Radio Transmission Device OFDM Subcarrier Interference Removal

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Solution Overview

Problem

Existing radio communication systems face challenges in removing interference signals from unrelated radio systems and specific frequency interference, such as continuous waves and short-time interference, which affect frequency deviation and temporal synchronization timing.

Innovation Solution

A radio transmission device transmits known signals using OFDM with guard intervals and null signals to prevent interference, allowing the reception device to estimate frequency deviation and synchronization timing accurately even in shared frequency bands.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional interference removal methods are used, then interference signals from the same radio system can be removed, but interference signals from unrelated radio systems and specific frequency interference cannot be removed

Engineering Contradiction:

Improveinterference removal capabilityVSAvoidapplicability to different interference types

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent segments the frequency band into multiple subcarriers and transmits known signals on specific subcarriers while leaving other subcarriers as null signals. This segmentation allows the reception device to identify and remove interference from specific frequency regions without affecting the entire band, enabling removal of both same-system and unrelated system interference.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces known signals as intermediary reference elements that facilitate interference detection and removal. These known signals serve as mediators between the transmission and reception devices, enabling the reception device to estimate channel characteristics and identify interference components even from unrelated radio systems.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If known signals are transmitted for frequency deviation estimation, then synchronization accuracy improves, but continuous wave interference and short-time interference at estimation timing cannot be removed

Engineering Contradiction:

Improvefrequency deviation estimation accuracyVSAvoidinterference at estimation timing

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent transmits known signals in advance before data transmission to enable preliminary channel estimation and synchronization. This preliminary action allows the reception device to establish baseline channel characteristics before actual data transmission begins, improving frequency deviation estimation accuracy while providing a reference for later interference removal.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies different signal characteristics to different subcarriers, with known signals transmitted on specific subcarriers and null signals on others. This local differentiation allows the system to maintain high measurement precision where known signals are transmitted while being less affected by interference on null subcarrier positions.

Inventive Principle:

Principle #3Local quality

3Reliability

If guard intervals are used in OFDM transmission, then multipath interference is reduced, but interference from other radio systems in shared frequency bands cannot be removed

Engineering Contradiction:

Improvemultipath interference resistanceVSAvoidinterference from shared frequency band systems

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the OFDM frequency band into subcarriers with known signals transmitted on specific subcarriers and null signals on others. This segmentation works in conjunction with guard intervals to provide two-level protection: guard intervals handle temporal multipath interference while subcarrier segmentation handles frequency-domain interference from other radio systems.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The known signals serve multiple functions simultaneously: they enable channel estimation, frequency deviation correction, temporal synchronization, and interference detection. This multi-functionality allows a single signal component to address both multipath effects and interference from unrelated radio systems.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP3790246B1Radio transmission device, radio reception device, radio communication device, radio transmission method, control circuit, and recording medium

Publication Date: 2023.06.21 MITSUBISHI ELECTRIC CORP

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AI summary

A radio transmission device includes: a known signal generating unit (112) that generates a first known signal (130a) and a second known signal (130b) mapped in such a manner that subcarriers for transmitting a first signal not being 0 do not overlap with each other in symbols of one time band; an IDFT unit (113a, 113b) that converts the first known signal (130a) and the second known signal (130b) from a frequency domain signal into a time domain signal; a GI inserting unit (114a, 114b) that inserts a guard interval into the first known signal (130a) and the second known signal (130b) converted into time domain signals; a transmission antenna (111a) that transmits the first known signal (130a) in which the guard interval is inserted; and a transmission antenna (111b) that transmits the second known signal (130b) in which the guard interval is inserted.