MME Inter-Domain Coordination for LTE to 2G/3G Call Setup

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Solution Overview

Problem

In scenarios where User Equipment (UE) operates in an LTE cell without IP Multimedia Subsystem (IMS) control plane functionality, establishing calls requires transitioning from the LTE network to a GSM or UMTS network, which is not supported, hindering call setup.

Innovation Solution

A Mobility Management Entity (MME) is introduced to handle this transition by translating Tracking Area Update (TAU) requests into Location Area Update (LAU) requests, communicating with a Mobile Switching Center (MSC) to identify suitable location area identifiers and Network Resource Identifiers, facilitating handover to a 2G/3G cell for call establishment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If UE operates in LTE network without IMS control plane functionality, then LTE network coverage is maintained, but call establishment capability is lost

Engineering Contradiction:

Improvecall establishment capabilityVSAvoidnetwork functionality support

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The MME acts as an intermediary between the LTE network and GSM/UMTS network. It translates TAU requests into LAU requests and coordinates with the MSC to enable call establishment in networks lacking IMS control plane functionality, thus bridging the capability gap

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If UE transitions from LTE to GSM/UMTS network for call establishment, then call setup capability is enabled, but network complexity increases

Engineering Contradiction:

Improvecall establishment capabilityVSAvoidnetwork architecture complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The MME is designed with multi-functionality, handling both normal LTE mobility management and the additional function of coordinating inter-domain handovers for call establishment. This universal approach avoids adding separate dedicated systems for each function

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If UE performs handover to GSM/UMTS for call establishment, then control plane signaling is enabled, but service continuity may be interrupted

Engineering Contradiction:

Improvecontrol plane signaling capabilityVSAvoidservice continuity

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The network performs preliminary actions by pre-configuring the handover parameters, selecting target cells, and preparing resources before the actual handover is triggered. This ensures that when the handover occurs, the transition is smooth and service interruption is minimized

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8837377B2Inter-domain coordination for MT and MO calls

Publication Date: 2014.09.16 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A mobility management entity (MME) for setting up a call includes a first network interface which receives a tracking area update (TAU) request from a user equipment (UE). The MME includes a processing unit which translates the TAU request into a location area update (LAU) request. The MME includes a second network interface in communication with the processing unit which sends the LAU request to a mobile switching center (MSC) selected as a tracking MSC thereby establishing the MME as a network node through which the UE is paged.