5G NR Initial Access in Unlicensed Bands via Segmented SSB COT
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a need for efficient and reliable communication methods and apparatuses to establish initial access in 5G New Radio (NR) systems operating in unlicensed bands, particularly for NR stand-alone technology, which lacks backward compatibility with LTE/LTE-Advanced and requires a listen before talk (LBT) procedure for channel access, but lacks sufficient discussion on communication methods for NR initial access in unlicensed bands.
Innovation Solution
The solution involves a terminal and base station configuration where the terminal receives candidate synchronization signal/physical broadcast channel blocks (SSBs) and transmits a physical random access channel (PRACH) preamble to the base station, with the base station transmitting SSBs within SSB channel occupancy time (COT) and receiving the PRACH preamble, utilizing a LBT procedure to manage channel access and optimize SSB transmission through segmented or non-segmented SSB transmission based on channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LBT procedure is implemented for NR channel access in unlicensed bands, then channel access reliability is improved, but initial access establishment complexity increases
Solution Approach 1:
The patent segments the SSB transmission process into multiple SSB COT (channel occupancy time) periods, where each period contains a subset of SSBs. This segmentation allows the terminal to perform LBT multiple times and select appropriate PRACH occasions associated with different SSB COTs, thereby maintaining reliability while managing complexity through structured division of the access procedure.
Solution Approach 2:
The patent introduces preliminary actions where the terminal first receives and evaluates multiple candidate SSBs transmitted in different SSB COTs before finally selecting a PRACH occasion for random access preamble transmission. This preliminary evaluation phase enables the terminal to prepare beam selection and timing information in advance, reducing the complexity of the subsequent access establishment.
2Measurement precision
If multiple candidate SSBs are transmitted within one or more SSB COT, then beam selection accuracy is improved, but time consumption increases
Solution Approach 1:
The patent divides the SSB transmission into segmented COTs, where each COT contains a manageable number of candidate SSBs. This segmentation allows the terminal to evaluate beam quality systematically across multiple time segments rather than processing all SSBs simultaneously, improving beam selection accuracy while controlling time consumption through structured progression.
Solution Approach 2:
The patent employs periodic transmission of SSBs in repeated COT cycles, allowing the terminal to periodically evaluate beam quality metrics. This periodic action enables the terminal to make incremental improvements in beam selection decisions while managing total time consumption through efficient periodic evaluation rather than continuous processing.
3Reliability
If PRACH occasion is associated with specific SSB, then communication reliability is improved, but system complexity increases
Solution Approach 1:
The patent segments the relationship between SSBs and PRACH occasions by associating specific PRACH occasions with specific SSB COTs. This segmentation creates a structured mapping where each PRACH occasion is linked to a specific set of candidate SSBs, improving communication reliability through targeted association while managing system complexity through organized, segmented mapping rather than all-to-all connections.
Data Source
AI summary
The present disclosure provides apparatuses and methods for establishing an initial access. The apparatuses include a terminal which comprises a receiver which, in operation, is configured to receive candidate synchronization signal/physical broadcast channel blocks (SSBs) in a synchronization signal (SS) burst set, the candidate SSBs being transmitted within one or more SSB channel occupancy time (SSB COT) from a base station. The terminal further comprises a transmitter which, in operation, is configured to transmit a physical random access channel (PRACH) preamble on a PRACH occasion (RO) to the base station, the RO being associated with one SSB among the received candidate SSBs.