Cell Reselection Thresholds Prevent Ping-Pong in Mobile Systems

Solution Overview

Problem

In mobile communications systems, the ping-pong effect occurs due to frequent cell reselections, especially in handover regions, leading to inefficient resource usage and poor communication quality, as high-speed UEs mistakenly use scaled-down cell reselection times, causing repeated handovers between cells.

Innovation Solution

A method and apparatus that allow User Equipment (UE) to detect ping-pong by setting specific thresholds (Ncr and Tcrmax) for cell reselections, determining if it is a high-speed UE, and adjusting cell reselection time limits (Treselection) based on these thresholds to prevent excessive reselections, thereby distinguishing between high-speed and stationary/slow UE states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the UE uses scaled-down cell reselection time limit for high-speed UEs, then the UE can respond faster to cell changes, but the UE mistakenly performs excessive reselections in handover regions causing ping-pong effect

Engineering Contradiction:

Improvecell reselection response speedVSAvoidcell connection stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where the UE counts the number of reselections to the same cell within a predetermined time period. If this count exceeds a threshold, the UE determines it is in a handover region and switches to a different cell reselection time limit, thereby using feedback information to adaptively adjust system parameters and prevent ping-pong effect.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent makes the cell reselection time limit dynamic by allowing the UE to switch between different time limit values based on its current state. The UE determines whether to use a first time limit (for high-speed scenarios) or a second time limit (for handover region scenarios) based on real-time detection of reselection patterns, thus adapting the system parameter dynamically to prevent excessive reselections.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the UE performs frequent cell reselections to find the best cell, then the UE can improve communication quality, but the UE wastes system resources and increases ping-pong effect in handover regions

Engineering Contradiction:

Improvecommunication qualityVSAvoidsystem resource consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent applies different cell reselection strategies for different local conditions. The UE detects whether it is in a handover region by counting reselections to the same cell within a time period, and then applies a different time limit parameter accordingly. This local differentiation allows the system to maintain communication quality where needed while reducing unnecessary reselections in handover regions, thereby saving system resources.

Inventive Principle:

Principle #3Local quality

3Reliability

If the UE uses a long cell reselection time limit, then the UE avoids frequent reselections and reduces ping-pong effect, but the UE cannot quickly adapt to actual high-speed movement scenarios

Engineering Contradiction:

Improvecell connection stabilityVSAvoidUE state adaptation capability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent makes the cell reselection time limit dynamic by allowing the UE to switch between different time limit values based on its current state. The UE determines whether to use a first time limit (for high-speed scenarios) or a second time limit (for handover region scenarios) based on real-time detection of reselection patterns, thus adapting the system parameter dynamically to prevent excessive reselections while maintaining adaptability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements a feedback mechanism where the UE counts the number of reselections to the same cell within a predetermined time period. If this count exceeds a threshold, the UE determines it is in a handover region and switches to a different cell reselection time limit, thereby using feedback information to adaptively adjust system parameters and prevent ping-pong effect.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7480519B2Cell reselection method and apparatus for preventing ping-pong in a mobile communications system

Publication Date: 2009.01.20 SAMSUNG ELECTRONICS CO LTD

AI summary

A method and apparatus are provided for enabling a UE to perform accurate and efficient cell reselection in a cellular mobile communications system. If reselection to the same cell is repeated, the UE releases itself from a high-speed UE state or excludes the number of reselections to the same cell from the number of cell changes counted for a duration set for deciding as to the high-speed UE state, according to a ping-pong duration threshold and a ping-pong occurrence number threshold. The UE uses a non-scaled down cell reselection time limit in a non-high-speed UE state, and a scaled-down cell reselection time limit in the high-speed UE state. Thus, the UE reselects to a non-serving cell having the highest ranking continuously for the cell reselection time limit.