Almost Blank Subframes for Idle Mode Paging Reliability

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Solution Overview

Problem

In heterogeneous wireless communication networks, time division approaches to minimize interference between base stations can lead to issues such as UEs in idle mode being unable to receive paging messages, incorrect cell measurements, and synchronization problems due to overlapping transmissions from neighboring cells.

Innovation Solution

Implementing almost blank subframes (AB subframes) where only critical information like CRS, PSS, SSS, PBCH, and paging messages are transmitted, allowing UEs to maintain synchronization and receive essential signals while minimizing interference, and adjusting paging occasions or reselection behaviors to avoid interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If time division approaches are used to minimize interference between base stations, then interference between cells is reduced, but UEs in idle mode cannot receive paging messages and synchronization is lost

Engineering Contradiction:

Improveinterference between cellsVSAvoidpaging message reception

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The time domain is segmented into different types of subframes: normal subframes for regular data transmission and almost blank subframes (ABS) for interference mitigation. This segmentation allows the system to provide different services at different time intervals, ensuring that idle mode UEs can receive paging messages in ABS while data transmission continues in normal subframes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Almost blank subframes are configured periodically in the time domain with a specific period and offset. This periodic structure ensures that idle mode UEs can predictably access resource elements for paging messages and synchronization signals at regular intervals, maintaining reliability while minimizing interference.

Inventive Principle:

Principle #19Periodic action

2Object-affected harmful factors

If almost blank subframes are used to transmit only critical information, then interference is minimized, but device complexity increases due to configuration management

Engineering Contradiction:

Improveinterference from neighboring cellsVSAvoidconfiguration management

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The system configures ABS by changing time domain parameters including period, offset, and duration. These parameter changes allow flexible control of interference patterns while providing a standardized configuration method that can be managed through existing radio resource control mechanisms, balancing interference mitigation with implementation complexity.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If normal subframes are used for data transmission, then network capacity is maintained, but idle mode UEs experience paging failures due to overlapping transmissions

Engineering Contradiction:

Improvenetwork capacityVSAvoidpaging message reception

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Almost blank subframes act as an intermediary time resource that provides a protected environment for idle mode UE operations. During ABS, interfering base stations transmit only essential signals, creating a temporary interference-free zone that mediates between the need for continuous data transmission and the need for reliable paging reception.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9485749B2Idle state interference mitigation in wireless communication network

Publication Date: 2016.11.01 GOOGLE TECHNOLOGY HOLDINGS LLC

AI summary

A method in a mobile station for ranking cells in order to perform reselection from a serving cell to a second cell is disclosed. The method includes detecting a second cell that the mobile station is not allowed to access, determining resources used for transmission of a signal of the second cell, and applying a reselection bias if the resources used for transmission of the signal of the second cell do not substantially overlap resources used for transmission of a signal of the serving cell.