Cross-Block Check Blocks for UE-Cooperative HARQ Retransmission
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Solution Overview
Problem
Conventional HARQ schemes are inefficient for multicast and broadcast communications due to significant feedback overhead, while fountain codes suffer from increased latency and performance degradation in non-erasure channels.
Innovation Solution
Implement a cross-block HARQ scheme with UE cooperation, using cross-block check blocks for retransmissions to enhance reliability and efficiency, allowing UEs to assist each other in decoding without relying on network nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional HARQ schemes are used for multicast and broadcast communications, then feedback overhead is significantly increased, but transmission reliability is improved
Solution Approach 1:
The patent extracts the feedback mechanism from the traditional BS-centric HARQ process and relocates it to UE-level operations. UEs independently generate ACK/NACK feedback and perform retransmissions without requiring centralized BS coordination, thereby eliminating the excessive feedback overhead while maintaining reliability through distributed error correction
Solution Approach 2:
UEs serve themselves by autonomously performing decoding, generating feedback, and executing retransmissions using stored packets. This self-service mechanism eliminates the need for BS-mediated feedback and retransmission coordination, significantly reducing feedback overhead while maintaining transmission reliability through autonomous error correction
2Loss of information
If fountain codes are used for error correction in multicast and broadcast, then feedback is not required, but latency is increased and performance deteriorates in non-erasure channels
Solution Approach 1:
The patent implements a dynamic retransmission mechanism where UEs adaptively determine whether to request retransmissions based on decoding outcomes. This dynamic approach combines the feedback-less advantage of fountain codes with the efficiency of HARQ retransmissions, reducing latency by avoiding unnecessary retransmissions while maintaining reliability through on-demand error correction
Solution Approach 2:
The system changes the operational parameters of error correction by switching between fountain code decoding and HARQ-based retransmission based on channel conditions and decoding success. This parameter adaptation allows the system to achieve low latency in good conditions while maintaining robustness in poor conditions, overcoming the fixed-latency limitation of pure fountain codes
3Measurement precision
If conventional HARQ requires indices of erroneous code blocks to be communicated back to the transmitter, then transmission accuracy is improved, but efficiency decreases when different CBs are in error at each receiver
Solution Approach 1:
The patent makes the feedback mechanism universal by having all UEs transmit ACK/NACK for any erroneous packet regardless of which specific CBs are affected. This universal feedback approach eliminates the need for precise error indexing while maintaining retransmission efficiency, as the BS retransmits the entire packet which benefits all UEs with errors
Data Source
AI summary
Methods and apparatuses for UE cooperation in a retransmission scheme using cross-block check blocks are described. A first receiver node receives an initial transmission from a first transmitter node that includes a plurality of code blocks. The first receiver node decodes the plurality of code blocks. The first receiver node generates one or more cross-block check blocks using bits selected from across the plurality of code blocks. The first receiver node transmits, in a retransmission, at least one cross-block check block to a second receiver node, where the first receiver node and the second receiver node are both intended recipients of the initial transmission.