Base station-subsystem-introduction-to-gprs-egprs-130915133623-phpapp01

© Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 1
EVOLIUM Base Station Subsystem
INTRODUCTION TO GPRS/EGPRS
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use and communication of its contents not permitted without
written authorization from Alcatel.
TRAINING MANUAL
3FL10472ACAAWBZZA2 – MARCH 2006

2Introduction to GPRS/EGPRS
All rights reserved © 2004, Alcatel
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1 What is GPRS ? 6
1.1 Definition 8
1.2 General architecture 9
1.3 MS Class 10
1.4 MS Multislot Class 11
1.5 GPRS Main Concepts 12
1.6 The benefits of GPRS 17
1.7 EGPRS 18
1.8 Quality of service profile 19
1.9 Services 20
2 GPRS Operation 23
2.1 Main Entities 25
2.2 MS Mobility Management States 30
2.3 MS Radio Resource Operating Modes 31
2.4 Basic procedures 32
2.5 Charging 45
2.6 Security 47
3 The Base Station Subsystem 52
3.1 3GPP Position 54
3.2 Alcatel’s Choice 55
3.3 Layered Model 56
3.4 Gb Interface 58
3.5 Radio Interface 60
4 Alcatel Solution 71
4.1 GPRS Network Overview 73
4.2 Alcatel 9135 MFS 74
4.3 Packet Switched Core Network 80
4.4 GPRS Network Management 82
4.5 Alcatel QoS offer 83
5 Annex and Glossary 88
Contents

Self assessment of the objectives Contract number :
Course title :
Client (Company, centre) :
Language : English dates from : to :
Number of trainees : Location :
Surname, First name :
Did you meet the following objectives ?
Tick the corresponding box
Please, return this sheet to the trainer at the end of the training
Instructional objectives
Yes (or
Globally
yes)
No (or
globally
no)
Comments
1 To be able toidentify the benefits of GPRS
2 To be able todescribe the organization of a
GPRS network,architecture, interfaces and
protocols.
3 To be able todescribe the main data
interchange mechanisms on a GPRS
network
4 To be able tocharacterize the solution
offered by Alcatel
Other comments

Instructional objectives
Yes (or
Globally
yes)
No (or
globally
no)
Comments
Self assessment of the objectives (continued)
Thank you for your answers to this questionnaire
Other comments

1 What is GPRS ?
Session presentation
> Objective: to be able to identify the technical
and commercial benefit of GPRS.
> Program:
• 1.1 Definition
• 1.2 General architecture
• 1.3 MS Class
• 1.4 MS Multislot Class
• 1.5 GPRS Main Concepts
• 1.6 GPRS Benefits
• 1.7 EGPRS
• 1.8 Quality of Service profile
• 1.9 Services

1 What is GPRS ?
1.1 Definition
> Definition (3GPP TS 22.060)
• GPRS provides data transfer capabilities between a sending entity and
one or more receiving entities.
• These entities may be an MS or a Terminal Equipment, the latter being
attached either to a GPRS network or to an external data network.
• The base station provides radio channel access for MSs to the GPRS
network.
w PDN (Packet Data Network)
IP networks = Internet (connectionless)

1 What is GPRS ?
1.2 General architecture
GPRS
Core Network
IP
Gb
NSS
A PSTN
Gi
PDN
IP / PPP
RADIO
ACCESS
NETWORK
BSS
Packet
switching
circuit
switching
w GPRS Core Network
The GPRS Core Network is also called GSS (GPRS Sub-System). It is an IP network, and therefore contains routers
(machines handling the packet switching function.)
w Routing Function
Data transmission between GPRS Support Node (GSN), may occur across external data networks that provide their own
internal routing functions, for example X.25 [34], Frame Relay or ATM networks.
w IP interworking
The GPRS Core Network supports interworking with networks based on the Internet protocol (IP). The GPRS Core
Network may provide compression of the TCP/IP header when an IP datagram is used within the context of a TCP
connection.
w X.25
X.25 PDP Type have been removed from the standard since R99.

1 What is GPRS ?
1.3 MS Class
> Class A
• Operates GPRS and other GSM services simultaneously.
> Class B
• Monitors control channels for GSM GPRS and other GSM services
simultaneously,
• but can only operate one set of services at one time.
> Class C
• Exclusively operates GPRS services.
w Classes A and B
Require dual scanning by the mobile for both GSM and GPRS service requests. Class A or B mobiles are "attached"
simultaneously to both networks.
w Class B
The exchange of packets is suspended to answer to an incoming GSM call (the GPRS subscriber is considered to be in
the "busy" or “on hold" state).
The PDP contexts are still active on the SGSN side until the Purge_Timer elapses.
w Class C
Exclusively operates GPRS services.

1 What is GPRS ?
1.4 MS multislot class
NAxx1
19 to 29
like 10
000NA88218
011NA77217
121NA66216
131NA55215
131NA44214
131NA33213
121544112
121534111
121524110
12152319
12151418
13143317
13142316
13142215
13141314
13232213
13231212
24221111
TrbTraTtbSumTxRxType
Multi-slot
class
w MS type
Type 1 are simplex MS, i.e. without duplexer: they are not able to transmit and receive at the same time
Type 2 are duplex MS, i.e. with duplexer: they are able to transmit and receive at the same time
w Rx
Maximum number of received timeslots that the MS can use per TDMA frame. The receive TS shall be allocated
within window of size Rx, but they need not be contiguous. For SIMPLEX MS, no transmit TS shall occur between
receive TS within a TDMA frame. This does not take into account measurement window (Mx).
w Tx
Maximum number of transmitted timeslots that the MS can use per TDMA frame. The transmit TS shall be
allocated within window of size Tx, but they need not be contiguous. For SIMPLEX MS, no receive TS shall occur
between transmit TS within a TDMA frame.
w SUM
Maximum number of transmit and receive timeslot (without Mx) per TDMA frame
w Meaning of Ttb, Tra et Trb changes regarding MS types.
For SIMPLEX MS (type 1):
Ttb Minimum time (in timeslot) necessary between Rx and Tx windows
Tra Minimum time between the last Tx window and the first Rx window of next TDMA in order to be able to
open a measurement window
Trb same as Tra without opening a measurement window
For DUPLEX MS (type 2):
Ttb Minimum time necessary between 2 Tx windows belonging to different frames
Tra Minimum time necessary between 2 Rx windows belonging to different frames in order to be able to
open a measurement window
Trb same as Tra without opening a measurement window

PDNPDNPDNPDN
PSPSPSPS
GSMGSMGSMGSM
networknetworknetworknetwork
CSCSCSCS
1 What is GPRS ?
1.5 GPRS Main Concepts (1/5)
> Use of radio resources in case of circuit switching
Fixed Rate
Radio timeslot
Radio interface
Access nodeAccess nodeAccess nodeAccess node
CS <CS <CS <CS <---->PS>PS>PS>PS
w Drawbacks of CS for data services
one radio channel at 9.6 kbit/s per user
fixed bit rate => waste (in the case of discontinuous service) and limitation on bit rate

GPRSGPRSGPRSGPRS
networknetworknetworknetwork
PSPSPSPS
PDNPDNPDNPDN
PSPSPSPS
1 What is GPRS ?
> Use of radio resources in case of packet switching
Radio timeslot
Radio interface
Variable Rate
w Benefits of Packet Switching
Variable bit rate becomes possible
One MS uses several RTSs. The maximum number of RTSs is given by the Operator (O&M parameters) and MS
capabilities (MS multislot class)
One RTS is shared by several MSs. The maximum number of MSs per RTS is given by the Operator (O&M
parameters) and 3GPP specifications (limitation due to addressing availability)

1 What is GPRS ?
> Radio resource assigned according to requirement
• Radio resource shared between users
• Various radio channel coding schemes are specified to allow bit rates
from 9 to more than 150 kb/s per user (according also to the quality of
radio transmission and the modulation used)
• High bit rates if several channels are assigned to one MS
• Low bit rates if one channel is shared by several MSs.
> Optimized use of the radio resource
• Use of the radio resources only when data is transferred
• Uplink and downlink resources reserved separately
w Radio resource sharing
The radio resources are shared by statistical multiplexing. As in GSM, no subscriber has their own permanent radio
resource.
w Bit rate
Maximum instantaneous bit rate provides 171,2 kb/s by the allocation of eight RTSs to one subscriber. The stated
maximum bit rates are different, because different coding schemes are used, which impacts the bit rate over a RTS. (see
Annex)
w Up link (UL) and downlink (DL)
It is possible to use a different bit rates in each transmission direction, whereas in CS (Circuit Switching) mode, there is a
maximum limit of 9.6 kb/s, in both directions and at all times.

1 What is GPRS ?
> Dynamic allocation and sharing of radio resources
User 1
User 2
User 3
User 4
User 5
1 RESOURCE SHARED BY X USERS (PDCH)
User 1
USER1 USES 3 RESOURCES (3 PDCH)
1 RESOURCE USED BY ONE USER NOT SHARED TCH
User 1
Number of resources according to the capability of the MS
w Caution: Animated slide that does not make sense if not in the slide-show mode.
w Optimized use
A radio resource (set of Radio Blocks over one or several RTS) is allocated only when data is being transferred, by
establishing and releasing Temporary Block Flow (TBF), that can be presented as micro-connections, each time a data
transfer has to be sent over the radio interface.
w Radio resource sharing
One TS can be shared by several MSs, by dynamic time multiplexing under control of the BSS.

> Variable useful transmission rate per Radio resource
Maximum security
Channel Transmission rate
about 22 k with GMSK
about 60k with 8PSK (Edge)
minimum throughput
Minimum security
Maximum throughput
When the radio transmission has a good quality the security can be reduced in
order to increase the useful transmission rate
1 What is GPRS ?

1 What is GPRS ?
1.6 The benefits of GPRS
> GPRS benefits
• BSS hardware (included OMC-R) is re-used from GSM
• Smooth GPRS introduction
• Higher data throughput thanks to EGPRS (EDGE)
• Data transfers can billed by volume instead of time
• An MS can exchange data by GPRS in parallel with a conventional GSM
call (if MS Class A)
w BSS is re-used
The same Radio Access Network is re-used, and a Packet Control Unit (PCU) function is implemented in the BSS.
w Compared to the GSM BSS
same frequency bands
same TDMA frame structure
same burst structure
same frequency hopping laws
...

1 What is GPRS ?
1.7 EGPRS
> EGPRS is an enhancement of GPRS
• allows higher bit rates on the radio interface
• achieved by using
– a new modulation (8-PSK)
– and new coding schemes (MCS-1 to MCS-9) in the MS and the BSS.
> The same set of services provided by GPRS is available in EGPRS.
w Shared = in other words: "the radio resources are shared by statistical multiplexing". As in GSM, no subscriber has their
own permanent radio resource.
w High or low bit rates = more than one time slot per MS or conversely, more than MS on the same TS (one TDMA frame
occupies 4.615 ms and is divided into 8 TS or channels).
w Maximum instantaneous bit rate provided = 171,2 kbps through the allocation of eight TSs to one subscriber. The stated
maximum bit rates are different (according to the BSS release), because different ways of encoding the data, or "coding
schemes", are used, which impacts the bit rate over a TS. (cf Annex)
w Optimized use:refer to Radio resource allocation in the slides to come + radio resource management in the BSS
Chapter.The radio resource allocation is suitable for variable, bursty traffic (downloading Web pages).
w Up link (UL) and downlink (DL): It is possible to use a different bandwidth (bit rate) in each transmission direction, whereas
in CS (circuit switching) mode, there is a maximum limit of 9,6 kbps, in both directions and at all times.
w QoS: Henceforth, QoS parameters are part of subscription data, according to the wide range of services provided to a
subscriber.

Precedence Class
relative importance of service under congestion3 classes
Delay Class
total delay measured between R or S point and Gi4 classes
Reliability Class
acknowledgement of packets5 classes
Peak throughput Class
Mean throughput Class
the maximum data rate allowed to the user
maximum data rate during a period
Throughput class
19 classes
9 classes
1 What is GPRS ?
1.8 Quality of service profile
w Precedence class
According to the class, user data packet can be discarded during the transfer due to a congestion state.
3 classes are defined : any, normal, high
w Delay class
The delay class depends on the operator network because a measurement is done between the R or S interface (between
the Mobile Terminal and the Terminal Equipment) and the Gi interface. For each operator, delay values are different so
delay classes are a reference not a strict value.
4 classes are defined : best effort, 1, 2, 3
w Reliability class
The reliability means that user data packets are acknwoledged during the transfer. The reliability classes are defined
according to the acknowledgement or not of the packet.
5 classes are defined
w Throughput class
The throughput class is defined by the 2 following parameters:
Mean Throughput : 9 classes are defined (from best effort to 111 Kb/s)
Peak Throughput : 19 classes are defined (from 8 Kb/s to 2048 Kb/s)

1 What is GPRS ?
1.9 Services
Always-on
Mobile OfficeMobile OfficeMobile OfficeMobile Office
•Voice (!)
•E-mail
•Agenda
•IntraNet/InterNet
•Corporate Applications
•Database Access
Vertical applicationVertical applicationVertical applicationVertical application
•Traffic Management
•Automation
•Mobile branches
•Health
Location servicesLocation servicesLocation servicesLocation services
•Traffic Conditions
•Itineraries
•Nearest Restaurant,
Cinema, Chemist,
Parking;, ATM ...
FunFunFunFun
•Games (Hangman, Poker, …)
•Screen Saver
•Ring Tone
•Horoscope
•Biorhythm
Media
TransportationTransportationTransportationTransportation
•Flight/train Schedule
•reservation
MusicMusicMusicMusic
•Downloading of
music files or
video clips
NewsNewsNewsNews
(general/specific)(general/specific)(general/specific)(general/specific)
•International/National News
•Local News
•Sport News
•Weather
•Lottery Results
•Finance News…
DirectoriesDirectoriesDirectoriesDirectories
•Yellow/White Pages
•International Directories
•Operator Services
M-commerce
PhysicalPhysicalPhysicalPhysical
•on-line shopping
•on-line food
Non physicalNon physicalNon physicalNon physical
•on-line Banking
•Ticketing
•Auction
•Gambling….
w Retrieval services
Provide the capability of accessing information stored in data base centers. The information is sent to the user on demand
only. An example of one such service in the Internet's World Wide Web (WWW).
w Messaging services
Offer user-to-user communication between individual users via storage units with store-and-forward mailbox, and/or
message handling (e.g., information editing, processing and conversion) functions;
w Conversational services
Provide bi-directional communication by means of real-time (no store-and-forward) end-to-end information transfer from
user to user. An example of such a service is the Internet's Telnet application;
w Tele-action services
Characterized by low data-volume (short) transactions, for example credit card validations, lottery transactions, utility meter
readings and electronic monitoring and surveillance systems.
w Distribution services
Characterized by the unidirectional flow of information from a given point in the network to other (multiple) locations.
Examples may include news, weather and traffic reports, as well as product or service advertisements;
w Dispatching services
Characterized by the bi-directional flow of information from a given point in the network (dispatcher) and other (multiple)
users. Examples include taxi and public utility fleet services;
w Conferencing services
Provide multi-directional communication by means of real-time (no store-and-forward) information transfer between
multiple users.

– True or False ?
– GPRS is a circuit switching technology
– The GSS is an IP network
– Data transfers are often conducted at variable bit rates
– With a class B mobile, a web page can be downloaded while speaking
– Billing by volume allows subscribers to be permanently on line
– Several channels can be assigned to a MS
– One channel is shared by several MSs
– EGPRS is GPRS with better Throughput
– The useful transmission rate depends on the radio quality
Time allowed :
5 minutes
1 What is GPRS ?
Exercise

Thank you for answering
the self-assessment
of the objectives sheet
1 What is GPRS ?
Evaluation
> Objective : to be able to identify the
technical and commercial benefit of GPRS

2 GPRS Operation

2 GPRS Operation
> Objective: to be able to describe the organization of a
GPRS network architecture, interfaces and protocols.
> Program:
• 2.1 Main Entities
• 2.2 MS Mobility Management States
• 2.3 MS Radio Resource Operating Modes
• 2.4 Basic Procedures
• 2.5 Charging
• 2.6 Security

2 GPRS Operation
2.1 Main Entities
> Overview
CELLS
BTS BSC
BSS RADIO ACCESS NSS CALL PROCESSING
circuits
To PSTN
GPRS
N7
AUC EIR
HLR
IP
SGSN
SGSN
NTP DNS
DHCP
To IP Networks
GGSN
BG To other operator
IP Networks
PCU included
in BSS
MSC
VLR
w PCU functions
LLC PDU segmentation / re-assembly into RLC/MAC PDU
PDCH scheduling (resource multiplexing)
Channel access control (access requests and grants)
ARQ function (RLC block Ack / Nak, buffering and retransmission of RLC blocks)
Radio channel management (power control, congestion control, broadcast control information).
w DNS (Domain Name Server) and DHCP (Dynamic Host Convergence Protocol)
w NTP server (Network Time Protocol) for GSN synchronization. In general an NTP application does not run on a
dedicated server. The OMC-G can play this role.
w HLR (Home Location Register) is involved in MS attachment to the GPRS network (authentication + services subscribed
to)

GSS
2 GPRS Operation
2.1 Main Entities
> SGSN and GGSN
IP
backbone
GGSN1
IP
network 1
IP
network 1
GGSN2
IP
network 1
GGSN3
IP
network 1
IP
network 1
SGSN1
SGSN2
SGSN5
SGSN3
SGSN4
w The SGSN (Serving GPRS Support Node) stores subscriber data:
Subscription information
IMSI
one or more temporary identities (P-TMSI)
zero or more PDP addresses
Location information
the cell or the RA where the MS is registered
the VLR number of the associated VLR (if the Gs interface is implemented)
the GGSN address of each GGSN for which an active PDP context exists
It also manages:
the transfer and routing of user data packets from the GSS towards the BSS
the mobility (GPRS attach/detach, data retrieval from the HLR, RA / Cell update)
the authentication and encryption (Access control and security)
the sessions (PDP context activation/deactivation)
The transfer of charging data.
w The GGSN (Gateway GPRS Support Node) stores subscriber data received from the HLR and the SGSN:
Subscription information
IMSI
zero or more PDP addresses
Location information
the SGSN address of the SGSN where the MS is registered
It also manages:
the allocation and use of dynamic @IP for MS,
the tunneling and encryption of user data at Gi interface,
the transfer of user data packets,
the charging data.

2 GPRS Operation
2.1 Main Entities
> Servers
GPRS
BACKBONE
SGSN GGSN
NTP
DNS DHCP
IP add
256.167.123.34
Alcatel.fr
w DNS
Resolve a name into an IP address
Use in Mobility procedure
w DHCP
Provide dynamically IP addresses
Split Users into pool of IP addresses
w NTP
Provide one time reference for all the network
Have a very precise time reference
Synchronization from satellite

MS
SGSNBSS VPLMN
BG
VISITED PLMN
GGSN
2 GPRS Operation
2.1 Main Entities
> Border gateway
INTER PLMN
NETWORK
HPLMN GGSN PDN
BG
HOME PLMN
w Border Gateway functions
Inter-PLMN routing and forwarding of user packets (IP router)
Security functions (firewall, access-list filtering)
w Connection of two Border Gateways
Via a private or public IP network, through the Gp interface.
w Choice of GGSN
If a subscriber wants to access an Intranet (PDN) in his home country, from the visited PLMN, the selected GGSN is the
one from the home PLMN
For Internet access a GGSN in the visited country could be used.

A
2 GPRS Operation
2.1 Main Entities
Gn
Signaling + data
Signaling
Mobile
GPRS
Gd
Um
GPRS network
Gb
BSS
Gc
Gs
Gr
Gi
PDN
SGSN
SGSN GGSN
HLRMSC
SMS-
GMSC
> Interfaces
w Signaling protocols
MAP/TCAP/SCCP/MTP on Gr, Gd and Gc,
GTP/UDP/IP on Gn,
BSSAP+/SCCP/MTP on Gs,
GMM/SM/LLC on Gb/Um.
w Gc interface
Used for network-requested PDP contexts activation (GGSN asks the HLR for SGSN routing information).
w Gs interface
Defines the Network Mode of Operation I (NMOI). It allows to perform LA + RA combined Location Update, and PS and
CS paging coordination (refer to ANNEX).
w Gr interface
Exchange of subscription information at GPRS attachment phase
w Additional interfaces
Gf (to the EIR)
Gd to deliver the SMS to the mobiles via the GPRS network (SGSN option and subscriber feature)

2 GPRS Operation
2.2 MS Mobility Management States
Idle
Ready
Stand-by
> MS MM states
GPRS Detach
PDU transmission
READY
timer expiry
GPRS Attach
Location at
CELL level Location at
RA level
Autonomous cell reselection NCO
Or controled by network NC 2
( In paquet transfert mode )
Autonomous cell reselection
w IDLE (GPRS) State
In GPRS IDLE state, the subscriber is not attached to GPRS mobility management. The MS and SGSN contexts hold no
valid location or routeing information for the subscriber. The subscriber-related mobility management procedures are not
performed.
Data transmission to and from the mobile subscriber and the paging of the subscriber is not possible. The GPRS MS is
seen as not reachable in this case.
In order to establish MM contexts in the MS and the SGSN, the MS shall perform the GPRS Attach procedure.
w STANDBY State
In STANDBY state, the subscriber is attached to GPRS mobility management. Pages for data or signalling information
transfers may be received. It is also possible to receive pages for the CS services via the SGSN. Data reception and
transmission are not possible in this state.
The MS performs GPRS Routeing Area (RA) and GPRS cell selection and re-selection locally. The MS executes mobility
management procedures to inform the SGSN when it has entered a new RA. The MS does not inform the SGSN on a
change of cell in the same RA. Therefore, the location information in the SGSN MM context contains only the GPRS RAI
for MSs in STANDBY state.
The MS may initiate activation or deactivation of PDP contexts while in STANDBY state. A PDP context shall be activated
before data can be transmitted or received for this PDP context.
w READY State
In READY state, the SGSN MM context corresponds to the STANDBY MM context extended by location information for the
subscriber on the cell level. The MS performs mobility management procedures to provide the network with the actual
selected cell. GPRS cell selection and re-selection is done locally by the MS, or may optionally be controlled by the
network.
An identifier of the cell, the Cell Global Identity including RAC and LAC, is included in the BSSGP header of the data
packet from the MS; see GSM 08.18 [21].
The MS may send and receive PDP PDUs in this state. The network initiates no GPRS pages for an MS in READY state.
Pages for other services may be done via the SGSN. The SGSN transfers downlink data to the BSS responsible for the
subscriber's actual GPRS cell.
The MS may activate or deactivate PDP contexts while in READY state.

2 GPRS Operation
2.3 MS Radio Resource Operating Modes
Packet
transfer mode
Packet
idle mode
Packet
idle mode
Ready Standby
RR
MM
> Packet transfer mode
In packet transfer mode, the mobile station is allocated radio resource providing a
Temporary Block Flow (TBF) on one or more physical channels. Continuous
transfer of one or more LLC PDUs is possible. Concurrent TBFs may be established
in opposite directions. Transfer of LLC PDUs in RLC acknowledged or RLC
unacknowledged mode is provided.
> Packet idle mode
In packet idle mode no Temporary Block Flow. Upper layers can require the
transfer of a LLC PDU which, implicitly, may trigger the establishment of TBF and
transition to packet transfer mode.
> MS RR operating modes vs MS MM states
w Packet idle mode
While operating in packet idle mode, a mobile station belonging to GPRS MS class A may simultaneously enter the different
RR service modes. A mobile station belonging to either of GPRS MS class B or C leaves both packet idle mode and
packet transfer modes before entering dedicated mode, group receive mode or group transmit mode.
w Packet transfer mode
When selecting a new cell, mobile station leaves the packet transfer mode, enters the packet idle mode
where it switches to the new cell, read the system information and may then resume to packet transfer mode in the new
cell.
While operating in packet transfer mode, a mobile station belonging to GPRS MS class A may simultaneously enter the
different RR service modes. A mobile station belonging to either of GPRS MS class B or C leaves both packet idle mode
and packet transfer modes before entering dedicated mode, group receive mode or group transmit mode.

Routers
IP network
2 GPRS Operation
2.4 Basic Procedures
ipip ipip ip
http httpftp ftpsmtp smtp
1tcp1tcp
wap wap
gtp
SGSN
GGSN
> IP overview

nK bytes MESSAGE
4K bytes PACKET 4K bytes PACKETTCP
TCPIP IP IP
TCPIP Z Ethernet 1.5k frames
Y Datagrams IP
TCP
x 4k TCP packets
L4
L 3
L2
2 GPRS Operation

DATASHEADER
456
HEADER
57 X 8
456
DATASHEADERIP / X25
HEADER DATASSNDCP
SNDCP
DATASHEADERLLC
RLC/
PCU
AIR INTERFACE
57 57
Max 1600Bytes SGSN to MSCRC
TRE / CCU
2 GPRS Operation

2 GPRS Operation
> Transmission plane
TCP HTTP FTP SMTP
Physical
layer
Physical
layer
Physical
layer
Physical
layer
Physical
layer
Physical
layer
Physical
layer
L2
IP
UDP
GTP
IP
L2
MAC
L2
IP
UDPLLC
GTP
BSSGP
(Frame
Relay)
(Frame
Relay)
LLC
Um Gb Gn Gi
MS
BSS
(with PCU) SGSN GGSN
Application
RLC
MAC
RLC
MAC
IPIP
relay
relay
BSSGP
SNDCP
SNDCP
w GTP (GPRS Tunnelling Protocol) tunnels user data between GPRS Support Nodes in the backbone network. The GPRS
Tunnelling Protocol shall encapsulate all PDP PDUs.
w UDP (User Datagram Protocol) carries GTP PDUs for protocols that do not need a reliable data link (e.g., IP), and
provides protection against corrupted GTP PDUs.
w IP (Internet Protocol) is the backbone network protocol used for routing user data and control signalling. The backbone
network may initially be based on the IPv4. Ultimately, IPv6 shall be used.
w SNDCP (SubNetwork Dependent Convergence Protocol ) maps network-level characteristics onto the characteristics of
the underlying network.
w LLC (Logical Link Control) provides a highly reliable ciphered logical link. LLC shall be independent of the underlying
radio interface protocols in order to allow introduction of alternative GPRS radio solutions with minimum changes to the
NSS.
w Relay. In the BSS, this function relays LLC PDUs between the Um and Gb interfaces. In the SGSN, this function relays
PDP PDUs between the Gb and Gn interfaces.
w BSSGP (Base Station System GPRS Protocol) conveys routing and QoS-related information between the BSS and the
SGSN. BSSGP does not perform error correction.
w (NS) Network Service transports BSSGP PDUs. NS is based on the Frame Relay connection between the BSS and the
SGSN, and may - multi-hop and traverse a network of Frame Relay switching nodes.
w RLC/MAC (Radio Link Control / Medium Access Control). The Radio Link Control function provides a radio-solution-
dependent reliable link. The Medium Access Control function controls the access signalling (request and grant) procedures
for the radio channel, and the mapping of LLC frames onto the GSM physical channel.

2 GPRS Operation
NSAPI
NSAPITLLITLLI
Radio layers
LLC
GMM/SM SMS
SNDCP
IP
NSAPIi
> MS high protocol layers
w SNDCP (Sub-Network Dependent Convergence Protocol)
Data compression, segmentation of large packets, recognition of PDP-PDU sessions (according to their NSAPI), inclusion
of QoS (use of SAPIs on the LLC link).
w NSAPI (Network Service Access Point Identifier)
This is used for a particular MS to distinguish different PDP contexts (= sessions)
by the PDP-type: X.25 or IP, or mainly by
the APN to be reached, or by
the required QoS.
w LLC (Logical Link Control)
Provides a safe link, encrypted and independent of the physical bearer, independent to BSS brand.
w TLLI (Temporary Logical Link Identity)
Identifies a logical link with the MS (one TLLI per MS)
w GMM/SM (GPRS Mobility Management / Session Management)
MS-SGSN signaling protocol for Gprs Mobility Management/ Session Management
w SMS (Short Message Service)

2 GPRS Operation
NMC-NSS
HPLMN
HLRMS
• APN accessible through FPLMN-GGSN ?
• etc ...
& MSISDN¨IMSI
¥ network access mode :
For each MS
GPRS | NSS | both
¥ subscribed « PDP contexts » (maximum of n) :
• PDP type :
• [PDP address (IP@) ]
• Access point name (APN) or * (= wild card)
• QoS profile
IP | PPP
n
times
> HLR GPRS data
w PDP address
Almost always empty. The network then dynamically assigns (using a DHCP server) an IP address to the subscriber when
he activates his PDP context (seen later).
w PDP contexts
Each PDP context can be considered as a BS (basic service = telephony, fax, etc). A PDP context is a dialog session with
an external IP network, identified with an APN. It is not always mandatory to subscribe (in the HLR) to PDP contexts,
access to some networks is free. For a user, the traffic of his different sessions will be recognized in the messages by the
use of different NSAPIs. A user can declare one of his PDP contexts as the default.
w APN (Access Point Name)
The APN represents an IP network. An APN has two parts: the APN-Network Id (example: wanadoo.fr) and the APN-oper
Id (example: mnc...gprs)
Examples of APN: wanadoo.fr.mnc001.mcc208.gprs,
APN = * (wildcard) potentially authorizes the MS to activate any APN.
w Valid APN
Boolean, if YES, indicates that this APN can be reached through the GGSN of the visited FPLMN.

2 GPRS Operation
> GPRS attachment
BSS

Authent_info_req()
Ž
Authent_info_respq)
|
Update_loc_req()
}
Insert_subs_data()
Update_loc_ack()
~
PLMN
Attach-Request
(IMSI)
ŒŒŒŒ
Attach_resp (P_TMSI)
Attach_complete () €€€€
MS_authentication_procedure GPRS IP
backbone
GGSN
SGSN
N7
HLR
w Attach Request.
The attach_request message is placed in an LLC frame. x
The MS sends its IMSI.
w Authentication
The SGSN gets the “authentication triplets” from the HLR:
triplets request message y
triplets response message z
The SGSN performs the “authentication procedure” with the MS: {
triplets request message y
triplets response message z
w Location Update
The SGSN performs the “location_update procedure” with the HLR:
location_update request message |
the HLR transfers the MS_subscription data to the SGSN }
the HLR terminates the location_update procedure ~
w Attach Complete
The SGSN terminates the attach_procedure with the MS :
attach_accept message (with a new P_TMSI allocation)
attach_complete message € (since a new P_TMSI has been allocated)

GPRS - CN
2 GPRS Operation
LLC layer
TLLI1
GPRS IP
backbone
> GPRS attachment
After a GPRS_Attach procedure The mobile is « connected » to the serving SGSN
SGSN
1
SGSN
2
GGSN
1
GGSN
2 PDN 2
PDN 1
w Attached MS
After running the attach procedure, the MS is “GPRS_attached”:
a logical connection is established between the MS and the SGSN
connection established between the peer LLC layers in the MS and the SGSN
this connection is identified by the TLLI (Temporary Logical Link Identity)
this logical connection remains established until the MS detaches
the MS can now access to GPRS services and is reachable for GPRS services

2 GPRS Operation
> PDP context activation
GPRS Core Network
GPRS
backbone
PDN
1
SGSN
DNS
GGSN
GGSN PDN
2
DHCP
BSS
PLMN
TLLI1
4
2
3Create_PDP_req (PDN2)
5 Create_PDP_resp (@IP_MS)
Activate_PDP_req (PDN2) ŒŒŒŒ
Activate_PDP_resp(@IP_MS)}}}}
w MS IP address
In case of IP PDP_type access with no additional mobile authentication procedure, the MS IP address is provided by the
PLMN, using either the subscription data, or the backbone DHCP server. No additional user authentication is needed on
top of the GPRS authentication mechanisms (i.e. using IMSI and authentication triplets)
w PDP Context Activation
Œ MS requests for a PDP_context activation, providing the name of target Packet Data Network (PDN2
parameter).
SGSN queries the backbone Name Server (here DNS) to identify the GGSN giving access to the Data Network
PDN2 (here GGSN2).
Ž SGSN sends a Create_PDP message to the corresponding GGSN2, in order to setup a GTP tunnel.
GGSN2 allocates an IP address to the MS (@IP_MS), using the backbone DHCP server.
GGSN2 acknowledges the Create_PDP message to the SGSN, returning the @IP_MS allocated to the MS.
‘ SGSN acknowledges the Activate_PDP message to the MS, with the allocated @IP_MS.

2 GPRS Operation
BSS
PLMN
TLLI1
GPRS Core Network
GPRS
backbone
SGSN
DNS
GGSN
GGSN
2
3Create_PDP_req (PDN2)
6 Create_PDP_resp (@IP_MS)
Activate_PDP_req (PDN2) ŒŒŒŒ
Activate_PDP_resp(@IP_MS)}}}}
ISP
INTRANET
DHCP
RADIUS
5
Authentication and
accounting
Address allocation
4
w MS address
IP PDP_type access with mobile authentication via a RADIUS. The address allocation server (i.e. DHCP) and/or
authentication server (i.e. RADIUS) may be located within the PLMN or in the ISP/Intranet network. Non-transparent
access is aimed for corporate intranet access, where additional user authentication is often required.
w PDP Context Activation
The authentication data are piggybacked in the Protocol Configuration Options (PCO) field of the PDP context
activation messages Œ and ’.
Œ , , Ž same as for IP PDP_type in transparent access.
GGSN performs the user authentication towards a RADIUS server.
GGSN allocates an @IP to the MS using the intranet/ISP DHCP server.
‘, ’ same as for a PDP context in transparent access.

2 GPRS Operation
LLC layer
GPRS - CN
TLLI1
GPRS IP
backbone
SGSN
1
SGSN
2
GGSN
1
GGSN
2 PDN 2
PDN 1TID 1 = IMSI + NSAPI 1
TID 2 = IMSI + NSAPI 2
by the GTP layer
after PDP_context_activation procedures
w User data transfer
In order to achieve a proper transfer of User Data, two main protocols are used: GTP (between GGSN and SGSN) and
LLC (between SGSN and MS), and two types of logical connections are established:
MS <-> SGSN. Logical Link used for signaling and data transfer, created at GPRS attach (unique per MS),
identified by a TLLI value;
SGSN <-> GGSN. Created with the activation of PDP context = when opening a session (several per MS),
identified each by a TID value.
w TLLI (Temporary Logical Link Identity)
Identifies uniquely a MS attached to the GPRS core network (Standby or Ready state).
w TID (Tunnel Identity)
Identifies a logical connection ("tunnel") between GGSN and SGSN (for each session of each MS). TID= IMSI+NSAPI.

2 GPRS Operation
LLC layer
GPRS - CN
TLLI1
GPRS IP
backbone
SGSN
1
SGSN
2
GGSN
1
GGSN
2 PDN 2
PDN 1TID 1 = IMSI + NSAPI 1
TID 2 = IMSI + NSAPI 2
by the GTP layer
after PDP_context_activation procedures
ul/dl data_transfers

SGSN
GGSN
within the MS
MS
over the Gn interface
over the Gi
interface
@ MS
@server
U-data
@sgsn
@ggsn
GTP
header
UDP
header
@ MS
@server
U-data
@ MS
@server
U-data
@server
@ MS
U-data
server
PDN
@ggsn
@sgsn
GTP
header
UDP
header
@server
@ MS
U-data
@server
@ MS
U-data
2 GPRS Operation
> User data transfer
w User data transfer
Data are transferred from header translation, then encapsulation in underlined protocol data unit.
At the GGSN, the IP address of the MS is used to retrieve a PDP context and therefore a TID and the address of the
current SGSN.
At the SGSN, the TID is used to work out the NSAPI and the IMSI (therefore the TLLI). If the MS is ready, no need for
paging because the MS is located to the exact cell.

2 GPRS Operation
2.5 Charging
> Charging process
MS
PDNGPRS
BACKBONE
GGSNSGSNBSS
TLLI
CCBS
CG
Attachment
M_CDR
PDP CONTEXT ACTIVATION AND DATA TRANSFERT
S_CDR
G_CDR
FTP
GTP
w CDR (Call Detail Record)
CDRs are used for subscriber charging, statistics and location purposes.
Three types of CDR are managed within the GPRS backbone:
M-CDR related to the GPRS mobility of a mobile station
S-CDR related to PDP-contexts activation and data transfers as seen by the SGSN
G-CDR related to PDP-contexts activation and data transfers as seen by the GGSN
CDRs, generated by the xGSN, are then sent to the CG (Charging Gateway) :
periodically,
using reliable transfers (GTP over TCP)
The CG forwards those CDRs to external CCBS (Customer Care and Billing System)
w CDR content
Here are the main information in the CDR :
IMSI
location information (LAC + RAC + Cell)
APN
PDP-context identifier
PDP-context start time and duration
negotiated QoS
volume of data sent / received
source and destination PDP addresses,
….

2 GPRS Operation
2.5 Charging
> Charging process
INTER PLMN NETWORK
HPLMN GGSN PDN
BG
CCBS
CG
S_CDRHOME PLMN
MS
SGSN
BSS
TLLI VPLMN
BG
CG CCBS
VISITED PLMN
G_CDR
w Charging data collection for inter-PLMN charging
Use of G_CDR and S-CDR as specified by GSM 12.15
Inter-operator agreement to transfer between Billing Systems

Public Internet
2 GPRS Operation
2.6 Security
1- Secured network access
• Authentication of MSs and confidentiality of
their identity
• Possibility of encrypting user data
• Possibility of verifying IMEI with an EIR (Gf)
2- Secured backbone IP network
Firewall = application-level filtering
Filtering by access lists (in the GGSNs)
GPRS Network
3- Secured intranet access
APN with mandatory subscription
APN with access lists
APN with tunneling on Gi (IPsec)
w Authentication and confidentiality
As in GSM, by security triplets and the use of the TLLI/P_TMSI instead of the IMSI.
w Encryption
The LLC frame is encrypted, so encryption from the MS to the SGSN and not just on Um.
w Firewall
Filtering function installed on routers (ex: GGSN). Packets are rejected by filtering at application level (for example: in http,
some URLs are barred). Also makes it possible to hide the IP addresses of MSs and backbone entities from external hosts
(Network Address Translation function).
w Access Lists (IP addresses lists)
A function of Cisco routers (and therefore of GGSNs). Each APN is linked to two lists of IP addresses to be checked during
the PDP context activation phase (calling address and called address in both UL and DL directions).
These lists are therefore used to protect access to the operator's backbone IP, but also to filter the access to external
PDNs.
At the GGSN, some APNs can be declared "with mandatory subscription" (at the HLR) and therefore inaccessible to other
MSs.
w Tunneling
Several ways:
by IPsec (Secured IP) = IP version in which the user data is encrypted (IP datagrams payload but not their header).
Or by Generic Routing Encapsulation (GRE)
by PPTP (Point-To-Point Tunneling Protocol). Refer to ANNEX for PPP Tunneling.

Time allowed :
5 minutes
2 GPRS Operation
Exercise (1/3)
– True or False?
– The GGSN reads the header of user packets arriving from the PDN
– The GPRS HLR knows the location of an MS to the nearest RA
– With each web page downloaded, a new PDP context must be
activated
– A CDR is generated for each packet sent or received
– The SGSN can be considered as PMSC and PVLR
– A TLLI is a virtual connection between a GPRS attached mobile and the
GGSN
w PMSC: Packet MSC.
w PVLR: Packet VLR.

Time allowed :
5 minutes
2 GPRS Operation
Exercise (2/3)
– True or False ?
– The Charging gateway provides a single interface towards the billing centers
– No need for paging to send a packet to a mobile in the "Ready" state
– Attachment to the network does not involve GGSN

Time allowed :
5 minutes
2 GPRS Operation
Exercise (3/3)
– What interfaces of the GPRS NSS does a packet cross from a PDN to an MS?
– Why , theoretically, is an RA smaller than an LA?

the self-assessment
2 GPRS Operation
Evaluation
> Objective : to be able to describe the
organization of a GPRS network :
architecture, interfaces, protocols,…

3 The Base Station Subsystem

> Objectives :
• To be able to briefly describe the data
interchange mechanisms through the BSS
> Program :
• 3.1 3GPP Position
• 3.2 Alcatel’s Choice
• 3.3 Layered Model
• 3.4 Gb Interface
• 3.5 Radio Interface

3.1 3GPP Position
> PCU function
BSSBTS
CCU PCU
BSC SGSN
BSSBTS
CCU
BSC SGSN
PCU
BSS
BTS BSC SGSN
CCU PCU
w PCU functions
RLC and MAC layers: LLC frame transportation (segmentation/reassembly),
Gb interface end point,
network access functions (radio resource management),
radio channel management (power control, congestion control, etc).
w CCU functions
encoding suited to radio channels,
radio measurements (receive quality, signal level, "timing advance" management).

3.2 Alcatel’s Choice
> PCU function
BTS
CCU
BSC SGSNMFS
Abis Ater Gb
GSL
LLC Transmission check between SGSN and MS
RLC Transmission check between PCU and MS
GCH transmission check between PCU and TRE
MFS is just the name of the
rack containing PCU functions
PCU
BSS
w The Multi BSS Fast packet Server (MFS):
w MFS is just the namee of the rack containing PCU functions
performs the GPRS Packet Control Unit (PCU) functions (3GPP 03.60 standard),
manages the Gb interface with the GPRS & EGPRS core network,
performs the Serving Mobile Location Center (SMLC) functions,
manages the SAGI interface with the A-GPS server.

3.3 Layered Model
BTS MFS SGSNMS
BSS
GP
Gb
Physical
layer
Frame
relay
RLC
MAC
RLC
Physical
layer
Frame
relay
BSSGP
Um Abis/Ater
PCU
IP
LLC
GMMSM
relay
LLC
GMM SNDCPSM
relay
Physical
layer
Physical
layer
L2-GCH
L1-GCH
L2-GCH
L1-GCH
MAC
SNDCP
> User plane
w For GPRS TRAFFIC, the BSS simply relays the LLC frames between the MS and the SGSN.
w BSSGP = BSS Gprs Protocol. Functions:
to relay LLC frame over the Gb, with no guarantee of integrity (relaying user data and GMM / SM messages :
session, RA_update and paging procedures). Conceals the FR layers for the LLC layer.
SGSN-MFS signaling = management of Gb interface objects (flush, paging, resume suspend, LLC-discarded and
other procedures).
cell-SGSN traffic management (identified by BssgpVCs): in particular cell update management (in the same RA):
the BSSGP header always indicates the current cell so if a "ready" MS moves into a new cell, then the SGSN
stores this new cell and sends all the unacknowledged LLC_PDUs to it (DL).
w The concept of handover has no meaning in packet switching (GPRS). There is no "circuit" to re-establish!
w RLC = Radio Link Control. (Provides a safe link for transporting LLC-PDUs in acknowledged or unacknowledged mode,
LLC-PDU segmentation into blocks and reassembly, management of TBF contexts. RLC depends on the physical bearer:
data encoding, error control and flow control suited to GSM channels.
w MAC = Medium Access Control. Multiplexing of RLC frames onto PDCH (transfer of blocks over the different PDCHi).
Including traffic sharing over several TSs or, conversely, the use of one TS for several users.

BSC MFSBTSMS
3.3 Layered Model
Gb
L2-GSL
L1-GSL
BSCGP
BSCGP
L2-GSL
L1-GSL
physical
layer
RRM
AterUm
relay
Abis
relay
physical
layer
RRM
> Signaling plane
w BSCGP protocol
administration interface of Radio Resource management :
(de)allocation of PDCH and MPDCH within a cell
activation / release of PDCH
System control information:
BSC reset procedure
cell and GIC group state management
Radio signalling :
GSM / GPRS paging,
GPRS access procedure
w RMM protocol
dynamic allocation of Radio Resources to a MS :
radio blocks from one or several PDCH
for uplink or downlink data transfers

NSE2
SGSN
NSE1NSE1
NSE2
F.RF.R
NetworkNetwork
PCM
3.4 Gb Interface
PCM
PCM
BVCI=2
BVCI=1
BVCI=3
BVCI=5
BVCI=6
BVCI=4
BSC1
BSC2
GPRS Core Network sideBSS side
BC PCMBCPVC
BC BCPVC
NSVC1
NSVC2
PCM
PCM
PCM
BC PCMBCPVC
BC BCPVC
NSVC3
NSVC4
BVCI=2BVCI=2
BVCI=1BVCI=1
BVCI=3BVCI=3
BVCI=5BVCI=5
BVCI=4BVCI=4
BVCI=6BVCI=6
> Managed entities
other procedures).

3.4 Gb Interface
GPRS Core Network sideBSS side
> Protocols
SGSNPacket Control Unit function
(PCU)
BSS GPRS Protocol
(BSSGP)
BSS GPRS Protocol
(BSSGP)
Network Service Control
(NSC)
Network Service Control
(NSC)
BVCI=2
BVCI=1
BVCI=3
BVCI=5
BVCI=
6
BVCI=4
BSC1
BSC2
Sub-Network Service
(SNS)
Physical layer
Sub-Network Service
(SNS)
Physical layer
Frame Relay
BVC
NS-VC
NSE
PVC
PCM PCM
BC
other procedures).

3.5 Radio Interface 1/8
> GPRS / EGPRS throughput
Coding Scheme Modulation
Maximum rate
per PDCH (kb/s)
CS2
CS1
GMSK
GMSK
13.4
9.05
CS4
CS3
GMSK
GMSK
21.4
15.6
GPRS
MCS9
MCS8
8-PSK
8-PSK
59.2
54.4
MCS7
MCS6
MCS5
MCS4
MCS3
MCS2
MCS1
8-PSK
8-PSK
8-PSK
44.8
29.6 / 27.2*
22.4
17.6
14.8 / 13.6*
11.2
8.8
GMSK
GMSK
GMSK
GMSK
* in case of padding
EGPRS

> Coding schemes
Bad radio condition
Max security
Good radio condition
Min security
Maximum number of bits to
have security
Max number of bits for
user data
POOR USER BIT RATE BETTER USER BIT RATE
CS2CS1 CS3 CS4

> GMSK / 8-PSK modulations
GMSK
8-PSK
1 0 1 1
001 101 011 001
GMSK270 kb/s
8-PSK810 kb/s
Gross bit rate
per carrier1 bit per
Symbol
3 bitS per
Symbol
8 PSK has 3times more capacity than GMSK
One TS 142 symbols
142 BitsONE TS
One TS 142 symbols
426 BitsONE TS
w Transmission and reception data flows are the same for GPRS and EGPRS, except for EGPRS MCS-9, MCS-8 and
MCS-7, where 4 normal bursts carry 2 RLC blocks (1 RLC block within 2 bursts for MCS-9 and MCS-8).
w Radio blocks are transported on the air interface (Um) over 4 consecutive normal bursts of the TDMA frame.
w The GMSK normal burst is composed of 156.25 symbols (1 bit for 1 symbol):
6 tail symbols,
26 training sequence symbols,
114 encrypted symbols,
2 stealing flags (2 symbols),
8.25 guard period (symbols).
For GMSK, the radio blocks are transported by 114 x 4 = 456 symbols.
w The 8-PSK normal burst is composed of 156.25 symbols (3 bits for 1 symbol):
6 tail symbols,
26 training sequence symbols,
116 encrypted symbols (there is stealing flags),
8.25 guard period (symbols).
For 8-PSK, the radio blocks are transported by 116 x 4 = 456 symbols.

> Transmission Rate with 8 PSK modulation
MCS9
59,2k
MCS8
54,4k
CHANNEL
MCS7
44,8k
MCS6
29,6k
MCS5
22,4k
MCS4
17,6k
MCS3
14,8k
MCS2
11,2k
MCS1
8,8k
Maximum number of bits to have security Max number of bits for user data
Bad radio condition Good radio condition

> Impact of EGPRS (Edge) on terrestrial transmissions in BSS
Extra capacity Extra capacity
Abis Ater
GMSk and Not a
good transmission
CS1 about 9K
MCS9 ABOUT 59K
8PSK good
transmission
MFS
PCU
BTS
TRX
BSC
relay
PDCH
BTS
TRX
BSC
relay
MFS
PCU16k resource 16k resourcePDCH

> Resources allocation according to the MCS
QUALITY OF TRANSMISSION LOT OF BITS LOST
INCREASE SECURITY DECREASE USEFUL TRANSMISSION RATE
MCS n
MFS
PCU
BTS
TRX
BSC
relay
PDCH
MCS n-1
PDCH
MFS
PCU
BTS
TRX
BSC
relay
Can be allocated to
another PDCH
Can be allocated to
other PDCH
w When the operator decide that the TRX will run MCS n all the terrestrial resources will be allocated , but if the quality of
the radio transmission is bad the PCU decides to increase the security on the air interface, the useful transmission rate on
the PDCH will be decreased and less capacity will be needed on the terrestrial transmission .
w The resource which is not used a that time can be allocated to another TRX if needed at BTS level
w The RLC blocks coming from different are multiplexed on the common resource for all the PDCH in the TRX which is
called M EGCH (Multiplexed EGCH)

networkMS
start
of TBF1
end of
TBF1 TBF2 TBF3
TBF4
time
fULi
Packet Channel Request
Packet Resource Assignment
(list of PDCHi, token=T,TFIk)
MS starts listening to all DL blocks token value on the allocated PDCHi
SEND on block b+1 (TFIk)
in block b
token =T ?
Y
N
Ø Ø T T Ø T Ø T T T ØDL PDCHi
? Ø Ø TFIk TFIk Ø TFIk Ø TFIk TFIk TFIkUL PDCHi
3.5 Radio interface 7/8
> UL transfer
PCU
TBF MAC
w This slide demonstrate that the radio resources (blocks) are used only when data need to be transferred (LLC-PDU) :
dynamic radio resource allocation. As a matter of fact, an MS shall specify its radio resource request at initiation of each
TBF for a better optimization of radio resource & MS capabilities.
w A TBF (the blue shape) comprises one or more consecutive LLC-PDUs.
w Temporary (Block) Flow Identity = TLLI + sequential number, used by the network to recognize data from different MSs.
Identifies uniquely a TBF in one direction within a cell.
The blocks are dynamically allocated upon the use of a token (Uplink State Flag) allocated to the MS at TBF
establishment. Any DL block includes a USF in the header.
The mobile "listens" to the PDCHi assigned, when block b (in DL) contains USF = T, the MS shall send one
PDTCH in UL on block b+1 on the UL PDCHi.
w The theoretical maximum of 160 kbit/s is given for one MS which would have 8 PDCHs of 21.4 kbit/s each. Those MS are
yet to be available on the market place.

PS Paging
Paging Request ("packet")
Packet Paging Response
Packet Resource Assignment
(list (PDCHj),TFIz)
The MS consumes the content of block b
in block b, TFI=TFIz ?
Y
N
PCU SGSN
UL TBF: refer to
previous slide
MS PDU
MS starts listening to all DL blocks TFI value on the allocated PDCHj
Ø Ø Z Z Ø Z Ø Z ZDL PDCHj
3.5 Radio interface 8/8
> DL transfer
MS IN STANB BY
MODE
MS IN READY
MODE
w In DL, each time an LLC-PDU is received, if there is no TBF in progress, it is essential to “establish" one.
w To respond to the paging, the MS needs to send a "paging response" to the SGSN (GMM) encapsulated in an LLC_PDU.
This response is carried by an UL TBF.
w Upon reception of the Paging response, the SGSN can send the DL PDU (LLC frame) to the MS through the MFS.
The MFS shall establish a DL TBF with the MS.
w DL TBF: each block of the DL TBF are identified by the DL TFI = TFIz
w After completion of the TBF establishment phase, the MS listen to all the DL blocks on the allocated PDCHs and keeps the
blocks tagged with the TFIz.

Time allowed :
5 minutes
Exercise (1/2)
– True or False?
– The SGSN is linked to the BSS by an interface based on
the Frame Relay protocol
– For each cell, the number of channels which can be
used for GPRS traffic is operator-configurable
– If a user packet is lost at the Gb interface, it can be
recovered using frame relay protocol mechanisms
– The LLC protocol is independent of the type of BSS
employed

Time allowed :
5 minutes
Exercise (2/2)
– True or False?
– In a cell, a TRX can carry eight PDCHs
– One PDCH can be allocated in its entirety to a single user
– If necessary, blocks on different PDCHs can be allocated to a
single user
– The NSEI is the identifier used by the SGSN to indicate the
destination cell of a LLC frame to the MFS
– The same quantity of PVCs is declared on the MFS and SGSN
sides

the self-assessment
Evaluation
> Objective : To be able to briefly describe
the data interchange mechanisms through
the BSS

4 Alcatel Solution

4 Alcatel Solution
> Objectives: to be able to characterize the solution
offered by Alcatel
> Program:
• 4.1 GPRS Network Overview
• 4.2 Alcatel 9135 MFS
• 4.3 Packet Switched Core Network
• 4.4 GPRS Network Management
• 4.5 Alcatel QoS Offer

GPRS Core Network
4 Alcatel Solution
4.1 GPRS Network Overview
BSS1
BSC
B
T
S
B
T
S
BSS--
BSC
B
T
S
B
T
S
A9135
MFS
BSS2
B
T
S
B
T
S
BSC
A9135
MFS
GSM/GPRS common servers
HLR
SMS-CMSC
GPRS IP
backbone
Radio subsystem
Frame
Relay
network
Border
Gateway Inter-PLMN
backbone
Internet
Intranet
SGSN
SGSN
access
router
SCP
CAMEL & IP based
Prepaid
Services
Firewall
Charging Gateway
OMC-CN
iGGSN
w Within the radio subsystem :
Existing Alcatel BTS and BSC from GSM are reused for GPRS :
no need of hardware change to provide GPRS features
need just software upgrade
The GSM-BSS now includes a proprietary equipment :
Alcatel A9135 = MFS (Multi BSS Fast packet Server)
which deals with the GPRS PCU functions
w Within the GPRS Core Network :
both SGSN and iGGSN are Alcatel proprietary equipments
Charging Gateway and OMC-CN are Alcatel components based on HP platform
Firewalls, Border gateway and access routers are standard IT components
w The HLR, MSC, SCP and SMS-C are reused from the GSM-NSS

Telecom Subsystem
4 Alcatel Solution
4.2 Alcatel 9135 MFS
Control Subsystem
Gb ifA-ter if
BSC1
B
T
S
B
T
S
> Functional architecture
GPU1
PCU
GPU2
PCU
S
G
S
N
LAN x 2
OMC-R
M
F
S
BSC2
B
T
S
B
T
S
GPU1
PCU
GPU1
PCU
w The duplex "Control subsystem" (two DS10 in active/standby mode, with 2 shared disks) :
controls the “telecom subsystem” (initialization, supervision, defence)
provides the management interface (OMC-R or local maintenance terminal)
w The “Telecom subsystem” is composed of GPU boards :
1. GPRS Processing Unit (GPU).
2. Each GPU board performs the PCU functions towards the BSC and the SGSN
16 PCM ports per GPU board
some PCM ports connected to the BSS, the other to the SGSN
w There are two different configurations regarding the support of BSC by the GPU boards :
only one GPU board supporting each BSC (in the B6.2 release)
multiple GPU boards supporting each BSC (from the B7 release)

PCU
PCU
PCU
PCU
PCU
SGSN
PMSC
PVLR
MFS
FRAME
RELAY
120 CICs
120 GICs 16K
TC SM
PVC
BEARER CHANNEL
Muxed ATer
A Interf
Gb
BSC
BSC
BSC
BSC
BSC
MSC
4 Alcatel Solution
4.2 Alcatel 9135 MFS CONNECTIONS

4 Alcatel Solution
4.2 Alcatel 9135 MFS
1 BSXTU
11 GPU (+1)
maxi
1 BSXTU
11 GPU (+1)
maxi
1 BSXTU
11 GPU (+1)
maxi
1 BSXTU
11 GPU (+1)
maxi
2 DS 10
Control
sub-rack
2 DS 10
Control
sub-rack
2 or 4
Switches
3 COM 3300
+ IOLAN module
2 or 4
Switches
3 COM 3300
+ IOLAN module
> Rack layout
w The "Control sub-rack" part is duplex (two DS10 in active/standby modes).
w each BSXTU sub-rack contains a maximum of 12 JBGPU boards.
The GPRS traffic of one BSC can be handled by several GPUs (up to six are foreseen from the same MFS rack)
Since B7, a full MFS contains from 4 to 22 BSS (BSC), due to multi-GPU feature
4 BSS per MFS: 2* (1 BSS / 6 GPU)+(1 BSS / 5 GPU)
22 BSS per MFS: 22*(1 BSS/GPU)
w One JBGPU board (= 1 PCU) offers 480 PDCH. Two uses of JBGPUs :
1. One JBGPU for each BSC, (Ater interface), so one MFS serves a maximum of 22 BSCs.
2. With 240 PDCH per GPU, a BSC can offer up to 6*240 = 1440 PDCH
3. To be connected to the FR network (Gb interface).
w Fast ethernet Switches (100 Mb/s) made by 3COM: 2 or 4 (as needed) to build LANs to which are connected
the Nectar stations (DS10)
GPU boards
printers and craft terminals (for local management, the terminal is called IMT = Installation & Maintenance
Terminal)

4 Alcatel Solution
4.2 Alcatel 9130 MFS (1/3)
ATCA
shelf
ATCA
shelf
w This platform is a high availability distributed platform composed of blades compliant with the Advanced Telecom
Computing Architecture (ATCA) open standard
w ATCA has been developed by the PCI Industrial Computers Manufacturers Group (PICMG).
w The related specifications are described in the PICMG 3.0 R1.0.

ATCA
shelf
ATCA
shelf
MFS
LIU LIU
MFS
MFS
O
M
C
P
S
S
W
S
S
W
O
M
C
P
G
P
G
P
G
P
G
P
G
P
G
P
G
P
G
P
G
P
G
P
4 Alcatel Solution
4.2 Alcatel 9130 MFS (2/3)
General Option 1 Option 2
ATCA shelf content
w LIU: Line Interface Unit – to collect the external PCM connections
w GP: GPRS Processing module
w OMCP: O&M Control Processing board – the control stations,
w SSW: Subrack SWitch

4 Alcatel Solution
4.2 Alcatel 9130 MFS (3/3)
GP
GP
GP
GP
GP
GP
GP
GP
GP
GP
M
U
X
OMCP
M
U
X
16 LIU X 16 E1
L
I
U
E1 connections
Abis
L
I
U
Ater
OMCP
S
S
W
S
S
W
MFS
9 PCU + 1SPARE
w LIU shelf: Multiplexes/demultiplexes and cross connects all E1 external links to/from NE multiplexed links (n E1 over
Ethernet) on the TP and the GP board. Equipped with two Mux boards and n LIU boards, depending on capacity.
w The LIU shelf hosts Two MUX boards which collect the E1 links from the 16 LIU boards on 16 serial links at 36.864 Mbit/s
and build packets sent towards up to 32 directions (125ms each) on a Gigabit Ethernet link.
w SSW: it’s an Ethernet switch which allows exchanges between all platform elements and externalIP/Ethernet equipment.
w OMCP: these control stations are used to process defense functions and platform Operation, Administration and
Maintenance (OAM) generic services..
w GP: Manages the user plane packet data flow processing.
w Ethernet links on the IP ports of the SSW switch: these links connect the platform to external IP equipment (i.e. OMC-R,
external alarm box).

> iGGSN
4 Alcatel Solution
4.3 Packet Switched Core Network
GPRS
signaling & user
Plane Blades
GPU
Gb
Ethernet LAN (internal com.)
Switching & Routing
O&M, Charging
SS7 Blades
Pilot Blades
> SGSN
Vigilon
Senteon
WN
PDN1
PDN2
GPRS IP
Backbone
OMC-CN
Charging
Gateway
Intra-PLMN
DNS
towards Prepaid Servers
O&M & service
provisioning
session control
logic
GTP control &
user planes
WN
Gr, Gs,
Gd, Ge
w The SGSN is ATCA based component (Advanced Telecom Computing Architecture). The main functions are distributed
over different hardware modules :
SS7 network interfaces (Gs, Gr, Gd) by a number of ATCA SS7 blades,
Gb interface by a number of Alcatel proprietary GPU boards,
SGSN O&M and GPRS charging agent (initialisation, defense, O&M, and CDR) by a cluster of ATCA Pilot blades,
GPRS signaling and user traffic handling by a number of ATCA control & user plane blades
SGSN internal communication, switching and routing of user traffic by a dedicated Ethernet switch
w The iGGSN is an Alcatel proprietary equipment, where the main functions are distributed over 3 hardware modules :
Vigilon server for iGGSN O&M, subscriber configuration and service provisioning,
Senteon server as a control logic for subscription and credit check during session establishment phase,
WN1200 node for full 3GPP GTP services

4 Alcatel Solution
4.3 Packet Switched Core Network
SGSN rack iGGSN rack
WN1200
Senteon 1&2
GPU boards
Ethernet
switch/routers
Ethernet
switch/routers
pilot blades
SS7 blades
GPRS control
& user plane
blades
ATCA platform
Internal control LAN
backbone rack
NS500
NS500
Firewalls
external DNS
NTS150
NTS150 NTP Servers
Intra-PLMN
DNS/DHCP
border router
access router
Gn switches

NMC
Q3
MFS
4 Alcatel Solution
4.4 GPRS Network Management
SGSN
NTPDNS/DHCP BG
B
T
S
B
T
S
BSC1
B
T
S
BSC2
OMC-
CN
Core Network part
Radio part
OMC-
R
Charging
Gateway
> Dedicated OMCs
iGGSN
w OMC-R: Called Alcatel 1353 RA = management of the radio subsystem :
Alcatel 9135 MFS.
BSCs and associated BTSs
w OMC-CN : called ALMA 1364 GPRS = management of the Core Network :
the SGSN server
the SGSN router
the GGSN.
The Charging Gateway (alarm supervision)
the DNS/DHCP server (supervision)
the GPRS network level (APN and Routing Areas)

4 Alcatel Solution
4.5 Alcatel QoS offer
ETSI R’97/98 QoS attributes Alcatel Offer
Precedence class Mean throughput
classDelay class Resulting QoS class
(4) Best Effort
1, 2 or 3
1, 2 or 3
1, 2 or 3
1, 2 or 3
any
(3) Low priority
Normal, High priority
(2) Normal priority
(1) High priority
any
any
Best Effort
specified, except BE
specified, except BE
Best-Effort
Best-Effort
Best-Effort
Normal
Premium
Reliability class: as required by the MS
> R97/98 QoS compliance
w These QoS attributes are associated with a PDP context performed by a R97/98 MS
w The five QoS parameters of the standard define more than 60 combinations ! Which is too much and leeds to simplification
:
Too complex to implement,
Many of the combinations have no meaning!
The standard "allows" more simple QoS implementations.
“-” = any value.
In bold, the main criterion for definition of the resulting QoS.
w Best effort = inexpensive, comparable to the Internet (no commitment). Ideal for foraging on the internet.
w Normal: Comparable to an intranet.
w Premium: Expensive, high performance.

4 Alcatel Solution
4.5 Alcatel QoS offer
Traffic handling priorityR99 Traffic class R97/98 Bearer QoS class
Premium
Premium
Premium
Normal
Normal
conversational
streaming
interactive
interactive
interactive
-
-
1
2
3
Best Effortbackground -
> R97/98 QoS mapping into R99 QoS
w The mapping of R97/98 QoS attributes to R99 QoS is applicable in the following cases :
hand-over of PDP context from GPRS R97/R98 SGSN to GPRS R99 or UMTS SGSN
when a R99 MS performs a PDP context activation in a R99 SGSN with a R97/98 GGSN
when the SGSN has received R97/98 QoS subscribed profile, but the MS is R99
w The mapping of R99 QoS attributes to R97/98 QoS is applicable in the following cases :
PDP context is handed-over from GPRS R99 to R97/R98
when a R99 MS performs a PDP context activation in a R99 SGSN while the GGSN is R97/98
when the SGSN sends user data to the BSS for a R99 MS
when the SGSN has received R99 QoS subscribed profile but the MS is R97/98
in the new SGSN, during an inter-SGSN RA_update procedure, or inter-system change, on receipt of the R99 QoS
attributes from the old SGSN

Time allowed :
5 minutes
4 Alcatel Solution
Exercise (1/2)
– True or False?
– Implementing GPRS in the BSS simply entails
adding A9135 or A9130 MFS servers
– The iGGSN is an Alcatel proprietary
equipment
– The SGSN server is an Alcatel proprietary
equipment based on IT devices
– The DNS/DHCP servers used in the GPRS
Core Network are IT standard servers

Time allowed :
5 minutes
4 Alcatel Solution
Exercise (2/2)
– True or False?
– GPRS Core Network equipments are managed from an
OMC- CN
– GPRS radio subsystem (BSS) equipments are managed
from an OMC-R
– Alcatel GPRS network handles simultaneously the UMTS
QoS classes (R99 QoS parameters) and the GPRS QoS
profiles (R97/98 QoS attributes)

the self-assessment
4 Alcatel Solution
Evaluation
> Objective : to be able to characterize the
solution offered by Alcatel

5 Annex and Glossary

5 Annex 1
Coding Schemes : CS1 -> CS4
0
5
10
15
20
0 10 20 30
Channelrate(kbps)
C/I (dBm)
CS4
CS3
CS2
CS1
BACK
w The data rate on a PDCH depends on the coding scheme :
for CS-1: PDCH data rate = 9.05 kbit/s (poor radio conditions or BSS signaling)
for CS-2: PDCH data rate = 13.4 kbit/s (better radio conditions)
for CS-3: PDCH data rate = 15.6 kbit/s
for CS-4: PDCH data rate = 21.4 kbit/s.
w The system selects automatically the best coding scheme :
the data rate is set according to the current C/l.
maximum data rate (160 kbit/s) only possible with CS4 on 8 parallel channels

UMTS
2 Mbps
384 Kbps
EDGE
GPRS
160 Kbps
64 Kbps
HSCSD
Bit rate
CS data - SMS, 9.6Kbps
9.6 Kbps
Technology
5 Annex 2
GPRS compared to other technologies
w SMS : With GPRS, the 160-character barrier for short messages will be able to be broken (when SMS over GPRS is
implemented).
w High Speed Circuit-Switched Data : This still involves circuit switching, meaning that, with a continuous use of radio
resources, so billed by time. HSCSD is based on the assignment of several traffic channels (TCH) to a single MS to offer a
higher bit rate. HSCSD is suited for services requiring a minimum bandwidth guaranteed.
w EDGE : (Enhanced data rates for GSM evolution) is a technology previously developed by Ericsson, based on TDMA and
offering a maximum theoretical speed of 384 kbit/s (8 channels, each 48 kbit/s, using a new modulation scheme: 8-PSK,
eight-phase shift keying, instead of GMSK for GSM and GPRS).
w EDGE-specific MTs are required! The BSS remains the same, except for the implementation of EDGE TRX (Evolium
product line).
Alcatel will offer EDGE from release B8 onwards. This is an important step towards UMTS
w UMTS : requires a new Radio Access Network based on W-CDMA technology.
The UMTS standard is part of the Third Generation (3G). Together with CDMA 2000 and other systems, they form a set of
ITU radio access technologies standardized by IMT 2000.

TFI = Temporary Flow Identifier
2 89 2 90 4 21 4 22 2 91 2 92 9 2 4 23 2 93 2 94 4 29 1
TBF = Temporary Block Flow BSN = Block Sequence Number
9 29 1 9 3 9 4 9 69 5 9 7
TBF TFI 9 TBF from SERVER 9
4 224 21 4 23 4 24 4 264 25 4 27 4 28 4 29 4 314 30
2 90 2 91 2 92 2 942 93 2 95 2 96 2 97 2 992 98 2 10
TS x dedicated to ONE PDCH one PDCH shared by N users
PCU JBGPU FUNCTION
5 Annex 3
PCU concept

PDCH
PCU
Gb
LLC Checks the transmission between SGSN and MS
RLC checks the trans between PCU and MS
n RLC
blocks
LLC blocks
RLC blocks
- token
- Data
- radio security
TRE /BTS
CCU
5 Annex 4
PCU concept

5 Annex 5
TDMA and PDCH
> TDMA frame and GPRS physical channels
0 1 2 3 4 5 6 7
FRAME 0
0 1 2 3 4 5 6 7
FRAME 1
0 1 2 3 4 5 6 7
FRAME 2
0 1 2 3 4 5 6 7
FRAME 3
Gmsk171 1718Psk 57 57
B0 B4B1 B2 B3 B5 B6 B7 B8 B9 B10 B11
52 FRAMES then 52 TS x and 240 ms
4
F00
4
F01
4
F02
4
F04
4
F05
4
F06
4
F07
4
F08
4
F09
4
F10
4
F11
4
F12
4
F13
4
F14
4
F15
4
F16
4
F17
4
F18
4
F19
4
F20
4
F21
4
F22
4
F23
4
F24
4
F25
4
F50
4
F51
4
F03
1 PDCH
12 BLOCS
PTCCH
Frame
12
Frame
38
BLOC 3

5 Annex 6
GPRS channels
> Master and Slave PDCHs
B0
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
PDCH
DOWN/UPLINK
All blocs can
be used as
- PDTCH
- PACCH
B0
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
B0
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
MASTER PDCH
DOWN /UPLINK
B0
B1
B2
All blocs can
be used as
- PRACH
- PDTCH
- PACCH
Blocs which
can be used
as
- PBCCH
Blocs which
can be used
as
- PAGCH
- PDTCH
- PACCH
Blocs which
can be used
as
- PPCH
- PAGCH
- PDTCH
- PACCH
w For each cell, it is possible to define the MINIMUM and MAXIMUM number of channels reserved for GPRS + the maximum
number of channels reserved for GPRS in case of high traffic load (when the BSC sends "Load indication" to the MFS
through BSCGP protocol).
w There are two types of PDCH : MPDCH and SPDCH
MPDCH = Master PDCH = PBCCH + PCCCH (PPCH + PAGCH + PRACH) -> carries GPRS signaling and system
information.
SPDCH = Slave PDCH -> carries the user traffic.
w Benefits of the Master Channel :
Preserves CCCH capacity for speech services
Higher GPRS signaling capacity, in line with GPRS traffic growth
Differentiated cell re-selection strategy between GPRS and non GPRS MS. When GPRS attached, a MS listen to
PSI broadcast on PBCCH. It allows a finer tuning of GPRS re-selection algorithms, for example in hierarchical
networks (C31 and C32 criteria). Otherwise, MS applies the basic Cell-reselection as in GSM Idle-Mode using the
C1 and C2 GSM criteria

B1
u3
B2
B1
un
B5
u3
B2
u3
B3
u3
B4
u3
B6
u3
B7
u3
B8
u3
B9
u6
B10
u6
B11
u2
B12
u2
B3 B4 B5 B6 B7 B8 B9 B10 B11 B12 B1
TBF from server 1
TBF from server 2
TBF from server 3
TBF from server 4
TFI 1
TFI 5
TFI 3
TFI 6
TBF server 5
TBF to server 7
TBF to server 6
TFI 2 USER 3
TFI 7 USER 6
TFI 6 USER 2
UP
DOWN
5 Annex 7
PDCH ,TBF, MAC concepts

> PCM E1 and Bearer Channel uses and concepts
TS 1 16K X 4
TS 3 64K 64K X 1
TS 2 32K X 2
TS 4
TS 5
128K 64K X 2
TS 3
TS 28
TS 31
TS 29 192K 64K X 3
2
M
B
E
1
TS 1
TS 2
TS 3
TS 4
TS 15
TS 17
TS 31
TS 18
TS 19
TS 20
BEARER CHANNEL =960K
BEARER CHANNEL=960K
2
M
B
E
1
TS 1 64K
TS 2 64K
TS 3 64K
TS 4 64K
TS 5 64K
TS 3 64K
TS 28 64K
TS 31 64K
TS 29 64K
2
M
B
E
1
5 Annex 8
Different uses for E1
w Minimum size for a bearer channel: 1 x 64k, Maximum size for a bearer channel: 31 x 64k.
w One PVC per bearer channel.

Node
15
6
9
27
PVC y
PVCn
12
5
16
DLCI Number
FRAME RELAY
PCU
MFS
SGSN
5 Annex 9
FRAME RELAY and PVC concepts

Permanent Virtual
Connection
FRAME
RELAY
NSVC Transmission check end to end
SGSN
PCU
MFS
PCM E1
BEARER
CHANNEL
5 Annex 10
PVC and NSVC concepts

PCM 1
P
C
U
BC 1
BC 2
BC1
PCM 1
NSE NSEIx
PVC / NSVC
PVC / NSVC
PVC / NSVC
There is One PVC/NSVC per Bearer Channel
There is one NSE for all the PVC of one PCU
PCM 2
BC 3
5 Annex 11
TDMA and PDCH

5 Annex 12
Network Mode of Operation I with Master Channel
BSC
CCCH
PCCCH
PACCH
Um
MSC
VLR
SGSN
A
Gb
Gs
CS paging for GPRS-attached MS in idle state (a), or in data transfer state (b)
CS paging for non GPRS-attached MS GPRS paging
(a)
(b)
w In this mode, the Gs interface is present in the core network. As far as GPRS-attached MS are concerned, the BSS
receives both GPRS and circuit-switched paging messages from the Gb interface.
w There is paging co-ordination because all paging messages towards GPRS-attached mobile stations are sent either on the
Master Channel, if present, or on the CCCH otherwise.
w In addition, whilst involved in a packet data transfer the GPRS mobiles receive the circuit-switched paging messages via
the GPRS traffic channel currently used.
w NMO II :
There is neither Gs interface nor Master Channel. There Paging coordination over the CCCH of GSM. Also, GPRS
Mobile Stations operating in Class B may lose CS Paging message if they are not able to monitor CCCH at the
same time.
w NMO III:
In this mode, there is no Paging coordination because Gs interface is not present while the Master Channel is.
Therefore, CS Paging is transmitted over CCCH when PS Paging is transmitted over PCCCH. Class C Mobile are
not able to manage both type of channels.

5 Annex 13
MOBILE ONE PHASE ACCESS ON PCCH (Master PDCH)
NETWORK
Packet channel request PRACH
Packet UL assignment + polling
indication PAGCH
Usf Scheduling
Packet Control ACK PACCH
RLC data bloc PDTCH
TFI
PDCH
USF
TA
Packet UL ACK NACK PACCH
w "Attach" the MS switches on (GMM protocol):
MS sends his previous P_TMSI, otherwise a random one. The attach_request message is placed in an LLC frame
with its old TLLI if its exists, or a randomly chosen TLLI if not.
w TLLI: This is allocated to the subscriber on his attachment to the network. In reality, the SGSN allocates the MS a P-TMSI,
from which the MS and the SGSN itself derive the TLLI.
w The functions of the HLR:
to supply the security triplets
to check roaming restrictions (or ODB)
to store the address of the current SGSN
to initiate the deletion of data from the old SGSN
to send subscriber data to the SGSN
w "Detach" proceeds as follow:
MS to SGSN: Detach request
SGSN to GGSN: Delete PDP context then Acknowledge
SGSN to MS: detach accept

Usf Scheduling
RLC data bloc PDTCH
Packet UL ACK NACK PACCH
5 Annex 14
MOBILE ONE PHASE ACCESS ON CCCH (no master PDCH)
NETWORK
Channel request RACH
Immediate assignment AGCH
Packet uplink assignment + polling
indication PACCH
TFI PDCH USF TA
TFI PDCH USF
Packet control ACK PACCH

5 Annex 15
MOBILE ORIGINATING DATA TRANSFERT
BSS SGSN
STAND BY
READY
PACKET DOWNLINK ASSIGNEMENT
UL UNIDATA
RLC PDU
Paquet channel request
Paquet UL assignement
UL TBF
Establishment
RLC PDU
RLC PDU
PACKET UPLINK ACK/NACK
RLC PDU
RLC PDU
RLC PDU
UL UNIDATA
UL TBF
Release

5 Annex 16
MOBILE TERMINATING DATA TRANSFERT
BSS SGSN
STAND BY
READY
LLC PDU
DL UNIDATA
UL UNIDATA
PACKET DOWNLINK ASSIGNEMENT
PAGING PS
Packet Paging Request
channel request
Paquet UL assignement
UL TBF
DL TBF

5 Annex 17
GMM - Combined GPRS and NSS attach with Gs (1)
HLR
Attach_request (IMSI)
Triplet request ( rand kc sres )
Authentication
Update_location
IMSI ↔↔↔↔ current SGSN
Insert_subscriber_data
Update_location_ack
IMSI ↔↔↔↔ TLLI + current RA + subscription data
Attach_accept (TLLI)
MS ↔↔↔↔ TLLI
TLLI Established
SGSN

5 Annex 18
GMM - Combined GPRS and NSS attach with Gs (2)
Location_Update_req (IMSI, LAI)
Insert_subscriber_data
Update_location_ack
Location_Update_accept
Update_ location (IMSI, @VLR)
IMSI ↔ current VLR
HLRSGSN MSC/VLR
w Location-Update-request: The SGSN determines the MSC/VLR based on the RA where the subscriber is located.
w At the HLR: If the MS was declared in another MSC, the HLR sends it a Cancel_Location before doing ISD to the new
MSC.
w Attach-accept: In practice, the SGSN sends the MS the P-TMSI (and not the TLLI) and the V-TMSI (TMSI of the VLR),
designated TMSI here.
w Once this combined-attach is done, the MS can make combined LA/RA update procedures (see GSM 03.60)..

5 Annex 19
GMM - RA update Inter-SGSN (1)
Routing_Area_update_req (RA1)
SGSN_context_req (RA1, TLLI, @SGSN2)
SGSN_context_resp (MM_ctxt, PDP_ctxt)
Update_PDP_context_req (TID, @SGSN2)
Update_PDP _context_resp
transfer of stored packets
SGSN_context_ack
new
SGSN
old
SGSN
GGSN
w RA1: This is the mobile's previous RA
The New SGSN retrieves the IP address of the old SGSN from RA1, after request to the DNS which translate RA1 into IP
@ of SGSN1.
w SGSN_context_req:To obtain any PDP contexts and the MM contexts (IMSI, RA, cell, IMEI, etc) = all the data stored in the
old SGSN concerning the MS, including the address of the GGSN related to each PDP context activated.
w SGSN_ctxt _ack: This message is sent only if the subscriber has PDP contexts activated. Used to inform the old SGSN
that receives and stores datagrams for the MS.
w Update_PDP_context_req: Mainly to inform the GGSN of the address of the new current SGSN for this MS. Thus, any new
packet arriving from the PDP network is routed to the new SGSN.
This operation is carried out in parallel with the retrieval of the old SGSN packets, and not afterwards as the figure above
seems to indicate.

5 Annex 20
GMM - RA update Inter-SGSN (2)
cancel_location (IMSI)
cancel_location_ack
Update_location (IMSI, @SGSN2)
Update_location_ack
insert_subscriber_data (+ack)
Routing_Area_update_accept (TLLI)
Routing_Area_update_complete
new
SGSN
old
SGSN HLR
w ISD: = ISD (IMSI, GPRS subscription data).
w The tunnel (SGSN-GGSN) moves with the subscriber: The GGSN is always the same and the SGSN is variable (same
TID).
w RA update accept: The SGSN allocates the subscriber a P-TMSI or TLLI, as mentioned (derived from the P-TMSI).

5 Annex 21
SMS-MT on GPRS -Gd interface-
SM transfer
SRI_for_SM ([GPRS supported])
forward_SM (SM)
SM transfer
report
SRI_for_SM_res (MSC@ and/or SGSN@)
forward_SM_res
report
SGSN HLR SMS
GMSC
SMS
SC
w Gd: This is the SGSN« SMS-GMSC interface.
w The HLR must include the option F_GPRS_002 "Support of SMS-MT over GPRS" to enable transmission of SMs to the
MSs (which have this subscription option) via GPRS.
w SRI: If the SMS-GMSC supports GPRS, it tells the HLR so.
w SRI-res: The HLR sends back the following addresses:
MS IMSI-attached only: VMSC@
MS GPRS-attached only: SGSN@
MS both IMSI and GPRS attached:
SMS-GMSC does not support GPRS: One address returned according to MS preference option.
SMS-GMSC supports GPRS: Both addresses returned. The SMS-GMSC first performs transfer through
NSS or GSS according to an option. If the transfer to the MS fails (Forward-SM-res), the SMS-GMSC
repeats the attempt through the second network.
w If the delivery through the GSS fails, the HLR sets the MNRG flag and stores the address of the SMS-GMSC.

5 Annex 22
"Mobile User Activity" Procedure
GPRS_Attach_request
Ready_for_SM (IMSI)
If MNRG=1
MNRG ←←←← 0
Alert_Service_Center
Alert_Service_Center_ack
SGSN HLR
SMS
GMSC
w Mobile user activity procedure: When the MS is reattached, the HLR indicates this to the SMS-GMSC (conventional GSM
"alerting" procedure) and to all the GGSNs which had tried in vain to activate PDP contexts to this MS.
w The SGSN sends Ready-for-SM to the HLR before sending the “update location” message.
w The SMS-GMSC obviously alerts the SMSC which makes a new attempt to deliver the SM to the mobile (as in the
previous slide).

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