Cable Modem Interference Measurement Using MER and Probing Signals
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Solution Overview
Problem
Current methods for measuring interference between cable modems are inaccurate and time-consuming, requiring multiple iterations to determine interference relationships, which affects spectral efficiency in cable communications systems.
Innovation Solution
A method involving a cable modem termination system (CMTS) that sends a broadcast message to cable modems to send probing signals in overlapping uplink and downlink spectrums, using modulation error ratio (MER) information to determine interference intensity and group modems based on threshold values, thereby improving interference measurement accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional interference measurement methods are used between cable modems, then interference relationships can be determined, but the measurement process is time-consuming and inaccurate, requiring multiple iterations
Solution Approach 1:
The CMTS pre-allocates specific uplink time slots for probing signals and configures the test environment before actual interference measurement begins. This preliminary setup includes designating which CMs send probing signals and which measure interference, eliminating the need for iterative measurement processes and reducing overall measurement time while maintaining accuracy
Solution Approach 2:
The patent introduces probing signals as intermediary test signals that facilitate interference measurement. These specially designed signals with known characteristics serve as mediators between transmitting and receiving CMs, enabling accurate interference measurement through correlation processing without requiring complex iterative procedures
2Productivity
If cable modems are grouped based on interference relationships, then spectral efficiency is improved, but accurate determination of interference relationships is difficult to achieve
Solution Approach 1:
The patent replaces traditional signal analysis methods with correlation processing mathematics. By calculating the correlation between received probing signals and locally generated reference signals, the system achieves precise interference measurement and relationship determination, enabling accurate CM grouping for improved spectral efficiency
Solution Approach 2:
The system implements feedback by having measuring CMs report their measured interference levels and MER values back to the CMTS. The CMTS uses this feedback information to accurately determine interference relationships and make informed grouping decisions, ensuring both measurement precision and spectral efficiency
Data Source
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AI summary
The present invention provides a method for measuring interference to a CM, an apparatus, and a system. The method includes: sending, by a CMTS, a broadcast message to all CMs connected to the CMTS, where the broadcast message includes information designating one of the CMs to send a probing signal by using a spectrum S in a timeslot T; broadcasting, by the CMTS, a pseudo random binary sequence PRBS by using the spectrum S in a downlink direction in the timeslot T; and obtaining, by the CMTS, modulation error ratio MER information recorded in the timeslot T by other CMs, and using a difference between MER information in the timeslot T and MER information in a normal data timeslot, of each of the other CMs, as intensity of interference to the corresponding CM. According to the solutions of the present invention, it can be ensured that measured interference to a CM is more accurate, and CM grouping can be fast completed directly based on a magnitude relationship between the interference and a threshold.