UE Uplink Suppression in DBT Window via SSB Detection
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Solution Overview
Problem
Current mechanisms for handling User Equipment (UE)-initiated uplink transmissions during a serving cell Discovery Burst Transmission (DBT) window in New Radio (NR) networks are inefficient, leading to unnecessary overhead and resource wastage due to the inability to accurately determine when New Radio base stations (gNB) will use specific synchronization signal block (SSB) positions, especially in scenarios where Listen-Before-Talk (LBT) procedures delay transmissions.
Innovation Solution
The UE suppresses UE-initiated uplink transmissions during the entirety of the DBT window or until it detects that the gNB has completed its SSB transmissions, using configuration information such as the ssb-PositionsInBurst IE to determine the intended transmission pattern and only resume transmissions after the last SSB has been sent, thereby avoiding collisions and optimizing resource use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE suppresses uplink transmissions during the entire DBT window to avoid collisions with gNB SSB transmissions, then collision avoidance is improved, but resource utilization deteriorates due to unnecessary suppression when gNB has already transmitted SSBs
Solution Approach 1:
The UE monitors the DBT window to detect whether the gNB has actually transmitted SSBs at the expected positions. Based on this feedback information, the UE dynamically adjusts its uplink transmission suppression behavior, resuming transmissions in resources that are confirmed to be unused by the gNB, thereby resolving the contradiction between collision avoidance and resource utilization
Solution Approach 2:
The system transitions from a static suppression approach (suppressing all uplink transmissions throughout the entire DBT window) to a dynamic approach where suppression is applied only to specific time-frequency resources where gNB SSB transmissions are detected or expected, allowing flexible adaptation to actual gNB transmission behavior
2Reliability
If the UE uses ssb-PositionsInBurst IE to determine candidate SSB positions and suppress transmissions at those positions, then transmission collision avoidance is improved, but overhead increases due to conservative resource allocation
Solution Approach 1:
Instead of suppressing transmissions at all candidate SSB positions indicated by ssb-PositionsInBurst IE (excessive action), the UE applies suppression only to the subset of positions where gNB transmissions are actually detected or highly likely to occur (partial action), reducing unnecessary overhead while maintaining collision avoidance
3Reliability
If the gNB delays SSB transmissions to perform LBT procedures in unlicensed spectrum, then channel access reliability is improved, but timing synchronization deteriorates as SSB positions shift from expected locations
Solution Approach 1:
The gNB performs LBT procedures in advance before transmitting SSBs, and the UE is configured with knowledge of the DBT window and candidate SSB positions. This preliminary action allows both parties to prepare for potential transmission delays while maintaining synchronization through pre-agreed timing structures
Solution Approach 2:
The system allows the actual SSB transmission positions to vary within the DBT window based on LBT outcomes, changing the timing parameter dynamically while maintaining the overall synchronization structure through the defined window boundaries and candidate position sets
Data Source
AI summary
Methods and systems for handling transmissions in a serving cell Discovery Burst Transmission (DBT) window are provided. According to one aspect, a method performed at a User Equipment (UE) comprises receiving a configuration indicating a serving cell DBT window, receiving a configuration for UE-initiated Uplink (UL) transmission, and suppressing UE-initiated UL transmissions during at least a portion of the serving cell DBT window. These transmissions may be suppressed for the entire serving cell DBT window or suppressed while a base station is transmitting SSBs according to an intended transmit pattern. The suppression may start from a beginning of the serving cell DBT window or from a beginning of a first SSB transmission detected by the UE. The UE may rate match around actual transmitted SSBs that are transmitted within the serving cell DBT window due to various constraints including restrictions on channel access.