Sisteme de Comunicatii
Mobile (SCMB)
- curs 12 -
Continutul prezentarii
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.
Top Related