PRACH Power Ramp-Up for Cross-Link Interference Mitigation
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Solution Overview
Problem
The challenge of cross-link interference (CLI) in 3GPP New Radio (NR) systems, particularly in TDD carriers, arises from the transmission of Physical Random Access Channel (PRACH) signals in uplink subbands over downlink or flexible symbols, which interferes with both gNB-to-gNB and UE-to-UE communications.
Innovation Solution
A method for determining PRACH transmission power based on a maximum value, a second power offset, and a quicker power ramp-up step when specific conditions are met, such as transmission in uplink subbands or flexible symbols, to mitigate CLI by enhancing power control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PRACH signal is transmitted in uplink subband over downlink or flexible symbols, then uplink transmission opportunity is created, but cross-link interference occurs between gNB and UE
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting PRACH transmission power based on the detected downlink signal strength. The UE measures the downlink reference signal power and uses this information to calculate an appropriate PRACH transmission power level, thereby adapting the transmission parameters to minimize cross-link interference while maintaining uplink communication capability.
2Reliability
If PRACH transmission power is increased to improve signal reception, then signal reception quality improves, but cross-link interference increases
Solution Approach 1:
The patent implements feedback mechanism where the UE continuously monitors the downlink signal strength and uses this feedback information to adjust the PRACH transmission power. The base station also provides feedback through downlink reference signals, enabling the UE to optimize its transmission power settings in real-time to balance signal reception quality and interference reduction.
Solution Approach 2:
The patent dynamically changes the PRACH transmission power parameter based on measured downlink signal conditions. The UE calculates the transmission power by considering the downlink reference signal power and applies appropriate power adjustment factors, thereby optimizing the power level for each transmission occasion to minimize cross-link interference while ensuring reliable signal reception.
3Speed
If power ramp-up step is increased for quicker power adjustment, then power adaptation speed improves, but transmission power control precision decreases
Solution Approach 1:
The patent applies dynamics by implementing a multi-step power ramp-up mechanism that can adapt to different transmission conditions. The system can use larger power steps when quick adaptation is needed and finer power adjustments when precision is critical, making the power control mechanism flexible and adaptive to varying operational requirements.
Data Source
AI summary
A method for transmitting a PRACH signal includes: transmitting a PRACH signal with a transmission power in one of multiple PRACH occasions in a random access procedure, where in response to the PRACH occasion satisfies a specific condition, the transmission power of the PRACH signal is determined based on an algorithm involving at least one of the following: a maximum value for PRACH transmission power; a second power offset besides a first power offset for PRACH transmission in the PRACH occasion; or a second power ramp-up step besides a first power ramp-up step for accomplishing power ramp-up, where the power ramp-up is quicker when the second power ramp-up step is used than when only the first power ramp-up step is used.