Evolium Base Station Subsystem Introduction to GPRS and EGPRS

© Alcatel University – 3FL10472ACAAWBZZA Ed.02

EVOLIUM Base Station SubsystemINTRODUCTION TO GPRS/EGPRS

© All rights reserved. Passing on and copying of this document, 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 objectivesYes (orGlobally

yes)

No (orglobally

no)Comments

1 To be able to identify the benefits of GPRS

2 To be able to describe the organization of aGPRS network, architecture, interfaces andprotocols.

3 To be able to describe the main datainterchange mechanisms on a GPRSnetwork

4 To be able to characterize the solutionoffered by Alcatel

Other comments


Instructional objectivesYes (orGlobally

yes)

No (orglobally

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 technicaland 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.

▼ PDN (Packet Data Network)

� IP networks = Internet (connectionless)




1 What is GPRS ?1.2 General architecture

GPRSCore Network

IPGb

NSSA PSTN

Gi

PDN IP / PPP

RADIOACCESSNETWORK

BSS

Packetswitching

circuitswitching

▼ 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.)

▼ 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.

▼ 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.

▼ X.25

X.25 PDP Type have been removed from the standard sinc e 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.

▼ 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.

▼ 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.

▼ Class C

Exclusively operates GPRS services.




1 What is GPRS ? 1.4 MS multislot class

NAxx119 to 29like 10

000NA88218011NA77217121NA66216131NA55215131NA44214131NA33213121544112121534111121524110121523191215141813143317131423161314221513141314132322131323121224221111

TrbTraTtbSumTxRxTypeMulti-slotclass

▼ 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

▼ 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).

▼ 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.

▼ SUM

� Maximum number of transmit and receive timeslot (without Mx) per TDMA frame

▼ Meaning of Ttb, Tra et Trb changes regarding MS type s.

� 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

▼ 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


> Use of radio resources in case of packet switching

Radio timeslot

Radio interface

Variable Rate

▼ 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)





> 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

▼ Radio resource sharing

The radio resources are shared by statistical multiplexing. As in GSM, no subscriber has their own permanent radio resource.

▼ 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)

▼ 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.





> Dynamic allocation and sharing of radio resources

User 1User 2User 3User 4User 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

▼ Caution: Animated slide that does not make sense if not in the slide-show mode.

▼ 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.

▼ 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 ?1.6 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)

▼ BSS is re-used

The same Radio Access Network is re-used, and a Packet Control Unit (PCU) function is implemented in the BSS.

▼ 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.

▼ Shared = in other words: "the radio resources are shared by statistical multiplexing". As in GSM, no subscriber has their own permanent radio resource.

▼ 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).

▼ 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)

▼ 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).

▼ 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.

▼ QoS: Henceforth, QoS parameters are part of subscription data, according to the wide range of services provided to a subscriber.




Precedence Classrelative importance of service under congestion3 classes

Delay Classtotal delay measured between R or S point and Gi4 classes

Reliability Classacknowledgement 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

▼ 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

▼ 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

▼ 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

▼ 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 ofmusic files orvideo 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….

▼ 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).

▼ 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;

▼ 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;

▼ 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.

▼ 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;

▼ 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;

▼ 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 answeringthe 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 OperationSession presentation

> Objective: to be able to describe the organization of aGPRS 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 Operation2.1 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 NetworksGGSN

BG To other operatorIP Networks

PCU includedin BSS

MSCVLR

▼ 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).

▼ DNS (Domain Name Server) and DHCP (Dynamic Host Convergence Protocol)

▼ 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.

▼ 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

IPbackbone

GGSN1

IP network 1

IP network 1

GGSN2

IP network 1

GGSN3

IP network 1

IP network 1

SGSN1

SGSN2

SGSN5

SGSN3

SGSN4

▼ 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.

▼ 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.





> Servers

GPRSBACKBONE

SGSN GGSN

NTP

DNS DHCPIP add

256.167.123.34

Alcatel.fr

▼ DNS

� Resolve a name into an IP address

� Use in Mobility procedure

▼ DHCP

� Provide dynamically IP addresses

� Split Users into pool of IP addresses

▼ NTP

� Provide one time reference for all the network

� Have a very precise time reference

� Synchronization from satellite




MS

SGSNBSS VPLMNBG

VISITED PLMN

GGSN


> Border gateway

INTER PLMN NETWORK

HPLMN GGSN PDNBG

HOME PLMN

▼ Border Gateway functions

� Inter-PLMN routing and forwarding of user packets (IP router)

� Security functions (firewall, access-list filtering)

▼ Connection of two Border Gateways

Via a private or public IP network, through the Gp interface.

▼ 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


Gn

Signaling + data

Signaling

Mobile GPRS

Gd

Um

GPRS network

Gb

BSS

Gc

GsGr

GiPDN

SGSN

SGSN GGSN

HLRMSCSMS-GMSC

> Interfaces

▼ 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.

▼ Gc interface

Used for network-requested PDP contexts activation (GGSN asks the HLR for SGSN routing information).

▼ 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).

▼ Gr interface

Exchange of subscription information at GPRS attachment phase

▼ 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 Operation2.2 MS Mobility Management States

Idle

Ready

Stand-by

> MS MM states

GPRS Detach

PDU transmission

READYtimer expiry

GPRS Attach

Location atCELL level Location at

RA level

Autonomous cell reselection NCOOr controled by network NC 2( In paquet transfert mode )

Autonomous cell reselection

▼ 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.

▼ 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.

▼ 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 Operation2.3 MS Radio Resource Operating Modes

Packettransfer mode

Packetidle mode

Packetidle mode

Ready Standby

RR

MM

> Packet transfer modeIn 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 modeIn 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

▼ 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.

▼ 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 Operation2.4 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





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






> Transmission plane

TCP HTTP FTP SMTP

Physicallayer

Physicallayer

Physicallayer

Physicallayer

Physicallayer

Physicallayer

Physicallayer

L2

IP

UDP

GTP

IP

L2

MAC

L2

IP

UDPLLC

GTP

BSSGP(FrameRelay)

(FrameRelay)

LLC

Um Gb Gn Gi

MSBSS

(with PCU) SGSN GGSN

Application

RLC

MAC

RLC

MAC

IPIP

relay

relay

BSSGP

SNDCPSNDCP

▼ GTP (GPRS Tunnelling Protocol) tunnels user data between GPRS Support Nodes in the backbone network. The GPRS Tunnelling Protocol shall encapsulate all PDP PDUs.

▼ 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.

▼ 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.

▼ SNDCP (SubNetwork Dependent Convergence Protocol ) maps network-level characteristics onto the characteristics of the underlying network.

▼ 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.

▼ 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.

▼ BSSGP (Base Station System GPRS Protocol) conveys routing and QoS-related information between the BSS and the SGSN. BSSGP does not perform error correction.

▼ (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.

▼ 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.





NSAPI

NSAPITLLITLLI

Radio layers

LLC

GMM/SM SMS

SNDCP

IP

NSAPI i

> MS high protocol layers

▼ 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).

▼ 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.

▼ LLC (Logical Link Control)

Provides a safe link, encrypted and independent of the physical bearer, independent to BSS brand.

▼ TLLI (Temporary Logical Link Identity)

Identifies a logical link with the MS (one TLLI per MS)

▼ GMM/SM (GPRS Mobility Management / Session Management)

MS-SGSN signaling protocol for Gprs Mobility Management/ Session Management

▼ SMS (Short Message Service)





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

▼ 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).

▼ 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.

▼ 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-operId (example: mnc...gprs)

� Examples of APN: wanadoo.fr.mnc001.mcc208.gprs,

� APN = * (wildcard) potentially authorizes the MS to activate any APN.

▼ Valid APN

Boolean, if YES, indicates that this APN can be reached through the GGSN of the visited FPLMN.




2 GPRS Operation 2.4 Basic Procedures

> GPRS attachment

BSS

➁

Authent_info_req()

➂

Authent_info_respq)

⑤

Update_loc_req()

⑥

Insert_subs_data()

Update_loc_ack()

⑦

PLMN

Attach-Request(IMSI) ➀➀➀➀

Attach_resp (P_TMSI)⑧⑧⑧⑧

Attach_complete () ⑨⑨⑨⑨

MS_authentication_procedure➃➃➃➃ GPRS IPbackbone

GGSN

SGSN

N7

HLR

▼ Attach Request.

� The attach_request message is placed in an LLC frame. ①

� The MS sends its IMSI.

▼ Authentication

The SGSN gets the “authentication triplets” from the HLR:

� triplets request message ②

� triplets response message ③

The SGSN performs the “authentication procedure” with the MS: ④

� triplets request message ②

� triplets response message ③

▼ Location Update

The SGSN performs the “location_update procedure” with the HLR:

� location_update request message ⑤

� the HLR transfers the MS_subscription data to the SGSN ⑥

� the HLR terminates the location_update procedure ⑦

▼ Attach Complete

The SGSN terminates the attach_procedure with the MS :

� attach_accept message ⑧ (with a new P_TMSI allocation)

� attach_complete message ⑨ (since a new P_TMSI has been allocated)




GPRS - CN


LLC layer

TLLI1

GPRS IPbackbone

> GPRS attachment

After a GPRS_Attach procedure The mobile is « c onnected » to the serving SGSN

SGSN1

SGSN2

GGSN1

GGSN2 PDN 2

PDN 1

▼ 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





> PDP context activation

GPRS Core Network

GPRSbackbone

PDN1

SGSN

DNS

GGSN

GGSN PDN2

DHCP

BSS

PLMN

TLLI1

4

2

3Create_PDP_req (PDN2)

5 Create_PDP_resp (@IP_MS)

Activate_PDP_req (PDN2) ➀➀➀➀

Activate_PDP_resp(@IP_MS)⑥⑥⑥⑥

▼ 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)

▼ PDP Context Activation

� ➀ MS requests for a PDP_context activation, providing the name of target Packet Data Network (PDN2 parameter).

� ➁ SGSN queries the backbone Name Server (here DNS) to identify the GGSN giving access to the Data Network PDN2 (here GGSN2).

� ➂ SGSN sends a Create_PDP message to the corresponding GGSN2, in order to setup a GTP tunnel.

� ➃ GGSN2 allocates an IP address to the MS (@IP_MS), using the backbone DHCP server.

� ➄ GGSN2 acknowledges the Create_PDP message to the SGSN, returning the @IP_MS allocated to the MS.

� ➅ SGSN acknowledges the Activate_PDP message to the MS, with the allocated @IP_MS.






BSS

PLMN

TLLI1

GPRS Core Network

GPRSbackbone

SGSN

DNS

GGSN

GGSN

2

3Create_PDP_req (PDN2)

6 Create_PDP_resp (@IP_MS)

Activate_PDP_req (PDN2) ➀➀➀➀

Activate_PDP_resp(@IP_MS)⑥⑥⑥⑥ISP

INTRANET

DHCP

RADIUS

5

Authentication andaccounting

Address allocation

4

▼ 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.

▼ PDP Context Activation

� The authentication data are piggybacked in the Protocol Configuration Options (PCO) field of the PDP context activation messages ➀ and ➆.

� ➀ , ➁ , ➂ same as for IP PDP_type in transparent access.

� ➃ GGSN performs the user authentication towards a RADIUS server.

� ➄ GGSN allocates an @IP to the MS using the intranet/ISP DHCP server.

� ➅, ➆ same as for a PDP context in transparent access.






LLC layer

GPRS - CN

TLLI1

GPRS IPbackbone

SGSN1

SGSN2

GGSN1

GGSN2 PDN 2

PDN 1TID 1 = IMSI + NSAPI 1

TID 2 = IMSI + NSAPI 2

by the GTP layer

after PDP_context_activation procedures

▼ 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.

▼ TLLI (Temporary Logical Link Identity)

Identifies uniquely a MS attached to the GPRS core network (Standby or Ready state).

▼ TID (Tunnel Identity)

Identifies a logical connection ("tunnel") between GGSN and SGSN (for each session of each MS). TID= IMSI+NSAPI.






LLC layer

GPRS - CN

TLLI1

GPRS IPbackbone

SGSN1

SGSN2

GGSN1

GGSN2 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




SGSNGGSN

within the MS

MS

over the Gn interface

over the Giinterface

@ MS @server

U-data

@sgsn@ggsn

GTPheader

UDPheader

@ MS @server

U-data

@ MS @server

U-data

@server@ MS

U-data

server

PDN

@ggsn@sgsn

GTPheader

UDPheader

@server@ MS

U-data

@server@ MS

U-data


> User data transfer

▼ 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

PDNGPRSBACKBONE

GGSNSGSNBSSTLLI

CCBS

CG

AttachmentM_CDR

PDP CONTEXT ACTIVATION AND DATA TRANSFERT

S_CDRG_CDR

FTP

GTP

▼ 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)

▼ 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 PDNBG

CCBS

CG

S_CDRHOME PLMN

MS

SGSN

BSS

TLLI VPLMNBG

CG CCBS

VISITED PLMN

G_CDR

▼ 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 networkFirewall = application-level filteringFiltering by access lists (in the GGSNs)

GPRS Network

3- Secured intranet accessAPN with mandatory subscriptionAPN with access lists APN with tunneling on Gi (IPsec)

▼ Authentication and confidentiality

As in GSM, by security triplets and the use of the TLLI/P_TMSI instead of the IMSI.

▼ Encryption

The LLC frame is encrypted, so encryption from the MS to the SGSN and not just on Um.

▼ 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).

▼ 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.

▼ 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

▼ PMSC: Packet MSC.

▼ PVLR: Packet VLR.




Time allowed :

5 minutes


– 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


– 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?






2 GPRS OperationEvaluation

> Objective : to be able to describe the organization of a GPRS network : architecture, interfaces, protocols,…



3 The Base Station Subsystem




3 The Base Station SubsystemSession presentation

> Objectives :

• To be able to briefly describe the datainterchange 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 The Base Station Subsystem3.1 3GPP Position> PCU function

BSSBTS

CCU PCU

BSC SGSN

BSSBTS

CCU

BSC SGSNPCU

BSSBTS BSC SGSN

CCU PCU

▼ 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).

▼ CCU functions

� encoding suited to radio channels,

� radio measurements (receive quality, signal level, "timing advance" management).




3 The Base Station Subsystem3.2 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

▼ The Multi BSS Fast packet Server (MFS):

▼ MFS is just the namee of the rack containing PCU funct ions

� 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 The Base Station Subsystem3.3 Layered Model

BTS MFS SGSNMS

BSSGP

Gb

Physicallayer

Framerelay

RLC

MAC

RLC

Physicallayer

Framerelay

BSSGP

Um Abis/Ater

PCU

IP

LLC

GMMSM

relay

LLC

GMM SNDCPSM

relayPhysical

layerPhysical

layerL2-GCHL1-GCH

L2-GCHL1-GCH

MAC

SNDCP

> User plane

▼ For GPRS TRAFFIC, the BSS simply relays the LLC frames between the MS and the SGSN.

▼ 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).

▼ The concept of handover has no meaning in packet switching (GPRS). There is no "circuit" to re-establish!

▼ 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.

▼ 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 The Base Station Subsystem3.3 Layered Model

Gb

L2-GSL L1-GSL

BSCGPBSCGP

L2-GSL L1-GSL

physicallayer

RRM

AterUm

relay

Abis

relayphysical

layer

RRM

> Signaling plane

▼ 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

▼ 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.RNetworkNetwork

PCM

3 The Base Station Subsystem3.4 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












3 The Base Station Subsystem3.4 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












3 The Base Station Subsystem3.5 Radio Interface 1/8

> GPRS / EGPRS throughput

Coding Scheme Modulation Maximum rateper PDCH (kb/s)

CS2

CS1

GMSK

GMSK

13.4

9.05

CS4

CS3

GMSK

GMSK

21.4

15.6G

PR

S

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

EG

PR

S




> Coding schemes

Bad radio conditionMax security

Good radio conditionMin 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 rateper carrier1 bit per

Symbol

3 bitS perSymbol

8 PSK has 3times more capacity than GMSK

One TS 142 symbols142 BitsONE TS

One TS 142 symbols426 BitsONE TS

▼ 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).

▼ Radio blocks are transported on the air interface (Um) over 4 consecutive normal bursts of the TDMA frame.

▼ 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.

▼ 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 AterGMSk and Not a good transmission

CS1 about 9K

MCS9 ABOUT 59K

8PSK good transmission


MFSPCU

BTSTRX

BSCrelay

PDCH

BTSTRX

BSCrelay

MFSPCU16k resource 16k resourcePDCH






> Resources allocation according to the MCS

QUALITY OF TRANSMISSION LOT OF BITS LOST

INCREASE SECURITY DECREASE USEFUL TRANSMISSION RAT E


MCS n


MFSPCU

BTSTRX

BSCrelay

PDCH


MCS n-1

PDCH



MFSPCU

BTSTRX

BSCrelay


Can be allocated to another PDCH

Can be allocated to other PDCH


▼ 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 .

▼ The resource which is not used a that time can be allocated to another TRX if needed at BTS level

▼ 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)




networkMSstart

of TBF1end ofTBF1 TBF2 TBF3 TBF4

timefULi

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 The Base Station Subsystem3.5 Radio interface 7/8> UL transfer

PCU

TBF MAC

▼ 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.

▼ A TBF (the blue shape) comprises one or more consecutive LLC-PDUs.

▼ 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.

▼ 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 PagingPaging 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 toprevious 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 The Base Station Subsystem3.5 Radio interface 8/8

> DL transfer

MS IN STANB BYMODE

MS IN READYMODE

▼ In DL, each time an LLC-PDU is received, if there is no TBF in progress, it is essential to “establish" one.

▼ 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.

▼ 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.

▼ DL TBF: each block of the DL TBF are identified by the DL TFI = TFIz

▼ 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

3 The Base Station Subsystem 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

3 The Base Station Subsystem 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






3 The Base Station SubsystemEvaluation

> Objective : To be able to briefly describe the data interchange mechanisms through the BSS



4 Alcatel Solution




4 Alcatel SolutionSession presentation

> Objectives: to be able to characterize the solutionoffered 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

BTS

BTS

BSS--

BSC

BTS

BTS

A9135

MFS

BSS2BTS

BTS

BSC

A9135

MFS

GSM/GPRS common servers

HLR SMS-CMSC

GPRS IPbackbone

Radio subsystem

FrameRelay

network

BorderGateway Inter-PLMN

backbone

Internet

Intranet

SGSN

SGSN

accessrouter

SCP

CAMEL & IP basedPrepaidServices

Firewall

Charging Gateway

OMC-CN

iGGSN

▼ 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

▼ 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

▼ 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

BTS

BTS

> Functional architecture

GPU1PCU

GPU2PCU

S

G

S

N

LAN x 2

OMC-RM

F

S

BSC2

BTS

BTS

GPU1PCU

GPU1PCU

▼ 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)

▼ 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

▼ 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

PMSCPVLR

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 BSXTU11 GPU (+1)

maxi

1 BSXTU11 GPU (+1)

maxi

1 BSXTU11 GPU (+1)

maxi

1 BSXTU11 GPU (+1)

maxi

2 DS 10Control

sub-rack

2 DS 10Control

sub-rack

2 or 4 Switches3 COM 3300

+ IOLAN module

2 or 4 Switches3 COM 3300

+ IOLAN module

> Rack layout

▼ The "Control sub-rack" part is duplex (two DS10 in active/standby modes).

▼ 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)

▼ 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).

▼ 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)

ATCAshelf

ATCAshelf

▼ This platform is a high availability distributed platform composed of blades compliant with the Advanced Telecom Computing Architecture (ATCA) open standard

▼ ATCA has been developed by the PCI Industrial Computers Manufacturers Group (PICMG).

▼ The related specifications are described in the PICMG 3.0 R1.0.




ATCAshelf

ATCAshelf

MFS

LIU LIU

MFS

MFS

O

M

C

P

S

S

W

S

S

W

O

M

C

P

GP

GP

GP

GP

GP

GP

GP

GP

GP

GP


General Option 1 Option 2ATCA shelf content

▼ LIU: Line Interface Unit – to collect the external PCM connections

▼ GP: GPRS Processing module

▼ OMCP: O&M Control Processing board – the control stations,

▼ SSW: Subrack SWitch





GPGPGPGPGP

GP

GPGPGPGP

MUX

OMCP

MUX

16 LIU X 16 E1

LIU

E1 connections

Abis

LIU

Ater

OMCP

S

S

W

S

S

W

MFS

9 PCU + 1SPARE

▼ 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.

▼ 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.

▼ SSW: it’s an Ethernet switch which allows exchanges between all platform elements and externalIP/Ethernet equipment.

▼ OMCP: these control stations are used to process defense functions and platform Operation, Administration and Maintenance (OAM) generic services..

▼ GP: Manages the user plane packet data flow processing.

▼ 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

GPRSsignaling & userPlane 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-CNChargingGateway

Intra-PLMNDNS

towards Prepaid Servers

O&M & service provisioning

session control logic

GTP control & user planes

WN

Gr, Gs,

Gd, Ge

▼ 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

▼ 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

Ethernetswitch/routers

Ethernetswitch/routers

pilot blades

SS7 blades

GPRS control& user plane

blades

ATCA platform

Internal control LAN

backbone rack

NS500

NS500

Firewalls

external DNS

NTS150NTS150

NTP Servers

Intra-PLMNDNS/DHCP

border router

access router

Gn switches




NMCQ3

MFS

4 Alcatel Solution 4.4 GPRS Network Management

SGSN

NTPDNS/DHCP BG

BTS

BTS

BSC1

BTS

BSC2

OMC-CN

Core Network part

Radio part

OMC-R

Charging Gateway

> Dedicated OMCs

iGGSN

▼ OMC-R: Called Alcatel 1353 RA = management of the radio subsystem :

� Alcatel 9135 MFS.

� BSCs and associated BTSs

▼ 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 throughputclass

Delay 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

▼ These QoS attributes are associated with a PDP context performed by a R97/98 MS

▼ 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.

▼ Best effort = inexpensive, comparable to the Internet (no commitment). Ideal for foraging on the internet.

▼ Normal: Comparable to an intranet.

▼ 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

▼ 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

▼ 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)






4 Alcatel SolutionEvaluation

> Objective : to be able to characterize the solution offered by Alcatel



5 Annex and Glossary




5 Annex 1Coding Schemes : CS1 -> CS4

0

5

10

15

20

0 10 20 30

Cha

nnel

rat

e (k

bps)

C/I (dBm)

CS4

CS3

CS2

CS1

BACK

▼ 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.

▼ 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

EDGEGPRS

160 Kbps

64 Kbps

HSCSD

Bit rate

CS data - SMS, 9.6Kbps

9.6 Kbps

Technology

5 Annex 2GPRS compared to other technologies

▼ SMS : With GPRS, the 160-character barrier for short messages will be able to be broken (when SMS over GPRS is implemented).

▼ 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.

▼ 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).

▼ 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

▼ 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 3PCU concept




PDCHPCU

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 4PCU concept




5 Annex 5TDMA 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 PDCH12 BLOCS

PTCCH

Frame 12

Frame 38

BLOC 3




5 Annex 6GPRS channels

> Master and Slave PDCHs

B0

B1

B2

B3

B4

B5

B6

B7

B8

B9

B10

B11

PDCHDOWN/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 PDCHDOWN /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

▼ 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).

▼ 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.

▼ 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 2TBF from server 3

TBF from server 4

TFI 1TFI 5TFI 3TFI 6

TBF server 5

TBF to server 7

TBF to server 6TFI 2 USER 3TFI 7 USER 6TFI 6 USER 2

UP

DOWN

5 Annex 7PDCH ,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 5128K 64K X 2

TS 3

TS 28

TS 31

TS 29 192K 64K X 3

2

MB

E

1

TS 1TS 2TS 3TS 4

TS 15

TS 17

TS 31

TS 18TS 19TS 20

BEARER CHANNEL =960K

BEARER CHANNEL=960K

2

MB

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

MB

E

1

5 Annex 8Different uses for E1

▼ Minimum size for a bearer channel: 1 x 64k, Maximum size for a bearer channel: 31 x 64k.

▼ One PVC per bearer channel.




Node

15

6

9

27

PVC y

PVCn

12

5

16

DLCI Number

FRAME RELAY

PCUMFS

SGSN

5 Annex 9FRAME RELAY and PVC concepts




Permanent Virtual Connection

FRAME

RELAY

NSVC Transmission check end to end

SGSNPCUMFS

PCM E1

BEARERCHANNEL

5 Annex 10PVC 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 PCUPCM 2

BC 3

5 Annex 11TDMA and PDCH




5 Annex 12 Network Mode of Operation I with Master Channel

BSC

CCCH

PCCCH

PACCH

Um

MSCVLR

SGSN

A

Gb

Gs

CS paging for GPRS-attached MS in idle state (a), o r in data transfer state (b)

CS paging for non GPRS-attached MS GPRS paging

(a)

(b)

▼ 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.

▼ 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.

▼ 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.

▼ 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.

▼ 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 13MOBILE 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

TFIPDCHUSFTA

Packet UL ACK NACK PACCH

▼ "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.

▼ 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.

▼ 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

▼ "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 14MOBILE 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 15MOBILE ORIGINATING DATA TRANSFERT

BSS SGSNSTAND BY

READY

PACKET DOWNLINK ASSIGNEMENT

UL UNIDATA

RLC PDU

Paquet channel requestPaquet UL assignement

UL TBFEstablishment

RLC PDU

RLC PDU

PACKET UPLINK ACK/NACK

RLC PDU

RLC PDU

RLC PDU

UL UNIDATA

UL TBFRelease

















5 Annex 16MOBILE TERMINATING DATA TRANSFERT

BSS SGSNSTAND BY

READY

LLC PDU

DL UNIDATA

UL UNIDATA

PACKET DOWNLINK ASSIGNEMENT

PAGING PSPacket Paging Request

channel request

Paquet UL assignement

UL TBF

DL TBF

















5 Annex 17GMM - Combined GPRS and NSS attach with Gs (1)

HLR

Attach_request (IMSI)Triplet request ( rand kc sres )

AuthenticationUpdate_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 18GMM - 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

▼ Location-Update-request: The SGSN determines the MSC/VLR based on the RA where the subscriber is located.

▼ 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.

▼ 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.

▼ Once this combined-attach is done, the MS can make combined LA/RA update procedures (see GSM 03.60)..




5 Annex 19GMM - 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

newSGSN

oldSGSN

GGSN

▼ 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.

▼ 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.

▼ 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.

▼ 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, @SGSN 2)

Update_location_ack

insert_subscriber_data (+ack)

Routing_Area_update_accept (TLLI)

Routing_Area_update_complete

newSGSN

oldSGSN HLR

▼ ISD: = ISD (IMSI, GPRS subscription data).

▼ The tunnel (SGSN-GGSN) moves with the subscriber: The GGSN is always the same and the SGSN is variable (same TID).

▼ 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 SMSGMSC

SMSSC

▼ Gd: This is the SGSN« SMS-GMSC interface.

▼ 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.

▼ SRI: If the SMS-GMSC supports GPRS, it tells the HLR so.

▼ 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.

▼ 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=1MNRG ←←←← 0

Alert_Service_Center

Alert_Service_Center_ack

SGSN HLRSMS

GMSC

▼ 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.

▼ The SGSN sends Ready-for-SM to the HLR before sending the “update location” message.

▼ The SMS-GMSC obviously alerts the SMSC which makes a new attempt to deliver the SM to the mobile (as in the previous slide).




5 Annex 23 SM - PDP context activation review

NSAPI1 + PDP context 1

NSAPI2 + PDP context 2

IMSI ↔TLLI- @ MS + IP/X25- APN- QoS

(NSAPI1 + PDP context 1 + @ of GGSN1) IMSI ↔TLLI + current RA+ subscription data (NSAPI2 + PDP context 2 + @ of GGSN2)

SGSN

TID1 + PDP context 1 IMSI ↔ @ current SGSNGGSN

IMSI ↔ @ current SGSNHLR

▼ The SGSN even knows the current cell, if the mobile is in the ready state by looking at the routing over the Gb interface of the PDU originated by the MS. For further explanation, please refer to the sub-chapter “The Base Station Sub-System, The Gb interface”




5 Annex 24 The Gb interface - Frame Relay overview

User connected to the frame relay network through a “synchronous access line”Based on semi-permanent connection, PVC

A PVC is identified on each end by a local connection identity : DLCI possible control of data loss (use of CRC )

User to network signaling is carried by a specific PVC tagged with the DLCI 0

Frame RelayFrame Relay DLCIb

access line

DLCImDLCIp

PVC 1

DLCI=0 (Sig)

DLCIpDLCIm

DLCIa PVC 2

access line

PVC 3

DLCIb

▼ Access Line = any synchronous line would do.

▼ On a FR access line, there can be a large number of PVCs (Permanent Virtual Circuits), identified each by a DLCI, (Data Link Connection Identifier), different on each side + a PVC for signaling (DLCI=0).

▼ Data Loss: all frames have a CRC field used to determine if the data (payload) is correct or not. The network discards any frame with an erroneous payload.

▼ user-to-network signaling is to check the

� local availability of the FR link ("Link Integrity Verification” procedure)

� end-to-end availability of each user's PVC ("Full Status Report" procedure)

▼ Security (redundancy): the user to the right has 2 access lines.




FrameFrameRelayRelay

SGSN

Gb

Physicallayer

SNS

BSSGP

NSC

Gb

Frame Relay

Physicallayer

SNS

BSSGP

NSC

PCU1

Physicallayer

SNS

BSSGP

NSC

PCU2

BC1 = TSa, TSb,...BC2 = TSu, TSv,…

Bearer ChannelBC3 = TSi, TSj,…BC4 = TSx, TSy,…

BCa = all TS

BCb

PCM2

PCMa

PCMb

PCM

PCM1

5 Annex 25The Gb interface - physical layer

▼ Physical layer = PCM links from the JBGPU boards.

▼ It is best to connect the MFS and the SGSN to the FR network by two PCM links for added protection.

▼ Bearer Channel: This is N x 64 kbit/s over a 2048 kbit/s link

� N time slots on one PCM link

� FR access line.

▼ SGSN end, a BC can recover all the TSs of the PCM link to have the fastest possible access to the FR network.

▼ MFS end, on a BC, only one PVC will be declared (option chosen by Alcatel for simplicity). Therefore, for security: two BCsper BSC, each on a different PCM link (see next slides).

▼ If no FR network, the declarations of the physical and SNS layers must be the same at both ends.




Gb

SGSN

Physicallayer

SNS

BSSGP

NSC

Gb

Frame Relay

Physicallayer

SNS

BSSGP

NSC

PCU1

BC1

Bearer Channel

BC4

BCa

Physicallayer

SNS

BSSGP

NSC

PCU2

FrameFrameRelayRelayPVC2

PVC3 PVC4

DLCIo

DLCIr

PVC

PVC1

DLCIm

DLCIp

5 Annex 26The Gb interface - SubNetwork Service layer

▼ The FR layer is part of the layer 2 in OSI model = Sub-Network Service layer (2.1). On top of this layer, and for telecom and quality of service purposes was added the Network Service Control layer (2.2).

▼ The "Bearer Channel" object of GPRS corresponds to the notion of FR access line. On a BC, there can be several PVCs(Permanent Virtual Circuits), each identified by a DLCI, which may be different at each end.

▼ Alcatel has set the limit on the BSS (MFS) side, to one PVC per BC.

▼ Several PVCs are needed:

� firstly because a PVC is used for traffic with a given BSC (and therefore several BSCs means several PVCs)

� secondly to provide security at Frame Relay level by introducing redundancy

▼ There is also, on each BC, a virtual link (with DLCI=0) for signaling with the FR switch.




5 Annex 27The Gb interface - Network Service Control layer

Gb SGSN

Physicallayer

SNS

BSSGP

NSC

Gb

Physicallayer

SNS

BSSGP

NSC

PCU1

Physicallayer

SNS

BSSGP

NSC

PCU2

FrameFrameRelayRelay

NS-VCI=12

NS-VCI=13

NS-VCI=14

NS-VC

NS-VCI= 11

BSC1

BSC2

NSEI x

NSEI y

NSE

▼ The Network Service Control layer is used:

� To transport BSSGP frames between MFS and SGSN

� To manage FR virtual circuits (offering in particular a common identifier for the PVCs: these are the NS-VCs (Network Service layer - Virtual Circuit) thanks to a range of standard procedures : (un)block, reset and test.

� To share dynamically the UL/DL traffic (BSC to SGSN) over the existing NS-VCs of the same NSE

▼ Multiplexing scheme: 1 NS-VC = 1 PVC.

▼ NSE = Network Service Entity, identified by its NSEI, representing the packet traffic to/from a given BSC. The NSE = ΣNS-VCs dedicated to the packet traffic for one BSC. NSEI is information included in the messages between SGSN and MFS.




Physicallayer

SNS

NSC

SGSN

Physicallayer

SNS

NSC

Gb

Physicallayer

SNS

NSC

PCU1

PCU2

BSC1

NSEBVCcellBVCI=i

BVCI=j

BVCI=k

BSC2

BVCI=m

BVCI=p

BVCI=n

BSSGP

BVCI=i, BVCI=j, BVCI=k

BVCI=m, BVCI=n, BVCI=p

5 Annex 28The Gb interface - BSS GPRS Protocol

▼ BVC = BSSGP Virtual Connection.

� One BVC for each cell (Point-To-Point BVC) to identify traffic to a particular cell within a NSE.

� One BVC-SIG (identified by BVCI0 : the fine black line) for signaling with the BSC (one per NSE).

▼ The standard also provides for BVC-PTMs. Not implemented.

▼ NSEI and BVCI are information items included in all messages between SGSN and MFS. This information must be consistent on either sides of the Gb interface.

▼ Review of the role of the BSSGP:

� to relay LLC frame (one LLC frame encapsulated into one BSSGP frame) and offer QoS over the Gb

� BVC management = management of packet traffic flow for a cell (DL flow control mechanisms, BVC supervision procedures, etc)

� MFS-SGSN signaling for LLC relay management and MS mobility management




5 Annex 29 R97/98 QoS attributes

Precedence Precedence Name Interpretation

1 High priority Service commitments shall be maintained ahead of precedence classes 2 and 3.

2 Normal priority Service commitments shall be maintained ahead of precedence class 3.

3 Low priority Service commitments shall be maintained after precedence classes 1 and 2.

R e lia b i l i t yC la s s

G T P M o d e L L C F ra m e M o d e

L L C D a taP ro te c t io n

R L C B lo c k M o d e

T ra f f ic T y p e

1 A c k n o w le d g e d A c k n o w le d g e d P ro te c te d A c k n o w le d g e d N o n re a l- t im e tra f fic ,e rro r-s e n s it iv ea p p lic a t io n th a t c a n n o tc o p e w ith d a ta lo ss .

2 U n a c k n o w le d g e d A c k n o w le d g e d P ro te c te d A c k n o w le d g e d N o n re a l- t im e tra f fic ,e rro r-s e n s it iv ea p p lic a t io n th a t c a nc o p e w ith in f re q u e n td a ta lo s s .

3 U n a c k n o w le d g e d U n a c k n o w le d g e d P ro te c te d A c k n o w le d g e d N o n re a l- t im e tra f fic ,e rro r-s e n s it iv ea p p lic a t io n th a t c a nc o p e w ith d a ta lo ss ,G M M /S M , a n d S M S .

4 U n a c k n o w le d g e d U n a c k n o w le d g e d P ro te c te d U n a c k n o w le d g e d R e a l- t im e t ra ff ic , e rro r-s e n s it ive a p p lic a tio n th a tc a n c o p e w ith d a ta lo s s .

5 U n a c k n o w le d g e d U n a c k n o w le d g e d U n p ro te c te d U n a c k n o w le d g e d R e a l- t im e t ra ff ic , e rro rn o n -s e n s itive a p p lic a tio nth a t c a n c o p e w ith d a talo s s .

Peak Throughput Class Peak Throughput in octets per second1 Up to 1 000 (8 kbit/s).2 Up to 2 000 (16 kbit/s).3 Up to 4 000 (32 kbit/s).4 Up to 8 000 (64 kbit/s).5 Up to 16 000 (128 kbit/s).6 Up to 32 000 (256 kbit/s).7 Up to 64 000 (512 kbit/s).8 Up to 128 000 (1 024 kbit/s).9 Up to 256 000 (2 048 kbit/s).

Mean Throughput Class Mean Throughput in octets per hour1 100 (~0.22 bit/s).2 200 (~0.44 bit/s).3 500 (~1.11 bit/s).4 1 000 (~2.2 bit/s).5 2 000 (~4.4 bit/s).6 5 000 (~11.1 bit/s).7 10 000 (~22 bit/s).8 20 000 (~44 bit/s).9 50 000 (~111 bit/s).

10 100 000 (~0.22 kbit/s).11 200 000 (~0.44 kbit/s).12 500 000 (~1.11 kbit/s).13 1 000 000 (~2.2 kbit/s).14 2 000 000 (~4.4 kbit/s).15 5 000 000 (~11.1 kbit/s).16 10 000 000 (~22 kbit/s).17 20 000 000 (~44 kbit/s).18 50 000 000 (~111 kbit/s).31 Best effort.




5 Glossary of abbreviations used A to L

> ALMAP: ALcatel MAnagement Platform

> APN: Access Point Name

> AS: Alpha Server (Compaq)

> BG: Border Gateway

> BSC: Base Station Controller

> BSS: Base Station Subsystem

> BSCGP: BSC-GPRS Protocol

> BSSGP: BSS-GPRS Protocol

> BVCI: BSSGP Virtual Connection Identifier

> CCBS: Customer Care and Billing Center

> CCU: Channel Codec Unit

> CDR: Call Detail Record

> CG: Charging Gateway

> CS: Circuit Switching

> DHCP: Dynamic Host Configuration Protocol

> DL: Down Link

> DLCI= Data Link Connection Identifier

> DNS: Domain Name System

> EDGE: Enhanced Data rates for GSM Evolution

> FUMO : Frame Unit Module

> FR: Frame Relay

> GPRS: General Packet Radio Service

> GGSN: Gateway GSN

> GMM: GPRS Mobility Management

> GR: GPRS Register

> GSL: GPRS Signaling Link

> GSM: Global System for Mobile communication

> GSN: GPRS Support Node

> GSS: GPRS Sub-System

> GTP: GPRS Tunneling Protocol

> HLR: Home Location Register

> HSCSD: High Speed Circuit-Switching Data




5 Glossary of abbreviations used M to R

> IMSI: International Mobile Subscriber Identity

> IP: Internet Protocol

> ISDN : Integrated Service Digital Network

> ISP: Internet Service Provider

> LAN: Local Area Network

> LLC: Logical Link Control

> MAC: Medium Access Control

> MFS: Multi-Bsc Fast packet Server

> MNRG: Mobile Not Reachable for Gprs

> MS: Mobile Station

> MSC: Mobile Switching Center

> MT: Mobile Terminal

> NDL :

> NE: Network Element

> NMC: Network Management Center

> NNM: Network Node Manager

> NRPA : Network Requested PDP Context Activation

> NSAPI: Network Service Access Point Identifier

> NSC: Network Service Control layer

> NSEI: Network Service Entity Identifier

> NSS: Network Sub-System

> NS-VC: Network Service- Virtual Circuit

> NTP: Network Time Protocol

> DB : On Demand Bandwidth

> OMC: Operation & Maintenance Center

> OS: Operation System

> PAGCH: Packet- Access Grant Channel

> PCCCH: Packet- Common Control CHannel

> PCO: Protocol Configuration Options

> PCU: Packet Control Unit

> PDCH: Packet Data CHannel

> PDN: Packet Data Network

> PDP: Packet Data Protocol (IP or X25)

> PDU: Protocol Data Unit

> PPCH: Packet- Paging CHannel

> PRACH: Packet- Random Access CHannel

> PS: Packet Switching




5 Glossary of abbreviations used R to Z

P-TMSI: Packet- Temporary Mobile Subscriber Identity

> PVC: Permanent Virtual Circuit

> P-VLR: Packet- Visitors Location Register

> QoS: Quality of Service

> RA: Routing Area

> RIP : Routing Information Protocol

> RLC: Radio Link Control

> RADIUS: Remote Authentication Dial In Use Service

> RRDTUF : Roaming Restriction Data Towards Unknown Foreign PLMN

> RRM: Radio Resource Management

> RSZ : Regional Subscription Zone

> SGSN: Serving GSN

> SM: Session Management | Short Message

> SMS: Short Message Service

> SMS-C: SMS-Center

> SNDCP: Sub Network-Dependent Convergence Protocol

> SNMP: Simple Network Management Protocol

> SNS: Sub-Network Service layer

> TBF: Temporary Block Flow

> TC: Trans Coder

> TCH: Traffic CHannel

> TCP: Transmission Control Protocol

> TDMA: Time-Division Multiplexing Access

> TFI: Temporary block Flow Identifier

> TID: Tunnel IDentity

> TLLI: Temporary Logical Link Identity

> TMN: Telecommunication Management Protocol

> TS: Time Slot

> UDP: User Datagram protocol

> UL: Up Link

> UMTS: Universal Mobile Transmission System

> WAP: Wireless Application Protocol

> WAN: Wide Area Network




5 Main GPRS Standards

> EN 301 344 (GSM 03.60) GPRS Service description stage 2

> TS 101 350 (GSM 03.64) Overall description of the GPRS radio interface, stage 2

> GSM 04.60 GPRS MS-BSS interface. RLC/MAC protocols

> TS 101 351 (GSM 04.64) MS-SGSN Logical Link Control layer

> TS 101 297 (GSM 04.65) MS-SGSN Sub-Network-Dependent Convergence Protocol layer

> TS 101 356 (GSM 07.60) MS supporting GPRS

> GSM 08.18 BSS-SGSN BSS GPRS Protocol (BSSGP)

> EN 301 347 (GSM 09.60) GPRS Tuneling Protocol (GTP) across the Gn and Gp interface

> TS 101 348 (GSM 09.61) GPRS inter-working between PLMN and PDN

> TR 10.18 (GSM 10.18) O&M in GPRS

> TS 101 393 (GSM 12.15) GPRS charging

▼ New ETSI standard designations:

� EN = ETSI Standard

� TS = Technical Specification

� TR = Technical Report

� TS and TR are less constraining than a true standard (EN).

▼ The designation GSM xx.xx remains valid.

Evolium Base Station Subsystem Introduction to GPRS and EGPRS

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Transcript of Evolium Base Station Subsystem Introduction to GPRS and EGPRS