By Richard S Prodan, Ph.D., Comcast Cable
Comcast has been deploying optical fiber deeper into its infrastructure, in “Node + 0” /, “N+0” mid-split configurations to support the ever-increasing demand for higher speeds and throughput to customers. The first step was the transition from traditional Node + N sub-split networks, with 5 to 42 MHz upstream and1002 MHz downstream bandwidth, to current mid-split Node + 0 networks with 5 to 85 MHz upstream and 1218 MHz downstream bandwidth.
Future Node + 0 networks will transition to Full-Duplex (FDX) DOCSIS, to significantly increase the upstream bandwidth to multi-gigabit speeds with high throughput. This will not be accomplished in one giant leap, but rather a transition from mid-split to high-split networks. The first step will be a shift to a 5to 204 MHz upstream and 1218 MHz downstream bandwidth, supporting a 1 Gbps upstream tier and multi-Gbps downstream. As demand for multi-gigabit services grows, FDX can be deployed, with overlapping bidirectional spectrum from 108 to 204 MHz that eventually increases up to the full 108 to684 MHz FDX limit plus legacy DOCSIS 3.0 to the 1002 MHz limit and legacy DOCSIS 3.1to the 1218MHz limit.
This paper will discuss considerations that need to be addressed in the transition. Scenarios will be described, as well as some node and modem architectures that provide flexible signal support to optimize the end-to-end performance, toward 10G Full-Duplex operation of the network.