Echo Cancellation Training in Full Duplex DOCSIS Cable Modems
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Solution Overview
Problem
In Full Duplex DOCSIS systems, upstream channel usage can cause 'noise' or 'echo' that affects adjacent downstream channels, necessitating a method to measure and offset these effects to minimize interference.
Innovation Solution
A cable modem is equipped with an echo cancellation training method that receives an echo cancellation service ID (EC SID) to perform echo cancellation training, transmitting a test signal upstream and measuring noise in downstream channels, using modified DOCSIS communication protocols to allocate echo cancellation training signals and implement echo cancellation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If downstream channels are used for upstream transmission in Full Duplex DOCSIS, then spectrum capacity is increased, but noise or echo is generated that affects other downstream channels
Solution Approach 1:
The system performs preliminary echo cancellation training before normal upstream transmission. The CMTS sends EC SID information elements in MAP messages to schedule dedicated training slots, where the CM transmits test signals and measures echo effects on downstream channels in advance, preparing cancellation filters before actual data transmission begins
Solution Approach 2:
The system implements feedback by measuring the actual echo effects on downstream channels during training slots and using these measurements to adjust and optimize the echo cancellation filters. The CM transmits test signals, measures the noise/echo on downstream channels, and uses this feedback information to refine cancellation parameters
2Object-generated harmful factors
If echo cancellation training is performed, then adverse impact to adjacent downstream channels is minimized, but additional training slots and signaling are required
Solution Approach 1:
The echo cancellation training infrastructure is integrated into the existing DOCSIS MAP messaging framework. The EC SID information elements reuse the established MAP message structure and scheduling mechanisms already present in the system, allowing echo cancellation training to share the same signaling infrastructure used for regular upstream bandwidth allocation, thereby reducing overall system complexity
Solution Approach 2:
The cable modem autonomously performs echo cancellation training during allocated EC SID slots without requiring external control signals for each training operation. Once the CMTS provides the EC SID scheduling information, the CM independently transmits test signals, measures echo effects, and updates its cancellation filters without continuous CMTS intervention
Data Source
AI summary
An echo cancellation training method in a cable modern is provided, comprising receiving an echo cancellation service ID (EC SID) assigned for echo cancellation training, the cable modem receiving the EC SID from a cable head end in an information element (IE) in a map (MAP or P-MAP) defining a time and frequency of upstream transmission opportunities for the cable modem, the EC SID establishing when the cable modem may perform the echo cancellation training in a downstream channel allocated to the cable modem, transmitting an echo cancellation test signal upstream to the cable head end via an upstream channel allocated to the cable modem and in a time slot specified by the received EC SID in the map, and measuring noise in one or more downstream channels allocated to the cable modem, with the noise resulting from the transmission of the echo cancellation test signal on the upstream channel.