RedCap Two-Step RACH Adaptation With Four-Step Fallback
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Solution Overview
Problem
Reduced capability (RedCap) UEs face challenges in performing the two-step random access process due to reduced device capabilities, leading to potential loss of cellular signal coverage and difficulty in successful initial access, which existing methods have not adequately addressed.
Innovation Solution
Adapting the standard two-step random access process by adjusting configurations based on RedCap UE capabilities, such as indicating device capabilities during MsgA transmission, and using the four-step process if the two-step is not successful, to enhance the likelihood of successful initial access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If RedCap UE uses standard two-step random access process, then initial access latency is reduced, but success rate decreases due to reduced device capabilities
Solution Approach 1:
The patent implements dynamic selection between two-step and four-step random access processes based on RedCap UE capabilities and channel conditions. The network configures both processes and the UE adapts its choice based on current conditions, making the system flexible rather than static. This resolves the contradiction by allowing the UE to use the faster two-step process when conditions permit, while falling back to the more reliable four-step process when capabilities or channel conditions are insufficient.
Solution Approach 2:
The patent changes key parameters of the random access process including message structure (combining Msg1 and Msg3 into MsgA), resource allocation configurations, and capability indicators. By modifying these parameters based on RedCap UE specific requirements, the system optimizes the balance between latency and success rate for reduced capability devices.
2Device complexity
If RedCap UE uses reduced device capabilities, then device complexity and cost are reduced, but cellular signal coverage is lost
Solution Approach 1:
The patent enables RedCap UEs to copy or emulate aspects of full-capability UE behavior through network configuration and adaptive random access procedures. By using capability indicators and configured grants, the system allows RedCap UEs to function similarly to full-capability UEs within their operational limits, effectively copying the access pattern while maintaining reduced hardware complexity.
Solution Approach 2:
The patent segments the random access process into configurable components that can be independently adjusted for RedCap UEs. By dividing the access procedure into selectable modes (two-step vs. four-step) and configurable message structures, the system tailors the access mechanism to match RedCap UE capabilities while maintaining coverage through adaptive resource allocation.
3Productivity
If network uses standard two-step random access configuration, then resource utilization is optimized, but RedCap UE access difficulty increases
Solution Approach 1:
The patent creates a universal random access configuration that serves both full-capability and RedCap UEs. The network configures both two-step and four-step processes with appropriate resources, allowing the same infrastructure to support different UE types. This multi-functional approach maintains resource utilization efficiency while accommodating the specific needs of RedCap U through capability-based selection.
Solution Approach 2:
The patent introduces capability indicators and network configuration messages as intermediaries between the standard random access protocol and RedCap UE requirements. These intermediaries translate RedCap UE capabilities into appropriate access mode selections and resource allocations, easing access difficulty without requiring fundamental changes to the overall system resource management.
Data Source
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AI summary
A method for performing initial access by a user equipment having reduced capabilities is provided. The method comprises transmitting, to a network node, an indication that the UE is a reduced capability (RedCap) UE. The method further comprises receiving, from the network node, a determination of whether a standard two-step random access process should either be used or continually be used for initial access. In response to a determination that the standard two-step random access process should either not be used or not continually be used for the RedCap UE, the method further comprises performing one of facilitating to adjust one or more configurations associated with the standard two-step random access process and facilitating to use a four-step random access process.