Blind Modulation Mode Identification via Autocorrelation

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Solution Overview

Problem

Conventional OFDM signal detection and demodulation systems require known modulating parameters, failing to operate effectively when these parameters are unknown, limiting their applicability in systems like monitoring illegal radio waves or communication using unoccupied bands.

Innovation Solution

An apparatus and method that identifies the modulation mode of an unknown communication signal by generating a duplicate signal for autocorrelation processing, detecting pilot and guard interval symbols, and determining the modulation mode based on the correlation values, without relying on pre-known information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional OFDM signal detection and demodulation systems are used, then reliable signal processing is achieved, but the system cannot operate when modulating parameters are unknown

Engineering Contradiction:

Improvecapability to process unknown signalsVSAvoidsignal detection reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system performs self-identification of modulation mode by automatically detecting characteristic parameters (cyclic prefix length, pilot symbol position, data symbol length) from the received signal itself without requiring external parameter information. The autocorrelation processing enables the system to serve itself by extracting necessary parameters from the signal structure.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system changes its processing parameters dynamically based on detected signal characteristics. By detecting the cyclic prefix length and pilot symbol position, the system adjusts its demodulation parameters accordingly, enabling adaptation to different OFDM configurations and modulation modes.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If parameter detection is performed on unknown signals, then adaptability is improved, but processing complexity increases

Engineering Contradiction:

Improvemodulation mode identification capabilityVSAvoidsignal processing complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The signal processing is divided into distinct functional segments: autocorrelation processing to detect cyclic prefix, pilot symbol detection, data symbol extraction, and modulation mode identification. This segmentation allows each component to be optimized independently and simplifies the overall complex processing task.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system performs preliminary autocorrelation processing and pilot symbol detection before main demodulation operations. By identifying the cyclic prefix length and pilot position in advance, the system prepares necessary parameter information that simplifies subsequent data extraction and modulation identification processes.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If blind parameter detection is implemented, then system versatility is enhanced, but detection precision may be compromised

Engineering Contradiction:

Improveunknown signal processing capabilityVSAvoidparameter detection accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The system uses feedback from autocorrelation results to refine parameter detection. The detected cyclic prefix length and pilot symbol position are fed back to adjust the demodulation process, and the system can iteratively refine its parameter estimates based on the quality of detected signals and synchronization performance.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces traditional mechanical parameter setting with signal processing-based detection. Instead of manually configuring parameters or using fixed parameter tables, the system uses autocorrelation and spectral analysis to automatically determine modulation parameters, substituting physical configuration with computational detection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS7756209B2Apparatus, method, and program for identifying modulation mode

Publication Date: 2010.07.13 NEC CORP

AI summary

An orthogonal frequency division multiplex signal and a digital modulation signal or an analog modulation signal can be identified by blind processing. The modulation mode identifying apparatus comprises: a correlation signal generating circuit which generates a duplicate signal for correlation processing based on an unknown communication signal; an autocorrelation circuit which performs autocorrelation processing through carrying out sliding processing on the duplicate signal with respect to the unknown communication signal; a detection unit which detects information regarding a pilot symbol and a guide interval symbol of the communication signal based on a correlation value output obtained by the autocorrelation processing; and an identifying circuit which identifies a modulation mode of the unknown communication signal based on the information regarding the pilot symbol and the guide interval symbol of the communication signal.