PRACH Repetition Windowing for NR Uplink Coverage Enhancement

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Solution Overview

Problem

In next-generation wireless communication systems like NR, uplink coverage is a bottleneck due to higher carrier frequencies leading to path-loss, especially for short PRACH formats, which are crucial for procedures like initial access and beam failure recovery.

Innovation Solution

Implementing multiple PRACH transmissions with PRACH repetition window determination based on synchronization signal blocks (SSBs) and association periods to enhance coverage, allowing for non-consecutive and frequency-division multiplexed PRACH occasions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If higher carrier frequencies are used in NR, then data rate and capacity are improved, but path-loss increases causing uplink coverage degradation

Engineering Contradiction:

Improvedata rateVSAvoiduplink coverage

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The PRACH transmission is segmented into multiple repetitions transmitted at different occasions. Each repetition carries the same preamble information, and the gNB combines these repetitions to improve detection reliability. This segmentation allows the system to maintain higher frequency benefits while compensating for coverage loss through multiple transmission attempts.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system performs preliminary actions by transmitting multiple PRACH repetitions before establishing a reliable connection. These preliminary transmissions ensure that the gNB has sufficient opportunities to detect the preamble despite path-loss, enabling subsequent reliable communication at higher frequencies.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If multiple PRACH transmissions are implemented, then coverage enhancement is achieved, but uplink transmission time and resource consumption increase

Engineering Contradiction:

ImprovecoverageVSAvoidtransmission time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

PRACH repetitions are transmitted periodically at different PRACH occasions according to a configured pattern. This periodic transmission allows the system to achieve coverage enhancement through multiple attempts while maintaining structured resource usage and enabling the gNB to expect repetitions at predictable intervals for efficient processing.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

If a PRACH preamble transmission fails to be detected or the RAR is not received, the UE discards the failed transmission attempt and recovers by transmitting the preamble again in subsequent PRACH occasions. This discard and recover mechanism ensures coverage reliability without requiring continuous transmission, optimizing time resource usage.

Inventive Principle:

Principle #34Discarding and recovering

3Productivity

If PRACH occasions are frequency-division multiplexed, then resource utilization is improved, but complexity of PRACH repetition window determination increases

Engineering Contradiction:

Improveresource utilizationVSAvoidrepetition window determination

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The PRACH repetition window is determined to include a number of consecutive valid PRACH occasions, ensuring continuous transmission opportunities for repetitions. This continuity approach simplifies the determination process by providing a straightforward window definition that works effectively even with frequency-division multiplexing, maintaining resource utilization while managing complexity.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS12550200B2Multiple physical random access channel (PRACH) transmissions for coverage enhancement

Publication Date: 2026.02.10 INTEL CORP

AI summary

Various embodiments herein provide techniques for multiple physical random access channel (PRACH) transmissions for coverage enhancement. For example, embodiments may relate to PRACH window determination for multiple PRACH transmissions. In one example, the PRACH repetition window is determined in accordance with a number of consecutive valid PRACH occasions associated with a synchronization signal block (SSB). Other embodiments may be described and claimed.