Frequency Channel Selection for Wireless Train Control Interference
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Solution Overview
Problem
In wireless train control systems using the 2.4 GHz ISM band, radio wave interference between base stations is significant due to their proximity and shared frequency channels, leading to reduced communication quality and increased interference.
Innovation Solution
A wireless communication apparatus that selects frequency channels for each time slot to minimize overlap with adjacent cells while allowing overlap with remote cells, extending the interval between cells using the same hopping pattern and frequency channels beyond the number of candidate channels, thereby reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If base stations are arranged closely along a railway track to improve coverage, then the area of stationary object increases, but radio wave interference between base stations increases
Solution Approach 1:
The frequency spectrum is segmented into multiple frequency channels, and different base stations are assigned different frequency channels in different time slots. This segmentation allows base stations to operate simultaneously without interference by dividing the shared resource (frequency spectrum) into distinct segments that are allocated based on spatial and temporal patterns.
Solution Approach 2:
The system implements periodic frequency hopping where base stations switch between different frequency channels in a predetermined periodic pattern. Each base station follows a specific hopping pattern that repeats over time, ensuring that adjacent base stations use different frequencies at the same time while maintaining regular switching behavior for predictable interference avoidance.
2Productivity
If the same frequency channel is used by multiple base stations to improve resource utilization, then the productivity increases, but radio wave interference increases
Solution Approach 1:
The frequency channel assignment is dynamic rather than static. Base stations dynamically switch between different frequency channels according to their specific hopping patterns, which are determined by their cell numbers and time slot positions. This dynamic allocation allows the system to maximize resource utilization while preventing simultaneous use of the same frequency by interfering base stations.
Solution Approach 2:
The system changes the frequency parameter over time according to predetermined hopping patterns. Each base station modifies its operating frequency in a systematic way based on its cell number and the current time slot, transforming a static frequency assignment problem into a dynamic parameter variation scheme that eliminates interference while maintaining high resource utilization.
3Object-affected harmful factors
If frequency channels are assigned to maximize non-overlap with adjacent cells, then radio wave interference decreases, but the complexity of frequency management increases
Solution Approach 1:
Each base station autonomously determines its frequency hopping pattern based on its cell number and the predetermined rules, without requiring centralized frequency management. The system implements self-service by allowing each base station to independently calculate and follow its hopping pattern, which automatically ensures non-overlapping frequencies with adjacent cells while reducing the complexity of centralized frequency management.
Data Source
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AI summary
A wireless communication apparatus (1A, 2A) includes a channel-usage selection unit (15) to select one frequency channel for each time slot from a plurality of predetermined candidate frequency channels, and a wireless communication unit (12) to perform wireless communication by using the frequency channel selected by the channel-usage selection unit. The channel-usage selection unit (15) selects a frequency channel that is different from a frequency channel to be used in a same time slot by an adjacent cell located at a cell interval, equal to or smaller than the predetermined first number of cells, from a cell used for the wireless communication, and allows the frequency channel selected to overlap with the frequency channel to be used in the same time slot by a remote cell located at a cell interval, greater than the first number of cells and equal to or smaller than the number of the candidate frequency channels, from a cell used for the wireless communication.