Directional LBT Beam Alignment for Unlicensed Spectrum Efficiency
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Solution Overview
Problem
In wireless communication systems, particularly in Unlicensed Spectrum above 52.6 GHz, the directional Listen Before Talk (LBT) technique for beam-based signal transmission is uncertain, making it challenging to predict successful beam directions for CSI measurement and channel access, leading to inefficiencies in spectrum multiplexing and transmission performance.
Innovation Solution
A method involving a first node that receives signaling to determine reference signal resource groups, allowing it to perform channel sensing operations based on spatial correlation, switching between LBT types (Cat 2 and Cat 4) to align with successful beam directions, thereby optimizing beam alignment and reducing transmission overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If directional LBT is used for beam-based signal transmission in Unlicensed Spectrum, then interference avoidance is improved, but transmission uncertainty increases due to inability to predict successful beam directions
Solution Approach 1:
The gNB performs downlink directional LBT and determines successful beam directions in advance before uplink transmission. The gNB notifies the UE of these pre-determined successful beam directions through signaling, allowing the UE to perform uplink directional LBT with known good directions, thereby reducing transmission uncertainty while maintaining interference avoidance benefits
Solution Approach 2:
The gNB provides feedback to the UE about which beam directions were successful in downlink LBT. This feedback mechanism allows the UE to adjust its uplink transmission strategy based on confirmed successful directions, resolving the uncertainty problem while preserving the interference avoidance advantage of directional LBT
2Object-affected harmful factors
If Cat 4 LBT is used for channel access, then collision avoidance is improved, but transmission delay increases due to uncertain backoff duration
Solution Approach 1:
The system dynamically switches between Cat 4 LBT and Cat 2 LBT based on channel conditions and beam direction success. When directional LBT succeeds and beam directions are confirmed, the system transitions to Cat 2 LBT for faster channel access. This dynamic adaptation maintains collision avoidance where needed while reducing transmission delay when conditions permit
Solution Approach 2:
The LBT category parameter is changed from fixed Cat 4 to a variable that can switch between Cat 4 and Cat 2. This parameter change allows the system to adapt the channel access mechanism to current conditions, achieving both collision avoidance and reduced transmission delay by selecting the appropriate LBT type based on directional LBT success and channel state
3Strength
If beam-based transmission is used to enhance coverage, then signal strength is improved, but system complexity increases due to multiple SSBs and CSI-RS requirements
Solution Approach 1:
The successful beam directions determined through downlink directional LBT and reference signal measurements are used for multiple purposes: downlink transmission, uplink transmission, and channel access. This multi-functionality reduces the need for separate beam management procedures and signaling, thereby reducing system complexity while maintaining enhanced signal strength through beam-based transmission
4Productivity
If spatial correlation is used to determine LBT type, then spectrum utilization is improved, but measurement and detection difficulty increases
Solution Approach 1:
The gNB acts as an intermediary that performs the complex spatial correlation measurements and LBT type determination. The gNB measures spatial correlation between downlink and uplink channels, determines successful beam directions, and provides this information to the UE. This intermediary approach enables improved spectrum utilization through spatial correlation while reducing the measurement and detection burden on the UE
Data Source
AI summary
The present application discloses a method and a device in nodes used for wireless communications. The first node receives a first signaling and a second signaling; and performs a first channel sensing operation on a first sub-band; and transmits a first radio signal in a first time-frequency resource group on the first sub-band, or, drops transmitting a first radio signal in a first time-frequency resource group on the first sub-band. Herein, the first signaling is used to determine a first reference signal resource group, the first signaling being non-unicast; the second signaling indicates a second reference signal resource group; when the first time-frequency resource group belongs to a first time window in time domain. With the method provided in the present application, the type of channel sensing operation can be determined according to spatial parameters of a radio signal, which helps enhance the transmission opportunity and reduce the overhead.