Sisteme de Comunicatii

Mobile (SCMB)

- curs 12 -

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Tendinta “all over IP”

3G - Arhitectura IMS (IP Multimedia Subsystem)

4G - Arhitectura EPS (Evolved Packet System)

EPC (Evolved Pachet Core)

Evolved UTRAN (e-UTRAN)

De ce “all over IP” ?

Avantaje:

support comun date si voce (protocol unic, aceeasi

infrastructura)

simplificarea arhitecturii sistemului de comunicatii

decuplarea partii de retea de partea de servicii

posibilitate transport voce prin Internet (cost redus)

integrare facila cu aplicatii de date (ex. web)

dispare monopolul operatorilor pe partea de telefonie

Probleme de rezolvat:

asigurarea QoS

IMS – IP Multimedia Subsystem

Standard international

Se ocupa de aspectele: mobilitate, interoperabilitate,

control transport date, securitate, convergenta fix-mobil,

voce-date

Integreaza tehnologii multiple de acces: GSM, WCDMA,

CDMA2000, Wireline broadband access, WLAN

VoIP pentru comunicatii vocale

Extinde capabilitatile protocolului SIP - Session Initiation

Protocol (protocol de semnalizari peste IP, permite

stabilirea de sesiuni de comunicare)

IMS – motivatie

Operatori – necesitati:

Oferirea de solutii diverse de acces fix si mobil de

catre un acelasi operator

Extinderea facila spre noi servicii – platforma flexibila,

scalabila

Utilizatori - interes pentru:

Servicii multimedia de banda larga

Servicii de comunicare diverse, multimedia

Servicii personalizate, integrate

IMS – un scenariu de utilizare

While in a taxi from the airport, Anna calls her work colleague Andrew on his mobile

number to discuss some issues with an important construction project. Anna

activates the phone’s video mode so that she can show Andrew exactly what she is

talking about. Andrew views the images on his mobile while they discuss how best to

move forward. The two decide that they need a little help from their colleagues back

in the office. Anna selects the project work group from her buddy list, sees who is

available, and initiates a push to talk group session. John and Jeff answer that they

have also been thinking about the problem, and have a few ideas that they would like

Anna to look at. When she gets to the hotel, Anna starts her laptop computer, opens

her personal buddy list and invites Andrew, John and Jeff to join a videoconference.

John opens up a presentation and shares it with his colleagues. At the start of the

videoconference, Andrew is still walking back to the office and participates on his

mobile phone, but swaps to his PC when he arrives at his desk a few minutes later.

IMS – Arhitectura simplificata

IMS – Componente arhitectura

Strat servicii/aplicatii

Servere de aplicatii si furnizare de continut

Application server (AS)

Strat control

Servere de gestiune a comunicatiei, functii O&M si

interoperare cu alte retele – CSCF (Call Session

Control Function) care este un server SIP (ex. de

functie: autentificare)

Strat conectivitate

Rutere si switch-uri IP

IMS – componente arhitectura P-CSCF – Proxy Call Session Control Function – nod de intrare in IMS,

trimite apoi mesajele la S-CSCF

S-CSCF – Serving Call Session Control Function – functii SIP registrar

si SIP proxy (control acces uilizatori)

I-CSCF – Interogating Call Session Control Function – proxy de

interogare HSS

HSS – Home Subscriber Server – baza de date cu profile utilizatori si

servicii la care acestia au acces (HLR evoluat)

MRF – Media Resource Functions – implementeaza facilitati necesare

stabilirii conferintelor (sesiuni multi-user)

MGCF – Media Gateway Control Functions – nod de tip SIP User

Agent, terminal, asigura interoperarea cu retele CS – include

componenta SG – Signalling Gateway (interfata SIP <-> SS7)

MGW – Media Gateway – transcodare stream voce mod pachete <->

mod circuit

IMS – integrare verticala versus

orizontala

Servicii reutilizabile (service enablers):

group/list management, presence,

provisioning, operation & management,

directory, charging, deployment

Arhitectura logica 2G/3G – conform specificatiei 3GPP TR 23.882 V8.0.0 (2008-09)

2G

3G

Arhitectura logica 4G LTE GERAN – GSM/EDGE Radio Access

Network

HSS – Home Subscriber Server

PCRF – Policy and Charges rule

Function

ePDG – evolved Pachet Data

Gateway

MME – Mobility Management Entity

UPE – User Plane Entity

SAE – System Architecture Evolution

PSS – Pachet Switched Service

Arhitectura LTE 4G - cerinte

Cerinte generale: debite marite, intarzieri reduse, nivel

securitate superior, QoS imbunatatit si negociabil,

support sisteme de acces diferite, continuitatea sesiunii

la schimbarea tipului de acces, sistem politici selectie

acces, compatibilitatea cu sistemele mai vechi

Alte caracteristici: suport IP v.4 si v.6 dinamic si fix,

clase de trafic (real-time, non real-time, mission critical),

handover intre diferite tipuri de acces (3GPP si non-

3GPP), etc.

Evolved-UTRAN (E-UTRAN)

Statiile de baza eNB (evolved Node

B) sunt conectate printr-o retea tip

‘mesh’ (interfata X2)

MME – Mobility Management Entities

S-GW – Serving Gateway

E-UTRAN - functii

Gestiune resurse radio – acces canale radio

Compresie/decompresie antete IP – pentru eficientizare

Securitate – criptare, protejare integritate

Transfer date – uplink, downlink

Transmitere appel (paging)

Difuzare informatii (broadcast)

Gestiune mobilitate – masuratori semnal, handover intra E-UTRAN,

mobilitate GERAN-UTRAN si non-3GPP (CDMA2000)

Localizare

Alarme cutremur, tsunami (ETWS) – pentru o anumita arie

Auto-configurare pentru nodurile noi adaugate, auto-optimizarea

retelei

E-UTRAN, EPC – protocoale S1

Componente EPC

MME – Mobility Management Entity

gestiune semnalizari, securitate (autentificare), paging, selectie

PDN-GW si S-GW, gestiune handover (selectie MME, SGSN),

support ETWS, etc.

S-GW – Serving Gateway

ancora mobilitate IP, buffer pachete, rutare pachete, marcare

pachete pt. stratul transport, etc.

PDN-GW – Pachet Data Network Gateway

filtrare pachete, alocare adresa IP pentru TE (user), control debit

Interfete: S1, X2, S3, S4, etc.

Bibliografie

Ericsson, October 2004, WHITE PAPER: IMS – IP Multimedia

Subsystem. The value of using the IMS architecture

3GPP TR 23.882 V8.0.0 (2008-09)

http://www.3gpp.org/ftp/Specs/html-info/23882.htm

Agilent 3GPP Long Term Evolution: System Overview, Product

Development, and Test Challenges. Application Note.

Stefania Sesia, ST-NXP Wireless/ETSI, France, Issam Toufik

ST-NXP Wireless, France, Matthew Baker, Philips Research,

UK, LTE – The UMTS Long Term Evolution From Theory to

Practice.