Buffer Partitioning for HARQ Reliability in UL-DL Config Changes
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Solution Overview
Problem
In 3GPP LTE systems, changing the UL-DL configuration can lead to interference and deterioration of HARQ retransmission performance due to incomplete ACK signals and varying IR buffer sizes, especially when switching between different UL-DL configurations.
Innovation Solution
A terminal apparatus that divides its buffer into regions based on the maximum number of retransmission processes defined in different configuration patterns, ensuring consistent data reading and transmission before and after a UL-DL configuration change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UL-DL configuration is changed to adapt to varying traffic conditions, then the adaptability of the communication system is improved, but interference between uplink and downlink communications occurs and HARQ retransmission performance deteriorates
Solution Approach 1:
The soft buffer is divided into multiple HARQ process buffers, each dedicated to a specific HARQ process. This segmentation allows independent management of data for different retransmission processes, preventing interference between processes when UL-DL configuration changes occur. Each buffer can be independently cleared or retained based on the specific HARQ process state, maintaining reliability while enabling configuration adaptability.
Solution Approach 2:
The terminal apparatus determines in advance which HARQ process buffers to clear based on the current UL-DL configuration and the maximum number of HARQ processes supported. By preliminarily identifying and clearing only the necessary buffers before configuration change, the system avoids unnecessary data loss and maintains ongoing HARQ retransmission operations, thus preserving reliability during adaptive configuration changes.
2Adaptability or versatility
If the buffer size is increased to support more HARQ processes, then the capability to handle retransmission is improved, but the device complexity increases
Solution Approach 1:
The buffer allocation is made dynamic rather than static. The terminal apparatus determines the number of HARQ process buffers to allocate based on the current UL-DL configuration and the maximum number of HARQ processes supported by the system. This dynamic allocation allows the system to adapt the buffer structure to actual operational requirements, supporting more HARQ processes when needed while avoiding excessive buffer allocation and associated complexity during normal operation.
Solution Approach 2:
The system changes the parameter of buffer allocation based on the UL-DL configuration. By adjusting the number of HARQ process buffers according to the maximum number of HARQ processes defined in the current configuration, the system optimizes resource utilization. This parameter change approach allows the system to handle varying HARQ process capacities without maintaining a fixed, overly complex buffer structure for all possible scenarios.
3Object-affected harmful factors
If the terminal clears all HARQ process buffers when UL-DL configuration changes, then the interference is avoided, but the data reading accuracy and retransmission continuity are lost
Solution Approach 1:
Instead of uniformly clearing all HARQ process buffers, the terminal applies local quality by selectively clearing only the specific buffers corresponding to HARQ processes that are no longer valid under the new UL-DL configuration. This selective clearing approach maintains data integrity for ongoing HARQ processes while eliminating interference from completed processes, thus preserving data reading accuracy and retransmission continuity where needed.
Solution Approach 2:
The terminal apparatus uses feedback from the UL-DL configuration change to determine which HARQ process buffers should be cleared. By analyzing the configuration change parameters and comparing them with the current HARQ process states, the terminal identifies the precise set of buffers that need to be cleared to avoid interference. This feedback-based approach ensures that only necessary buffers are cleared, maintaining data accuracy for active retransmission processes while preventing UL-DL interference.
Data Source
AI summary
Provided is a terminal device with which deterioration in hybrid automatic repeat request (HARQ) retransmission performance can be inhibited by continuing a downlink (DL) HARQ process for DL data before and after changing the uplink link-DL configuration. In this device, a decoder stores, in a retransmission buffer, DL data transmitted from a base station, and decodes the DL data, and a wireless transmitter transmits a response signal generated using a DL-data-error detection result. A soft buffer is partitioned into a plurality of regions for each retransmission process on the basis of the highest values among retransmission process numbers respectively stated in a plurality of configuration patterns which can be set in the terminal.