Sidelink Synchronization Signal Transmission in Unlicensed Bands
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Solution Overview
Problem
Existing sidelink communication systems face challenges in efficiently configuring and transmitting sidelink synchronization signal blocks (S-SSBs) in unlicensed frequency bands, leading to inefficiencies in resource utilization and synchronization processes.
Innovation Solution
A method and apparatus for a user equipment (UE) to identify the frequency band as licensed or unlicensed, determining the subcarrier spacing and transmission period for S-SSBs, and adjusting the number of S-SSB transmissions based on the spectrum type, allowing for at least two S-SSBs in unlicensed bands to enhance synchronization and resource efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of S-SSB transmissions is increased in unlicensed bands, then synchronization reliability is improved, but device complexity and resource overhead increase
Solution Approach 1:
The patent applies local quality by differentiating S-SSB transmission configurations between licensed and unlicensed frequency bands. Specifically, in unlicensed bands, the system transmits multiple S-SSBs (at least two) with different time offsets to enhance synchronization reliability in challenging radio environments, while in licensed bands, a single S-SSB transmission suffices. This localized adaptation optimizes synchronization performance without unnecessarily increasing complexity across all bands.
Solution Approach 2:
The patent changes key transmission parameters including the number of S-SSB transmissions, time offsets between transmissions, and subcarrier spacing based on the frequency band type. In unlicensed bands, parameters are adjusted to transmit multiple S-SSBs with specific time offsets and subcarrier spacings (e.g., 15 kHz or 30 kHz) to overcome poor propagation conditions, while licensed bands use standard single-transmission parameters, thereby achieving reliability improvement without universal complexity increase.
2Reliability
If multiple S-SSBs are transmitted with different time offsets, then coverage and synchronization robustness are improved, but resource utilization efficiency deteriorates
Solution Approach 1:
The patent implements dynamic S-SSB transmission by adjusting the number of transmissions and time offsets based on the frequency band characteristics. In unlicensed bands with poor propagation, multiple S-SSBs are transmitted with dynamic time offsets (e.g., 0, 2, 4, 6, 8, or 10 slots) to ensure robustness. In licensed bands, the system dynamically reduces to single S-SSB transmission, thereby adapting resource usage to actual needs and preventing wasteful resource consumption while maintaining synchronization robustness where required.
3Reliability
If S-SSB transmission parameters are optimized for unlicensed bands, then synchronization performance is improved, but system adaptability to different frequency bands deteriorates
Solution Approach 1:
The patent segments the S-SSB transmission configuration into band-specific parameters. Different transmission schemes are defined for licensed versus unlicensed bands, with unlicensed bands receiving optimized multi-transmission configurations including specific time offsets and subcarrier spacings. This segmentation allows each band type to have tailored parameters that maximize synchronization performance in its specific radio environment, while the overall system maintains versatility through this modular, band-aware approach.
Data Source
AI summary
A method performed by a user equipment (UE) in a wireless communication system is provided. The method includes identifying whether a frequency band in which the UE operates corresponds to an unlicensed spectrum or a licensed spectrum, identifying a period for a transmission of a sidelink synchronization signal block (S-SSB) and a subcarrier spacing associated with the S-SSB, identifying a number of S-SSB transmissions within the period, and in case that the frequency band corresponds to the unlicensed spectrum, transmitting at least two S-SSBs, wherein the number of S-SSB transmissions relates to the subcarrier spacing and depends on whether the frequency band corresponds to the unlicensed spectrum or the licensed spectrum, and wherein a number of S-SSB transmissions in a case of the frequency band corresponding to the unlicensed spectrum is greater than a number of S-SSB transmissions in a case of the frequency band corresponding to the licensed spectrum.