Multi-Beam LBT for NR-U Hidden Node Mitigation
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Solution Overview
Problem
Directional Listen Before Talk (LBT) in unlicensed spectrum for New Radio (NR-U) causes a serious hidden node problem, with existing solutions failing to effectively mitigate interference from interfering nodes.
Innovation Solution
A data transmission method where a base station performs LBT operations on multiple beams, sending channel occupation request signals and receiving feedback signals to determine channel availability, allowing data transmission on beams with the most multiplexing users or largest transmission capacity, while maintaining counters for retry mechanisms and configurable time granularity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If directional LBT is implemented for NR-U, then transmission opportunities for NR-U are increased, but hidden node problem becomes more serious
Solution Approach 1:
The patent segments the LBT process into multiple stages: initial LBT in a first direction, and subsequent LBT in a second direction. This segmentation allows the system to perform directional channel sensing in different directions sequentially, enabling the base station to detect hidden nodes that would otherwise be undetectable in a single directional LBT approach, thus resolving the hidden node problem while maintaining increased transmission opportunities.
Solution Approach 2:
The patent introduces a spatial dimensionality change by performing LBT operations in multiple directions (first direction and second direction) rather than a single fixed direction. This multi-directional approach adds a dimensional aspect to the channel sensing process, enabling the system to detect interference from hidden nodes in different spatial directions while preserving the beam-based transmission advantages for NR-U.
2Device complexity
If LBT operation is performed in a single direction, then the process is simple, but transmission opportunities are limited
Solution Approach 1:
The patent divides the LBT operation into distinct segments: an initial LBT in a first direction followed by a second LBT in a different direction. This segmentation maintains relative simplicity in each individual LBT phase while collectively providing multiple transmission opportunities through sequential directional sensing, thus balancing complexity and productivity.
Solution Approach 2:
The patent implements periodic LBT actions by performing channel sensing in alternating directions (first direction, then second direction) in a sequential manner. This periodic execution of LBT in different directions creates multiple transmission opportunities over time while maintaining a regular, manageable pattern that does not excessively increase system complexity.
3Speed
If channel occupation request signal is sent without waiting for feedback, then transmission speed is fast, but channel access reliability is reduced
Solution Approach 1:
The patent incorporates a feedback mechanism where the base station sends a channel occupation request signal to the terminal and waits for a feedback signal indicating whether the channel can be occupied. This feedback loop ensures that the base station receives confirmation before initiating data transmission, thereby improving channel access reliability while maintaining efficient transmission speed through rapid one-way LBT operations in both directions.
Data Source
AI summary
Disclosed are a data transmission method and device. The data transmission method comprises: after executing an LBT operation in a direction corresponding to at least one beam, a base station sending to a terminal a channel occupation request signal to request channel occupation; and after receiving a signal indicating that a channel is allowed to be occupied, the base station transmitting data on the beam sending the channel occupation request signal. The signal feedback method comprises: the terminal receiving the channel occupation request signal sent to the terminal by the base station on the at least one beam, and the channel occupation request signal is a signal for requesting channel occupation; and after correctly receiving the channel occupation request signal, the terminal feeding back, on the beam on which the signal is received, to the base station the signal indicating that the channel is allowed to be occupied.