UE Reselection Control via Path-Loss Threshold for CSG Interference

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Solution Overview

Problem

The presence of Closed Subscriber Group (CSG) cells causes interference with macro cell UEs, leading to service degradation and battery life issues due to unnecessary reselections, as UEs attempt to avoid accessing CSG cells, resulting in frequent reading of system information and potential battery drain.

Innovation Solution

A method where the macro cell broadcasts a path-loss threshold, and UEs only read system information from CSG cells if accessible, with the use of an Intra-frequency reselection indication (IFRI) and a timer-based mechanism to minimize unnecessary readings, allowing UEs to reselect or ignore CSG cells based on path-loss and IFRI settings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If UEs read system information from CSG cells to determine accessibility, then UE can make informed reselection decisions, but battery life is severely adversely impacted

Engineering Contradiction:

Improvereselection decision accuracyVSAvoidbattery life

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The macro cell eNodeB performs preliminary action by broadcasting the path-loss threshold in advance, allowing UEs to pre-determine whether to read CSG cell system information based on current signal conditions, thereby avoiding unnecessary battery-consuming readings

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The path-loss threshold acts as an intermediary parameter that mediates between the UE's need to assess CSG cell accessibility and the battery life constraint, enabling informed decisions without direct reading of all CSG cell information

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If UEs frequently reselect to avoid CSG cells, then interference to CSG cells is reduced, but unnecessary reselections cause battery drain

Engineering Contradiction:

Improveinterference to CSG cellsVSAvoidbattery life

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The system changes the parameter used for reselection decisions from binary CSG cell avoidance to a continuous path-loss threshold comparison, allowing UEs to make more nuanced decisions that reduce unnecessary reselections while maintaining interference protection

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The mechanism provides feedback through the path-loss threshold broadcasting, enabling UEs to adjust their behavior dynamically based on current signal conditions rather than following fixed reselection rules

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If IFRI is set to disallowed, then UE bars frequency and avoids CSG cells, but frequent reselections occur causing battery drain

Engineering Contradiction:

Improveinterference managementVSAvoidtime for reselection operations

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The system changes the control parameter from the binary IFRI flag to a continuous path-loss threshold, enabling gradient-based decisions that reduce unnecessary reselection operations and associated time consumption

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8958794B2Efficient reselections in the presence of closed subscriber group cells

Publication Date: 2015.02.17 GOOGLE TECHNOLOGY HOLDINGS LLC

AI summary

A method in a mobile station for avoiding interference to restricted access cells, including detecting presence of a restricted access cell, determining that a measured path-loss is larger than a path-loss threshold, determining that the mobile station is not allowed to access the restricted access cell, and barring a carrier frequency on which the restricted access cell is deployed when the measured path-loss is larger than the path-loss threshold and when the mobile station is not allowed access to the restricted access cell.