You can freely build on How Cable Modems Fix Signal Distortions Before Sending Data

What this patent covers

This patent describes a way to clean up digital signals sent from a home modem to a central office. Instead of the central office doing all the work to fix signal distortion, it calculates the necessary corrections and sends those instructions back to the home modem. The home modem then uses a precode filter to adjust its own signal before it even leaves the house. This ensures that by the time the data travels through the noisy cable lines, it is already optimized to be read correctly by the central receiver.

What is now free to use

All 0 claims of US 6665308 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover signal equalization that happens entirely within the central office without sending instructions back to the remote unit.

• Does not cover analog signal modulation techniques that do not involve digital precode filtering.

• Does not cover systems where the remote unit calculates its own equalization coefficients without receiving them from the central unit.

• Does not cover general data transmission that lacks a training phase for channel characterization.

Who is building on this today

Major cable infrastructure providers like Cisco, Arris (now CommScope), and Broadcom have built upon these foundational signal processing techniques. The principles of iterative channel adaptation remain a core part of modern high-speed broadband standards.

Products built on expired version of this technology

How to cite this patent in your documentation

Terayon Communication Systems Inc. US Patent 6665308. Apparatus and method for equalization in distributed digital data transmission systems. Granted 2003, expired 2018. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.