OFDM Receiver Tone Tracking for Interference Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing radio receivers face challenges in effectively detecting and canceling interfering tones in orthogonal frequency division multiplexing (OFDM) systems, leading to system degradation and decoding errors due to noise floor rise and correlation failures.
Innovation Solution
A closed loop tone tracking and cancellation method using digital signal processing circuitry, which estimates the interfering tone location in one OFDM symbol and cancels it in subsequent symbols through vector generation and frequency component analysis, reducing complexity and improving precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional tone detection methods are used in OFDM systems, then tone interference can be detected, but the system experiences noise floor rise and correlation failures leading to decoding errors
Solution Approach 1:
The patent applies preliminary action by detecting and canceling interfering tones before they cause decoding errors. The tone cancellation is performed in the time domain prior to FFT processing, preventing the interference from propagating through the decoding chain and causing noise floor rise and correlation failures.
Solution Approach 2:
The patent extracts and removes the interfering tone component from the received signal. By identifying the tone's frequency, phase, and amplitude characteristics and subtracting this component from the received signal, the harmful interference is separated and eliminated before further processing.
2Reliability
If comprehensive tone detection is performed across all OFDM symbols, then all interfering tones can be detected, but the computational complexity increases significantly
Solution Approach 1:
The patent performs tone detection on a subset of OFDM symbols (e.g., every fourth symbol) rather than all symbols, reducing computational complexity. The detected tone parameters are then tracked and applied to subsequent symbols, maintaining detection accuracy while significantly lowering the processing burden.
Solution Approach 2:
The patent applies partial action by detecting tones in only certain OFDM symbols rather than all symbols. This selective detection approach reduces the total number of detections required while still providing sufficient coverage to maintain system reliability through tracking and interpolation between detected symbols.
3Device complexity
If tone cancellation is performed without tracking across symbols, then processing is simpler, but the interfering tone location drift causes detection failures
Solution Approach 1:
The patent implements feedback through tone tracking across consecutive OFDM symbols. The detected tone parameters from one symbol are used as initial estimates for the next symbol, and adjustments are made based on the actual detected values. This closed-loop tracking maintains accurate tone location estimation even when frequency drift occurs, without requiring complex re-detection algorithms.
Solution Approach 2:
The patent applies dynamics by making the tone detection process adaptive to changing conditions. Instead of using fixed detection parameters, the system dynamically adjusts tone location estimates based on tracking the tone's movement across symbols, allowing the detection mechanism to follow the interfering tone as it drifts in frequency.
Data Source
AI summary
Aspects of this disclosure relate to canceling a tone in a radio signal. A location of an interfering tone can be estimated in an orthogonal frequency division multiplexing symbol (OFDM). An interfering tone can be detected in a subsequent OFDM symbol based on the estimate of the location of the interfering tone in the OFDM using closed loop tone detection. The interfering tone in the subsequent OFDM can be canceled. Tone cancellation can be performed using digital signal processing circuitry. Tone cancellation can be performed in radio systems.