Soft Buffer Management in Hybrid ARQ Systems
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Solution Overview
Problem
In hybrid ARQ systems with soft combining, insufficient soft buffer memory in mobile terminal apparatuses leads to deterioration of transmission characteristics during data transmission.
Innovation Solution
The communication control method involves channel coding and rate matching of information bits, with the base station discarding parity bits based on the mobile terminal's soft buffer size to ensure that only necessary parity bits are transmitted, and the mobile terminal discards and stores received data accordingly to maintain transmission reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soft buffer memory size is increased in mobile terminal apparatus, then transmission characteristics are improved, but device complexity and cost increase
Solution Approach 1:
The patent applies partial action by having the mobile terminal apparatus discard a portion of the received parity bits when the soft buffer memory is insufficient. Instead of requiring full parity bit storage to achieve optimal transmission characteristics, the system selectively retains only the necessary portion of parity bits that contribute most significantly to decoding reliability, thereby reducing the memory burden while maintaining acceptable transmission performance
Solution Approach 2:
The patent changes the parameter of parity bit retention ratio based on the available soft buffer memory size. When buffer memory is sufficient, all parity bits are retained; when buffer memory is insufficient, the system dynamically adjusts the number of retained parity bits to match the available buffer capacity, optimizing the trade-off between transmission characteristics and device constraints
2Reliability
If all parity bits are transmitted to mobile terminal apparatus, then decoding reliability is improved, but transmission efficiency decreases when soft buffer memory is insufficient
Solution Approach 1:
The patent extracts and transmits only the necessary portion of parity bits to the mobile terminal apparatus based on its soft buffer memory capacity. The base station determines the appropriate number of parity bits to transmit by considering the terminal's buffer size, thereby avoiding the transmission of redundant parity bits that would occupy valuable buffer space without contributing proportionally to decoding reliability, thus improving transmission efficiency
Solution Approach 2:
The system transmits a partial set of parity bits rather than the complete set, matching the transmission amount to the receiver's buffer capabilities. This partial transmission approach ensures that the transmitted parity bits are sufficient for acceptable decoding reliability while avoiding the excessive transmission that would waste radio resources and reduce overall system productivity
3Device complexity
If soft buffer memory is reduced in mobile terminal apparatus, then device complexity decreases, but transmission characteristics deteriorate
Solution Approach 1:
The patent enables mobile terminal apparatus with reduced soft buffer memory to achieve acceptable transmission characteristics by discarding a controlled portion of received parity bits. The terminal retains only the essential parity bits needed for decoding, using a discarding strategy that prioritizes maintaining transmission reliability while adapting to the constrained buffer size
Solution Approach 2:
The system adapts the parity bit retention parameter according to the available soft buffer memory size. When buffer memory is reduced, the terminal dynamically adjusts how many parity bits to retain and how many to discard, optimizing the balance between device complexity constraints and transmission characteristic requirements
Data Source
AI summary
The present invention is designated to reduce the deterioration of transmission characteristics upon data transmission, even when soft buffer memory for retransmission control is not sufficiently secured in a mobile terminal apparatus. The present invention provides the steps of, in a base station apparatus (eNB), performing channel coding of information bits (ST 802), performing a rate matching process for the coded bits after interleaving (ST 804), and transmitting transmission data to match the coded bit length after rate matching, to a mobile terminal apparatus (UE) (ST 806), and, in the mobile terminal apparatus (UE), receiving the transmission data (ST 807), performing channel decoding of the received data (ST 810), and discarding part of the received data in accordance with the size of the soft buffer memory in the mobile terminal apparatus (UE) and storing this in the soft buffer memory (ST 812 and ST 813).