RRC-Configured NR Sidelink for Unlicensed Spectrum Access
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Solution Overview
Problem
Existing wireless communication networks face challenges in enabling efficient sidelink communications in the unlicensed spectrum, particularly in high-throughput and low-latency scenarios, due to issues with channel occupancy times, interference, and resource allocation.
Innovation Solution
Implementing techniques for NR sidelink communications in the unlicensed spectrum using radio resource control (RRC) messaging for grant configuration, channel occupancy time (COT) sharing, clear channel assessment (CCA) procedures, and transmission power control, along with channel state information (CSI) feedback to optimize unidirectional and bidirectional sidelink communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sidelink communications are enabled in unlicensed spectrum, then spectral efficiency is improved, but interference and channel occupancy conflicts increase
Solution Approach 1:
The base station performs preliminary channel occupancy time (COT) allocation and clear channel assessment (CCA) configuration before sidelink communications begin. UEs receive pre-configured grants and COT information through RRC messaging, allowing them to proceed with transmissions without real-time contention, thereby reducing interference while maintaining high spectral efficiency
Solution Approach 2:
The system implements channel state information (CSI) feedback mechanisms where UEs report channel conditions to the base station. This feedback enables the base station to dynamically adjust COT allocations and resource grants, optimizing spectral efficiency while preventing interference through informed resource management
2Productivity
If channel occupancy time is extended to support high-throughput applications, then data rate is improved, but latency increases
Solution Approach 1:
The base station segments COT into multiple sub-COTs or transmission opportunities within the allocated COT period. UEs can perform multiple transmissions or retransmissions within the segmented structure, achieving high throughput through aggregated data rates while maintaining low latency by distributing transmissions across segments rather than waiting for complete COT expiration
Solution Approach 2:
The system employs periodic COT allocations and configured grants with defined periodicities. This allows UEs to have recurring transmission opportunities within each COT, enabling high data rates through periodic high-throughput transmissions while keeping latency bounded by the periodic interval rather than requiring continuous extended COT
3Object-affected harmful factors
If resource allocation is centralized through base station control, then interference coordination is improved, but system complexity increases
Solution Approach 1:
UEs are equipped with self-service capabilities through pre-configured grants and COT information received via RRC messaging. Once configured, UEs autonomously perform CCA procedures, select transmission resources, and manage their own transmissions within allocated COTs, reducing the need for continuous base station intervention and simplifying overall system complexity while maintaining interference coordination
Solution Approach 2:
The base station acts as an intermediary that provides centralized COT allocation and resource configuration through RRC signaling, but then steps back to allow autonomous UE operation. This intermediary role establishes the coordination framework upfront, after which UEs independently manage transmissions, achieving interference coordination without ongoing complex base station control
4Reliability
If clear channel assessment procedures are implemented in unlicensed spectrum, then collision avoidance is improved, but access time increases
Solution Approach 1:
The base station performs preliminary CCA assessments and provides COT information to UEs before transmissions begin. UEs receive pre-validated channel availability information, allowing them to skip real-time CCA delays and proceed directly to transmissions, thereby maintaining collision avoidance through base station-performed CCA while reducing access time at the UE level
Solution Approach 2:
Once the base station performs initial CCA and allocates COT, the channel access remains continuous for the duration of the COT without requiring repeated CCA procedures. This continuous access pattern eliminates repeated assessment delays, maintaining collision avoidance through the initial CCA while minimizing access time through uninterrupted transmission opportunities
Data Source
AI summary
Techniques described herein include solutions for enabling NR sidelink (SL) communications by using radio resource control (RRC) to provide ser equipment (UEs) with grant configuration (CGs) for unidirectional and/or bidirectional SL communications. These techniques also include solutions for UEs to obtain channel occupation times (COTs) for SL communications, and procedures for sharing COTs with other UEs, and procedures for CG uplink control information (UCI) of physical uplink shared channels (PUSCH) transmissions for NR in the unlicensed spectrum (NR-U). The techniques described herein also include solutions for channel state information (CSI) feedback for CGs of SL in the unlicensed spectrum (CG-Sidelink-U). Also described herein are SL techniques for transmission power control of SL communications and clear channel assessment (CCA) procedures.