Synchronization Signal Block Design for Unlicensed Spectrum Access
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Solution Overview
Problem
Current wireless communication systems face challenges in effectively utilizing unlicensed spectrum for 5G-NR communications, particularly in achieving timing synchronization and beamforming tracking due to issues with listen-before-talk (LBT) procedures and regulatory requirements such as Occupied Channel Bandwidth (OCB), which can lead to disruptions and failure in synchronization.
Innovation Solution
The solution involves transmitting multiple copies of synchronization signal blocks (SSBs) and remaining minimum system information (RMSI) blocks within a single time instance, using distinct beamforming configurations and frequency-domain multiplexing, to ensure successful timing synchronization and beamforming tracking, even in cases where LBT fails, while complying with OCB regulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple SSBs are transmitted at different time instances to ensure timing synchronization, then timing synchronization reliability is improved, but channel occupancy time increases and LBT failures are more likely to occur
Solution Approach 1:
The patent combines multiple SSB transmissions into a single time instance by frequency-domain multiplexing. Multiple SSBs are transmitted simultaneously at different frequency positions within the same time instance, eliminating the need for sequential transmissions and reducing channel occupancy time while maintaining synchronization reliability.
Solution Approach 2:
The patent transitions from time-domain multiplexing to frequency-domain multiplexing. Instead of transmitting multiple SSBs at different time instances (time dimension), the system transmits them at the same time but different frequency positions (frequency dimension), thereby resolving the contradiction between reliability and time loss.
2Reliability
If LBT procedure is performed before each SSB transmission to comply with unlicensed spectrum regulations, then regulatory compliance is improved, but synchronization establishment time increases
Solution Approach 1:
The patent performs a single LBT procedure in advance before the SSB burst window, rather than before each individual SSB transmission. This preliminary LBT action allows multiple SSBs to be transmitted without repeating the LBT process, reducing synchronization establishment time while maintaining regulatory compliance.
Solution Approach 2:
The patent merges multiple LBT procedures into a single LBT action. By performing one LBT check before the entire SSB burst window instead of before each SSB, the system reduces the total time spent on LBT while ensuring regulatory compliance for unlicensed spectrum access.
3Reliability
If SSBs are transmitted using single-frequency network configuration to reduce OCB, then regulatory compliance is improved, but beamforming tracking capability deteriorates
Solution Approach 1:
The patent shifts from time-domain separation to frequency-domain multiplexing. By transmitting multiple SSBs with different beamforming configurations at the same time but different frequency positions, the system maintains OCB compliance while preserving beamforming tracking capability through frequency-domain differentiation.
Solution Approach 2:
The patent applies different beamforming configurations to different frequency positions within the SSB burst window. Each frequency position is optimized for specific beamforming directions, allowing precise beamforming tracking while maintaining overall OCB compliance through the single-frequency network configuration.
4Measurement precision
If multiple SSBs are transmitted in sequence to provide timing information, then timing synchronization accuracy is improved, but susceptibility to LBT failures increases
Solution Approach 1:
The patent transitions from sequential time-domain transmission to parallel frequency-domain transmission. Multiple SSBs are transmitted simultaneously at different frequency positions, eliminating the sequential vulnerability to LBT failures while maintaining timing synchronization accuracy through frequency-domain timing indicators.
Solution Approach 2:
The patent creates multiple copies of SSBs with identical timing information but different frequency positions and beamforming configurations. This copying strategy ensures that if one copy fails due to LBT issues, other copies at different frequencies can still deliver the timing synchronization information.
Data Source
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AI summary
Apparatuses, systems, and methods for performing timing synchronization between a base station and a user equipment device within an unlicensed spectrum band. In some scenarios, beamforming tracking may also be performed. Upon determining that a transmission medium within the unlicensed spectrum band is available for transmission, a base station may transmit a plurality of synchronization signal blocks (SSBs), or a plurality of copies of one SSB, with associated remaining minimum system information (RMSI) blocks, within a single time instance within a SSB burst window. The SSBs may be transmitted at different frequency positions and according to distinct beamforming configurations. The SSBs and RMSI blocks may be configured such that a receiving user equipment device may determine the time-domain, and optionally the frequency-domain, position of the SSB and RMSI within the SSB burst window, to allow timing synchronization and optionally beamforming tracking.