Fallback PRACH Power Derivation After Two-Step RACH Failure
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Solution Overview
Problem
Existing two-step RACH procedures in 5G NR networks often fail, leading to inefficient fallback to four-step RACH procedures due to suboptimal power settings, resulting in increased latency, signaling overhead, and power drain.
Innovation Solution
The UE derives PRACH transmit power parameters for the four-step RACH procedure based on the performance of the failed two-step RACH procedure, optimizing power settings for improved msg1 transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE falls back to a four-step RACH procedure after a failed two-step RACH procedure, then the UE can attempt to establish synchronization with the base station using a different procedure, but the latency increases and power consumption increases due to suboptimal power settings
Solution Approach 1:
The UE performs preliminary actions during the two-step RACH procedure by measuring downlink reference signals and calculating pathloss values. These measurements and calculations are prepared in advance and reused during the fallback four-step RACH procedure, eliminating the need to restart measurements and reducing latency.
Solution Approach 2:
The UE uses feedback from the two-step RACH procedure outcomes to adjust power settings for the four-step RACH procedure. By deriving PRACH transmit power parameters based on previously measured pathloss and downlink signal quality, the system optimizes transmit power to improve success rate while avoiding excessive power consumption.
2Reliability
If the UE falls back to a four-step RACH procedure with default power settings, then the procedure can be initiated, but power drain increases due to suboptimal power settings
Solution Approach 1:
The system dynamically changes power parameters by deriving PRACH transmit power based on measured downlink pathloss and signal quality from the two-step RACH procedure. This parameter optimization ensures sufficient power for successful transmission while minimizing excessive power consumption.
Solution Approach 2:
The UE autonomously determines optimal transmit power settings for the four-step RACH procedure by using its own measurements of downlink reference signals and previously calculated pathloss values. This self-service approach eliminates the need for extensive power probing and reduces overall power consumption.
3Reliability
If the UE retransmits data during the two-step RACH procedure, then the transmission reliability can be improved, but fallback to four-step RACH is triggered which increases overall procedure complexity
Solution Approach 1:
The UE employs universal power calculation methods that work across both two-step and four-step RACH procedures. By calculating pathloss and deriving transmit power parameters that are applicable to both procedure types, the system reduces complexity when transitioning between procedures while maintaining reliability.
Data Source
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AI summary
A user equipment (UE) is configured to initiate a two-step random access channel (RACH) procedure to synchronize with a base station, initiate a fallback four-step RACH procedure after the two-step RACH procedure, configure a random access preamble transmission for the four-step RACH procedure, wherein configuring the random access preamble transmission comprises deriving a physical random access channel (PRACH) transmit power parameter value based on a parameter used to perform a transmission during the two-step RACH procedure and transmit the random access preamble for the four-step RACH procedure to the base station.