Increased throughput demands, driven by applications like Peer-2-Peer file sharing and social networking, has intensified the demands placed on upstream spectrum.Those demands have been met with advanced DOCSIS tools like SCDMA and Channel Bonding. Additionally, plant architectures are evolving towards fiber-rich networks with reduced RF cascades, potentially improving overall plant performance and creating opportunity to support higher-order modulation schemes.
The benefits of advancing modulation to 256-QAM over 64-QAM is well-understood for the downstream. For example, a 33% throughput increase would also apply to the upstream. As previously explored for downstream spectrum, this throughput increase comes at the expense of increased sensitivity to noise, distortion, and interference. However, the upstream spectrum hosts a different class of impairments as well as DSP tools available to overcome them including equalization, forward error correction, spread-spectrum techniques, ingress cancellation, and interleaving.