PUSCH Transmission Scheduling with LBT Failure Handling in 5G NR-U
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Solution Overview
Problem
In 5G NR-U systems operating in unlicensed spectrum, the listen-before-talk (LBT) procedure often fails, leading to inefficiencies in scheduling multiple consecutive PUSCH transmissions, as existing solutions do not adequately handle channel access priority and cyclic prefix extensions for subsequent transmissions after a failed LBT.
Innovation Solution
The proposed solution involves continuing or restarting the LBT operation based on the indicated LBT type and channel access priority class for subsequent PUSCH transmissions, with specific cyclic prefix extensions applied to ensure efficient operation and minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LBT procedure is performed before each PUSCH transmission in unlicensed spectrum, then channel access reliability is improved, but transmission efficiency deteriorates due to multiple LBT failures and retransmission delays
Solution Approach 1:
The patent applies preliminary action by performing LBT procedure once before a group of consecutive PUSCH transmissions instead of before each individual transmission. The gNB schedules multiple PUSCH transmissions in advance, and the UE performs LBT once at the beginning of the scheduled group, determining the LBT result applies to all subsequent transmissions in that group. This preliminary LBT action resolves the contradiction by ensuring channel access reliability for the group while avoiding repeated LBT procedures that would reduce transmission efficiency.
Solution Approach 2:
The patent merges multiple LBT procedures into a single LBT operation that covers a group of consecutive PUSCH transmissions. By combining the channel access decision for multiple transmissions into one LBT event, the system maintains reliability (the LBT result governs all transmissions in the group) while improving efficiency (only one LBT procedure instead of multiple). This merging principle directly addresses the technical contradiction between reliability and productivity.
2Productivity
If multiple consecutive PUSCH transmissions are scheduled by a single DCI, then scheduling efficiency is improved, but complexity of handling LBT failures and cyclic prefix extensions increases
Solution Approach 1:
The patent uses preliminary action by having the gNB pre-configure LBT failure handling parameters and cyclic prefix extension settings in the DCI before transmissions occur. When LBT fails, the UE follows pre-defined rules established in advance, such as applying cyclic prefix extensions to subsequent transmissions or adjusting the number of transmissions based on pre-configured parameters. This preliminary configuration reduces real-time decision complexity while maintaining scheduling efficiency.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting transmission parameters such as cyclic prefix length, number of repetitions, and time offsets based on LBT outcomes and channel conditions. The gNB can modify these parameters in subsequent DCIs or RRC configurations based on observed LBT failure patterns, allowing the system to adapt to unlicensed spectrum characteristics while managing complexity through standardized parameter sets defined in specifications.
3Reliability
If LBT operation is restarted for each subsequent PUSCH after failure, then channel access reliability is improved, but power consumption increases due to repeated LBT procedures
Solution Approach 1:
The patent merges multiple LBT operations into a single LBT procedure that covers a group of consecutive PUSCH transmissions. By combining the channel access attempt for multiple transmissions into one LBT event, the system maintains reliability (the single LBT result applies to all transmissions in the group) while reducing power consumption (only one LBT procedure instead of multiple). This merging principle directly addresses the contradiction between reliability and energy efficiency.
Solution Approach 2:
The patent applies continuity of useful action by maintaining the LBT result validity across multiple consecutive transmissions within a scheduled group. Once LBT succeeds for the group, the transmission action continues without interruption or repeated LBT procedures, allowing the UE to efficiently transmit multiple PUSCHs back-to-back. This continuous transmission approach preserves reliability while minimizing the energy expenditure associated with repeated LBT operations.
Data Source
AI summary
The present disclosure is related to listen-before-talk (LBT) operations for multiple consecutive physical uplink shared channel (PUSCH) transmissions scheduled by a single downlink control information (DCI) or multiple DCIs. In a fifth generation (5G)/new radio (NR) system operating in an unlicensed spectrum, when multiple physical uplink shared channel (PUSCH) transmissions are scheduled (e.g., by one or more DCIs), and if LBT operation has failed before the start of a first PUSCH transmission of the multiple PUSCH transmissions, an LBT type and cyclic prefix (CP) extension for a subsequent PUSCH transmission of the multiple PUSCH transmissions is determined. In some examples, the multiple PUSCH transmissions are consecutive PUSCH transmission. Other embodiments may be described and/or claimed.