DBTW SSB Indexing for LBT-Compliant Initial Access
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Solution Overview
Problem
In wireless communication systems, the mandatory Listen Before Talk (LBT) requirement in unlicensed radio spectrum causes network nodes to forego transmitting Signal Synchronization Blocks (SSBs), necessitating a Discovery Burst Transmission Window (DBTW) for later transmission, which complicates UE synchronization and initial access, especially in licensed or unlicensed bands without LBT.
Innovation Solution
The UE determines the presence and configuration of a DBTW by signaling Q values through PBCH and SIB1, employing various methods to infer QCL assumptions and timing, allowing for efficient SSB sweeping across multiple DBTWs, and utilizing different synchronization rasters or RRC signaling to manage DBTWs in licensed and unlicensed bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Listen Before Talk is mandated in unlicensed spectrum, then the gNB can comply with LBT requirements, but the gNB may forego transmitting SSBs and require DBTW management
Solution Approach 1:
The patent uses parameter changes by introducing a beam value parameter Q from the MIB that determines the modulo operation for SS/PBCH block index calculation. This parameter change enables the UE to adapt its indexing strategy based on whether DBTW is employed, resolving the complexity of managing different transmission scenarios while maintaining LBT compliance.
Solution Approach 2:
The patent segments the SS/PBCH block indexing into two distinct cases: when DBTW is employed (using modulo Q operation) and when DBTW is not employed (using direct candidate index). This segmentation allows the system to handle LBT-compliant transmissions with DBTW separately from traditional transmissions, reducing overall management complexity.
2Measurement precision
If the UE calculates SS/PBCH block index using modulo operation with beam value Q, then the UE can correctly identify SSBs in DBTW, but the calculation complexity increases
Solution Approach 1:
The patent implements self-service by having the UE autonomously determine whether DBTW is employed based on the beam value Q from the MIB. The UE automatically selects the appropriate indexing method (modulo operation or direct mapping) without requiring additional network signaling or complex configuration, thereby maintaining identification accuracy while minimizing calculation complexity.
3Speed
If the UE determines DBTW employment based on beam value equality to predetermined value, then the UE can quickly identify DBTW status, but the method lacks flexibility for different configurations
Solution Approach 1:
The patent achieves universality by using the beam value Q parameter for multiple functions: it serves as both the modulus for SS/PBCH block index calculation when DBTW is employed and as an indicator for determining whether DBTW is employed (by checking equality to a predetermined value). This multi-functionality maintains configuration flexibility while enabling fast DBTW status determination.
Data Source
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AI summary
A system and method for managing a Discovery Burst Transmission Window in a wireless communication system. In some embodiments, the method includes: receiving, by a User Equipment, UE, a first Signal Synchronization Block, SSB; decoding a first Physical Broadcast Channel, PBCH, from the first SSB; determining, from a Master Information Block, MIB, of the first PBCH, a first beam value; determining, from the first PBCH, a first candidate Synchronization Signal/Physical Broadcast Channel, SS/PBCH, block index; and calculating a first SS/PBCH block index as A mod Q, wherein A is the first candidate SS/PBCH block index and Q is the first beam value.