SSB Transmission in Unlicensed Spectrum via Extended DRS Window
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Solution Overview
Problem
Conventional techniques are unable to handle the increased number of candidate SSB positions required for unlicensed operation, particularly in scenarios where Listen-Before-Talk (LBT) failures occur, making it challenging for user equipment (UE) to determine cell timing effectively.
Innovation Solution
The implementation of an extended discovery reference signal (DRS) window that allows for the transmission of multiple SSBs to UE only when the unlicensed spectrum is determined to be unoccupied, along with mechanisms to determine the SSB index using combinations of DM-RS and PBCH channels, and implicit signaling techniques to handle a larger number of candidate SSB positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of candidate SSB positions is increased to account for LBT failure in unlicensed spectrum, then the reliability of synchronization is improved, but conventional techniques become unable to handle the increased complexity of determining cell timing
Solution Approach 1:
The patent segments the cell timing determination process into two independent parts: (1) determining the DRS window timing using LBT success indication and SSB position information, and (2) determining the SSB index within the DRS window using DM-RS and PBCH channels. This segmentation allows the system to handle a large number of candidate SSB positions (up to 64 or 128) without overwhelming the UE's processing capabilities, as each segment can be resolved independently using dedicated signaling mechanisms.
Solution Approach 2:
The patent introduces intermediate signaling elements to bridge the gap between the increased number of SSB positions and the UE's ability to determine timing. Specifically, it uses LBT success indication signals to mark valid SSB positions within the DRS window, and employs DM-RS and PBCH channels as intermediaries to convey SSB index information. These intermediaries enable the UE to efficiently identify the correct timing without having to process all candidate positions simultaneously.
2Adaptability or versatility
If multiple SSBs are transmitted in unlicensed spectrum to account for LBT failure, then the coverage and synchronization opportunity are improved, but the difficulty of detecting and measuring cell timing increases
Solution Approach 1:
The patent applies preliminary action by having the network pre-configure the DRS window parameters and candidate SSB positions before transmission. The network also performs LBT sensing in advance and provides LBT success indication signals to mark which candidate positions contain valid SSB transmissions. This preliminary preparation allows the UE to efficiently identify valid SSB positions without having to blindly search through all candidates, significantly reducing detection difficulty while maintaining adaptability to LBT outcomes.
3Reliability
If the number of candidate SSB positions exceeds conventional limits for unlicensed operation, then the robustness against LBT failure is improved, but conventional acquisition techniques become inadequate
Solution Approach 1:
The patent transitions from conventional single-dimension SSB indexing to a two-dimensional approach: (1) DRS window dimension, where multiple windows can be configured with different timing configurations, and (2) SSB position dimension within each window, where up to 64 or 128 candidate positions can be defined. This dimensional expansion allows the system to support a much larger total number of candidate SSB positions while providing structured methods for the UE to navigate and acquire timing in each dimension separately.
Solution Approach 2:
The patent changes key parameters to enable handling of increased SSB positions: it extends the DRS window duration and flexibility, increases the maximum number of candidate SSB positions per window, and modifies the SSB index signaling mechanism to support larger ranges. These parameter changes are accompanied by enhanced signaling procedures using DM-RS and PBCH channels to convey the extended index information, making the system capable of handling robustness requirements for unlicensed spectrum operation.
Data Source
AI summary
A cell transmits synchronization signal blocks (SSB) to a user equipment (UE) for the UE to synchronize with the cell. The cell configures a discovery reference signal (DRS) window for synchronization signal block (SSB) transmission to a user equipment (UE), determines that a channel in an unlicensed spectrum is not occupied and transmits multiple SSBs to the UE in response to determining that the channel in the unlicensed spectrum is not occupied.