NTN HARQ Retransmission Scheme Indication via LCP
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Solution Overview
Problem
In non-terrestrial communication networks, long communication delays due to distance lead to HARQ stalling and reduced throughput, necessitating innovative retransmission schemes to reduce latency and improve peak throughput.
Innovation Solution
The implementation of a mechanism to indicate and manage hybrid automatic repeat request (HARQ) retransmission schemes through logical channel prioritization (LCP) and radio resource control (RRC) signaling, allowing for dynamic scheduling and configuration of HARQ processes with different retransmission schemes, such as no retransmissions, blind retransmissions, or retransmissions based on decoding results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If HARQ retransmissions are disabled for NTN, then HARQ process ID can be reused before full HARQ RTT has elapsed to avoid HARQ stalling and reduce transmission latency, but reliability of data transmission deteriorates due to loss of retransmission capability
Solution Approach 1:
The patent applies dynamics by making the HARQ retransmission behavior configurable and adaptable rather than fixed. The network can dynamically select between different HARQ retransmission schemes (enabled, disabled, or selective) based on channel conditions, service requirements, and latency constraints. This allows the system to optimize between reliability and latency by adjusting the retransmission strategy in real-time, resolving the contradiction by making the feature flexible rather than static.
Solution Approach 2:
The patent changes the parameter of HARQ retransmission behavior from a binary state (enabled/disabled) to a multi-state configurable parameter. By introducing different HARQ retransmission schemes that can be selected and configured through RRC signaling, the system can adjust the retransmission parameter according to specific service requirements, thereby resolving the contradiction between reliability and latency for different use cases.
2Reliability
If HARQ retransmissions are enabled for NTN, then reliability of data transmission is improved, but transmission latency increases due to waiting for full HARQ RTT before reusing HARQ process ID
Solution Approach 1:
The patent resolves this contradiction by enabling dynamic selection of HARQ retransmission schemes. Instead of always enabling HARQ retransmissions, the network can dynamically choose to disable them or use selective retransmission based on current channel conditions and service requirements, thereby reducing latency when high reliability is not critical while maintaining reliability when needed.
Solution Approach 2:
The patent introduces configurable parameters that allow the system to adjust HARQ retransmission behavior. By changing the retransmission parameter from always-enabled to conditionally-enabled or disabled, the system can optimize for lower latency in scenarios where reliability can be maintained through other means, thus resolving the contradiction.
3Adaptability or versatility
If multiple HARQ retransmission schemes are supported for different logical channels, then scheduling flexibility is enhanced and peak throughput is improved, but device complexity increases due to multiple configuration and indication mechanisms
Solution Approach 1:
The patent applies segmentation by associating different HARQ retransmission schemes with different logical channels or logical channel groups. Each LCH or LCG can be independently configured with its own HARQ retransmission scheme, allowing fine-grained control without requiring complex global configuration. This segmentation reduces overall system complexity by breaking down the configuration into manageable, independent units.
Solution Approach 2:
The patent creates a universal configuration mechanism that can handle multiple HARQ retransmission schemes through a unified RRC signaling approach. The same signaling framework is used to configure different schemes for different LCHs/LCGs, providing multi-functionality without requiring separate configuration mechanisms for each scheme, thereby reducing complexity while maintaining versatility.
Data Source
AI summary
This disclosure presents solutions for a communication system of a non-terrestrial network (NTN) node and a user equipment (UE) to determine, where the NTN node can determine one or more HARQ retransmission schemes for one or more LCHs used by the UE. The HARQ retransmission scheme can be mapped into one, two, or five bits of the DCI signal, depending on the mapping algorithm selected. In some example embodiments. LCHs can be grouped by using similar LCH prioritization or similar HARQ retransmission schemes. HARQ retransmission schemes can be mapped to the LCG. If there remains sufficient data space in the TBS/UL, other LCH can be included into the transmission even though the other LCH utilize different HARQ retransmission schemes. The UE can encode its HARQ transmission using the HARQ retransmission scheme indicated for the LCH the UE is utilizing.