Two-Step Random Access for IAB Backhaul Nodes
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Solution Overview
Problem
Wireless communications systems face latency issues in backhaul node random access procedures, particularly for mobile IAB nodes, where static IAB-specific four-step random access procedures introduce significant latency due to frequent random access attempts, affecting communication efficiency.
Innovation Solution
Implementing a two-step random access procedure for backhaul nodes, where the parent base station transmits system information indicating either a two-step or a four-step random access configuration, allowing the IAB node to select based on RSRP, mobility, or previous procedure failures, to reduce latency and improve communication efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a four-step random access procedure is used for backhaul nodes, then the procedure is more reliable and compatible with existing systems, but the latency is significantly increased
Solution Approach 1:
The patent implements dynamic random access procedure selection, where the IAB node can adaptively choose between two-step and four-step RACH procedures based on current system conditions, mobility state, and channel quality. This dynamic approach resolves the contradiction by allowing the system to use the faster two-step procedure when conditions permit (reducing latency) while falling back to the more reliable four-step procedure when necessary (maintaining reliability).
Solution Approach 2:
The patent changes the parameter of random access procedure type from a fixed configuration to a selectable mode. By introducing multiple RACH configuration options (two-step and four-step procedures) and enabling conditional selection based on RSRP thresholds, mobility state, and previous procedure outcomes, the system can optimize the balance between latency and reliability for different operating conditions.
2Device complexity
If a static IAB-specific random access configuration is used, then the configuration is simple to implement, but it introduces latency for mobile IAB nodes
Solution Approach 1:
The patent transforms the static RACH configuration into a dynamic one by introducing mobility-state-aware selection mechanisms. The IAB node determines its mobility state based on RSRP variations and selectively applies either two-step or four-step RACH procedures. This dynamic configuration maintains simplicity for static nodes while optimizing performance for mobile nodes, resolving the contradiction between configuration simplicity and latency reduction.
Solution Approach 2:
The patent introduces mobility state as a new parameter that influences RACH procedure selection. By defining mobility states based on RSRP threshold variations and using this parameter to select between different RACH configurations, the system achieves adaptive optimization without significantly increasing implementation complexity. The parameter change enables mobile IAB nodes to use the faster two-step procedure while maintaining simple configuration management.
3Reliability
If frequent random access attempts are made by mobile IAB nodes, then the connection is maintained, but the latency accumulates significantly
Solution Approach 1:
The patent implements dynamic RACH procedure selection that adapts to the IAB node's mobility state and channel conditions. By using the faster two-step RACH procedure for mobile nodes with suitable channel conditions, the system reduces the time required for each access attempt while maintaining connection reliability. This resolves the contradiction by reducing cumulative latency without sacrificing connection maintenance capability.
Solution Approach 2:
The patent introduces conditional parameters including RSRP thresholds, mobility state indicators, and previous procedure success/failure status that influence RACH procedure selection. These parameter changes enable the system to optimize the balance between connection reliability and access latency by selecting the appropriate RACH procedure type based on current conditions, thereby reducing cumulative latency for mobile nodes while maintaining robust connection management.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. For example, a first wireless node (e.g., an integrated access and backhaul (IAB) node) may receive, from a parent base station, system information that is indicative of two random access procedure configurations. The first random access procedure configuration may be for a two-step random access procedure and the second random access procedure configuration may be different from the first random access procedure configuration (for example, an IAB-specific, a user equipment (UE)-specific, or a four-step random access procedure). The first wireless node may determine to use the first random access procedure configuration (e.g., for establishing a wireless backhaul connection with the parent base station) and may perform the two-step random access procedure with the parent base station accordingly.