NR Random Access Control for Two-Step RACH in Large Cells
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Solution Overview
Problem
The two-step RACH in NR is limited by cell radius, restricting its use to cells with a maximum radius equal to or less than the distance it can cover, thereby limiting its applicability.
Innovation Solution
User equipment determines whether to execute a two-step or four-step RACH based on instructions from the base station, threshold values, or beam-specific SSB indices, allowing it to adapt the random access procedure without relying on cell radius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If two-step RACH is used to reduce latency and power consumption, then the random access procedure efficiency is improved, but the applicable cell radius is limited to a short distance
Solution Approach 1:
The patent applies dynamics by making the random access procedure selectable between two-step and four-step methods based on real-time distance measurement. The user equipment dynamically determines which procedure to use by measuring distance to the base station and comparing it against a threshold, allowing the system to adapt the procedure length to actual propagation conditions rather than being fixed or limited by maximum cell radius assumptions
Solution Approach 2:
The patent changes the parameter of procedure step count based on distance conditions. When the measured distance exceeds the threshold, the system switches from two-step to four-step RACH, effectively changing the operational parameters of the random access procedure to match the propagation environment and enable deployment in larger cells
2Reliability
If two-step RACH is enabled only in cells with maximum radius within a certain distance, then the procedure reliability is maintained, but the coverage area is greatly limited
Solution Approach 1:
The system dynamically adapts the RACH procedure selection based on measured distance rather than being constrained by predetermined cell radius limits. This allows the network to expand coverage area by enabling two-step RACH in larger cells when distance measurements indicate suitable propagation conditions, while falling back to four-step RACH when necessary to maintain reliability
Solution Approach 2:
The patent makes the random access procedure universal by allowing the same user equipment to use different RACH methods (two-step or four-step) depending on the deployment scenario and distance conditions. This multi-functionality enables the system to serve both small-cell and large-cell deployments without requiring separate equipment or configurations
Data Source
AI summary
A user equipment includes a receiving unit configured to receive, from a base station apparatus, an instruction designating a method in which a random access procedure is performed, and includes a control unit configured to determine, in accordance with the instruction, whether to execute a random access procedure of a method in which a first message is transmitted using a preamble resource and a PUSCH resource.