Sidelink Off-loading via Network-Controlled LBT in Unlicensed Bands
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing sidelink transmissions in unlicensed frequency bands, particularly in coordinating transmission opportunities and avoiding interference, which affects data rates and spectral efficiency.
Innovation Solution
The method involves a base station transmitting downlink control information associated with listen-before-talk (LBT) times to user equipment (UE), allowing the UE to determine sidelink transmission opportunities in unlicensed frequency bands, and utilizing a two-stage DCI technique for early or late access, along with cyclic prefix extensions and channel access priority configurations, to schedule contiguous transmissions and minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sidelink transmissions are performed in unlicensed frequency bands, then data rates and spectral efficiency are improved, but interference and collision risks increase
Solution Approach 1:
The base station performs Listen-Before-Talk (LBT) procedures before granting sidelink transmission opportunities, and provides advance notification to UEs about upcoming transmission opportunities. This preliminary channel assessment and notification mechanism allows UEs to prepare transmissions in advance while avoiding interference with ongoing transmissions in the unlicensed band.
Solution Approach 2:
The base station monitors channel conditions and transmission outcomes in the unlicensed band, then adjusts transmission opportunity grants and LBT parameters based on observed interference levels and collision patterns. This feedback loop enables dynamic optimization of sidelink transmissions to maintain high data rates while adapting to changing interference conditions.
2Object-affected harmful factors
If transmission opportunities are coordinated through base station control, then interference is reduced, but system complexity and signaling overhead increase
Solution Approach 1:
The base station divides unlicensed spectrum resources into discrete transmission opportunities with specific time-frequency allocations for different UE pairs. Each transmission opportunity is independently granted and managed, allowing localized interference control without requiring complex system-wide coordination. This segmentation simplifies the control mechanism while maintaining interference reduction benefits.
Solution Approach 2:
UEs autonomously perform LBT procedures and execute transmissions during granted opportunities without requiring continuous base station intervention. The base station provides initial grants and periodic updates, but UEs self-manage their transmissions within allocated opportunities, reducing signaling overhead and system complexity while maintaining coordinated interference avoidance.
3Object-affected harmful factors
If Listen-Before-Talk procedures are implemented, then interference avoidance is improved, but transmission latency increases
Solution Approach 1:
The base station performs LBT procedures in advance and provides transmission opportunity grants to UEs before actual data transmission is needed. This preliminary channel assessment allows UEs to skip or reduce LBT steps during actual transmission, thereby maintaining interference avoidance while reducing transmission latency for time-sensitive sidelink communications.
Solution Approach 2:
The system dynamically adjusts LBT parameters and transmission opportunity timing based on channel conditions and traffic priorities. For high-priority or time-sensitive traffic, the base station may grant immediate transmission opportunities with reduced or waived LBT requirements, while maintaining strict LBT procedures for normal traffic. This dynamic adaptation balances interference avoidance with latency requirements.
Data Source
AI summary
Wireless communications systems and methods related to sidelink communications in an unlicensed frequency band are provided. A user equipment (UE) receives, from a base station (BS), a first downlink control information (DCI) associated with a first listen-before-talk (LBT) time. The UE determines a first sidelink transmission opportunity for communicating in an unlicensed frequency band at the first LBT time based on the first DCI.