PTT Service Prioritization in Roamed 3G Networks

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Public Safety users in Land Mobile Radio (LMR) communication systems face service degradation and call interruptions when roaming from 4G to 3G or 2G networks, particularly for Push-To-Talk (PTT) services, due to prioritization of voice calls over data services in these networks.

Innovation Solution

A communication system that includes a 4G Packet Switched Network, 3G Circuit Switched Network, PTT Server, and Mobile Device, where the HSS authorizes and registers mobile devices for PTT services, ensuring only packet-switched mode communication upon roaming to 3G networks, preventing circuit-switched service activation and maintaining priority for PTT calls.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a mobile device roams to a 3G network from a 4G network, then the device can maintain connectivity, but ongoing voice calls may block priority PTT calls and ongoing PTT calls may be interrupted by incoming voice calls

Engineering Contradiction:

ImprovePTT call reliabilityVSAvoidService priority management

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The HSS pre-authorization mechanism determines before the mobile device roams to 3G whether the device is authorized for PTT services. This preliminary determination prevents circuit-switched service activation and ensures packet-switched mode communication is maintained, thereby preventing voice calls from blocking or interrupting PTT calls before the problem can occur

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The HSS acts as an intermediary between the mobile device and the 3G network's circuit-switched service. By intercepting service activation requests and making authorization decisions based on pre-stored PTT service status, the HSS mediates to prevent inappropriate circuit-switched activation that would disrupt PTT calls

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If the network allows circuit-switched service activation in 3G, then voice call functionality is available, but PTT service priority and continuity are compromised

Engineering Contradiction:

ImproveVoice call availabilityVSAvoidPTT service continuity

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system performs preliminary authorization determination at the HSS before the mobile device attempts to activate circuit-switched services in 3G. The HSS stores PTT service status and uses this information to pre-determine whether circuit-switched service should be activated, preventing PTT disruption before it occurs

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts the PTT service authorization logic from the real-time call management process and places it in the HSS as a pre-configured authorization parameter. This separation allows the HSS to independently control circuit-switched service activation based on PTT service status, preventing voice calls from interfering with PTT services

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS11368887B2Method for prioritizing push-to-talk service in a roamed network

Publication Date: 2022.06.21 MOTOROLA SOLUTIONS INC

AI summary

A method is provided that allows for prioritizing Push-To-Talk (PTT) service in a roamed network. PTT service is enabled for a mobile device at a first network. The mobile device roams to a second network that is of an older generation than the first network. It is determined that the mobile device has an active PTT subscription. PTT service is prioritized for the mobile device over circuit switched services on the second network.