Comcast Expects 10-Gbps Downstream Upgrade to Cost "Less than $200 Per Passing"

Comcast says it can initially upgrade its network to eventually handle symmetrical 10-Gbps internet access (supporting 10 Gbps initially) for “less than $200 a home passed,” according to Elad Nafshi, Comcast EVP and chief network officer. 

It is a nuanced statement. 

That initial upgrade cost includes revamping networks from low-split to mid-split, including changes to active and passive network elements when necessary to support an upgrade to DOCSIS 4.0 10-Gbps downstream bandwidth. Upstream will increase to perhaps 1 Gbps. 

Significantly, Comcast’s initial deployment does not require full fiber distribution, but can accommodate as many as four amplifiers in cascade. 

That means the upgrade to 10-Gbps downstream service can be done without upgrading the whole network to fiber, which uses passive coaxial cable only for the last 100 feet or so of drop cable. 

Upgrading to symmetrical 10-Gbps service will require replacing all the radio frequency amplifiers. Typically, Comcast has built out fiber to an optical node, then delivered signals to home using a string (cascade) of up to four amplifiers running on coaxial cable. 

In the first stage of DOCSIS 4.0 deployment,  most of Comcast’s facilities can continue to operate with fiber distribution to a node, then retain as many as four RF  amplifiers for service to homes. There are huge cost implications for retaining that capability, since Comcast can continue to use the in-place amplifiers and coaxial cable. 

Future “Node + 0 amplifier” networks will transition to Full-Duplex (FDX) DOCSIS, to significantly increase the upstream bandwidth to multi-gigabit speeds, such as symmetrical 10-Gbps service. But that also will require deploying a full fiber network, using coaxial cable only for the drops. 

The first step will be a shift to a 5-MHz to 204-MHz upstream bandwidth and 1218 MHz downstream bandwidth, supporting a 1 Gbps upstream tier and multi-Gbps downstream. In the following illustration, blue frequencies are available for downstream traffic, while red frequencies are available for upstream traffic. 

As usual, the upgrades can be implemented incrementally, in stages, with incremental capital investment. . 

source: Comcast 

Then overlapping bidirectional spectrum from 108 to 204 MHz can be activated. that eventually increases up to the full 108-MHz  to 684-MHz FDX limit. In that implementation DOCSIS 3.0 can be supported up to the 1002 MHz limit and legacy DOCSIS 3.1 to the 1218-MHz limit.

The point is that Comcast still believes it can upgrade its bandwidth over time to symmetrical 10-Gbps service while remaining the low-cost provider compared to rival fiber-to-home networks.