PRACH Preamble Selection via RSRP Thresholds for 5G Random Access

Solution Overview

Problem

In 5G cellular systems, cell-edge user equipment (UEs) experience delays due to poor connectivity during the random access procedure, particularly in identifying UE types through physical random access channel (PRACH) resources, which affects the extension of 5G service coverage.

Innovation Solution

A method where user equipment (UE) receives system information including PRACH configuration with RSRP thresholds and preamble index ranges associated with synchronization signal blocks (SSBs), allowing it to select an SSB and preamble based on RSRP levels to optimize random access, thereby improving connectivity and reducing latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cell-edge UEs use standard random access procedure, then they can establish basic connectivity, but they experience delays due to poor connectivity

Engineering Contradiction:

Improveconnectivity reliabilityVSAvoidrandom access delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The base station performs preliminary classification of UEs into different RSRP levels and pre-associates specific preamble index ranges with each level. This preliminary organization allows cell-edge UEs to immediately select appropriate preambles without trial-and-error, reducing random access delay while ensuring reliable connectivity through matched resource allocation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter of preamble selection from random to deterministic based on RSRP measurements. By mapping RSRP levels to specific preamble index ranges, the system adapts the random access parameters to channel conditions, allowing cell-edge UEs to use preambles optimized for their signal quality, thereby improving reliability and reducing access time.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If UEs select preambles randomly, then the procedure is simple, but cell-edge UEs experience coverage limitations and delays

Engineering Contradiction:

Improvepreamble selection simplicityVSAvoidrandom access success rate

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The base station performs preliminary classification of UEs into different RSRP levels and pre-associates specific preamble index ranges with each level. This preliminary organization allows cell-edge UEs to immediately select appropriate preambles without trial-and-error, reducing random access delay while ensuring reliable connectivity through matched resource allocation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter of preamble selection from random to deterministic based on RSRP measurements. By mapping RSRP levels to specific preamble index ranges, the system adapts the random access parameters to channel conditions, allowing cell-edge UEs to use preambles optimized for their signal quality, thereby improving reliability and reducing access time.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If multiple UEs use the same PRACH resources, then resource utilization is efficient, but collision probability increases causing delays

Engineering Contradiction:

ImprovePRACH resource utilizationVSAvoidcollision resolution time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent segments the preamble index space into multiple non-overlapping ranges, each assigned to a specific RSRP level. This segmentation divides the previously shared PRACH resources into dedicated subsets, reducing collision probability among UEs with different signal conditions while maintaining overall resource utilization efficiency through systematic allocation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different preamble index ranges are assigned to UEs based on their local RSRP conditions. Cell-edge UEs with lower RSRP values receive specific preamble ranges optimized for their channel conditions, while cell-center UEs receive different ranges. This local optimization reduces collisions by matching resource quality to UE conditions, decreasing collision resolution time.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20240237076A9User equipment apparatus, base station apparatus, and communication method

Publication Date: 2024.07.11 SHARP KK

AI summary

A UE includes reception circuitry configured to receive PRACH configuration information comprising a first RSRP threshold and a first list of preamble index ranges, and control circuitry configured to, if one of one or more SSBs with SS-RSRP above the first RSRP threshold is available, select an SSB with SS-RSRP above the first RSRP threshold; else select any SSB, wherein in a first case that the PRACH configuration information further provides a second list of preamble index ranges, the control circuitry is further configured to select a preamble from the preamble index range associated with the selected SSB among the preamble index ranges in second list, in a second case that the PRACH configuration information does not provide the second list, the control circuitry is further configured to select a preamble from the preamble index range associated with the selected SSB among the preamble index ranges in the first list.