Subband Uplink Access via UE CCA Feedback in NR Shared Spectrum
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Solution Overview
Problem
In wireless communication networks, especially in 5G NR-SS systems, managing uplink access in multi-band environments is challenging due to differing interference profiles between base stations and user equipment (UEs), leading to inefficiencies and potential mismatches in subband allocation for uplink grants, which can result in reduced transmission reliability and increased signaling overhead.
Innovation Solution
The method involves a UE receiving an uplink grant and performing a clear channel assessment (CCA) on candidate subbands, determining successful subbands, and adjusting uplink transmissions accordingly, while the base station also performs CCA and refines subband allocation based on CCA success indicators from UEs, ensuring coordinated subband usage to manage interference and optimize transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the base station performs CCA and allocates subbands for uplink grants without considering UE-specific interference, then the base station can simplify its operation, but the uplink transmission reliability deteriorates due to mismatches in subband allocation between base station and UE
Solution Approach 1:
The UE performs CCA on candidate subbands and feeds back CCA success indicators to the base station. This feedback mechanism enables the base station to identify which subbands are actually available for uplink transmission from the UE's perspective, resolving the mismatch between base station and UE interference perceptions without requiring the base station to perform complex UE-specific interference analysis
Solution Approach 2:
The UE performs CCA on candidate subbands before uplink transmission to determine which subbands are free from interference. This preliminary action allows the UE to identify suitable subbands in advance and communicate this information to the base station, ensuring that uplink grants are allocated on subbands that the UE can actually use for reliable transmission
2Reliability
If the system performs CCA on all candidate subbands to ensure reliable uplink transmission, then the uplink transmission reliability improves, but the signaling overhead increases due to extensive CCA trigger signaling
Solution Approach 1:
Instead of requiring CCA on all candidate subbands, the system applies CCA selectively based on local interference conditions. The base station provides a set of candidate subbands, and the UE performs CCA only on those specific subbands where interference conditions warrant assessment. This localized approach reduces signaling overhead while maintaining reliability on subbands that actually need protection
Solution Approach 2:
The system performs CCA on a subset of candidate subbands rather than all possible subbands. The base station identifies and signals a limited set of candidate subbands that are most likely to be affected by interference, and the UE performs CCA only on these partial candidates, reducing the overall signaling overhead while still protecting against the most critical interference scenarios
3Productivity
If the base station allocates uplink grants on all system allocated subbands without refinement, then the resource utilization improves, but the interference management deteriorates due to lack of coordination with actual channel conditions
Solution Approach 1:
The system dynamically refines subband allocation based on real-time channel conditions and interference measurements. The base station starts with a set of system-allocated subbands, performs CCA to identify candidate subbands free from interference, and then allocates uplink grants only on these refined candidate subbands. This dynamic refinement process ensures high resource utilization while effectively managing interference by adapting to actual channel conditions
Data Source
AI summary
Subband based uplink access for new radio (NR) shared spectrum (NR-SS) is disclosed. A base station performs a listen before talk (LBT) procedure on system allocated subbands of a shared communication channel. The base station determines a first set of candidate subbands that are signaled to a user equipment (UE). The UE performs an LBT procedure on the first set to identify a second set of candidate subbands including the successful LBT subbands of the first set. Aspects of the disclosure provide for managing and refining the subbands for transmissions. A first aspect provides the UE to determine a transmission behavior based on mismatch between the first and second sets. A second aspect provides the first and second sets in handshaking between the base station and UE for refining the eventual transmission set of subbands. A third aspect provides cross-band LBT reporting for further refining subband selection in later slots.