HARQ LLR Compression for Smaller Buffers and Reliable Retransmission
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Solution Overview
Problem
Existing HARQ systems face inefficiencies due to fixed compression schemes for Log Likelihood Ratios (LLRs) that result in sub-optimal buffer usage and degraded performance, particularly in varying modulation schemes.
Innovation Solution
Implementing an adaptive LLR compression scheme that optimizes buffer size and performance by using a mapping function based on the bit-index of soft bits, reducing the HARQ buffer size while maintaining network throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ is implemented for retransmission of downlink shared channel, then reliability of data transmission is improved, but device complexity increases due to additional processing requirements at both transmitter and receiver
Solution Approach 1:
The patent segments the HARQ process into distinct components: acknowledgment bits are separated into individual bits corresponding to different downlink shared channels, and the processing is divided into separate operations at transmitter and receiver. This segmentation allows for more manageable complexity while maintaining reliability through targeted retransmission of specific channels.
Solution Approach 2:
The patent implements feedback mechanisms where acknowledgment bits are transmitted from receiver to transmitter to indicate successful reception or need for retransmission. This feedback loop enables reliable data transmission by allowing the transmitter to adjust its behavior based on receiver status, while the feedback structure is designed to minimize added complexity through efficient bit utilization.
2Reliability
If multiple acknowledgment bits are transmitted for multiple downlink shared channels, then reliability is improved through selective retransmission, but loss of time increases due to additional transmission overhead
Solution Approach 1:
The patent applies partial action by transmitting only the necessary acknowledgment bits corresponding to specific downlink shared channels that require attention, rather than transmitting acknowledgment for all channels uniformly. This selective approach maintains reliability for affected channels while minimizing unnecessary transmission time for channels that are already successfully received.
Solution Approach 2:
The patent implements periodic acknowledgment transmission where acknowledgment bits are sent at specific intervals rather than continuously. This periodic action reduces transmission time overhead while maintaining reliable feedback about the status of downlink shared channels, allowing the system to balance reliability requirements with time efficiency.
Data Source
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AI summary
Some demonstrative embodiments may include an apparatus including a Hybrid Automatic Repeat Request (HARQ) buffer configured to buffer compressed Log Likelihood Ratio (LLR) values corresponding to an unsuccessfully-decoded transmission of a data block, a bit size of the HARQ buffer is equal to or less than 2.5 times a supported HARQ receive (Rx) size, which is to be reported to a transmitter of the data block; and a decoder configured to decode a retransmission of the data block according to the HARQ scheme based on combined LLR values, which are based on the compressed LLR values and on LLR values corresponding the retransmission of the data block, wherein a HARQ gain of decoding the retransmission of the data block based on the combined LLR values is at least 2 Decibel (dB) for an Additive White Gaussian Noise (AWGN) channel.