Wireless Train Control Frequency Hopping Interference Reduction

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Solution Overview

Problem

The wireless train control system faces significant interference from other systems using the 2.4 GHz ISM band, leading to reduced transmission quality and increased interference between base stations using the same frequency channel, which affects the distance and placement of base stations in the frequency-hopping method.

Innovation Solution

A wireless communication apparatus that allocates radio resources by using a transmission quality measurement unit to evaluate and improve frequency channel transmission quality, dynamically reallocating time slots between reserved and spare resources to minimize interference and enhance transmission quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If base stations are arranged closer together to improve coverage and communication reliability, then the reception level at cell edges improves, but interference from other base stations using the same frequency channel increases

Engineering Contradiction:

Improvecommunication reliabilityVSAvoidinterference from other base stations

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by making the frequency channel allocation dynamic rather than fixed. Base stations dynamically select and switch between multiple frequency channels based on real-time interference conditions and transmission quality measurements, allowing the system to adapt to changing environmental conditions and minimize interference while maintaining coverage

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of frequency channel assignment from static to variable. By introducing multiple frequency channels and allowing base stations to switch between them based on measured transmission quality and interference levels, the system optimizes the balance between coverage and interference avoidance

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If base stations use the same frequency channel to simplify resource allocation, then device complexity is reduced, but transmission quality deteriorates due to interference

Engineering Contradiction:

Improveresource allocation complexityVSAvoidtransmission quality

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent segments the frequency spectrum into multiple distinct channels. Instead of using a single frequency channel for all base stations, the system divides available frequencies into multiple channels that can be selectively assigned to different base stations, reducing co-channel interference while maintaining manageable resource allocation through centralized control

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements feedback mechanisms where base stations measure transmission quality and interference levels on each frequency channel, then report this information to the resource allocation controller. The controller uses this feedback to make informed decisions about channel assignment, optimizing transmission quality while maintaining systematic resource management

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If frequency hopping is used to avoid interference from other systems, then resistance to external interference improves, but interference from base stations with the same hopping pattern increases

Engineering Contradiction:

Improveinterference from other systemsVSAvoidinterference between base stations

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent applies asymmetry by assigning different hopping patterns to different base stations. Instead of using identical frequency hopping sequences, each base station is assigned a unique or differently phased hopping pattern, ensuring that even when base stations operate in the same geographic area, their frequency usage over time is asymmetric and thus reduces mutual interference

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent uses periodic frequency hopping where base stations systematically change frequency channels in a periodic manner. By coordinating these periodic hops across multiple base stations with different phase offsets or sequences, the system maintains the benefits of frequency diversity while minimizing the probability of simultaneous interference on the same channel

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS11930434B2Wireless communication apparatus, wireless communication system, wireless communication method, control circuit, and recording medium

Publication Date: 2024.03.12 MITSUBISHI ELECTRIC CORP

AI summary

A wireless communication apparatus that allocates radio resources is a base station or a mobile station that transmits a data series on a frequency channel in a frequency hopping pattern corresponding to a radio resource time slot. The apparatus includes a transmission quality measurement unit that measures radio waves in a frequency band used in the transmission of the data series and evaluates transmission quality, and the radio resources including a reserved resource and spare resources, a resource allocation unit that allocates, to the mobile station lower than or equal to a threshold value in transmission quality of a frequency channel used in a reserved resource time slot, a time slot that improves frequency channel transmission quality, of spare resource time slots. The mobile station transmits the data series, using the spare resource time slot when allocation information on the spare resource is obtained, or using the reserved resource time slot when the allocation information on the spare resource is not obtained.