Selective Retransmission Feedback for HARQ Outage Tolerance
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Solution Overview
Problem
Current 5G NR systems face challenges with HARQ outages and data reception continuity due to mismatched propagation delay and Soft Buffer dimensioning, especially in non-terrestrial communication systems.
Innovation Solution
The proposed Selective Retransmission Protocol allows UEs to group Retransmission Request (RTQ) feedback information bits for multiple transport blocks, enabling the non-terrestrial transmit receive point (NT-TRP) to selectively retransmit blocks that were not decoded properly, thus reducing the need for continuous acknowledgement waiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple parallel HARQ processes are used to ensure continuous data reception, then data reception continuity is improved, but device complexity and power consumption increase due to the need to dimension and manage multiple processes
Solution Approach 1:
The patent extracts and removes the need for multiple parallel HARQ processes by implementing a single HARQ process with selective retransmission. The base station transmits multiple transport blocks using the same HARQ process ID, and the UE selectively requests retransmission of only failed blocks, eliminating the complexity of managing multiple parallel processes while maintaining continuous data reception.
Solution Approach 2:
The single HARQ process is made multi-functional by enabling it to handle multiple transport blocks sequentially. The same HARQ process ID is reused across different transport blocks, allowing one process to perform the work of multiple processes through selective retransmission requests, thereby reducing overall system complexity.
2Measurement precision
If feedback is transmitted for all transport blocks, then decoding accuracy is improved, but uplink power consumption and feedback payload size increase
Solution Approach 1:
The patent extracts and transmits only the essential feedback information - specifically, indicators for failed transport blocks - rather than feedback for all blocks. The UE generates feedback information bits that identify which transport blocks failed decoding, and the base station retransmits only those specific blocks, reducing uplink power consumption while maintaining decoding accuracy.
Solution Approach 2:
Instead of providing complete feedback for all transport blocks, the patent uses partial feedback action by only reporting failed blocks. This selective feedback approach reduces the feedback payload size and uplink power consumption while still enabling the base station to identify and retransmit only the necessary blocks for maintaining decoding accuracy.
3Loss of time
If the number of HARQ processes is dimensioned to match round-trip time, then delay tolerance is improved, but productivity decreases due to HARQ outages and bottlenecking from Soft Buffer mismatch
Solution Approach 1:
The patent enables continuous data reception by implementing selective retransmission within a single HARQ process. When transport blocks are successfully decoded, the UE can immediately request the next block without waiting for retransmission acknowledgments, maintaining continuous useful action. This eliminates HARQ outages and bottlenecking while preserving delay tolerance.
Solution Approach 2:
The base station pre-transmits multiple transport blocks using the same HARQ process ID before receiving feedback. This preliminary action allows the UE to decode successful blocks immediately and generate selective retransmission requests only for failed blocks, improving productivity by eliminating waiting periods while maintaining delay tolerance through the pre-sent blocks.
Data Source
AI summary
In aspects of a Selective Retransmission Request (SeRQ) protocol proposed herein for wireless communication, a UE may group Retransmission Request (RTQ) feedback information bits for a plurality of transport blocks (TBs). The RTQ feedback information may be understood to indicate, to a non-terrestrial transmit receive point (NT-TRP), which TBs, among the plurality of TBs in the window, were not decoded properly. UEs may generate RTQ feedback information bits for a group of TBs received during a single window or TBs that have been received during multiple, distinct windows. The generation, by the UEs, of the RTQ feedback information bits for a group of TBs may be encoded based on, e.g., source coding, codebooks, binomial coefficients, etc. Upon receipt of a retransmitted version of a given TB, the UE may combine previously received bits of the given TB with the retransmitted TB version of the given TB.