Ad-hoc Network Reference Signal for DRX Synchronization

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Solution Overview

Problem

Ad-hoc wireless networks lack an explicit discontinuous reception (DRX) mechanism, leading to inefficient power usage and increased delay in connection re-establishment, particularly for time-critical services like gaming, due to the absence of a central infrastructure to configure and agree on DRX parameters among nodes.

Innovation Solution

A node provides a reference signal pattern to enable UEs to maintain synchronization during DRX operation, allowing them to enter and maintain DRX mode, even in the absence of a central infrastructure, by determining and requesting a suitable node to transmit a reference signal for synchronization, which can be periodic or quasi-periodic, aligned with DRX cycles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If UEs continuously monitor the channel to maintain connection in ad-hoc networks, then connection reliability is improved, but power consumption increases

Engineering Contradiction:
Improveconnection reliabilityVSAvoidpower consumption
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent implements discontinuous reception (DRX) where UEs periodically wake up to monitor control channels and reference signals, then return to sleep mode. This periodic monitoring maintains connection reliability while significantly reducing power consumption compared to continuous monitoring, directly resolving the contradiction between reliability and energy usage.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent introduces a reference signal as an intermediary that enables UEs to maintain synchronization during DRX periods. The reference signal acts as a mediator between the UE and the network, allowing the UE to quickly re-synchronize upon waking from sleep mode without requiring continuous monitoring, thus maintaining reliability while enabling power saving.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Use of energy by moving object

If UEs enter DRX mode to save power, then power consumption is reduced, but connection re-establishment delay increases

Engineering Contradiction:
Improvepower consumptionVSAvoidconnection re-establishment delay
Core Design Contradiction:
Use of energy by moving objectVSLoss of time

Solution Approach 1:

The patent applies preliminary action by having UEs perform synchronization operations in advance during their active periods. UEs use the reference signal to pre-synchronize their timing and frequency before entering DRX mode, so that when they wake up, they are already prepared for rapid connection re-establishment without requiring lengthy synchronization procedures.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The reference signal serves as an intermediary that enables fast re-synchronization. When UEs wake from DRX mode, they can quickly acquire timing and frequency information from the reference signal without requiring extensive pilot signals or synchronization sequences, thereby reducing re-establishment delay while maintaining power saving benefits.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Adaptability or versatility

If ad-hoc networks implement DRX operation without central infrastructure, then network autonomy is improved, but synchronization maintenance becomes difficult

Engineering Contradiction:
Improvenetwork autonomyVSAvoidsynchronization maintenance
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent extracts the synchronization function from the central infrastructure and implements it through distributed reference signals transmitted by individual UEs or relay nodes. This extraction enables ad-hoc networks to maintain synchronization autonomously without requiring a central base station, directly improving network autonomy while maintaining reliability through the reference signal mechanism.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent implements self-service by enabling UEs to autonomously generate and transmit reference signals for mutual synchronization. Nodes in the ad-hoc network serve themselves and their neighbors by providing reference signals, eliminating the need for centralized synchronization control and enabling autonomous operation while maintaining reliable synchronization through distributed participation.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP2556718B1Methods and arrangements for ad-hoc wireless networks
Publication Date: 2020.06.03 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
  • EP2556718B1 patent drawingFigure 1
  • EP2556718B1 patent drawingFigure 2
  • EP2556718B1 patent drawingFigure 3

AI summary

The present invention relates to methods and arrangements in an ad-hoc network wherein the ad-hoc devices are configured to enter DRX mode. The basic concept of the embodiments of the present invention is to let a node initiate and maintain transmission of a specific reference signal pattern during the DRX operation of an adhoc device, referred to as a UE. The transmission of the reference signal pattern enables the UE to maintain synchronization.