HARQ ACK/NACK Confirmation for NTN MAC CE Timing
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Solution Overview
Problem
Existing HARQ mechanisms in NR are ill-suited for non-terrestrial networks with large propagation delays, leading to inefficiencies and potential mismatches in HARQ feedback due to insufficient HARQ processes and increased propagation delays, which affect the reliability and throughput of communication systems.
Innovation Solution
Implementing a method where at least one HARQ process is configured with feedback enabled while others are disabled, and defining a revised timeline for applying activation/deactivation commands in Non-Terrestrial Networks (NTN) to ensure synchronized understanding between the UE and gNB, using a revised timeline for applying MAC CE commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ feedback is enabled for all HARQ processes in terrestrial networks, then communication reliability is maintained, but system complexity increases and feedback overhead grows in non-terrestrial networks with large propagation delays
Solution Approach 1:
The patent applies local quality by enabling HARQ feedback selectively for specific HARQ processes rather than uniformly for all processes. The gNB configures the UE with a subset of HARQ processes that have feedback enabled, allowing differentiated treatment based on local requirements of each HARQ process while reducing overall system complexity and feedback overhead in NTN environments with large propagation delays
Solution Approach 2:
The patent segments the HARQ feedback mechanism by dividing HARQ processes into two categories: those with feedback enabled and those with feedback disabled. This segmentation allows the system to manage HARQ processes independently based on their specific requirements, reducing the burden of managing feedback for all processes simultaneously in NTN scenarios
2Productivity
If the number of HARQ processes is increased to handle large propagation delays in NTN, then communication throughput is improved, but feedback timing synchronization between gNB and UE becomes difficult to maintain
Solution Approach 1:
The patent applies preliminary action by having the gNB pre-configure the UE with a specific subset of HARQ processes that have feedback enabled, along with pre-defining the feedback timing for these processes. This preliminary configuration establishes a synchronized understanding of which processes require feedback and when, before actual data transmission begins, thereby maintaining timing synchronization even with increased numbers of HARQ processes to handle large NTN propagation delays
Solution Approach 2:
The patent introduces dynamics by allowing the gNB to flexibly configure and adjust which HARQ processes have feedback enabled based on current network conditions and propagation delay characteristics. This dynamic configuration enables the system to adapt the number and selection of feedback-enabled processes to optimize throughput while maintaining synchronization, rather than using a fixed number of processes
3Loss of energy
If HARQ feedback is disabled for some HARQ processes to reduce overhead, then feedback overhead is reduced, but reliability of critical MAC CE command transmission is compromised
Solution Approach 1:
The patent applies feedback by enabling HARQ feedback specifically for HARQ processes that carry critical MAC CE commands, while disabling feedback for other non-critical processes. This selective feedback mechanism ensures that reliability is maintained for critical command transmissions while reducing overall feedback overhead by not requiring acknowledgments for less important data transmissions in NTN environments
Data Source
AI summary
Systems and methods for reliable Medium Access Control (MAC) Control Element (CE) ACK/NACK confirmation are provided. In some embodiments, a method performed by a wireless device includes: being configured with at least one feedback enabled Hybrid Automatic Repeat Request (HARQ) process while the remaining HARQ processes of the wireless device have feedback disabled; receiving an activation/deactivation command requiring feedback, where the receiving uses the at least one feedback enabled HARQ process; and/or transmitting feedback regarding the activation/deactivation command. In this way, the wireless device is enabled to send HARQ ACK/NACK feedback related to critical activation/deactivation MAC CE commands in a Non-Terrestrial Network (NTN). Furthermore, in the presence of large one way delay, this ensures that there is no mismatch between the base station and the wireless device as to when the wireless device can assume the activation/deactivation information in the MAC CE command can takes effect at the wireless device.