Access Node Synchronization Collision Avoidance

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Solution Overview

Problem

In Ultra-Dense Networks (UDNs) employing hierarchical synchronization, synchronization collisions occur when the root Access Node (AN) fails, leading to disruptions in synchronization maintenance.

Innovation Solution

Implementing a method in ANs at synchronization level 1 and above, where a random back-off procedure is initiated upon detecting a failed root AN, and a synchronization signal is generated and broadcast only if no signal is received from another AN during the back-off, preventing direct and indirect synchronization collisions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple ANs at synchronization level 1 autonomously take over as root ANs when the level-0 AN fails, then synchronization continuity is maintained, but synchronization collisions occur between level-1 ANs

Engineering Contradiction:

Improvesynchronization continuityVSAvoidsynchronization collision

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

ANs at synchronization level 1 perform a preliminary random back-off procedure before taking over as root ANs. This preliminary action allows potential root ANs to wait for a random duration and listen for other ANs' synchronization signals before broadcasting their own, preventing synchronization collisions while maintaining synchronization continuity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

ANs at synchronization level 1 implement a feedback mechanism where they listen for synchronization signals from other ANs during the back-off period. If a signal is detected, the AN adjusts its behavior accordingly (waits or synchronizes to the detected signal), preventing collisions through real-time feedback from the network environment.

Inventive Principle:

Principle #23Feedback

2Speed

If ANs at synchronization level 1 immediately broadcast synchronization signals upon detecting root AN failure, then synchronization is quickly restored, but direct synchronization collisions occur between nearby level-1 ANs

Engineering Contradiction:

Improvesynchronization restoration speedVSAvoiddirect synchronization collision

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

Before immediately broadcasting synchronization signals, ANs perform a preliminary random back-off procedure where they wait for a random duration and listen for other ANs' signals. This preliminary action reduces the probability of direct collisions between nearby level-1 ANs while still enabling relatively quick synchronization restoration.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The synchronization restoration process uses periodic actions with random intervals. ANs attempt to become root ANs in periodic rounds, with each round involving a random back-off period followed by a signal broadcast attempt, balancing speed with collision avoidance.

Inventive Principle:

Principle #19Periodic action

3Area of stationary object

If ANs at synchronization level 1 broadcast synchronization signals simultaneously after root AN failure, then synchronization coverage is maximized, but indirect synchronization collisions occur through level-2 ANs

Engineering Contradiction:

Improvesynchronization coverage areaVSAvoidindirect synchronization collision

Core Design Contradiction:

Area of stationary objectVSObject-generated harmful factors

Solution Approach 1:

ANs perform a preliminary random back-off procedure before broadcasting synchronization signals. This preliminary action ensures that even if multiple ANs broadcast simultaneously to maximize coverage, the random timing differences prevent level-2 ANs from receiving conflicting signals, thereby avoiding indirect synchronization collisions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The synchronization broadcast process is made dynamic through random back-off periods. Instead of simultaneous static broadcasting, ANs dynamically adjust their broadcast timing based on random delays and detected network conditions, allowing maximum coverage while preventing indirect collisions.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10111195B2Methods implemented in access nodes for maintaining synchronization in radio access network and associated access nodes

Publication Date: 2018.10.23 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method implemented in Access Nodes (ANs) for maintaining synchronization in a radio access network employing a hierarchical synchronization mechanism. One of the methods is implemented in an Access Node (AN) at synchronization level 1 and comprises detecting that an AN at synchronization level 0 is down and initiating a random back-off procedure. The method further comprises determining whether a first synchronization signal generated at another AN at synchronization level 1 is received during the random back-off procedure. If it is determined that no first synchronization signal is received during the random back-off procedure, a second synchronization signal providing a synchronization reference is generated and broadcast upon completion of the random back-off procedure. The method also provides ANs for maintaining synchronization in a radio access network employing a hierarchical synchronization mechanism.