VoLTE Call Establishment Cause Selection in LTE Networks

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Solution Overview

Problem

Current LTE specifications do not allow for the regulation of VoLTE calls separately from packet calls, as there is no Establishment cause defined for VoLTE calls, making it impossible for base stations to determine and prioritize VoLTE calls using existing regulation control methods.

Innovation Solution

A user apparatus that determines the presence of a predetermined indicator in broadcast information from the base station and sets an appropriate Establishment cause in the RRC connection request message to request an RRC connection for VoLTE calls, allowing the base station to identify and manage VoLTE calls appropriately.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a cause indicating a VoLTE call is newly added to the Establishment causes, then it becomes possible for the base station to determine whether a call is a VoLTE call, but backward compatibility must be maintained requiring the user apparatus to determine in advance whether the base station is adapted to the new cause

Engineering Contradiction:

Improvebase station's ability to identify VoLTE call typeVSAvoiduser apparatus needs to determine base station adaptation status and select appropriate cause

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The base station performs preliminary action by including an indicator in broadcast information to indicate whether it is adapted to a cause indicating a VoLTE call. This allows the user apparatus to determine in advance whether the new cause can be used, avoiding compatibility issues without requiring complex real-time negotiation protocols.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The indicator in broadcast information serves as an intermediary between the base station's adaptation status and the user apparatus's cause selection. Instead of direct complex interaction, the indicator mediates the information flow, enabling the user apparatus to appropriately select Establishment causes based on base station capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the second regulation control method is used where the base station identifies connection request type, then regulation can be applied based on network load, but it is not possible to provide an operation where voice call is allowed while only packet call is regulated due to lack of VoLTE-specific Establishment cause

Engineering Contradiction:

Improvenetwork load management efficiencyVSAvoidability to differentiate between VoLTE and packet calls for selective regulation

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The Establishment causes are segmented into distinct types, including a specific cause indicating a VoLTE call. This segmentation allows the base station to identify and differentiate VoLTE calls from packet calls, enabling selective regulation where voice calls can be allowed while packet calls are regulated during high network load.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10897783B2User apparatus and indication method for VoLTE communication

Publication Date: 2021.01.19 NTT DOCOMO INC

AI summary

A user apparatus according to an embodiment is provided. The user apparatus communicates with a base station, and includes a determination unit configured to, in the case of making a VoLTE call, determine whether a predetermined indicator is included in broadcast information received from the base station; and a transmission unit configured to transmit to the base station an RRC connection request message in which information is included indicating a request for an RRC connection to be established for making a VoLTE call.