RACH Procedure CFRA Selection Thresholds
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Solution Overview
Problem
Current 5G NR random access procedures in wireless communications often result in inefficient resource utilization and increased power consumption due to the selection of Contention-Based Random Access (CBRA) over Contention-Free Random Access (CFRA) when reference signal received powers (RSRPs) are below thresholds, leading to potential handover failures and resource wastage.
Innovation Solution
The client device selects Contention-Free Random Access (CFRA) resources based on predefined thresholds and rules, even if RSRPs are below a certain threshold T1, allowing for direct CFRA performance if CFRA resources are explicitly provided, thereby avoiding CBRA and its associated collisions and power consumption issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the client device selects Contention-Based Random Access (CBRA) when RSRP is below threshold, then the device can perform random access, but resource utilization efficiency deteriorates and power consumption increases due to collisions and repeated attempts
Solution Approach 1:
The patent introduces a second threshold T2 (where T2 < T1) to create a new decision parameter. When RSRP is between T2 and T1, the device performs CFRA instead of CBRA, optimizing the trade-off between access reliability and power consumption by avoiding unnecessary contention in moderate signal conditions.
Solution Approach 2:
The patent dynamically adjusts the random access strategy based on RSRP measurements. The device transitions from a static threshold-based approach to a dynamic multi-threshold approach, adapting the access method (CFRA or CBRA) based on current signal conditions to minimize power consumption while maintaining reliability.
2Ease of operation
If the client device performs Contention-Based Random Access (CBRA), then random access can be established, but network resource efficiency deteriorates due to preamble collisions and repeated access attempts
Solution Approach 1:
The patent changes the operational parameters by introducing dual thresholds T1 and T2. When RSRP exceeds T2, the device performs CFRA which eliminates preamble collisions and improves network resource efficiency, while still maintaining random access capability through the fallback to CBRA when RSRP is below T2.
Solution Approach 2:
The patent introduces an intermediary decision mechanism that selects between CFRA and CBRA based on RSRP thresholds. This intermediary layer optimizes network resource efficiency by preferring CFRA in moderate conditions while ensuring access capability is maintained through CBRA as a fallback option.
3Device complexity
If the client device uses a single threshold for selecting between CFRA and CBRA, then the selection process is simple, but handover reliability deteriorates in conditional handover scenarios
Solution Approach 1:
The patent segments the RSRP range into three distinct zones using two thresholds T1 and T2: above T1 (CFRA preferred), between T1 and T2 (CFRA with fallback), and below T2 (CBRA). This segmentation improves handover reliability in conditional handover scenarios while maintaining manageable complexity through clear decision rules.
Solution Approach 2:
The patent implements a dynamic threshold-based selection mechanism that adapts to different handover scenarios. The dual-threshold approach provides different behaviors for different RSRP ranges, improving reliability in conditional handover while keeping the device complexity manageable through systematic decision logic.
Data Source
Figure 1A~1B
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Figure 2B
AI summary
An example embodiment relates to Random Access Channel, RACH, procedure, for example in the New Radio, NR. Random access procedures may be of two types, contention based CBRA and contention free, CFRA. A client devicemay only perform CBRA fallback when none of the reference signal received strengths, RSRPs,of the synchronization signal blocks, SSBs, which is associated with the CFRA resources is above a predefined threshold, T1. All SSBs and CSI-RS with associated CFRA resources may be below the threshold. Then, the client device may select an SSB or CSI-RS according to a predefined rule and perform CFRA when CFRA resources are associated. Devices, methods and computer programs are disclosed accordingly.