Random Access Preamble Selection for Coverage Enhancement

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In wireless communication systems, user equipment (UE) devices, especially those using coverage enhancement (CE) techniques, face challenges in establishing reliable random access procedures due to lack of coordination with the network regarding CE levels, leading to disruptions and delays in communication link establishment.

Innovation Solution

A method where UE selects a coverage enhancement level based on coverage limitations, receives system information about available CE levels and corresponding physical random access channel (PRACH) configurations from a base station, and transmits a random access message according to the selected CE level, allowing coordinated CE techniques for improved reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If UE uses coverage enhancement techniques to improve communication reliability, then reliability is improved, but coordination with the network regarding CE levels is lost, causing disruptions and delays in access procedure

Engineering Contradiction:

Improvecommunication link reliabilityVSAvoidaccess procedure coordination

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The base station performs preliminary action by broadcasting CE level configurations and PRACH parameters before the UE attempts random access. The UE selects a CE level based on these pre-provided configurations, ensuring coordinated operation without real-time negotiation during the access procedure.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The UE autonomously selects the appropriate CE level and corresponding PRACH configuration based on its coverage conditions and the broadcasted configurations. This self-service mechanism eliminates the need for network coordination during the access procedure while maintaining reliability through pre-defined CE techniques.

Inventive Principle:

Principle #25Self-service

2Ease of operation

If UE selects CE level autonomously based on coverage limitations, then access procedure coordination is improved, but communication reliability may deteriorate without network coordination

Engineering Contradiction:

Improveaccess procedure coordinationVSAvoidcommunication link reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

Multiple PRACH configurations are defined with different parameters (preamble formats, time/frequency resources, power levels) corresponding to different CE levels. The UE changes these parameters based on its selected CE level, allowing autonomous operation while maintaining reliability through appropriate parameter selection for the coverage conditions.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If multiple PRACH configurations are defined for different CE levels, then communication reliability is improved through coordinated CE techniques, but device complexity increases

Engineering Contradiction:

Improverandom access reliabilityVSAvoidUE configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The PRACH configuration space is segmented into multiple distinct configurations, each optimized for a specific CE level. This segmentation allows the UE to select the appropriate configuration based on its coverage conditions, improving reliability while keeping the selection process straightforward through clear mapping between CE levels and configurations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each PRACH configuration is optimized with local quality tailored to its corresponding CE level, with specific parameters (preamble formats, resources, power) optimized for that coverage condition. This allows the UE to achieve reliable access by selecting the configuration with the appropriate local quality for its specific coverage scenario.

Inventive Principle:

Principle #3Local quality

4Adaptability or versatility

If CE techniques are used to extend coverage, then coverage limitation is improved, but access procedure delays occur due to lack of network coordination

Engineering Contradiction:

Improvecoverage extension capabilityVSAvoidaccess procedure time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11019656B2Random access procedures under coverage limitations

Publication Date: 2021.05.25 QUALCOMM INC

AI summary

Methods, systems, and devices for wireless communication are described. A user equipment (UE) may select a coverage enhancement (CE) level based on a coverage limitation. The UE may then receive system information from a base station indicating an index of CE levels and corresponding physical random access channel (PRACH) configurations, and the UE may transmit a random access preamble using the PRACH configuration for the selected CE level. For example, the UE may transmit the preamble based on a frequency offset that corresponds to the selected CE level. In some cases, the UE and base station may also associate groups of preambles with downlink (DL) CE levels. The UE may select a preamble from a group corresponding to a desired DL CE level for a random access response message. The base station may determine the DL CE level based on the group the preamble was selected from and respond accordingly.