Maintaining Control in the Multiple Vendor Environment: A Case Study

1
Migration Toward 4G and All-IP Concept
2
Global Standardization Activities
3
IMT2000 Main Participants
Industry Standard Groups - ARIB - Association of
Radio Industries and Business (Japan) ETSI -
European Telecommunications Standards Institute
(Europe) ITU - International Telecommunications
Union TIA - Telecommunications Industry
Association (USA) TTA - Telephone and Telegraph
Association (S.Korea)
4
IMT-2000 Radio Transmission Technology Candidates

• Universal Wireless Communications (UWC-136) - USA
  TIA TR45.3
• Time-Division Synchronous CDMA (TD-SCDMA) - China
  Academy of Telecommunication Technology (CATT)
• Wireless Multimedia Messaging Services Wideband
  CDMA (WIMSCDMA) USA TIA TR46.1
• UMTS Terrestrial Radio Access Wideband CDMA
  (UTRA W-CDMA) -ETSI SMG2
• Wideband CDMA (W-CDMA) - Japan ARIB
• Wideband CDMA IS-95 (cdma2000) - USA TIA
  TR45.5
• Multiband synchronous DS-CDMA (CDMA I) - S. Korea
  TTA
• Digital Enhanced Codeless Telecommunications
  (DECT) - ETSI

5
Current Standardization Activities
3GPP (Third Generation Project Partnership) Membe
rs ETSI (Europe) ARIB/TTC (Japan) T1 (USA
) TTA (S.Korea) CWTS (China
-Associate) System Specification Access
network WCDAM (FDD) TDCDMA (TDD) Core
network Evolved GSM All-IP
6
Current Standardization Activities
3GPP2 (Third Generation Project
Partnership2) Members TIA (USA) ARIB/TTC (J
apan) TTA (S.Korea) CWTS (China) System
Specification Access network cdma2000 (1x
3x) Core network Evolved IS-41 All-IP
7
Path to 3G
1989-1999
1984-1988
2000-2002
2003-2005
14.4 kbps
2 Mbps
144 kbps
384 kbps
Today
IS-136
EDGE
iDEN
GPRS
CDMA 2000
IS-95
HDR
1xRTT
Source CSFB
8
GSM Network Architecture
AUC
other VLRs
Base Station Subsystem (BSS)
H
G
D
HLR
EIR
VLR
OMC
B
C
F
BTS
other BSSs
A-bis
Mobile Services Switching Centre (MSC)
A
BSC
BTS
PSTN ISDN CSPDN PSPDN
Um
E
MS
other MSCs
BTS Base Transceiver Station BSC Base
Station Controller HLR Home Location
Register VLR Visited Location Register OMC
Operation Maintenance Centre EIR Equipment
Identity Register AUC Authentication Centre
9
GPRS Concept

• The General Packet Radio Service (GPRS)
• is a new value added service introduced in order
  to provide more efficient access to packet data
  networks from cellular networks.
• utilizes packet switching technology where
  information is transmitted in short bursts of
  data over an IP-based network.
• It provides a quick session set up and fast data
  transmission speeds. Supports immediacy (no
  dial-up connection is necessary)
• It can use multiple time slots for data transfer
  as opposed to a normal single time slot.
• Enables the Internet applications not available
  previously on GSM networks
• It supplements today's Circuit Switched Data and
  Short Message Service in GSM networks.
• theoretically supports maximum speeds of up to
  171.2 kbps
• GPRS shares GSM frequency bands with voice and
  circuit switched data traffic, and makes use of
  many properties of the physical layer of the
  original GSM system to simplify the introduction
  of new services

10
GPRS Services and Applications

• Supports two kinds of end-to-end packet switched
  data transfer
• Point-to-Point (PTP) services
• PTP connectionless network services for IP
• PTP connection oriented network services for X.25
• Point-to-Multipoint (PTM) services
• PTM-M Multicast services broadcasts packets in
  certain geographical areas
• PTM-G Group call services address packets to a
  group of users in a particular geographical area
• Always on and pay per byte concept
• New Applications

11
Quality of Service

• QoS classes are set per session, they include
• Service precedence priority of a service in
  relation to other services
• Reliability required transmission
  characteristics (3 classes are defined)
• Throughput maximum peak bit-rate and the mean
  bit rate
• Delay maximum value of mean delay
• Billing is based on data volume, type of service
  and QoS profile

12
GPRS Mobile Classes

• There are three classes of mobile stations (MSs)
• Class A mobile station supports simultaneous
  operation of GPRS and conventional GPRS services
• Class B mobile station is able to register with
  network for both GPRS and conventional GSM
  services simultaneously. In contrast to an MS of
  class A, it can only use one of the two services
  at a given time
• Class C mobile station ca attach for either GPRS
  or conventional GSM services. Simultaneous
  registration or usage is not possible. An
  exception are SMS messages which can be received
  and sent at any time
• Mobile stations also have different classes based
  on their multi-slot capabilities on the TX and RX
  sides
• e.g. 3 Time slot Receive and 1 Transmit

13
GPRS Main Attributes

• Consists of packet wireless access network and
  IP-based backbone
• Shares mobility databases with circuit voice
  services and adds new packet switching nodes
  (SGSN GGSN)
• Will support GPRS, EDGE WCDMA air interfaces
• Radio resources shared dynamically between speech
  and data services
• GPRS is designed to minimize hardware
  modifications on existing network elements
• Addition of a new hardware component in the BSS,
  the PCU, which integrates most of the BSS new
  functions and manages RLC/MAC layers
• BSC and BTS are impacted as few as possible
• Entirely new core network with many functions,
  for the packet-switched services
• The HLR is enhanced with GPRS subscriber data and
  routing information

14
GPRS Network Components and Interfaces
PSTN CN (Core Network)
PDN (Internet) CN (Core Network)
Gi
Gp
GMSC
GGSN
Gc
C
50
40
HLR/ AC
Gn
Gr
D
Gp
MSC/ VLR
SGSN
Gs
Q100
EIR
Gf
F
CN (Core Network) RAN (Radio Access Network)
A
Gb
Mobile data solution built upon the existing GSM
Infrastructure and Mobility Management Gateway
GPRS Support Node (GGSN) is responsible for
routing data packets entering and leaving the
radio network Serving GPRS Support Node is
responsible for packet delivery to mobiles in
different areas and interrogates the GSM
databases for mobile profiles
P C U
BSC
Abis
CS (Circuit Switch) PS (Packet Switch)
BTS
BTS
Um
15
GPRS Protocol Stack
Application
IP / X.25
IP / X.25
Relay
Relay
GTP
SNDCP
SNDCP
GTP
LLC
LLC
UDP /
UDP /
TCP
TCP
Relay
RLC
BSSGP
RLC
BSSGP
IP
IP
MAC
MAC
Network
L2
L2
Network
Service
Service
GSM RF
L1bis
GSM RF
L1bis
L1
L1
Um
Gb
Gn
Gi
MS
BSS
SGSN
GGSN
16
Required Changes in the Current GSM Networks

• GPRS is implemented on the top of GSM
  infrastructure by adding two main network
  elements
• Gateway GPRS support node (GGSN)
• Serving GPRS Support Node (SGSN)
• In addition to the new GPRS elements, existing
  GSM and TDMA (IS136) network elements should also
  be enhanced in order to support GPRS. Following
  two must be enhanced
• Base Station System (BSS) must be enhanced
  (software upgrade) to recognize and send users
  data to SGSN that is serving the area. PCU
  interface is required to cater data traffic.
• Home Location Register (HLR) changes (software
  upgrade) should be made in HLR to register GPRS
  users profile and respond to queries originating
  from SGSNs regarding these profiles.
• MSC/VLR Existing hardware could be used but
  Software upgrade is required.
• Mobile stations also need to be upgraded both in
  hardware and software to allow for multislot
  operation and variable coding.

17
GGSN Functions

• Acts as a logical interface between the GPRS
  network and the external public data networks
  such as IP and X.25
• It converts the GPRS packets coming from SGSN
  into appropriate PDP format (e.g., IP or X.25)
  and sends them out on the corresponding packet
  data network (PDN).
• It is connected to SGSNs via an IP GPRS backbone
  network
• GGSN support routing functionality and manages
  information for attached/detached procedures for
  GPRS users
• GGSN performs mobility management functions
  requesting location information from the HLR
• GGSN is responsible for tunneling data, using
  GPRS Tunneling Protocol (GTP), to encapsulate and
  de-capsulate packets for delivery to SGSN

18
SGSN Functions

• SGSN is at the same hierarchical level as the MSC
  
• SGSN responsible for the delivery of data packets
  from and to the mobile stations (MSs) within its
  service area
• It is responsible for mobility management
• SGSN keeps track of the individual MSs location,
  attached and detached procedure
• Interaction with VLR/HLR
• SGSN supports authentication and charging
  functions

19
PCU Functions

• GPRS radio resource allocation and management
• GPRS radio connection establishment and
  management
• Data transfer
• Coding scheme selection
• PCU statistics
• Interface with Billing Center
• It is possible that a single PCU (in this case
  known as PCU Serving Node) interacts with
  different BSCs

BSC
PCUSN
Frame Relay
Gb
P C U
BSC
Agprs
(Vendor defined)
20
GPRS Protocol Stack (MS-BSS-SGSN)

• LLC provides six Service Access Points (SAPs) to
  the upper layer protocols
• SAPs act as tunnels to pass data between the
  layer 2 and layer 3 entities as follow
• Four SAPs are dedicated to the Subnetwork-Dependen
  t Convergence Protocol (SNDCP) that manage data
  packet transmission
• One SAP is dedicated to GPRS mobility management
  transmission
• One SAP is dedicated to SMS
• A Service Access Point Identifier (SAPI)
  identifies each SAP
• A Data Link Connection Identifier (DLCI)
  identifies this logical link
• A DLCI is composed of the SAPI at the LLC and the
  TLLI
• SAPIs are points at which the LLC provides access
  to the SNDCP, that is Network SAPIs (NSAPIs)

LLC
LLC
NSAPI 1
SAPI 1
TLLI
SAPI 2
SGSN
MS
21
GPRS Protocol Stack (MS-BSS-SGSN)

• The SAPIs that the LLC provides to the SNDCP
  layer are essentially the four QoS levels
  provided for data communications for different
  levels of reliability
• In wireless data transmission, the logical link
  connections are maintained even when the lower
  layer physical link no longer exist (mobile is in
  idle state)

22
GPRS Protocol Stack (MS-BSS-SGSN)

• The Logical Link management Entity (LLME) manages
  the resources that have an impact on individual
  connections
• One LLME exists per TLLI and provides the
  following functions
• Initializing the parameters to be used
• Error processing
• Invoking connection flow control

23
GPRS Protocol Stack (MS-BSS-SGSN)

• The SAPI parameter is in the address field of the
  LLC frame (4 bits)
• The address field of the LLC frame is 1 octet
  (fixed)
• There is a 3 octets (fixed) for frame check
  sequence (FCS)

SAPI
24
Required Changes in the Current GSM Networks

• GPRS is implemented on the top of GSM
  infrastructure by adding two main network
  elements
• Gateway GPRS support node (GGSN)
• Serving GPRS Support Node (SGSN)
• In addition to the new GPRS elements, existing
  GSM network elements should also be enhanced in
  order to support GPRS as follow
• Base Station System (BSS) must be enhanced
  (software upgrade) to recognize and send users
  data to SGSN that is serving the area. PCU
  interface is required to cater data traffic
• Home Location Register (HLR) changes (software
  upgrade) should be made in HLR to register GPRS
  users profile and respond to queries originating
  from SGSNs regarding these profiles
• MSC/VLR Existing hardware could be used but
  Software upgrade is required
• Mobile stations also need to be upgraded both in
  hardware and software to allow for multi-slot
  operation and variable coding

25
GPRS Physical Channels

• Radio channels of GPRS are same as GSM
• Same 200KHz Carrier Spacing
• Same Frame size 4.615ms
• 8 time slots per radio frame
• Same GMSK modulation as GSM
• More Flexible Resource Allocations
• Adds 4 Channel Coding Modes/Schemes (CS1-CS4)
• Allows Flexible and independent time slot
  allocation (1-8) in the FW and Rev links
• Radio resources shared dynamically between speech
  and data services

26
GPRS Logical Channels
Group
Name
Direction
Function
PBCCH
PBCCH
Down-link
Broadcast
PCCCH
PRACH
Up-link
Random Access
PPCH
Down-link
Paging
PAGCH
Down-link
Access Grant
PNCH
Down-link
Multicast
PTCH
PDTCH
Down up-link
Data
PACCH
Down up-link
Associated ctrl
27
Packet Common Control Channels (PCCCHs)

• Broadcast Channels
• Packet Broadcast Control Channels (PBCCH)
• The PBCCH Transmits system information to all
  GPRS terminals in a cell
• Common Channels
• Packet Random Access Channel (PRACH)
• is used by the MSs to initiate packet transfers
  or respond to paging messages.
• On this channel, MSs transmit access burst with
  long guard times. On receiving access bursts, the
  BSS assigns a timing advance to each terminal
• Packet Paging Channel (PPCH)
• is used to page an MS prior to downlink packet
  transfer
• ??The PPCH is used for paging both
  circuit-switched and GPRS services, depending on
  the network operation modes and the class of
  mobile. (Class A or B will support this
  functionality).
• Packet Access Grant Channel (PAGCH)
• is used in the packet transfer establishment
  phase to send resource assignment to an MS prior
  to the packet transfer
• ??Additional resource assignment messages are
  also sent on a PCCH if the mobile is already
  involved in packet transfer.
• Packet Notification Channel (PNCH)
• is used to send a PTM multicast notification to a
  group of MSs prior to a PTM packet transfer. The
  notification has the form of a resource
  assignment for the packet transfer

28
Packet Traffic Channels (PTCHs)

• Packet Data Traffic Channel (PDTCH)
• It is used for data transfer. It is dedicated
  temporarily to one or a group of mobiles for
  multicast applications.
• More than one PDTCH can be used in parallel
  (multislot operation) for individual packet
  transfers. The PDTCH can be shared between many
  users (8/PDTCH)
• Packet Associated Control Channel (PACCH)
• It is used to convey signaling information
  related to a given MS such as acknowledgements
  (ACK) and power control (PC) information.
• also carries resource assignment messages, either
  for allocation of a PDTCH or further occurrences
  of a PACCH.
• One PACCH is associated with one or several
  PDTCHs concurrently assigned to one MS
• Packet Timing Advance Control Channel (PTCCH)
• It is used in the uplink for transmission of
  random access burst. It allows the timing advance
  required by the mobile in the packet transfer
  mode to be estimated.
• In the downlink, the PTCCH can be used to update
  the timing advance to multiple mobiles.

29
Introducing GPRS in GSM

• Two options are available for establishing GPRS
  air interface channels
• Option 1 uses the GSM signaling resources but
  establishes separate packet data channels for
  traffic control. Traffic channels can be fixed or
  dynamic
• Option 2 separates the GPRS resources entirely
  from those of GSM. There are several possible
  configurations with this option
• A PBCH can be used to carry GPRS-BCH information,
  common control channels, GPRS packet data
  channels, and traffic-associated channels
• If the packet data channels are not carried by
  the PBCH or if additional PDCH resources are
  required, separate timeslots can be configured

30
Mixing or Separating PCCCH CCCH

• When no PCCCH is allocated in a cell, all GPRS
  attached MSs automatically camp on the existing
  GSM CCCH as they do in the idle state
• The allocation of a PCCCH is the result of either
  an increased demand for packet data transfer or
  whenever there are enough physical channels in a
  cell
• If the network releases the PCCCH, the MSs return
  to the CCCH

31
GPRS Air Interface Protocol

• A physical channel dedicated to packet traffic
  channel is called packet data channel (PDCH)
• The allocation of TCHs and PDCHs is done
  dynamically according to the capacity on demand
  principle
• A GPRS cell may have one or more PDCHs allocated
  from channels otherwise used as traffic channels
  (TCH)
• The Master Slave Concept
• At least one PDCH (mapped on one physical time
  slot) acts as a master
• The master accommodates packet common control
  channels (PCCCHs) carrying control signaling for
  initiating packet transfer as well as user data
  and dedicated signaling.
• The other channels, acting as slaves, are only
  used for user data transfer.
• The existence of PDCHs does not imply the
  existence of PCCCH

32
Capacity on Demand

• The number of allocated PDCHs in a cell can be
  increased or decreased according to demand
• Load supervision is done in the MAC layer to
  monitor the load on the PDCHs
• Unused TCHs can be allocated as PDCHs to increase
  the overall QoS for GPRS. If services with higher
  priority request resources, reallocation of PDCHs
  can take place
• This concept is used in cells with few or not
  GPRS users without the need for permanently
  allocated resources

33
Mapping GPRS Packets to GSM Bursts
Packet (N-PDU)
Network Layer
PH
User data
Segment
Segment
SNDCP Layer
LLC Frame
FH Info FSC
LLC Layer
Segment
Segment
Segment
RLC/MAC Layer
RLC Block
BH

Info BSC Tail
456
Normal burst
Convolutional encoding
Physical Layer
114
114
114
114
Data Block
Burst
Burst
Burst
Burst
PH
Packet header
FCS Frame check sequence
FH Frame header
BSC Block check sequence
BH Block header
34
Packet Data Channel in GPRS
TDMA frame
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
Idle burst
PDCH1
PDCH0
12 block structure (52 TDMA frames)
Radio Block
RLC Data (size depending on coding scheme)
BCS
MAC Hdr
RLC Hdr
456 bits
Coding/ puncturing
35
Random Access Uplink Data Transmission
MS
BSS
Packet channel request
PRACH or RACH
Packet immediate assignment
PAGCH or AGCH
Packet resource request
PACCH
Packet resource assignment
PACCH
Random access
Transmission
Frame transmission
PDTCH
Negative
acknowledgement
PACCH
Retransmission of blocks in error
PDTCH
Acknowledgement
PACCH
36
Packet paging Uplink Data Transmission
MS
BSS
Packet paging request
PPCH or PCH
Packet channel request
PRACH or RACH
Packet immediate assignment
PAGCH or AGCH
Packet paging response
PACCH
Packet resource assignment
PACCH or PAGCH or AGCH
Paging
Transmission
PDTCH
Frame transmission
PACCH
Negative acknowledgement
PDTCH
Retransmission of blocks in error
Acknowledgement
PACCH
37
Dynamic Allocation of Time Slots (Example)
Uplink state flag (MS allowed on uplink block)
Message type (downlink) and target MS
TS1
1 Dt(3)
1 Dt(3)
1 Dt(3)
2 Dt(3)
1 Dt(3)
Downlink
TS0
R
1
1 PUA(2)
2
1
1 Ack(2)
BSS
Ack
PUA
PCR
Data
MS2
TS0
PCR(2)
Dt(1)
Dt(1)
Dt(2)
Dt(1)
Uplink
TS1
Dt(1)
Dt(1)
Dt(1)
Dt(2)
Dt(1)
PCR Packet channel request (PRACH) Ack Packet
uplink ack/nack (PACCH) Dt Data
block PUA Packet uplink assignment
(PAGCH) PCA Packet control acknowledgment
38
Routing Areas and Location Areas

• One LA consists of a number of cells belonging to
  BSCs that are connected to the same core network
  node
• One RA consists of a number of cells belonging to
  BSCs that are connected to the same core network
  node
• One LA is handled by only one core network
  serving node (one combined MSCSGSN)
• One RA is handled by only one core network
  serving node (one combined MSCSGSN)
• The GSM/GPRS defined relations between LA and RA
  as follow
• RA and LA is equal in hierarchical level
• One RA is a subset of one, and only one LA,
  meaning that a RA do not span more than on LA

Cell
Cell
RA
RA
LA
39
GPRS Identities

• International Mobile Subscriber Identity (IMSI)
• Packet Temporary Mobile Subscriber Identity
  (P-TMSI)
• Temporary Logical Link Identity (TLLI)
• It is an identifier that uniquely identifies an
  MS within a routing area
• Local TLLI (derived from P-TLLI), Random TLLI
  (generated by MS),
• Foreign TLLI (derived from Local TLLI)
• Network layer Service Access Point Identifier
  (NSAPI)
• Tunneling Identity (TID which is IMSINSAPI)
• PDP address (IPv4/6, X.25,)
• Routing Area Identity (RAI which is
  MCCMNCLACRAC)
• GSN address
• GSN number (SS7 network), GSN address (IP
  address/logical name)
• Access Point Name (APN)
• DNS name of GGSNroute to external network

40
PDP Context and Session Management

• After GPRS attachment, to exchange data packets
  with external PDNs, the mobile must apply for one
  or more address used in the PDN
• An IP address in case of the IP networks
• This is called a Packet Data Protocol address
  (PDP address)
• For each session a PDP context is created
  describing its characteristics and includes
• PDP type (IPv4, etc)
• PDP address (172.129.23.10)
• Requested QoS
• The address of the GGSN that serves as the access
  point to the PDN
• The PDP context is stored in the following nodes
• MS
• SGSN
• GGSN

41
PDP Address Allocation

• PDP address allocation can be
• Static Users home PLMN network operator assigns
  a permanent PDP address to the user
• Dynamic A PDP address is assigned to the user
  upon activation of a PDP context, this can be
  assigned by
• Home PLMN (dynamic home PLMN PDP address)
• Visited PLMN (dynamic visited PLMN PDP address)
• The home PLMN decides which alternative is used
• In the case of dynamic PDP address, the GGSN is
  responsible for the allocation and
  activation/deactivation of PDP address

42
PDP Context Activation
GGSN
Gn
Um
Gb
Gn
MS
BSS
SGSN
GGSN
1. Activate PDP Context
2. Create PDP Context Request
3. Create PDP Context Response
4. Activate PDP Context Accept
43
Functional PDP State Model
INACTIVE
Deactivate PDP Context or MM state change to
IDLE or PMM-DETACHED
Activate PDP Context
ACTIVE
44
Definition of PDP States

• A GPRS subscription contains the subscription of
  one or more PDP addresses
• Each PDP address is described by one or more PDP
  contexts in the MS, SGSN and GGSN
• Each PDP context may be associated with a Traffic
  Flow Template (TFT)
• Every PDP context exists independently in one of
  two PDP states
• Inactive The data service for a certain PDP
  address of a subscriber is not activated
• Active The PDP context for that address in use
  is activated in MS, SGSN and GGSN

45
GPRS Network Access

• Once a GPRS MS has begun operation, it introduces
  itself to the network by sending a GPRS attach
  request
• Network access can be achieved from either fixed
  side or the mobile side of the GPRS network by
  making PTP and PMP available
• As is cellular networks, several administrative
  functions are performed to validate user,
  including
• User Registration
• Associates the mobile ID with users PDP (Packet
  Data Protocol) and address with in PLMN. Within
  the home area of the MS, traditional HLRs are
  enhanced to reference GPRS data. Outside the home
  area, dynamically allocated records are
  referenced in VLRs.
• Authentication
• Ensures the availability of GPRS MS and its
  associated services. GMM protocol (Mobility
  Management) functions are used for this part of
  signaling.
• CAC (Call Admission Control)
• it determines the required network resources for
  the QoS that is requested. It these resources are
  available, they will be reserved.

46
GPRS Attach

• Network can/should check MSs identity
• Download MSs subscription information from HLR
  to SGSN (if SGSN doesnt already have that info)
• Update MSC/VLR (if IMSI Attach is also performed)
• Attach types
• Attach the first time
• Attach again in the same SGSN
• Attach again in a new SGSN
• Attach when SGSN has detected the context

47
GPRS Attach Procedure (1)

• The request for a GPRS attach is made to the SGSN
  
• Mobile sends SGSN its identity as an IMSI
  (international mobile subscriber identity) or
  P-TMSI (packet temporary mobile subscriber
  identity), this message will also contain a
• Network Service Area Point Identifier (NSAPI),
  which is specific to a particular network
  application at the mobile station. SNDCP layer
  uses this to communicate with the network
  applications (Internet browser, email, etc have
  their own NSAPI)
• The latter indicates to the SGSN whether the
  mobile wants to attach as a GPRS device, a GSM
  device, or both
• The SGSN will attach the mobile and inform the
  HLR if there has been a change in the RAI, if the
  desired attach type is both GPRS and GSM, the
  SGSN will also update the location with the VLR,
  provided that the Gs interface exists
• Note that a GPRS attach does not enable the
  mobile phone to transmit and receive data, for
  this, the mobile has to activate a communication
  session using PDP context

48
GPRS Attach Procedure (2)

• After authorization, the SGSN sends back a reply
  to the mobile station with a Temporary Logical
  Link Identifier (TLLI)
• The TLLI is specific to the mobile and is used by
  the LLC layer to provide a temporary ID to the
  mobile station, which can be used for a data
  communication
• A database is maintained at the SGSN that maps
  the mobile identity with the TLLI assigned to it,
  the NSAPI is associated with and the QOS
  subscription parameters required by the
  application

TLLI1, NSAPI2
MS1
More files to come after activation
TLLI2, NSAPI3
MS2
TLLI3, NSAPI2
MS3
Table update example for SGSN with 3 attached
users
49
GPRS Attach Procedure
Gs
Gb
Um
MAP
VLR
MS
BSS
SGSN
VLR
1. Attach Request
2. Security Procedures
2. Security Procedures
3. Location Update
4. Location Update
5. Attach Accept
50
GPRS Detach Procedure (1)

• GPRS detach procedure allows
• MS to inform the network that it does not want
  access the SGSN-based services any longer
• The network to inform the MS that it does not
  have access to the SGSN-based service anymore
• Different types of detach are
• IMSI detach
• GPRS detach
• combine GPRS/IMSI detach (MS initiated only)

51
GPRS Detach Procedure (2)

• There two different ways for detaching a MS
• Explicit The network or the MS explicitly
  requested detach
• A Detached Request is sent by the SGSN to the MS,
  or by the MS to the SGSN
• Implicit The network detached the MS without
  notifying the MS
• The MS can make an IMSI detach in one of two ways
  depending on if it is GPRS-attached or not
• A GPRS-attached MS sends a Detached Request
  message to SGSN, indicating and IMSI detach
• A MS that is not GPRS-attached makes the IMSI
  detach as already defined in GSM
• In the network-originated Detach Request message
  there may be an indication to tell the MS that it
  is requested to initiate GPRS attach and PDP
  context activation procedure for the previously
  activated PDP contexts

52
Mobility Management Main Issues

• The main task of mobility management is to keep
  track of the users current location, so that in
  coming packets can be router to his/her MS
• The main issues in mobility management are as
  follow
• READY timer function
• Periodic RA update timer function
• Mobile reachable timer function

53
Mobility Management

• As a mobile station moves from one area to
  another, mobility management functions are used
  to track its location within each PLMN
• The mobile station's profiles are preserved in
  the VLRs that are accessible to SGSNs via the
  local MSC
• A logical link is established and maintained
  between the mobile station and the SGSN at each
  PLMN
• At the end of transmission or when a mobile
  station moves out of the area of a specific SGSN,
  the logical link is released and the resources
  associated with it can be reallocated

54
Mobility Management-MS State

• IDLE The subscriber is not attached to the
  GPRS MM
• STANDBY The subscriber is attached to the GPRS
  MM
• READY The SGSN MM context extended by location
  information for the subscriber on cell level

MM State model of MS
55
Mobility Management-SGSN Model state

• This function of Mobility Management (MM) is
  needed in GPRS to
• Attach know who is the MS and what it can or is
  allowed to do.
• Detach leaving the system
• Location update know the location of MS

IDLE
GPRS Detach or Cancel location
Implicit Detach or Cancel Location
GPRS Attach

• In the STANDBY state the subscriber is
• known in the accuracy of the RA
• In the READY state the subscriber is
• know in the accuracy of the LA (cell)

READY
READY timer expiry or Force STANDYBY
PDU reception
STANDBY
MM State Model of SGSN
56
Mobility Management- RA and LA Update

• Interaction between SGSN and MSC/VLR
• IMSI attached and detached via SGSN
• Co-ordination of LA update and RA update,
  including periodic updates
• Paging for a CS connection via the SGSN
• Alert procedures for non-PS services
• Identification procedure
• MM information procedure

57
Routing and Data Transfer

• Once a mobile station begins data transmission,
  routing is performed by the GSNs on a hop-by-hop
  basis through the mobile network using the
  destination address in the message header
• Routing tables are maintained by the GSNs
  utilizing the GTP layer which may carry out
  Address Translation and Mapping functions to
  convert the external PDN addresses to an address
  that is usable for routing within PLMNs.
• The data itself will go through several
  transformations as it travels through the network
• Depending on the destination PDN, the data can
  be
• Forwarded, using the relay function, to go from
  one node to the other in the route,
• Tunneled to transfer data from one PLMN to
  another,
• Compressed to use the radio path in an efficient
  manner (Compression algorithms may be used for
  manufacturers to differentiate themselves,
  however, they may face interoperability issues in
  heterogeneous networks), and/or
• Encrypted to protect the mobile station from
  eavesdropping (Encryption algorithms can also be
  used as a differentiating factor).

58
Location Management-Routing Area Update

• When MS changes RA
• It tells to the network (old RA) it came from
• MS doesnt know if SGSN changes
• Simple update , if same SGSN handles both RAs
• If SGSN changes, then
• get MSs active information from the old SGSN
• new SGSN needs to get users subscription
  information from HLR
• all GGSNs must be updated
• MS detects RA change but not SGSN changes
• Intra-SGSN routing area update
• No need to update HLR or GGSN
• Inter-SGSN routing area update
• Both HLR and GGSN need to be updated

59
Session Setup Example
IP
GGSN
GMSC
SGSN
MSC
BSC
BTS
60
Packet Forwarding Example
GMSC
GGSN
SGSN
MSC
BSC
BTS
Allocate a few bursts and send it!
61
RA Reselection Example
PSTN/ISDN
IP
Still same IP address!
GMSC
GGSN
SGSN
MSC
BSC
BTS
62
GSM/GPRS Link Budget Comparison (1)

• The Receiver Sensitivity depends on the coding
  scheme
• Each type of modulation and coding scheme
  requires, for a given BLER, different minimum
  Eb/No
• As the data rates increases the error protection
  is reduced and therefore more Eb/No is required
  to meet the same BLER, this translates into
  different receiver sensitivities associated to
  each coding scheme
• There is smaller or no body loss
• The typical 3 dB body loss associated with voice
  service is excluded from the GPRS link budget
  (the user does not use the MS close to his/her
  head)
• Due to this 3 dB, the cell radius for CS1 (CS2)
  is larger (equal) than for voice service

63
GSM/GPRS Link Budget Comparison (2)

• The Down-link Interference Level Increase
• The effect of GPRS load on the existing GSM
  service will be of the order of up to 2dB
  degradation in the down-link TCHs
• Since down link GPRS power control will not be
  used, extra load is anticipated that will
  increase the interference level when GPRS
  services are introduced
• No effect is anticipated on the down-link BCCH
• Permanently keyed carriers and the absence of
  down-link power control serve to keep the
  interference at a fixed amount
• Power control is implemented in the up-link case,
  hence, the effect of the GPRS traffic is not a
  problem and there is no differences between BCCH
  and TCH cases
• Different Coding Schemes can be used in different
  parts of markets depending on
• The future demand for the data rates and
  marketing strategies
• The ability to offer different coding schemes
  without (or the minimum) modification in the
  existing network

64
GSM/GPRS Link Budget Promoters (Examples)
Receiver Sensitivity Effect
Body Loss Effect
65
Coding Schemes and Coverage Impact
66
A Review of UMTS
67
UMTS Goals
UMTS will be a mobile communications system that
can offer significant user benefits including
high-quality wireless multimedia services to a
convergent network of fixed, cellular and
satellite components. It will deliver
information directly to users and provide them
with access to new and innovative services and
applications. It will offer mobile personalised
communications to the mass market regardless of
location, network and terminal used.
UMTS Forum 1997
68
UMTS Vision
69
UMTS Bearer Services

• The UMTS radio access network and fixed network
  are expected to provide four classes of bearer
  services
• Class A - Circuit-switched bit pipe
• Class B - Circuit-switched bit pipe for variable
  bit rate
• Class C - Connection-oriented packet switched
  bearer service
• Class D - Connectionless packet switched bearer
  service

70
UMTS Services Capabilities
Both Real-Time and Non-Real-Time cases may
include packet or circuit type of
connections Speech bearers shall be supported in
all operating environments
71
Migration Approach to UMTS

• Europe has decided to adopt an evolutionary
  approach for the UMTS core network based on
  migration from the GSM/GPRS infrastructure
• For the actual air interface, a revolutionary
  approach has been chosen. That is a new radio air
  interface for UMTS Terrestrial Radio Access
  (UTRA)
• There are two other parallel activities
  concerning the UMTS air interface, both using an
  evolutionary approach (an intermediate approach)

72
Migration Approach to UMTS
GSM Infrastructure
Public Network
Air Interface
Dual-mode
Multi-mode
GSM DCS-1800 PCS-1900 DECT TETRA HIPERLAN SATELLIT
E IS-54 IS-95 PACS PDC PHS
Evolved GSM Air Interface
PSTN N-ISDN CSPDN PSPDN B-ISDN
NSS and/or BSC
New Air Interface
Dual-mode
Evolution approach based on GSM Infrastructure
73
UMTS Network
IP
PSTN/ISDN
CS core network
Packet core network
GMSC
GGSN
SGSN
MSC
UTRAN
UTRAN transport ATM New tricks Soft Handover
using IP
BSC
UTRAN UMTS Terrestrial Radio Access Network RNC
Radio Network Controller
Node B
74
UTRAN Architecture
RNS Radio Network Subsystem (BSS) RNC Radio
Network Controller (BSC) Node B Logical node
for radio Tx/Rx in one or more cells to/from
UE (BTS)
75
General Protocol Architecture
The Radio Access bearer service is offered from
SAP to SAP by the Access Stratum
Iu and Uu user plane
76
Overall Protocol Structure
Network Layer (L3) - Partitioned into Control
(C-) Plane User (U-) Plane. - Sublayer RRC
interfaces with layer-2 and terminates _at_ UTRAN. -
Sublayer Duplication Avoidance Terminates _at_ CN
Data Link Layer (L2) - Partitioned into 4
sublayers, (I) Medium Access Control
(MAC) (II) Radio Link Control (RLC) (III) Packet
Data Convergence Protocol (PDCP)
(IV) Broadcast/Multicast Control (BMC)
Physical Layer (L1) - Partitioned to several
Physical Transport channels
77
Radio Interface Protocol Architecture
Radio Interface Protocol Architecture
Logical Channel
Transport Channel (SAP)
Physical Channels
78
Channel Definitions
Logical Channel MAC layer provides data
transfer services on Logical channels
Transport Channel the services offered by
Layer 1 to higher layers Transport channel
defines the method and the characteristics by
which data are transferred over the air-interface
Physical Channel Physical channel, usually
consisting of radio Frames and timeslots, is the
mechanism with which the data are transferred
over the physical resources such as code,
frequency, phase and time.
79
Logical Channel Structure
(TDD)
(TDD)
(ODMA)
(ODMA)
80
Transport Channels
Common Transport Channel Common Transport
Channels require inband identification of the UEs
when addressing particular UEs.
Dedicated Transport Channels Dedicated
Transport Channels require the UEs to be
identified by the physical channel , i.e. code
and frequency for FDD (code, frequency and
timeslot for TDD).
81
Transport Channels
Transport Channels
Common Channels
Dedicated Channels
Common Packet Channel (CPCH) (Uplink)
Paging
Channel (PCH)
(Downlink)
Downlink Shared Channel(DSCH) (Downlink)
Random-Access
Channel (RACH)
(Uplink)
82
Transport Channels

• Common Transport Channels
• BCH The Broadcast Channel (BCH) is a downlink
  transport channel that is used to broadcast
  system- and cell-specific information. The BCH is
  always transmitted over the entire cell with a
  low fixed bit rate.
• FACH The Forward Access Channel (FACH) is a
  downlink transport channel. The FACH is
  transmitted over the entire cell or over only a
  part of the cell using beam-forming antennas. The
  FACH uses slow power control.
• PCH The Paging Channel (PCH) is a downlink
  transport channel. The PCH is always transmitted
  over the entire cell. The transmission of the
  PCH is associated with the transmission of a
  physical layer signal, the Paging Indicator, to
  support efficient sleep-mode procedures.
• RACH The Random Access Channel (RACH) is an
  uplink transport channel. The RACH is always
  received from the entire cell. The RACH is
  characterised by a limited size data field, a
  collision risk and by the use of open loop power
  control.

83
Transport Channels

• Common Transport Channels
• CPCH The Common Packet Channel (CPCH) is an
  uplink transport channel. The CPCH is a
  contention based random access channel used for
  transmission of bursty data traffic. CPCH is
  associated with a dedicated channel on the
  downlink which provides power control for the
  uplink CPCH.
• DSCH The downlink shared channel (DSCH) is a
  downlink transport channel shared by several Ues.
  The DSCH is associated with a DCH.

• Dedicated Transport Channel
• DCH The Dedicated Channel (DCH) is a downlink
  or uplink transport channel. The DCH is
  transmitted over the entire cell or over only a
  part of the cell using beam-forming antennas. The
  Dedicated Channel (DCH) is characterised by the
  possibility of fast rate change (every 10ms),
  fast power control and inherent addressing of UEs.

84
Logical onto Transport Channel Mapping
85
Physical Channels (Uplink)
Uplink Physical Channels
Common Physical Channels
Dedicated Physical Channels
Physical Common Packet Channel (PCPCH)
Physical Random Access Channel (PRACH)
Dedicated Physical Control Channel (Uplink
DPCCH)
Dedicated Physical Data Channels (Uplink DPDCH)
86
Physical Channels (Downlink)
Downlink Physical Channels
Common Physical Channels
Dedicated Physical Channels
TMUX
Dedicated Physical Control Channel (DPCCH)
Dedicated Physical Data Channel (DPDCH)
Synchronisation Channel (SCH)
Common Pilot Channel (CPICH)
Page Indication Channel (PICH)
Primary Common Control Physical Channel (P-CCPCH)
Physical Downlink Shared Channel (PDSCH)
Secondary Common Control Physical Channel
(S-CCPCH)
Secondary CPICH
Acquisition Indication Channel (AICH)
Primary CPICH
87
Physical onto Transport Channel Mapping
CPICH (PS), AICH, DPCCH PICH used for L1
signaling
88
Physical Channels (Uplink)
Dedicated Physical Channels (DPCH)
DPDCH Dedicated Physical Data Channel DPCCH
Dedicated Physical Control Channel
89
Iu Interface

• UTRAN shall support two logically separate
  signaling flows via Iu to combined or separate
  network nodes of different types (MSC and SGSN)
• the protocol architecture for the User Plane of
  the Iu interface towards the IP domain shall be
  based on the same principles as for the (evolved)
  Gn interface
• One or several AAL5/ATM Permanent VCs may be used
  as the common L2 resources between the UTRAN and
  the IP domain of the CN.

Protocol architecture for the Iu user plane
toward the IP domain
90
Iu User Plane

• the standard shall support that the user data
  flows transported over the Iu reference point
  to/from the IP domain shall be multiplexed on
  top of common L2 resources
• if the Iu data transport bases on ATM PVCs then
  the Iu IP layer provides the Iu network layer
  services
• a tunneling protocol is used on top of the common
  L2, this tunneling protocol corresponds to an
  evolution of the user plane part of the GTP
  protocol used in GPRS put on top of UDP/IP
• the user data plane in the UMTS network is made
  up of two tunnels
• a first IP/UDP/GTP tunnel between RNC and 3G SGSN
  on Iu
• a second IP/UDP/GTP tunnel between GGSN and 3G
  SGSN on Gn.

91
User Plane Protocol Stack for Data Retrieve
Between GPRS and UMTS
92
User Plane Protocol Stack for Data Retrieve in
UMTS
93
Separate Core Network Architecture for UMTS
94
Integrated Core Network Architecture for UMTS
95
Packet Data Network with Various Radio
Technologies
PSTN GW
Internet
Intranet
Modular, main parts are independent of radio
access
96
Common architecture 2005
3G Network based on the same Server/Gateway
architecture for wireline for wireless
Media Gateway
97
Toward an All-IP Network
Service Environment Home Network
Third Party Service Provider
SSP
SCF
SG
MGCF
PSTN
MSC Server
MG
SSP
SCF
CSCF
SG
UTRAN
SSP
GGSN
MG
PDN
RNC
MG
SGSN
IP Backbone
Signaling Interface Data Interfaces
98
Toward All-IP Concept
99
WLAN Integration, the First Step toward 4G
100
Evolution Toward Advanced Services
Cellular
2G Voice GSM, IS-95
2.5G Voice Data services GPRS, EDGE
3G Voice Broadband Data services UMTS, cdma2000
Wireless LANS
QoS Multi-services
802.11a/Hiperlan II Up to 54 Mbps 5 GHz Band
802.11b Up to 11 Mbps 2.4 GHz Band
But what will fuel the revenue growth?
101
Motivation for 3G-WLAN Integration

• 3G technologies may not meet be a real solution
  for high bit rates
• It will be expensive
• Planning picocell networks has several technical
  issues
• WLANs are capable of providing real high bit
  rate and
• They are cheaper to manufacture
• They are cheaper to purchase
• They are cheaper to deploy
• They are cheaper to operate
• New revenue streams
• Corporate customers becomes more mobile
• Consumer customers become more demanding

102
Potential Operational Models

• Cellular operators expands their network and
  cover the hot spots as a part of their network by
  WLAN
• Pros Good operational experience and more
  capital
• Cons Need to add several new classes of
  equipment into their network
• Infrastructure owners deploy and leases access to
  the operators
• Pros They have already access to the customers
• Cons New in this business
• ISPs or another third party acts as a reseller

103
Interworking Solutions

• No Coupling
• Independent 3G and WLAN networks, independent
  data and control paths
• Independent AAA functions
• Loose Coupling
• Independent 3G and WLAN data paths
• Using 3G AAA functions
• Tight Coupling
• WALN acts as an integrated part of 3G

104
Interworking Challenges

• Mobility Management
• Vertical handoffs
• Authentication/Authorization/Accounting (AAA)
• Identification
• Billing mechanisms
• Quality of Service
• How to map the services between cellular and WLAN
  networks?
• How to maintain the QoS between networks

105
Why Cellular Operators need WLAN?

• Operators need more bandwidth (or at least they
  think)
• WLAN radio technologies provide superior
  bandwidth
• And
• It is cheaper to manufacture
• It is cheaper to purchase
• It is cheaper to deploy
• It is cheaper to operate

106
Design Objectives

• Operators should maintain compatibility with
  GSM/GPRS/UMTS core network roaming and billing
  functions
• A GSM Subscriber Identity Module (SIM) is a
  natural choice for WLAN subscriber management
• In the first phase the focus of the WLAN business
  will be wireless data
• The system should be optimized for terminal
  initiated IP data services
• To minimize complexity and cost, the WLAN system
  must utilize the existing GPRS billing system

107
Combined Cellular/WLAN Architecture
MSC/HLR
GPRS Charging Gateway
BSC
SS7
Inter-System Handoff
Cellular Core
SGSN
Intra-System Handoff
GGSN
10/100 Base-T
Operator Core IP
Mobility Router/Switch
Authentication Server
(Access Controller)
108
Authentication Procedure
MSC/HLR
3) GSM authentication and charging messaging
SS7
GPRS RAN
Public WLAN
Cellular Core
SGSN
1) Terminal authentication through WLAN (SIM)
GGSN
Operator Core IP
Mobility Router/Switch
Authentication Server
(Access Controller)
SIM
2) SIM authentication and user accounting
through IP
109
Main Challenges

• Standard GSM subscriber authentication signaling
  from the terminal to the cellular modules must go
  through IP based networks
• In the combined scenario, voice and data, handoff
  scenarios between WLAN and WWAN is not clear and
  defined

110
WLAN Elements in Cellular Systems
Access Operator
Cellular Operator
GPRS Charging Gateway
MAP
RADIUS
MSC
HLR
Mobility Router/Switch
Authentication Server
(Access Controller)
111
Authentication Server

• Authentication server acts as the main control
  point for the WLAN management
• A single authentication server can support
  multiple access controller
• Authentication server hides the cellular
  infrastructure from the WLAN access network
• A predefine bit pattern in the HLR subscriber
  service profile indicate the WLAN subscription

112
Access Controller

• The access controller provides an Internet
  gateway between the WLAN network and the fixed IP
  core
• Access controller will be the DHCP termination
  point
• Access controller is in charge of gathering
  information for billing

113
C/WLAN Control Plane
CDR Transmission
RADIUS
GTP
Through Controller Manager
Through Accounting Manager
WLAN XAP
WLAN XAP
RADIUS
GTP
SIM Authentication
UDP
TCP
TCP
UDP
TCP
UDP
UDP
IP
IP
IP
IP
IP
802.11
802.11
802.3
802.3
WAN
WAN
802.3
802.3
GPRS Charging Gateway
Authentication Server
Mobile Terminal
Access Point
Access Controller
114
Accounting and Billing

• The authentication server converts the accounting
  data to standard GPRS charging data record (CDR)
• The authentication server verifies the received
  accounting data related to an IMSI
• The authentication server delivers the generated
  CDRs to the charging gateway

115
Simplified WLAN Network Model
Intranet / Internet
Includes Computer, WLAN card, etc.
Diameter or Radius Server
WLAN Access Network (with or without an
intermediate network)
AAAServer
UE
Includes WLAN access points and may include
routers, or intermediate AAA elements
116
WLAN Radio Technologies (1)
117
WLAN Radio Technologies (2)
118
High Level Requirements and Principles

• There is a set of high level functional
  requirements that have to be met when
  inter-working between WLAN and 3GPP is to be
  carried out.
• The specifications classify these requirements
  in
• Access Control Principles and Requirements
• Authentication Methods
• User Identity
• Charging Requirements and Principles
• Network Selection Principles

119
Access Control Requirements (1)

• The specifications require that all legacy WLAN
  terminals be supported
• However software upgrades may be required for
  e.g. security reasons.
• There must be minimal impact on
• the user equipment (UE) (i.e. client software)
• existing WLAN networks
• the HSS/HLR/AuC
• The need for operators to administer and maintain
  end user software shall be minimised
• Existing SIM and Universal SIM (USIM) shall be
  supported
• R6 USIM may include new functionality if seemed
  necessary e.g. in order to improve privacy.

120
Access Control Requirements (2)

• The WLAN connection established for a 3GPP
  subscriber shall have no impact to the
  capabilities of having simultaneous Packet
  Switched (PS) and Circuit Switched (CS)
  connections for the same subscriber
• Methods for key distribution to the WLAN access
  network shall be supported
• Authorisation shall occur upon the success of the
  authentication procedure
• The authorisation mechanism shall be able to
  inform the user and WLAN immediately of any
  change in service provision.

121
Access Control Requirements (3)

• Policy control applies to the services authorised
  for the user (I.e. voice, data, SMS, etc.)
• It shall be possible to indicate to the user any
  conditions for use of an authorised service
• Results of authorisation requests shall be
  indicated to the WLAN, so that the WLAN can take
  appropriate action

122
Access Control Principles (1)

• End to End Authentication
• It is to be executed between WLAN UE and 3GPP AAA
  Server
• It has to be independent on the WLAN technology
  utilised within WLAN Access network and shall be
  based on Extensible Authentication Protocol (EAP)
• Transporting Authentication Signalling over WLAN
  Radio Interface
• It is carried between WLAN UE and WLAN Access
  Network by WLAN Access Technology specific
  protocols
• For IEEE 802.11 type of WLAN radio interfaces the
  WLAN radio interface shall conform to IEEE
  802.11i standard,
• ETSI HIPERLAN2 shall be conform with TS 101 761,
  101 493 , Draft TS H2-3G interworking.

123
Access Control Principles (2)

• Transporting Authentication Signalling between
  WLAN and 3GPP network
• The transport of Authentication signalling
  between WLAN and 3GPP network shall be based on
  standard Diameter or RADIUS (Remote
  Authentication Dial In User Service) protocols.
• Service Selection
• The end to end signalling shall include means for
  delivering encrypted service selection
  information from the UE to the 3GPP AAA server.
• The service selection information may contain
  APN(???) and External Protocol Configuration
  Options as they are defined in 3GPP TS 24.008.
• Before admitting the user to access WLAN, 3GPP
  AAA server shall verify users subscription to the
  indicated APN against the WLAN subscriber profile
  retrieved from HSS

124
Authentication Methods

• The following is a list of a certain number of
  proposals with regards to authentication methods
  for WLAN and 3GPP inter-working.
• Universal SIM (USIM) based Authentication
• The USIM does not need to be included in the WLAN
  card. The WLAN device can be linked with a UE
  supporting a USIM via, for example Bluetooth,
  Irda, USB or serial cable.
• GSM SIM based Authentication
• Useful for GSM subscribers that do not have a
  UICC(??) card wit