First PUSCH Power Control During Random Access Uplink

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Solution Overview

Problem

In wireless communication systems, particularly in LTE, the Physical Uplink Shared Channel (PUSCH) transmission during a Random Access Channel (RACH) procedure lacks effective transmit power control, as the Physical (PHY) layer is unaware of the required power level for the first message, leading to potential transmission failures.

Innovation Solution

Implementing transmit power control (TPC) for the first PUSCH message based on the power spectral density of the successfully transmitted RACH preamble, with the Medium Access Control (MAC) layer communicating TPC data to the PHY layer, and adjusting power levels accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If transmit power control is not implemented for the first PUSCH message during RACH procedure, then the system maintains simplicity in power control implementation, but transmission reliability deteriorates due to PHY layer being unaware of required power level

Engineering Contradiction:

Improvetransmission reliabilityVSAvoidpower control complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The MAC layer serves as an intermediary between the PHY layer and power control information. It receives TPC commands from the network and translates them into appropriate transmit power levels for PUSCH messages, bridging the information gap without requiring direct complex power control logic in the PHY layer

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system performs preliminary power control setup by having the MAC layer pre-calculate and store TPC commands based on RACH preamble transmission power. This preliminary action ensures that when the first PUSCH message needs to be transmitted, the correct power level is already determined, avoiding transmission failures

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If TPC commands are frequently updated for PUSCH transmission, then transmission accuracy improves, but signaling overhead and processing complexity increase

Engineering Contradiction:

Improvepower level accuracyVSAvoidprocessing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system applies TPC commands selectively rather than continuously. The MAC layer updates PUSCH power control only when necessary (when TPC commands are received in RACH responses), avoiding unnecessary processing while maintaining sufficient power level accuracy for successful transmission

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentEP3761723B1Method and apparatus for power control of first data transmission in random access procedure of FDMA communication system

Publication Date: 2025.12.31 QUALCOMM INC

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AI summary

Transmit power is controlled for a first uplink data transmission on Physical Uplink Shared Channel (PUSCH) during random access channel (RACH) procedure. Power control adjustment for the first PUSCH transmission is performed relative to the power spectral density used for successful PRACH transmission as adjusted for bandwidth difference, etc. The uplink Physical random access channel carries the RACH information that is transmitted by the user equipment (UE) during registrations or base station originated calls. A PRACH is composed of a number of preambles and a message portion. The preambles are a series of radio frequency power "steps" that increase in power according to the power step setting until the maximum number of preambles is reached or the base station acknowledges. Once the UE receives a positive indication, it transmits the message portion of the PRACH which consists of message data and control data with independent power gain control.