Relay Node HARQ Using Compress-and-Forward Nested Quantization
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Solution Overview
Problem
The Hybrid Automatic Repeat Request (HARQ) technique in relay wireless communication systems using the Compress-and-Forward (CF) scheme experiences significant delay due to the need for end-to-end HARQ processing, especially when channel uncertainty occurs between relay and destination nodes, leading to increased processing and transmission delays.
Innovation Solution
A hybrid automatic repeat request method that employs nested quantization to compress data, transmitting the most significant part of the quantized information initially and retransmitting the residual part when a negative acknowledgement (NACK) is received, with channel coding adapted for each transmission to optimize channel efficiency and reduce delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If end-to-end HARQ processing is used in CF scheme relay systems, then data transmission reliability is improved, but HARQ processing delay increases significantly
Solution Approach 1:
The patent segments the quantized data into multiple parts (most significant part and residual part) and transmits them separately. The relay node performs partial decoding on the most significant part immediately, while the residual part is transmitted later. This segmentation allows the system to achieve reliable data transmission through incremental decoding while reducing HARQ processing delay by avoiding waiting for complete data reception before starting decoding operations.
2Productivity
If complete data compression is performed before transmission, then transmission efficiency is improved, but decoding complexity at the relay node increases
Solution Approach 1:
The patent divides the compressed quantized data into a most significant part and a residual part. The relay node only needs to decode the most significant part initially, which has lower complexity, while the complete data compression is maintained for transmission efficiency. The residual part is decoded later if needed, thus balancing transmission efficiency with manageable decoding complexity at the relay node.
3Speed
If all quantized data is transmitted in one packet, then transmission speed is improved, but error propagation risk increases under channel uncertainty
Solution Approach 1:
The patent segments quantized data into a most significant part transmitted in the first packet and a residual part transmitted in subsequent packets. This segmentation allows the destination node to perform incremental decoding, reducing error propagation risk under channel uncertainty while maintaining transmission speed. If the first packet contains errors, the system can request retransmission of only the affected parts rather than the entire data set.
Solution Approach 2:
The patent transmits the most significant part of the quantized data first, allowing the destination node to perform preliminary decoding and assessment before receiving the complete data. This preliminary action enables early error detection and facilitates faster retransmission requests if needed, reducing the impact of channel uncertainty while maintaining overall transmission speed.
Data Source
AI summary
The present disclosure relates to a 5G or pre-5G communication system which will be provided in order to support a higher data transmission rate than in 4G communication systems such as LTE. A method at a relay node according to one example of the present invention is a hybrid automatic repeat request method at the relay node in a relay wireless communication system using a compress-and-forward (CF) scheme, and may comprise the steps of: when receiving data from a previous node, performing mesh quantization so as to have redundant information at the time of quantization for transmitting, to a next node, the data received from the previous node; transmitting to the next node by channel-coding only an amount transmittable to a channel set for transmitting to the next node from upper information among the quantized information; and when receiving negative acknowledgement (NACK) from the next node, retransmitting to the next node by channel-coding only an amount transmittable to the set channel among the other information which is not transmitted among the quantized information.