PowerPoint Presentation

ActixOne VoLTE Analysis

07/02/14Confidential and Proprietary Information of T-Mobile USA

T-Mobile | stick togetherWednesday, July 02, 2014Confidential and Proprietary Information of T-Mobile USA#VoLTE Drop TriggersProprietary and Confidential2SIP INVITE message for a new call.Abnormal SIP BYE release. The drop is pegged at the SIP BYE message.RTP timeout: more than 18 seconds (configurable threshold) during which there were no RTP packets sent or received by the UE.Change of technology (handover or reselection) without SRVCC.Proprietary and Confidential3VoLTE Setup Failure TriggersSIP INVITE message for a new call.Abnormal SIP message indicating a failure in the SIP INVITE procedure.Call setup timeout: the SIP call setup phase take more than 18 seconds (configurable threshold).Proprietary and Confidential4Handover FailuresLTE RRC drop after a RRC Connection Reconfiguration message that indicated a handover. The handover is considered complete when:The UE receives a DL-DCCH message orThere was no LTE RRC drop within 2 seconds (configurable threshold) of the RRC Connection Reconfiguration Complete messageNote that a RRC Connection Reconfiguration Complete message does NOT indicate a successful handover because it is sent on RACH, it is a fairly common scenario to see a LTE RRC drop just after a RRC Connection Reconfiguration Complete for a handover procedure.LTE RRC drop just after the UE sent a Measurement Report where the best neighbour cell was stronger than the serving cell in terms of RSRP or RSRQ.Proprietary and Confidential5Voice Service TransitionLTE systems do not support circuit switching of 2G/3G mobile phone systems. All LTE services use IP-based technologies.Voice communications supported by circuit switching up to 3G will be replaced by VoLTE (Voice over LTE).

VoLTE OutlineProprietary and Confidential6Centered on the One Voice Initiative promoted by mobile carriers and communications equipment makers in November 2011, technology specifications called One Voice Voice over IMS profile have been gathered together to produce technical specifications for achieving voice and SMS services over LTE systems, generally called VoLTE. Currently, the GSMA (GSM Association) VoLTE Initiative promotes these specifications as IMS Profile for Voice and SMS.VoLTE (Voice over LTE) also called Voice over IMS Profile and IMS VoIP is the standard to support voice communications on IMS and controls communications using SIP (Session Initiation Protocol).The OTT (Over The Top) IP phone using software on LTE service is also available, but the bandwidth allocation priority is lower than VoLTE, which is secured by QoS control.

Proprietary and Confidential7

VoLTE Outline Example of Protocol Sequence (IMS Registration)

VoLTE Outline Example of Protocol Sequence (Voice Call)Proprietary and Confidential8

High level principle of SRVCCProprietary and Confidential9

Network architechture for SRVCCProprietary and Confidential10

Initial situation before SRVCCProprietary and Confidential11

Signalling and media paths after SRVCCProprietary and Confidential12

SRVCC signaling flowProprietary and Confidential13

Recommended AttributesProprietary and Confidential14

Anatomy of Successful CallProprietary and Confidential15

Successful Redirect to CSFBProprietary and Confidential16

Complete call L3 messagesProprietary and Confidential17

Drop call New INVITEProprietary and Confidential18

Drop call -- RTP TimeoutProprietary and Confidential19

T-Mobile | stick togetherWednesday, July 02, 2014Confidential and Proprietary Information of T-Mobile USA#Drop Call RRC DropProprietary and Confidential20

Drop Call -- SIP Release [Reason = Service Unavailable]Proprietary and Confidential21

SIP Release Normal Release [false drop]Proprietary and Confidential22

Drop call after HO to UMTS [false drop]Proprietary and Confidential23

Drop call when call is redirected to UMTS and eventually ended on CSFB[false drop]Proprietary and Confidential24

Access FailureProprietary and Confidential25