Wireless%20and%20Mobile%20All-IP%20Networks

1
Wireless and Mobile All-IP Networks

• Yi-Bing Lin
• liny_at_csie.nctu.edu.tw

2
Contents 1/3

• Chapter 1 Short Message Service and IP Network
  Integration
• Chapter 2 Mobility Management for GPRS and UMTS
• Chapter 3 Session Management for Serving GPRS
  Support Node
• Chapter 4 Session Management for Gateway GPRS
  Support Node
• Chapter 5 Serving Radio Network Controller
  Relocation for UMTS

3
Contents 2/3

• Chapter 6 UMTS and cdma2000 Mobile Core Networks
• Chapter 7 UMTS Charging Protocol
• Chapter 8 Mobile All-IP Network Signaling
• Chapter 9 UMTS Security and Availability Issues
• Chapter 10 VoIP for the Non-All-IP Mobile
  Networks
• Chapter 11 Multicast for Mobile Multimedia
  Messaging Service
• Chapter 12 Session Initiation Protocol

4
Contents 3/3

• Chapter 13 Mobile Number Portability
• Chapter 14 Integration and WLAN and Cellular
  Networks
• Chapter 15 UMTS All-IP Network
• Chapter 16 Issues on IP Multimedia Core Network
  Subsystem
• Chapter 17 A Proxy-based Mobile Service Platform

5
Chapter 1 Short Message Service and IP Network
Integration
GSM SMS Network Architecture
6
SMS-IP Integration SM-SC-based
In most commercial implementations, SMS and IP
networks are integrated through SM-SC.
Mobile Network
IP Network
SM-SC
Gateway
7
NCTU-SMS
8
iSMS
9
Mobility and Session Management

• Three types of mobility radio mobility, core
  network mobility and IP mobility
• Radio mobility supports handoff of a mobile user
  during conversation
• Core network mobility provides tunnel-related
  management for packet re-routing in the core
  network due to user movement
• IP mobility allows the mobile user to change the
  access point of IP connectivity without losing
  ongoing sessions.
• Session management maintains the routing path for
  a communication session, and provides packet
  routing functions including IP address assignment
  and QoS setting.

10
Chapter 2 Mobility Management for GPRS and UMTS
11
LAs, RAs, URAs, and Cells
12
Chapter 3 Session Management for Serving GPRS
Support Node
13
Chapter 4 Session Management for Gateway GPRS
Support Node

• The GGSN plays the role as a gateway, which
  controls user data sessions and transfers the
  data packets between the UMTS network and the
  external PDN.
• The meta functions implemented in the GGSN are
  described as follows network access control,
  packet routing and transfer, and mobility
  management.

14
Access Point Name (APN)
15
IP Address Allocation
APN label INTERNET WAP ISP COMPANY
Access mode Transparent Transparent Non- transparent Non- transparent
IP address allocation GGSN/ DHCP GGSN/ DHCP DHCP/ RADIUS RADIUS
IP address type IPv6/IPv4 IPv4 IPv4 IPv4
16
Chapter 5 Serving Radio Network Controller
Relocation for UMTS
DriftRNC
Serving RNC
Serving RNC
17
Lossless SRNC Relocation

• In 3GPP TS 23.060, a lossless SRNC relocation
  procedure was proposed for non-real-time data
  services.
• 1. The source RNC first stops transmitting
  downlink packets to the UE, and then forwards the
  next packets to the target RNC via a GTP tunnel
  between the two RNCs.
• 2. The target RNC stores all IP packets forwarded
  from the source RNC.
• 3. After taking over the SRNC role, the target
  RNC restarts the downlink data transmission to
  the UE.
• No packet is lost during the SRNC switching
  period.
• Real-time data transmission is not supported
  because the IP data traffic will be suspended for
  a long time during SRNC switching.

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Fast SRNC Relocation Stage I

• Stage I (the same as Stage I in SD) initiates
  SRNC relocation.
• The IP packets are delivered through the old
  path UE?Node B2?target RNC? source
  RNC?SGSN1?GGSN
• Steps 1 and 2 Source RNC initiates SRNC
  relocation by sending Relocation_ Required to
  SGSN1.
• Step 3 SGSN1 sends Forward_Relocation_ Request
  to request SGSN2 to allocate the resources for
  the UE.
• Step 4 SGSN2 send Relocation_Request with RAB
  parameters to the target RNC. After all necessary
  resources are allocated, the target RNC send
  Relocation_Request_ Acknowledge to SGSN2.

19
Fast SRNC Relocation Stage II

• GGSN routes the downlink packets to the old path
  receiving Update_PDP_Context_ Request.
• After GGSN has received the message, the downlink
  packets are routed to the new path
  GGSN?SGSN2?target RNC.
• The new packets arriving at the target RNC are
  buffered until the target RNC takes over the SRNC
  role.
• Step 5 SGSN2 sends Update_PDP_Context_ Request
  to GGSN. GGSN updates the corresponding PDP
  context, and the downlink packet routing path is
  switched from the old path to the new path.
• Steps 6-7 SGSN2 informs SGSN1 that all resources
  for the UE are allocated. SGSN1 forwards this
  information to the source RNC.

20
Fast SRNC Relocation Stage III

• The Iur link (i.e., the old path) disconnected.
  The old downlink packets arriving at the source
  RNC later than Step 7 (Relocation_Command) are
  dropped.
• The SRNC role is switched from the source RNC to
  the target RNC.
• Step 8 The source RNC transfers SRNS context
  (e.g., QoS profile) to the target RNC.
• Steps 9 and 10 The target RNC informs SGSN2 that
  the target RNC will become the SRNC. At the same
  time, the target RNC triggers the UE to send the
  uplink IP packets to the target RNC.

21
Fast SRNC Relocation Stage IV

• The target RNC informs the source RNC that SRNC
  relocation is successfully performed. Then the
  source RNC releases the resources for the UE.
• Step 11 The target RNC indicates the completion
  of the relocation procedure to SGSN2, and SGSN2
  forwards this information to SGSN1.
• Step 12 SGSN1 requests the source RNC to release
  the resources allocated for the old path.

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Chapter 6 UMTS and cdma2000 Mobile Core Networks

• UMTS and cdma2000 are two major standards for 3G
  mobile telecommunication.
• Two important functionalities of mobile core
  network are mobility management and session
  management.
• This chapter describes these two functionalities
  for UMTS and cdma2000, and compare the design
  guidelines for these two 3G technologies.

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cdma2000 Architecture
24
cdma2000 CS Domain

• BSC connects to the core network through the SDU.
• The SDU distributes the circuit switched traffic
  (e.g., voice) to the MSC.
• A1 interface supports call control and mobility
  management between MSC and BSC.
• A2 and A5 interfaces support user traffic and
  circuit switched data traffic between MSC and BSC.

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cdma2000 PS Domain

• The SDU distributes the packet switched traffic
  to PCF and then to the PDSN.
• Interfaces A8 and A9 support packet switched data
  and signaling between PCF and SDU, respectively.
• Interfaces A10 and A11 (R-P interface) support
  packet switched data and signaling between PCF
  and PDSN.
• GRE tunnel is used for data routing in A10 with
  standard IP QoS.
• MIP is used for signaling routing in A11.
• The R-P interface also supports PCF handoff
  (inter or intra PDSN).

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PDSN

• Maintaining link-layer sessions to the MSs
• Supporting packet compression and packet
  filtering before the packets are delivered
  through the air interface
• Providing IP functionality to the mobile network,
  which routes IP datagrams to the PDN with
  differentiated service support
• Interacting with AAA to provide IP
  authentication, authorization and accounting
  support
• Acting a MIP FA in the mobile network
• The interfaces among the PDN nodes (i.e., PDSN,
  HA, AAA) follow the IETF standards.

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cdma2000 Control Plane
28
UMTS Control Plane
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cdma2000 User Plane
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UMTS User Plane
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Protocol Stacks 1/2

• The control plane carries out tasks for
  MM/SM/SMS.
• In cdma2000, the mobility and session tasks are
  based on the same lower layer protocol (IP based
  protocols) for user data transportation.
• In UMTS, the lower layer protocols supporting
  MM/SM tasks in the control plane are different
  from the lower layer protocols in the user plane.
• The signaling path between MS and SGSN consists
  of an RRC connection between MS and UTRAN, and an
  Iu connection between UTRAN and SGSN.

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Protocol Stacks 2/2

• In UMTS, the PS domain services are supported by
  PDCP in the user plane.
• PDCP contains compression methods, which provide
  better spectral efficiency for IP packets
  transmission over the radio.
• In cdma2000, the header and payload compression
  mechanism is provided by PPP between MS and PDSN.
• Both UMTS RLC and cdma2000 LAC provide
  segmentation and retransmission services for user
  and control data.
• cdma2000 LAC supports authentication
  functionality for wireless access, which is
  equivalent to GPRS transport layer authentication
  in UMTS.

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PPP

• In both control and user planes for cdma2000, PPP
  is carried over the LAC/MAC, and R-P tunnels are
  utilized to establish the connection between an
  MS and the PDSN.
• In cdma2000, a PPP connection is equivalent to a
  packet data session, which is comparable to the
  UMTS PDP context.
• In the UMTS control plane, no PPP/IP connection
  is established between MS and SGSN. Signaling is
  carried over the RRC and Iu connections.
• UMTS user plane provides two alternatives for IP
  services.
• IP is supported by non-PPP lower layer protocols.
  
• IP is supported by PPP.
• Dial-up application
• Mobile IP is introduced to UMTS

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Chapter 7 UMTS Charging Protocol

• The GTP protocol is used for communications
  between a GSN and a CG, which can be implemented
  over UDP/IP or TCP/IP.
• Above the GTP protocol, a Charging Agent (or CDR
  sender) is implemented in the GSN and a Charging
  Server is implemented in the CG.

35
The GTP Service Model

• Our GTP service model follows the GSM Mobile
  Application Part (MAP) service model.
• A GSN communicates with a CG through a dialog by
  invoking GTP service primitives.
• A service primitive can be one of four types
• Request (REQ)
• Indication (IND)
• Response (RSP)
• Confirm (CNF)

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GTP Connection Setup

• Before a GSN can send CDRs to a CG, a GTP
  connection must be established between the
  charging agent in the GSN and the charging server
  in the CG.

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GTP CDR Transfer

• The charging agent is responsible for CDR
  generation in a GSN. The CDRs are encoded using,
  for example, the ASN.1 format defined in 3GPP
  32.215. The charging server is responsible for
  decoding the CDRs and returns the processing
  results to the GSN.

38
GTP Failure Detection

• In a GSN, an entry in the CG list represents a
  GTP' connection to a CG.
• The CG Address attribute identifies the CG
  connected to the GSN.
• The Status attribute indicates if the connection
  is active or inactive.
• The Charging Packet Ack Wait Time Tr is the
  maximum elapsed time the GSN is allowed to wait
  for the acknowledgement of a charging packet.
• The Maximum Number of Charging Packet Tries L is
  the number of attempts (including the first
  attempt and the retries) the GSN is allowed to
  send a charging packet.
• The Maximum Number of Unsuccessful Deliveries K
  is the maximum number of consecutive failed
  deliveries that are attempted before the GSN
  considers a connection failure occurs.
• The Unsuccessful Delivery Counter NK attribute
  records the number of the consecutive failed
  delivery attempts.
• The Unacknowledged Buffer stores a copy of each
  GTP' message that has been sent to the CG but has
  not been acknowledged.
• A record in the unacknowledged buffer consists of
  an Expiry Timestamp te , the Charging Packet Try
  Counter NL and an unacknowledged GTP' message.

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Path Failure Detection Algorithm
The Path Failure Detection Algorithm (PFDA)
detects path failure between the GSN and the CG.
PFDA works as follows

• Step 1. After the connection setup procedure is
  complete, both NL and NK are set to 0, and the
  Status is set to active. At this point, the GSN
  can send GTP messages to the CG.
• Step 2. When a GTP message is sent from the GSN
  to the CG at time t , a copy of the message is
  stored in the unacknowledged buffer, where the
  expiry timestamp is set to tet Tr.
• Step 3. If the GSN has received the
  acknowledgement from the CG before te , both NL
  and NK are set to 0.
• Step 4. If the GSN has not received the
  acknowledgement from the CG before te , NL is
  incremented by 1. If NL L, then the charging
  packet delivery is considered failed. NK is
  incremented by 1.
• Step 5. If NK K, then the GTP connection is
  considered failed. The Status is set to
  inactive.

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Chapter 8 Mobile All-IP Network Signaling

• Traditional SS7 signaling is implemented in
  MTP-based network, which is utilized in the
  existing mobile networks including GSM and GPRS.
• In UMTS all-IP architecture, the SS7 signaling
  will be carried by IP-based network.
• The low costs and the efficiencies for carriers
  to maintain a single, unified telecommunications
  network, guarantee that all telephony services
  will eventually be delivered over IP.
• This chapter describes design and implementation
  of the IP-based network signaling for mobile
  all-IP network.

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SS7 Architecture

• Service Switching Point (SSP) is a telephony
  switch that performs call processing.
• Service Control Point (SCP) contains databases
  for providing enhanced services.
• Signal Transfer Point (STP) is a switch that
  relays SS7 messages between SSPs and SCPs.

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SS7 Link Types

• Access Links (A-links) connect the SSP/STP or the
  SCP/STP pairs.
• Bridge Links (B-links) connect STPs in different
  pairs.
• Cross Links (C-links) connect mated STPs in a
  pair.
• Diagonal Links (D-links) are the same as the
  B-links except that the connected STPs belong to
  different SS7 networks.
• Extended Links (E-links) provide extra
  connectivity between an SSP and the STPs other
  than its home STP.
• Fully-Associated Links (F-links) connect SSPs
  directly.

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SS7 Protocol Stack
44
SS7 Protocol Stack MTP SCCP

• Message Transfer Part (MTP) consists of three
  levels corresponding to the OSI physical layer,
  data link layer, and network layer, respectively.
  
• The MTP level 1 (MTP1) defines the physical,
  electrical, and functional characteristics of the
  signaling links connecting SS7 components.
• The MTP level 2 (MTP2) provides reliable transfer
  of signaling messages between two directly
  connected signaling points.
• The MTP level 3 (MTP3) provides the functions and
  procedures related to message routing and network
  management.
• Signaling Connection Control Part (SCCP) provides
  additional functions such as Global Title
  Translation (GTT) to the MTP.

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SS7 Protocol ISUP, TCAP, MAP

• Integrated Services Digital Network User Part
  (ISUP) establishes circuit-switched network
  connections (e.g., for call setup).
• Transaction Capabilities Application Part (TCAP)
  provides the capability to exchange information
  between applications using non-circuit-related
  signaling.
• Operations, Maintenance, and Administration Part
  (OMAP) is a TCAP application for network
  management.
• Mobile Application Part is a TCAP application
  that supports mobile roaming management.

46
Stream Control Transmission Protocol (SCTP)

• IETF Signaling Transport (SIGTRAN) working group
  addresses the issues regarding the transport of
  packet-based SS7 signaling over IP networks.
• SIGTRAN defines not only the architecture but
  also a suite of protocols, including the SCTP and
  a set of user adaptation layers (e.g. M3UA),
  which provides the same services of the lower
  layers of the traditional SS7.
• Why not TCP ?
• TCP provides strict order-of-transmission which
  causes head-of-line blocking problem.
• The TCP socket does not support multi-homing.
• TCP is vulnerable to blind Denial-of-Service
  (DoS) attacks such as flooding SYN attacks.

47
SCTP Features

• Like TCP
• To provide reliable IP connection.
• To employ TCP-friendly congestion control
  (including slow-start, congestion avoidance, and
  fast retransmit)
• Unlike TCP
• To provide message-oriented data delivery service
  and new delivery options (ordered or unordered)
• To provide selective acknowledgments for packet
  loss recovery
• To use a four-way handshake procedure to
  establish an association (i.e., a connection).
• To offer new features that are particularly for
  SS7 signaling
• Multi-homing
• Multi-streaming

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Chapter 11 Multicast for Mobile Multimedia
Messaging Service

• Short Message Service (SMS) allows mobile
  subscribers to send and receive simple text
  message in 2G systems (e.g. GSM).
• Multimedia Message Service (MMS) is introduced to
  deliver messages of sizes ranging from 30K bytes
  to 100K bytes in 2.5G systems (e.g. GPRS) and 3G
  systems (e.g. UMTS)
• The content of an MMS can be text (just like
  SMS), graphics (e.g., graphs, tables, charts,
  diagrams, maps, sketches, plans and layouts),
  audio samples (e.g., MP3 files), images (e.g.,
  photos), video (e.g., 30-second video clips), and
  so on.

49
MMS Architecture 1/2
50
MMS Architecture 2/2

• The MMS user agent (a) resides in a Mobile
  Station (MS) or an external device connected to
  the MS, which has an application layer function
  to receive the MMS.
• The MMS can be provided by the MMS value added
  service applications (b) connected to the mobile
  networks or by the external servers (d) (e.g.,
  email server, fax server) in the IP network.
• The MMS server (c) stores and processes incoming
  and outgoing multimedia messages.
• The MMS relay (e) transfers messages between
  different messaging systems, and adapts messages
  to the capabilities of the receiving devices. It
  also generates charging data for the billing
  purpose. The MMS server and the relay can be
  separated or combined.
• The MMS user database (f) contains user
  subscriber data and configuration information.
• The mobile network (g) can be a WAP (Wireless
  Application Protocol) based 2G, 2.5G or 3G
  system. Connectivity between different mobile
  networks is provided by the Internet protocol.

51
Short Message Multicast Architecture
MCH (HLR)
VLR1 1
VLR2 2
VLR3 0
MCV (VLR3)
LA5 0
LA6 0
MCV (VLR1)
MCV (VLR2)
LA3 0
LA4 2
LA1 0
LA2 1
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MMS Multicast 1/2
MCc (CBC)
RA1 0
RA2 1
RA3 0
RA4 2
RA5 0
RA6 0
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MMS Multicast 2/2

• Step 1. The multimedia message is first delivered
  from the message sender to the Cell Broadcast
  Entity (CBE).
• Step 2. The CBE forwards the message to the Cell
  Broadcast Center (CBC).
• Step 3. The CBC searches the multicast table MCC
  to identify the routing areas RAi where the
  multicast members currently reside (i.e., MCC
  RAi gt 0 in the CBC). In Figure 1.7, i 2 and
  4.
• Step 4. The CBC sends the multicast message to
  the destination RNCs (i.e., RNC1 and RNC2 in
  Figure 1.7) through the Write Replace message
  defined in 3GPP TS 23.041.
• Step 5. The RNCs deliver the multimedia messages
  to the multicast members in the RAs following the
  standard UMTS cell broadcast procedure.
• Like SMS multicast, a multicast table MCC is
  implemented in the CBC to maintain the identities
  of the RAs and the numbers of the multicast
  members in these RAs.

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Chapter 12 Session Initiation Protocol

• SIP is an application-layer signaling protocol
  over the IP network.
• SIP is designed for creating, modifying and
  terminating multimedia sessions or calls.
• SIP message specifies the Real-Time Transport
  Protocol / Real-Time Transport Control Protocol
  (RTP/RTCP) that deliver the data in the
  multimedia sessions.
• RTP is a transport protocol on top of UDP, which
  detects packet loss and ensures ordered delivery.
• A RTP packet also indicates the packet sampling
  time from the source media stream. The
  destination application can use this timestamp to
  calculate delay and jitter.

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Network Elements User Agent

• The user agent resides at SIP endpoints (or
  phones). A user agent contains both a User Agent
  Client (UAC) and a User Agent Server (UAS).
• The UAC (or calling user agent) is responsible
  for issuing SIP requests
• The UAS (or called user agent) receives the SIP
  request and responds to the request.

(a) SIP UA Developed in the National Chiao Tung
University
(b) Windows Messenger 4.7-based SIP UA (with
phone number 0944021500)
56
Network Elements Network Servers

• Registrar A UA can periodically register its SIP
  URI and contact information (which includes the
  IP address and the transport port accepting the
  SIP messages) to the registrar.
• Proxy Server A proxy server processes the SIP
  requests. The proxy server either handles the
  request or forwards it to other servers, perhaps
  after performing some translation.
• Redirect Server A redirect server accepts the
  INVITE requests from a UAC, and returns a new
  address to that UAC.

57
SIP Registration and Call Setup
58
Chapter 13 Mobile Number Portability

• Number Portability (NP) is a network function
  that allows a subscriber to keep a unique
  telephone number.
• NP is an important mechanism
• to enhance fair competition among
  telecommunication operators and
• to improve customer service quality.
• Three types of NP are discussed
• location portability,
• service portability, and
• operator portability.

59
Terminologies

• Number range holder (NRH) network the network
  which the number is assigned
• Subscription network the network with which the
  customers mobile operator has a contract to
  implement services for a specific mobile phone
  number
• Donor (release) network subscription network
  from which a number is ported in the porting
  process
• Recipient network network that receives the
  number in the porting process

60
MDN vs MIN

• An MS is associated with two number.
• Mobile directory number (MDN) is dialed to reach
  the MS (e.g., MSISDN in GSM).
• Mobile identification number (MIN) is a
  confidential number that uniquely identifies an
  MS in Mobile Network (e.g., IMSI in GSM).
• When mobile number portability is introduced, a
  porting mobile user would keep the MSISDN (the
  ported number) while being issued a new IMSI in
  GSM.

61
Simplified GSM Call Termination Procedure without
NP
Step 1 After calling party dials the MSISDN of
MS2, the call route to the GMSC of MS2. Step 2
GMSC query HLR to query the location of MS2.
Step 3 The call is routed to the destination
MSC and eventually set up.
62
Call Routing Mechanism with NP

• In 3GPP TS 23.066, two approaches are proposed to
  support number portability call routing
• Signaling Relay Function (SRF)-based solution,
  and
• Intelligent Network (IN)-based solution.
• Both approaches utilize the Number Portability
  Database (NPDB) that stores the recodes for the
  ported numbers.

63
SRF-based Approach

• The SRF node is typically implemented on the
  Signal Transfer Point (STP).
• Three call setup scenarios have been proposed for
  SRF-based approach direct routing (DR) and
  indirect routing (IR).
• DR The mobile number portability query is
  performed in the originating network.
• IR The mobile number portability query is
  performed in the NRH.

64
DR Call Setup Scenario 1
Step 1 After calling party dials the MSISDN of
MS2, the call is routed to the GMSC of the
originating network. Step 2 The GMSC queries SRF
for the subscription network information of MS2.
Step 3 By consulting the NPDB, the SRF obtains
the subscription network information, and
forwards it to the originating GMSC. Step 4 The
originating GMSC routes the call to the
subscription GMSC (i.e., GMSC of MS2). The call
is then set up following the standard GSM
procedure.
65
DR Call Setup Scenario 2
Step 1 After calling party dials the MSISDN of
MS2, the call is routed to the GMSC of the
originating network. Step 2 The GMSC queries
SRF for the subscription network information of
MS2. Step 3 By consulting the NPDB, the SRF
obtains the subscription network information. If
the originating network is the subscription
network of MS2, then SRF forward message to query
HLR to obtain the routing information of MS2.
Step 4 The information will then be returned to
the originating GMSC. Then call is set up
following the standard GSM procedure.
66
Chapter 14 Integration and WLAN and Cellular
Networks

• Service aspects
• Access control aspects
• Security aspects
• Roaming aspects
• Terminal aspects
• Naming and address aspects
• Charging and billing aspects

UMTS Universal Mobile telecommunication System
HLR Home Location Register UTRAN UMTS
Terrestrial Radio Access Network PDN Packet
Data Network RNC Radio Network
Controller WGSN WLAN-based GPRS Support
Node SGSN Serving GPRS Support Node AP
Access GGSN Gateway GPRS Support Node MS
Mobile Station
67
WLAN/Cellular Integration Scenarios
Service Capabilities Scenario 1 2 3 4 5 6
Common Billing ? ? ? ? ? ?
Common Customer Care ? ? ? ? ? ?
Cellular-based Access Control ? ? ? ? ? ?
Cellular-based Access Charging ? ? ? ? ? ?
Access to Mobile PS Services ? ? ? ? ? ?
Service Continuity ? ? ? ? ? ?
Seamless Service Continuity ? ? ? ? ? ?
Access to Mobile CS Service with Seamless Mobility ? ? ? ? ? ?
68
The MS Architecture
Perform MS Attach and detach procedure.(The
authentication action is included in the attach
procedure.)
Set up network Configuration.
69
The WGSN Node Architecture
70
Chapter 15 UMTS All-IP Network

• Mobile system history
• The advantages of evolution from UMTS R99 to
  all-IP network
• Mobile network will benefit from all existing
  Internet applications.
• The telecommunications operators will deploy a
  command backbone for all type of access, and thus
  to reduce capital and operating cost.
• New applications will be developed in an all-IP
  environment, which guarantees optimal synergy
  between the mobile network and Internet.

71
All-IP Architecture

• Option 1
• Support PS-domain multimedia and data service.
• Option 2
• Extend option 1 network by accommodating
  CS-domain voice service over a packet switched
  core network.

72
All-IP Architecture (option 1)
73
All-IP Architecture (option 1)

• Radio Network
• Can be GERAN or UTRAN.
• Home Subscriber Server
• Act as master database containing all 3G
  user-related subscriber data.
• GPRS Network
• Support mobility management and session
  management.
• IP Multimedia Core Network Subsystem
• Provide mobility management and session
  management.
• Application and Service Networks
• Support flexible services through service
  plateform.

74
Call Session Control Function (CSCF)

• Function
• Communicate with HSS for location information
• Handle control-layer functions related to
  application level registration and SIP-based
  multimedia session.
• Logical components
• Incoming Call Gateway
• Communicate with HSS to
• perform routing of incoming calls.
• Call Control Function
• Handle call setup and call-event
• report for billing and auditing.

75
CSCF (cont.)

• Serving Profile Database
• Interact with HSS in the home network to obtain
  profile information.
• Address Handing
• Analyze, translate, and may modify address.
• Three types of CSCF
• P-CSCF
• Be assigned to a UE while it attaches to the
  network.
• Forward the requests to the I-CSCF at home
  network.
• I-CSCF
• Contact point for the home network of the
  destination UE.
• Route the request towards the S-CSCF.
• S-CSCF
• Be assigned to a UE after successful application
  level registration.
• Support signing interactions with the UE for call
  setup and supplementary services control.

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HSS, BGCF, and MGCF

• Home Subscriber Server (HSS)
• Keep a list of features and services associated
  with users, and maintain the location of the
  users.
• Provide the HLR functionality required by the PC
  and CS domain, and the IM functionality required
  by the IMS.

• Breakout Gateway Control Function (BGCF)
• Select appropriate PSTN breakout point
• (another BGCF or an MGCF).

• Media Gateway Control Function (MGCF)
• Acts as the media gateway controller in a VoIP
  network.
• Control the media channels in an MGW.

77
T-SGW, MRF, and MGW

• Transport Signaling Gateway Function (T-SGW)
• Map call related signing from/to the PSTN on an
  IP bearer and send it to/from the MGCF.

• Media Resource Function (MRF)
• Perform multiparty call, multimedia conference,
  tones and announcements functionalities.

• Media Gateway (MGW)
• Provide user plane data transport between UMTS
  core network and PSTN.
• Interact with MGCF for resource
• control.

78
All-IP Architecture (option 2)

• Two control elements are introduced MSC server
  and GMSC server.
• Support Media Gateway Control Protocol (MGCP) or
  H.248 to handle control layer functions related
  to CS domain.
• MSC server MGW MSC (in UMTS R99)

Control plane
User plane
79
Application Level Registration
Step 1. UE sends SIP REGISTER to
P-CSCF.
Step 2. P-CSCF performs address translation of
UEs home domain name to find I-CSCF address.
Step 3. I-CSCF determines the HSS address, and
queries the HSS about the registration status of
the UE.
Step 4. I-CSCF obtains the required S-CSCF
capability information and selects an appropriate
S-CSCF.
Step 5. I-CSCF forwards SIP REGISTER to S-CSCF.
Step 6. S-CSCF presents its name and subscriber
identity to HSS.
Step 7. S-CSCF obtains the UEs subscriber data
from HSS.
Step 8. SIP 200 OK is replied.
Step 9. P-CSCF stores the home contact name and
forwards SIP 200 OK.
80
Author Biography

• Yi-Bing Lin is Chair Professor of College of
  Computer Science, National Chiao Tung University.
• His current research interests include mobile
  computing and cellular telecommunications
  services. Dr. Lin has published over 200 journal
  articles and more than 200 conference papers.
• He is the co-author of the books Wireless and
  Mobile Network Architecture (with Imrich
  Chlamtac published by Wiley, 2001) and Wireless
  and Mobile All-IP Networks (with Ai-Chun Pang
  published by Wiley, 2005).
• Dr. Lin is an IEEE Fellow, ACM Fellow, AAAS
  Fellow, and IEE Fellow.