Cell Selection Threshold Adjustment for Obstructed Coverage
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Solution Overview
Problem
Existing cell selection and reselection processes in terminal devices fail to ensure normal communication when signal coverage is obstructed, leading to low received signal communication parameter values and inability to meet communication requirements in environments like buildings or basements.
Innovation Solution
A terminal device with measurement and setting units to determine if the received signal communication parameter value is greater than or less than specific thresholds, adjusting cell selection based on these measurements and broadcast message parameters, including thresholds, offsets, and hysteresis to set the appropriate serving cell, and sending update messages to the base station for mobility management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal device uses existing cell selection criteria (criterion S) to select a serving cell, then the cell selection process is simple and fast, but the terminal device cannot communicate normally in obstructed environments (buildings, basements) where received signal strength is low
Solution Approach 1:
The patent introduces a coverage enhancement level parameter that can take multiple values (first level, second level, third level). By changing this parameter, the terminal device can switch between different cell selection criteria: criterion S for normal coverage, criterion S_ce for enhanced coverage, and criterion R for cell reselection. This allows the system to adapt to obstructed environments by selecting appropriate parameters without fundamentally changing the selection mechanism.
Solution Approach 2:
The patent makes the cell selection criterion dynamic by allowing the terminal device to determine the coverage enhancement level based on measured signal parameters (received signal strength, received signal quality) and select different criteria accordingly. The system transitions from static criterion S to a dynamic selection process that adapts to environmental conditions, enabling normal communication in obstructed areas while maintaining simplicity in normal conditions.
2Reliability
If the terminal device repeatedly measures and reselects cells in obstructed environments, then communication reliability may improve, but ping-pong effects occur causing excessive reselection and communication instability
Solution Approach 1:
The patent applies hysteresis mechanisms as a cushioning measure against ping-pong effects. When selecting cells using criterion R, the system incorporates hysteresis margins that prevent immediate reselection when signal conditions fluctuate near threshold values. This beforehand cushioning stabilizes the cell selection process in obstructed environments by requiring more significant signal changes before triggering reselection, thereby reducing unnecessary reselection cycles and communication interruptions.
3Reliability
If the terminal device scans all available radio frequency channels to find the best cell, then comprehensive cell coverage is achieved, but the cell selection time increases significantly
Solution Approach 1:
The patent segments the cell selection process into different stages based on coverage enhancement levels. Instead of always scanning all channels comprehensively, the system first attempts cell selection using criterion S (faster, less comprehensive). Only when this fails and coverage enhancement is detected does the system proceed to more comprehensive scanning with criterion S_ce or criterion R. This segmentation maintains comprehensiveness when needed while reducing time in normal conditions.
Solution Approach 2:
The patent performs preliminary cell selection using the simpler criterion S before attempting more comprehensive selection methods. The terminal device first tries to camp on a cell using standard criteria, and only if this preliminary action fails (indicating obstructed environment) does it proceed to enhanced coverage cell selection with more comprehensive scanning. This preliminary action approach achieves comprehensiveness only when necessary, reducing overall selection time.
Data Source
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AI summary
Embodiments of the present invention relate to the communications field, and provide an apparatus, a method, and a system for cell selection, so that a terminal device can communicate normally. The method includes: measuring a received signal communication parameter value of a first cell; determining whether the communication parameter value is greater than a first threshold; if the communication parameter value is less than or equal to the first threshold, obtaining a second threshold; determining whether the communication parameter value is greater than the second threshold; and if the communication parameter value is greater than the second threshold, setting the first cell as a serving cell of the terminal device. The apparatus, the method, and the system for cell selection provided in the embodiments of the present invention are used to select a cell.