IAB Node Initial Access via SSB Parameter Redefinition
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Solution Overview
Problem
Existing solutions for initial access in cellular communications networks, specifically designed for User Equipments (UEs), face challenges when reused for Integrated Access and Backhaul (IAB) nodes, particularly in Non-Stand-Alone (NSA) deployments and in scenarios where IAB nodes need to perform initial access without transmitting SIB1, and require enhanced methods for SSB detection and system information retrieval.
Innovation Solution
The implementation of specific methods and systems by IAB nodes to detect Synchronization Signal (SS)/Physical Broadcast Channel (PBCH) Blocks (SSBs), read system information parameters like ssb-SubCarrierOffset, and determine the presence of additional system information, allowing IAB nodes to perform initial access by mapping predefined values to indicate frequency offsets and system information availability, distinct from UE operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing UE-based initial access solutions are reused for IAB nodes, then device compatibility is maintained, but IAB nodes cannot perform initial access when SIB1 is not transmitted
Solution Approach 1:
The patent changes the interpretation of existing SSB parameters (ssb-SubCarrierOffset, pdcch-ConfigSIB1) to enable IAB nodes to identify cells suitable for initial access. By redefining what these parameters indicate for IAB nodes versus UEs, the system allows IAB nodes to find accessible cells without requiring new parameter structures or increasing procedural complexity.
2Loss of information
If SSB parameters indicate frequency offsets for UEs, then UE synchronization is achieved, but IAB nodes cannot distinguish cells with additional system information
Solution Approach 1:
The patent applies local quality by making parameter interpretation device-specific. The same SSB parameters have different meanings for UEs versus IAB nodes. UEs interpret ssb-SubCarrierOffset as frequency offset only, while IAB nodes interpret it as a combination of frequency offset and system information availability indicator, allowing differentiated access based on node type.
Solution Approach 2:
The patent uses the existing SSB parameters as intermediaries to convey dual information. The ssb-SubCarrierOffset value serves both as the frequency offset indicator (for both UEs and IAB nodes) and as a coded indicator of additional system information presence (for IAB nodes), eliminating the need for separate signaling.
3Ease of operation
If IAB nodes use the same synchronization raster as UEs, then frequency alignment is simplified, but IAB nodes cannot perform initial access without SIB1 transmission
Solution Approach 1:
The patent applies preliminary action by having IAB nodes perform preliminary checks on SSB parameters before attempting initial access. IAB nodes first detect the SSB, then examine the ssb-SubCarrierOffset and pdcch-ConfigSIB1 values to determine if additional system information is present, only then proceeding with access procedures. This preliminary verification ensures reliable access while maintaining simple synchronization.
Data Source
AI summary
Embodiments of a method performed by an Integrated Access and Backhaul (IAB) node to perform initial cell access in a cellular communications network and corresponding embodiments of an IAB node are disclosed. In some embodiments, the method performed by the IAB node comprises detecting a Synchronization Signal/Physical Broadcast Channel Block (SSB) of a cell and reading system information comprising a value of a parameter from the SSB. The method further comprises determining that the value of the parameter is a predefined value that serves as an indication to IAB nodes that additional system information is present on the cell and searching for the additional system information in accordance with the value of the parameter. In some embodiments, the predefined value of the parameter serves as an indication to one or more other types of nodes that additional system information is not present on the cell.