UE Random Access Power Ramping and Timing Advance for NTN

Solution Overview

Problem

In non-terrestrial networks (NTN), the large propagation delays and inaccuracies in GNSS information lead to issues with the transmission and reception of random access preambles, resulting in failed initial access attempts by user equipment (UE) due to incorrect timing advances and power settings.

Innovation Solution

The UE adjusts its transmission timing and power settings based on GNSS location and time information, incorporating reliability measures to ensure accurate timing advance (TA) and power ramping procedures, allowing for successful random access within the configured cyclic prefix.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the UE uses standard power ramping procedure for random access, then the transmit power is increased to ensure reception, but the timing advance becomes inaccurate due to large propagation delays in NTN

Engineering Contradiction:

Improverandom access success rateVSAvoidtiming advance accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The base station performs preliminary estimation of the uplink timing advance based on the downlink timing measured from the random access preamble, and provides this preliminary timing advance value to the UE before the UE transmits uplink data. This preliminary action allows the UE to compensate for propagation delays without needing to wait for the standard timing advance command, thereby resolving the contradiction between ensuring reliable random access and maintaining timing accuracy in NTN environments with large propagation delays

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If the UE waits for timing advance command before transmitting, then timing accuracy is improved, but the access delay increases due to large propagation delays in NTN

Engineering Contradiction:

Improvetiming advance accuracyVSAvoidaccess delay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The base station performs preliminary estimation of the uplink timing advance based on the downlink timing measured from the random access preamble, and provides this preliminary timing advance value to the UE before the UE transmits uplink data. This preliminary action allows the UE to compensate for propagation delays without needing to wait for the standard timing advance command, thereby resolving the contradiction between ensuring reliable random access and maintaining timing accuracy in NTN environments with large propagation delays

Inventive Principle:

Principle #10Preliminary action

3Use of energy by moving object

If the UE transmits random access preamble with initial power, then energy consumption is reduced, but the signal may not be received due to path loss in NTN

Engineering Contradiction:

Improvetransmit power consumptionVSAvoidsignal reception reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The base station measures the received power of the random access preamble and provides feedback to the UE about the received signal quality. Based on this feedback, the base station determines the appropriate timing advance value and transmits power for uplink data. This feedback mechanism allows the system to balance energy consumption and reception reliability by adjusting transmit power based on actual channel conditions rather than using fixed high power levels

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12550081B2Adjusted UE TX power ramping for initial access for support of NR over NTN

Publication Date: 2026.02.10 NOKIA TECHNOLOGIES OY

AI summary

In a non-terrestrial network, the delay in reception time may prevent reception of a random access preamble. A combination of increasing transmit power and changing the timing with which the random access preamble is transmitted may enable reception of the random access preamble. One or more criteria may be used to determine whether the timing advance value with which the random access preamble is transmitted should be changed before retransmission is attempted.