Mobile Station HARQ Threshold Control for Diversity Handover
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Solution Overview
Problem
In mobile communication systems employing diversity handover, the introduction of Hybrid Automatic Repeat Request (HARQ) retransmission does not adequately reduce delay caused by retransmissions, leading to deterioration in radio transmission efficiency due to frequent Radio Link Control (RLC) retransmissions.
Innovation Solution
A mobile station with a retransmission control section performing HARQ retransmission control in the physical layer and MAC sublayer, and a threshold setting section that adjusts the acknowledgement signal threshold based on the number of connected radio base stations, optimizing transmission power to minimize RLC retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If HARQ retransmission is introduced in EUL with diversity handover, then retransmission speed is improved, but RLC retransmission frequency increases due to control signal errors
Solution Approach 1:
The patent changes the threshold parameter used for determining acknowledgement signal presence based on the number of connected radio base stations. When multiple base stations are connected (diversity handover), a different threshold is applied to account for the increased probability of control signal errors, thereby resolving the contradiction between fast retransmission and error control
Solution Approach 2:
The threshold is made dynamic rather than fixed, adapting automatically based on the number of connected radio base stations. This dynamic adjustment allows the system to optimize performance for different handover scenarios, maintaining reliability while preserving the speed benefits of HARQ
2Reliability
If diversity handover is employed in EUL, then connection reliability is improved, but RLC retransmission frequency increases
Solution Approach 1:
By changing the threshold parameter based on the number of connected base stations, the patent reduces unnecessary RLC retransmissions that occur during diversity handover, thereby reducing retransmission delay while maintaining connection reliability
Solution Approach 2:
The system uses feedback about the number of connected radio base stations to dynamically adjust the threshold, creating a closed-loop control mechanism that optimizes retransmission behavior for current network conditions and prevents excessive RLC retransmissions
3Device complexity
If fixed threshold is used for acknowledgement signal determination, then device complexity is reduced, but radio transmission efficiency deteriorates under diversity handover
Solution Approach 1:
The threshold is made dynamic based on the number of connected radio base stations, improving radio transmission efficiency during diversity handover while maintaining relatively simple implementation by using a straightforward conditional adjustment rule
Data Source
AI summary
A mobile station includes; a retransmission control section configured to perform retransmission control of user data in a physical layer and a MAC sublayer with one or more radio base stations; and a threshold setting section configured to set a threshold used for determining presence or absence of an acknowledgement signal of the user data, according to the number of the radio base stations to which the mobile station connects.