IP Multimedia Subsystem (IMS)
Download
Report
Transcript IP Multimedia Subsystem (IMS)
IP Multimedia Subsystem
(IMS)
江培文
Agenda
Background
IMS Definition
IMS Architecture
IMS Entities
IMS-CS Interworking
Background - AMPS
Advanced Mobile Phone System
(AMPS)
First
generation (1G) cellular network
Analog mobile phone system
Standardized by ANSI
Operate in the 800 MHz band
Voice call
Background - GSM
Global System for Mobile
communications (GSM)
Second generation (2G) cellular network
Digital mobile phone system
Most GSM networks operate in 900 MHz
or 1800 MHz bands
Each radio channel bandwidth is 200
kHz
Standardized by ETSI
Voice call, short message service
Background - GPRS
General Packet Radio Service (GPRS)
2.5G
packet oriented mobile network
Provide data rates from 56 up to 114
kbps
Standardized by ETSI/3GPP
Short Message Service (SMS), Wireless
Application Protocol (WAP), Multimedia
Messaging Service (MMS), Internet Access
Background - EDGE
Enhanced Data rates for GSM
Evolution (EDGE)
2.75G
packet oriented mobile network
Data rate up to 236.8 kbps
Standardized by 3GPP
Multimedia services, Internet access
Background - WCDMA
Wideband Code Division Multiple
Access (WCDMA)
Third generation (3G) cellular network
1885–2025 MHz for uplink band and
2110–2200 MHz for downlink band
Each radio channel bandwidth is 5 MHz
Data rate up to 384 kbps
Standardized by 3GPP
The world's first commercial WCDMA
network, FOMA, was launched by NTT
DoCoMo in Japan in 2001.
Background - HSDPA
High Speed Downlink Packet Access
(HSDPA)
3.5G
packet oriented mobile network
Adaptive Modulation and Coding (AMC)
Depend on signal quality and cell usage
QPSK in initial scheme, 16QAM in good radio
condition.
Data
rate up to 14.4 Mbps for downlink
and 384 kbps for uplink
Standardized by 3GPP (since release 5)
Background - LTE
Long Term Evolution (LTE)
Fourth generation
Orthogonal FDMA
(4G) cellular network?
(OFDMA) for downlink and
Single Carrier FDMA (SC-FDMA) for uplink
Support Multiple-Input and Multiple-Output
(MIMO)
Improve communication performance
Increase data throughput
Without additional bandwidth or transmit power
Channel bandwidth between 1.5 and 20 MHz
All IP Network (AIPN)
Data rate up to 326.4 Mbps for downlink and
86.4 Mbps for uplink
Standardized by 3GPP (since release 8)
IMS Definition
3GPP Release 5 introduced the IMS as
part of 3GPP specifications in March
2002
The IMS is supposed to be a
standardized access-independent IPbased architecture that interworks
with existing voice and data networks
for both fixed (e.g., PSTN, Internet)
and mobile (e.g., GSM, WCDMA) users
IMS in Converged Networks
IMS Architecture
IMS Entities
Routing and Session Management
Databases
Services
Interworking Functions
Support Functions
Routing and Session Management
Call Session Control Functions (CSCF)
Proxy
Call Session Control Function (PCSCF)
Interrogating Call Session Control
Function (I-CSCF)
Serving Call Session Control Function (SCSCF)
P-CSCF
The first contact point for users within
the IMS
SIP compression
IPSec security association
Interaction with Policy Decision
Function (PDF)
Emergency session detection
I-CSCF
Obtain the name of the S-CSCF or
Application Server (AS) from the Home
Subscriber Server (HSS)
Assign an S-CSCF based on received
capabilities from the HSS
Route incoming requests to an
assigned S-CSCF or AS
S-CSCF
Handle registration process
Store service profile
Make routing decision
Maintain session state
IMS Entities
Routing and Session Management
Databases
Services
Interworking Functions
Support Functions
Databases
Home Subscriber Server (HSS)
Subscription Locator Function (SLF)
HSS
The main data storage for all
subscriber and service-related data
User
identities
Private and public user identities
Registration
information
Access parameters
Allocated S-CSCF names
Service
triggering information
SLF
The resolution mechanism that
enables the I-CSCF, the S-CSCF and
the AS to find the address of the HSS
that holds the subscriber data for a
given user identity when multiple and
separately addressable HSSs have
been deployed by the network
operator.
IMS Entities
Routing and Session Management
Databases
Services
Interworking Functions
Support Functions
Services
Multimedia Resource Function
Controller (MRFC)
Multimedia Resource Function
Processor (MRFP)
Application Server (AS)
MRFC
A signalling plane node
Provide the mechanism for bearerrelated services such as
announcement
Handle SIP communication to/from
the S-CSCF
Control the MRFP
MRFP
A media plane node
Mix the incoming media streams for
multiple parties
Process the media stream source for
multimedia announcements
AS
Provide value-added multimedia
services
Process the incoming SIP sessions
from the S-CSCF
Originate SIP requests
Send accounting information to the
charging functions
IMS Services
Presence
Multimedia Chat
Push to talk Over Cellular (POC)
Conferencing
IMS Entities
Routing and Session Management
Databases
Services
Interworking Functions
Support Functions
Interworking Functions
For exchanging signalling and media
between IMS and CS Core Network
Breakout Gateway Control Function
(BGCF)
Media Gateway Control Function
(MGCF)
Signalling Gateway (SGW)
IMS Media Gateway (IMS-MGW)
BGCF
It chooses where a breakout to the CS
domain occurs
If the breakout happens in the same
network, then the BGCF selects a
MGCF to handle the session.
If the breakout takes place in another
network, then the BGCF forwards the
session to another BGCF in a selected
network.
MGCF
Send a converted request via the
Signalling Gateway (SGW) to the CS
CN
Control the IMS Media Gateway (IMSMGW)
Perform protocol conversion between
SIP and ISDN User Part (ISUP)
SGW
Perform signalling conversion at the
transport level between the IP-based
transport of signalling and the
Signalling System No. 7 (SS7)
i.e., between SCTP and SS7
IMS-MGW
Provide the user plane link between
CS domain and IMS domain
Perform transcoding for the user plane
traffic
i.e., between TDM and RTP
IMS Entities
Routing and Session Management
Databases
Services
Interworking Functions
Support Functions
Support Functions
Policy Decision Function (PDF)
Security Gateway (SEG)
PDF
Session establishment in the IMS
involves the end-to-end messages
exchange using SIP and SDP
The P-CSCF forwards the relevant
SDP information to the PDF
The PDF authorizes the IP flows of the
media components and transfers the
authorized IP QoS parameters to the
GGSN to establish an IMS session
SEG
Protect control plane traffic between
security domains
Enforce the security policy of a
security domain
Coincide with operator borders
IMS-CS Interworking
CS-IMS Interworking
Thank You