During the handover preparation, data flows between ue and the core. Now lets dig deeper into the detailed flow for lte to 3g csfb call. General s1 based handover information the s1based handover procedure is used when the x2based handover cannot be used. Protocol signaling procedures in lte radisys white paper 3 classify traffic streams using dpi and then, based on the operators policies, offload part of the traffic directly onto the internet while sending the remaining traffic to the core network. The key step in the evolution to ifom is to completely separate the flow management from the access network. Aug 19, 2018 in comparison, ues are the same, different radios, on one end lte, and into the future a 5g radio. Pdf the deployment of femtocell as the emerging wireless and mobile. Srvcc procedure is used for transferring an ongoing ps voice call ims in lte to a cs voice call via handover from lte to geranutran. Lte call flows lte telecommunication mobile phones. Lte x2 handover sequence diagrams detailed message flow analysis of lte x2 handovers eventstudio system designer sequence diagram based systems engineering tool.
Introduction this article describes the background and motives for developing enhancedsrvcc esrvcc. X2 handover messaging presentation messages involved in lte x2 handover are explored in detail. In comparison, ues are the same, different radios, on one end lte, and into the future a 5g radio. Data packets are transferred tofrom the ue tofrom the network in both directions dl as well as ul. Dec 21, 2016 the circuit switched fallback, or csfb, is a service handover procedure, of lte protocol, devised to deliver voice and sms to lte devices with a circuit switch network 3g or 2g. We will have a look at the call flow diagrams about different procedures. Before we will see detailed call flow please keep in mind few general s1 handover information. Lte to wifi handoff theltetowifihandoffoccursasfollows. With long term evolution lte comes a new and exciting attributes. Gsm, lte, umts etsi 650 route des lucioles f06921 sophia antipolis cedex france.
Nov 29, 2018 old call is cleared on wifi access with reason as context replacement and call is processed like a new call over lte. Lte doesnt support circuit switched calls, because it is an ip based network. Volte service description and implementation guidelines version 2. Dl data packets are forwarded from the senb to tenb via the sgw during the handover as the sgw is not changed here. Lte x2 handover messaging call flow sequence diagram. Interdomain handover technologies in lte for voice volte and tv phone volte esrvcc vsrvcc 1. It includes background information on the standardization process, and the commercial implications. Pdf umtslteepc call flows for handovers jachang ma. This keeps information about the users phone number, home network identity and security keys etc. Jun 30, 2017 4g lte to 3g circuit switched fallback call flow overview circuit switch fall back call flow. Volte service description and implementation guidelines. If the handover indication is included in step 23, the serving gw.
Ue performs frequency synchronization and reads mibsibs from pbch to acquire system information. Interoperable ue handovers in lte radisys white paper 6 7. Based on the measurement report from the ue, the senb decides to handover the ue to another enodeb tenb. Lte to 3g circuit switched fallback csfb call flowa 4g lte subscriber initiates a voice call in an lte network that does not support volte. In such cases, the ue falls back to 3g networks to establish a voice call.
Handover process in lte, lte handover tutorial teletopix. This registration is known as the network attachment. Back in 2014 i was musing about that the time has come for network operators to introduce a feature to handover an ongoing 3g connection to lte. The source enodeb initiates a handover by sending handover required message over the s1mme reference point. Handover sgw mme source target enb enb enb enb sgw ue ue moving enb enb enb enb inter eutran and sgw handover intra eutran handover pgw related blogs basic requirement of handover ue ip address should not be changed packet loss and. Lte call flows0 computer standards internet standards. Jul 10, 2015 an interesting part of lte s1 handovers is the indirect tunnel that is established to carry the downlink data during the handover process. Message sequence diagram of handover procedure in 3gpplte 6. Even if voice itself is cheap or free, every time a user makes voice call with nontelco mobile apps for example, they are lost to the network operator. Overview of lte handover 1, we have discussed the procedures. Lte handover call flow software defined radio information. In an lte network, these two enbs can directly communicate with each other via the x2 interface, which differentiates the. Voice over lte, or volte is a gsma profile of the standards definition for the delivery of.
Well first, the ue needs to register with the network to receive services that require registration. I have a confusion, couldnot understand why we have again rrc connection procedure and repeatition of some other subsequent messages in last ladder diagram of service request. Visualether protocol analyzer wireshark based visual protocol analysis and system design reverse engineering tool. Pdf handover scenario and procedure in ltebased femtocell. It is a handbook of umts lte epc handover call flows. Mar 30, 2012 few last articles were about handover in lte network. In fact, call flow and signaling is unique for lte, and is driven by 3gpp standards. Network architecture for lte and wifi interworking lte overview. S1 interface based handover lte and beyond techblog on. Lte call flow following call flows have been discussed initial call setup s1 based inter enb handover x2 based inter enb handover initial call setup initial call setup continues brief description. What is the difference between lte and lte advanced. Interdomain handover technologies in lte for voice volte. Though it is not sufficient to address rise in demand.
It also mentions wlanwifi to lte handover with message flow diagram. Test measurement challenges and field environment test planning school of electrical engineering master. Lte attach procedure call flow the lte attach procedure call flow is a subject that may seem hard to understand. Long term evolution signaling flows and tutorials for lte. So when we say wifi offloading, it usually mean that wifi offload handover between lte network and wifi network. Srvccsingle radio voice call continuity srvcc stands for single radio voice call continuity. Call flow is how signaling and sessions are established across an lte network. Jun 02, 2017 an interesting part of lte s1 handovers is the indirect tunnel that is established to carry the downlink data during the handover process. Sorry guys, today i dont have time to create abstract picture which we could use to start from. An interesting part of lte s1 handovers is the indirect tunnel that is established to carry the downlink data during the handover process.
More complicated probably the most complicated cases are the multi cell scenario among different technologies different rats. Nov 11, 2018 lte attach call flow in complete basic form. Hss lte intra mme handover procedure message flow via s1. The message flow is shown in figure 1 followed by the description. Evolved universal terrestrial radio access network. In the ue, the uplink tft maps a traffic flow aggregate. If the target cell id is known by enodeb, it will proceed with the handover. Session recovery and icsr during the transition period, old access is considered as stable state and full checkpoint is triggered once handover is complete from lte to wifi s2bgtp. We call this kind case as intrarat multi cell scenario. Another work models the lte handover scheme on an open source platform. S1 interface based handover lte and beyond techblog. Lte ue can detect intra lte neighbors without neighbor lists which simplifies network management.
Jul 07, 2017 handover process in lte, handover in 4g telecom, lte handover types, lte handover call flow, intra enodeb handover lte, lte handover events, lte handover tutorial, handover in lte, sharetechnote, handover in lte 4g parameter. Putting it simple, it is a handover technology between voip over ims in lte and voice call cs in a legacy system e. Source enodeb hands over ue data flow to the target enodeb over the x2 interface. Refer to the s1 handover call flow for a detailed signaling flow. The highlevel network architecture of lte is comprised of following three main components.
Performance evaluation of voice call handover between umts. Handover principles and handover measurements in lte. The schemes evaluated were voice call continuity vcc for umts to lte handover and single radio voice call continuity srvcc for lte to umts handover. Measurement are enabled by rrc procedures measurement report handover request rrc rrc connection reconfig. Lte handover call flow software defined radio information and. Voice and sms in lte white paper this white paper summarizes the technology options for supporting voice and short message service sms in lte, including circuit switched fallback csfb, sms over sgs, and voice over lte volte. Handover process in lte, handover in 4g telecom, lte handover types, lte handover call flow, intra enodeb handover lte, lte handover events, lte handover tutorial, handover in lte, sharetechnote, handover in lte 4g parameter. Due to huge increase of data traffic, telecom operators are adopting technologies like lte, lte advanced. Lte inter enb handover procedure message flow via x2 senb tenb mme. Lte x2 handover sequence diagrams detailed message flow analysis of lte x2 handovers. This document is originally edited by justin ma and it is free to share to everyone who are interested. The continuing importance of voice in the carrier model.
X2 handover is performed between a source enb and a target enb through the x2 interface. Intralte handover using the s1 interface 3glteinfo. Today we will be talking about handovers from eutran to utran, from 4g to 3g. From old enb to new enb, with or without using new mmesgw, with or without using x2 interface, and so on. Mar 24, 2012 before we will see detailed call flow please keep in mind few general s1 handover information. Troubleshooting failed calls unable to attach to the lte network on the lte side, when subscribers cant connect to the data network, voice isnt the only service. Lte x2 handover between enodebs served by the same mme. Handover between lte and 3g radio access technologies. The circuit switched fallback, or csfb, is a service handover procedure, of lte protocol, devised to deliver voice and sms to lte devices with a circuit switch network 3g or 2g. Traffic offloaders typically will be deployed as bumpinthewire boxes between the. Wifi offload means a kind of handover or selectionreselection technology between nonwifi network and wifi network. Ue is handed over using an s1 handover if the x2 interface is not available between.
Handover happens within the current lte nodes intramme and intrasgw. This video explains lte radio procedures, lte intial access and downlink physical channels, pssprimary synchronization signal,ssssecondary synchronization signal lte uplink physical channels. Before we begin, lets check what is a tracking area in lte. Handover in lte lte telecommunication transmission. It is not a new concept, but it has become hot issue recently especially after lte network is wide spread. Lte attach call flow in complete basic form youtube. As the gsm 2g network is normally more extensive than the 3g network, this type of handover does not normally occur when the ue leaves. Jun 07, 2016 i have a confusion, couldnot understand why we have again rrc connection procedure and repeatition of some other subsequent messages in last ladder diagram of service request. For me and those who frequently tether their pc while on the move, this is an important feature when the network makes a handover of an ongoing connection from. Lte to 3g circuit switched fallback csfb lte medium. This form of handover is supported within gsm and a neighbour list was established to enable this occur easily. The research topic of this thesis which is lte handover performance evaluation. Voice and sms in lte white paper this white paper summarizes the.
When the reporting threshold condition is fulfilled, the ue sends handover measurement reports to the serving enodeb. Srvcc is the short form of singleradio voice call continuity. The simplest multi cell cases would be between two lte cells. This report investigates the performance of interradio access technology voice handover between lte and umts. Dec 06, 20 intra lte handover using the s1 interface call flow. Intra eutran handover is used to hand over a ue from a source enodeb to a target enodeb using x2 when the mme is unchanged. In this tutorial, we will discuss the overview of lte tracking area update and then discuss in details the endtoend call flow signalling procedure. The x2 handover flow is shown in the following sequence diagram.
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