SRS Transmit Power Control via RACH Measurement

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Solution Overview

Problem

Current methods for determining the location of user equipment (UE) in cellular networks, such as those using 4G LTE or 5G NR, face inefficiencies and inaccuracies in positioning due to uncontrolled transmit output power of uplink positioning sounding reference signals (SRS), which can lead to incorrect decoding by the network.

Innovation Solution

The method involves determining an unused Random Access Channel (RACH) occasion to measure the output power of the UE's transmit chain, calculating a transmit output power offset based on this measurement, and adjusting the power output for positioning SRS transmissions to ensure accurate power levels, using either a predetermined offset or characterizations of the transmit chain and SRS signal characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the transmit output power of uplink positioning SRS is not controlled, then the positioning process can be performed without additional power adjustment mechanisms, but the network may incorrectly decode the SRS signals leading to positioning inaccuracies

Engineering Contradiction:

Improvepositioning accuracyVSAvoidpower control mechanism complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent performs preliminary power measurement during unused RACH occasions before actual positioning SRS transmission. The UE measures the output power of its transmit chain and determines a power offset in advance, so that when positioning SRS needs to be transmitted, the correct power level is already known and can be applied immediately without real-time adjustment complexity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The UE autonomously performs power measurement and offset determination without requiring network assistance or additional signaling. The device uses its own unused RACH occasions to measure transmit chain power characteristics and self-determines the appropriate power offset for positioning SRS, eliminating the need for complex network-coordinated power control mechanisms

Inventive Principle:

Principle #25Self-service

2Measurement precision

If the UE uses unused RACH occasions for power measurement, then accurate transmit chain characterization can be achieved, but the RACH resources that could be used for random access are consumed

Engineering Contradiction:

Improvetransmit chain power measurement accuracyVSAvoidRACH occasion availability

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent converts previously wasted or unused RACH occasions into beneficial measurement opportunities. Instead of these idle time slots representing lost random access capacity, the UE utilizes them to perform transmit chain power measurements and determine power offsets, thereby transforming resource underutilization into a source of positioning accuracy improvement

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS11564178B2Sounding reference signal (SRS) transmit power control

Publication Date: 2023.01.24 QUALCOMM INC

AI summary

Transmit output power for an uplink (UL) positioning sounding reference signal (SRS) may be determined by measuring output power of a transmit chain of a user equipment (UE) during an unused RACH occasion. A transmit output power offset is determined based on a difference between the measured output power and a predetermined output power. The transmit output power offset may be used to adjust the power output of the UE.