadelphia.

DOCSIS 3.1 supersedes the current DOCSIS 3.0 technology, allowing far faster speeds by freeing up around 50 percent capacity on the cable through more efficient transmission of data over the available spectrum.

"At a home in the Philadelphia area, we took the next important step forward in delivering gigabit-speed broadband over our hybrid fiber-coaxial network," Comcast executive vice president and CTO Tony Werner said in a blog post.

"The test used the standard cable connections that we have in homes across the country. All we needed was a new modem, a software upgrade to the device that serves that neighborhood, and a few good engineers."

Comcast added that it will continue undertaking real-world tests of the technology by activating several more "test homes" in Pennsylvania, Northern California, and Atlanta, Georgia, over the next few months. It will begin delivering DOCSIS 3.1 services offering 1Gbps speeds to customers across the United States before the end of 2016.

"The beauty of DOCSIS 3.1 is that it is backwards compatible, so no digging up streets or backyards," Werner added.

"This technology, when combined with the extensive upgrades we have already completed on our advanced hybrid fiber-coaxial network, will provide more gigabit choices for our customers."

A Q&A on DOCSIS 3.1, published on the website of Australian Communications Minister cum Prime Minister Malcolm Turnbull nine months ago, said the technology would be coming to the National Broadband Network (NBN) HFC network by 2017.

"We plan to run DOCSIS 3.1 trials in 2016 and we plan to have DOCSIS 3.1 services commercially available in 2017," Turnbull wrote.

"Bringing DOCSIS 3.1 on board is the cherry on the cake that will give us even more capacity and really make sure that there is plenty of bandwidth for everyone on the network to have a great experience."

The wide-scale rollout of NBN HFC was approved by the Australian Competition and Consumer Commission (ACCC) in June, with a revised AU$11 billion deal allowing NBN to take ownership of Telstra's HFC and copper assets and Optus' HFC network.

The new deal came about as a result of NBN moving away from Labor's full fibre-to-the-premises (FttP) rollout following the Coalition's election at the end of 2013 to the present so-called multi-technology mix (MTM), which proposes to cover 20 percent of the population with FttP; 38 percent with fibre-to-the-node (FttN) and fibre-to-the-basement (FttB); 34 percent with HFC; 5 percent with fixed wireless; and 3 percent with satellite services.

On Monday, Telstra and NBN announced they had entered a memorandum of understanding for a "significant contract" to manage the design, engineering, procuring, and construction of NBN's HFC network, which will include Telstra updating HFC to DOCSIS 3.1 technology in order to deliver end users speeds of up to 1Gbps.

Telstra is also set to prepare exchange locations and planning and design prior to and during the contract's negotiation. Telstra has already been continually building out its HFC network despite its impending transfer of ownership to NBN.

Last month, however, a leaked draft from NBN revealed that Optus' HFC network is "not fully fit for purpose", with 470,000 premises in the footprint needing to be overbuilt by either Telstra HFC or fibre services.

The leaked document, called HFC Plan B: Overbuilding Optus, dated November 2015, states that the necessary work of overbuilding Optus' HFC network with FttN, FttB, or fibre to the distribution point (FttdP) will lead to a peak funding increase of between AU$150 million and AU$375 million, with NBN to miss its FY17 ready-for-service target by 300,000 premises, and its FY18 target by 333,000.

"Overbuilding the Optus HFC network with either Telstra HFC or FttX could deliver higher probability of success given the current state of the network [and] significant operational simplicity," the document says.

"Optus network is not fully fit for purpose. Optus nodes are oversubscribed compared with Telstra, and will require node splits. Existing Optus CMTS don't have sufficient capacity to support NBN services. Noise (ingress) [is] causing interference and degrading end users speeds."

HFC will connect 4 million Australian premises in total, with 3.6 million of these coming from the old Telstra HFC network. The network will also be extended and infilled, with the Optus network likely to be infilled and overbuilt in the remaining 400,000 premises.

NBN is currently conducting a 4,500-premises HFC trial in Redcliffe, Queensland, and said it has not found any "unexpected" technical issues with the Optus network.

The HFC network will be launched by June 2016, and completed along with the rest of the NBN by 2020.