NTN HARQ Feedback Control for Long-Delay Downlink Synchronization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenges of downlink synchronization and HARQ transmission in non-terrestrial networks (NTN) due to long propagation delays and significant Doppler shifts, which impact the effectiveness of existing PRACH preamble formats and HARQ processes in 5G communication systems.
Innovation Solution
Enhancements to PRACH preamble formats and methods to disable HARQ feedback in specific scenarios, including new PRACH preamble sequence lengths and sub-carrier spacings, and managing HARQ processes to accommodate large cell sizes and propagation delays in NTN.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing PRACH preamble formats and HARQ processes are used in NTN, then standard 5G communication protocols are maintained, but downlink synchronization and HARQ transmission effectiveness deteriorate due to long propagation delays and significant Doppler shifts
Solution Approach 1:
The patent modifies PRACH preamble parameters including sequence lengths (839, 139, 1151, 2297, 4603, 8191, 16383, 32767) and sub-carrier spacings (1.25kHz, 5kHz, 15kHz, 30kHz, 60kHz, 120kHz, 240kHz, 480kHz) to accommodate long propagation delays and Doppler shifts in NTN environments, thereby improving synchronization reliability without requiring completely new protocols
Solution Approach 2:
The patent introduces dynamic HARQ process management where the network can disable HARQ feedback in specific scenarios through DCI signaling, allowing the system to adapt HARQ behavior based on current propagation conditions and mobility levels, thus maintaining reliability while reducing time loss in challenging NTN scenarios
2Reliability
If HARQ feedback is enabled in NTN, then transmission reliability is improved, but system complexity and processing overhead increase due to long round trip times
Solution Approach 1:
The patent implements dynamic HARQ feedback control where the network can enable or disable HARQ feedback based on current propagation conditions, mobility levels, and traffic requirements through DCI signaling, allowing flexible adaptation between reliable HARQ operation and simplified no-HARQ operation to balance reliability and complexity
Solution Approach 2:
The patent applies HARQ feedback selectively in specific time-frequency resources and for specific users based on their propagation conditions, rather than uniformly enabling HARQ for all transmissions, thus reducing overall system complexity while maintaining reliability where needed
3Adaptability or versatility
If DCI format is extended to include HARQ feedback disable indication, then HARQ management flexibility is improved, but DCI message size and processing complexity increase
Solution Approach 1:
The patent utilizes existing reserved bits in DCI formats (such as the 2 reserved bits in DCI format 1_1 and 1 bit in DCI format 1_2) to convey HARQ feedback disable indication, avoiding the need to significantly expand DCI message size while still providing the necessary control flexibility
Solution Approach 2:
The patent makes existing DCI reserved fields multi-functional by using them to indicate HARQ feedback disable status in addition to their traditional purposes, thereby achieving enhanced HARQ management flexibility without increasing overall DCI processing complexity
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
A user equipment (UE), a base station, and a method for managing hybrid automatic repeat request (HARQ) feedback for downlink synchronization. The UE includes at least one transceiver configured to receive downlink control information (DCI) in a physical downlink control channel (PDCCH), and at least one processor operably connected to the at least one transceiver. The at least one processor is configured to determine, based on a first field in the DCI, whether a hybrid automatic repeat request (HARQ) feedback is disabled, and determine, if the HARQ feedback is disabled, a second field in the DCI to be one of a reserved field or a zero bitwidth field based on a format of the DCI.