02_tm2110eu01tm_0004_gprs
TRANSCRIPT
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Contents
1 GPRS Objectives and Advantages 31.1 GPRS Objectives and Advantages 41.2 Standardization 62
Basic Principles 9
2.1 Management of Radio Resources/ Coding Schemes 102.2 GPRS Subscriber Profile 122.3 Quality of Service (QoS) Profiles 143 GPRS-Architecture 213.1 GPRS Architecture 223.2 GSM Phase 2+, Interfaces 243.3 New Network Elements for GPRS 264 Logical Functions 354.1 Logical Functions in the GPRS Network 364.2 Allocation of Logical Functions 445 Exercises 476 Solutions 55
GPRS - General Packet Radio Services
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1.1 GPRS Objectives and Advantages
The transmission of data is becoming increasingly important in the field of telecom-munication. In the fixed network, the transmission of extensive data files and E-mailand contacts to the Intra- and Internet is by far in excess of language transmission.The need for mobile data transport is increasing at a similarly impressive rate, yet thepresently available mobile communication systems, even GSM, still present a num-ber of shortcomings.
Disadvantages for the user in GSM Phase 1/2:
In GSM (phase 1/2), the data rate is limited to a peak value of 9.6 kbit/s
Links to the data networks need to be routed via PSTN/ISDN (Additional charging ofthe user for using a transit network)
The user is billed for the connection duration instead of being billed for his/her actualuse of the network (data volume)
The set-up of a connection takes more time (ca. 20s if a modem is used)
The length of SMS is limited (160 alphanumerical characters)
Disadvantages for the provider in GMS Phase 1/2:
Inefficient resource management & the number of users is limited.
HSCSD (High Speed Circuit Switched Data)In principle, transmission rates of up to 115.2 kbit/s can be achieved with HSCSD.Combining 4 timeslots, the ISDN transmission rate can be matched. One problem ofHSCSD, however, is the circuit switched data transmission. Efficient resource man-agement is impossible. Additional costs arise for the user. For this reason HSCSD isessentially suited for applications involving high but constant transmission rates(videotelephony).
GPRS (GENERAL PACKET RADIO SERVICES)
GPRS is, on the one hand, intended to provide the possibility of transmitting largevolumes of data in a very short time. On the other hand it is meant to ensure effectivemanagement of available resources, which will increase the number of users and re-duce the costs arising for the individual user (volume-oriented fees).
Another positive consequence of the introduction of GPRS is its direct access to theIntra- and Internet and the possibility to use point-to-point and point-to-multipoint ser-vices side by side. An important aspect is that GSM networks are prepared for the in-troduction of UMTS.
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GPRS Objectives
& Advantages
PSTN
Modem
ISDN
Service provideraccess point
BSSSSS
IP
Modem
SMSC
SMS
PDNs
Intranet
Internet
PSPDN
BS-udi
BS-
3.1 kHzaudio
GPRS: high data rates reducing costs (volume dependent charging) resource efficient Point-to-Multipoint services for PMR market no SMS restrictions direct IP/X.25 connection
prerequisite for UMTS introduction future proof solution
Fig. 2 Limitations of the network architecture
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1.2 Standardization
The introduction of GPRS into the GSM Recommendations is carried out in twophases.
Phase 1 of GPRS introduction was completed by ETSI in the Annual Release 1997(03/98) and includes all central GPRS functions.
Phase 1 supports:
Point-to-point transfer of user data
TCP/IP and X.25 bearer services
GPRS identities
GPRS safety (a new ciphering algorithm specially designed for packet data)Support of volume-oriented billing
In Phase 2, further extensions are planned for all requirements to be met by GPRS:
Support of point-to multipoint (PTM) services
Support of special point-to-point and point-to-multipoint services for applications suchas traffic telematics and GSM-R (PTM-Group Call: PTM-Multicast)
Support of further additional services
Support of additional interworking functions (e.g. ISDN)Phase 2 will be completed in 1998 or 1999.
GPRS Phase 1 includes the introduction of a number of new recommendations;some of the existing recommendations have been modified to cover other GPRSfunctions, too.
The following recommendations are of central importance:
Rec. 02.60 General GPRS Overview
Rec. 03.60 GPRS System and architecture descriptionRec. 03.64 Radio architecture description
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GPRS-Standardisation
ETSI/GERAN
GPRS Standardisation in 2 Phases
Rec. 02.60
General GPRS Overview
Rec. 03.60
GPRS system &architecture description
Rec. 03.64
Radio architecture descriptionVery important:
PtP Data transmission TCP/IP & X.25 Bearer Services
GPRS Identities GPRS Security (Ciphering) SMS via GPRS volume dependent charging
Phase 1:
(Rel.`97)
PtM data transmission Broadcast & Group Call
traffic telematic, GSM-R further interworking
functionality further services
Phase 2:(Rel.`98/99)
Fig. 3 Standardization of GPRS in phases
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2 Basic Principles
Basics
GPRSGeneral Packet Radio Services
Fig. 4
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2.1 Management of Radio Resources/ CodingSchemes
In a GPRS-supported cell, one or several physical channels can be allocated toGPRS transmission. These physical channels (Packet Data Channels PDCHs) areshared by GPRS mobile stations and are taken from the common/shared pool of allavailable physical channels of the cell.
Distribution of the physical channels for various logical packet data channels is basedon blocks of 4 normal bursts each. Uplink (UL) and downlink (DL) for GPRS packetdata are assigned separately (consideration of asymmetrical traffic peaks). Allocationof circuit switched services and GPRS is achieved dynamically, depending on whatcapacities are required (capacity on demand). PDCHs need not be allocated per-
manently; however, it is possible for the operator to permanently or temporarily re-serve a number of physical channels for GPRS traffic.
New GPRS coding schemes (CS) - CS1 - CS4 - have been defined for the transmis-sion of packet data traffic channel PDTCH (Rec. 03.64). Coding schemes can be as-signed as a function of the quality of the radio interface. Normally, groups of 4 burstblocks each are coded together.
CS-1 makes use of the same coding scheme as has been specified for SDCCH inGSM Rec. 05.03. It consists of a half rate convolutional code for forward error correc-
tion FEC. CS-1 corresponds to a data rate of 9.05 kbit/s.CS-4 has no redundancy in transmission (no FEC) and corresponds to a data rate of21.4 kbit/s.
CS-2 and CS-3 represent punctured versions of the same half rate convolutionalcode as CS-1.
CS-2 corresponds to a rate of 13.4 kbit/s, while CS-3 corresponds to a data rate of15.6 kbit/s.
In principle, 1 to 8 time slots TS of a TDMA frame can be combined dynamically for auser for the transmission of GPRS packet data. Theoretically it is thus possible to
achieve peak performances of up to 171.2 kbit/s (8x21.4 kbit/s) with GPRS.
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9,05 kbit/s
13,4 kbit/s
15,6 kbit/s
21,4 kbit/s
CS-1
CS-2
CS-3
CS-4
Coding
Schemes
different
redundancy (FEC)
Um transmission quality
Radio Resource Management / Coding Schemes
CS & PS (GPRS):
capacity on demand
Physical channel of one cell
GPRS-MSs:
sharing physical channel
GPRS-MSs:combining 1-8 TS
Up to
171,2 kbit/s(theoretically)
1 - 8
channel
GPRS-MSs:
asymmetric UL / DL
Fig. 5 Management of radio resources: coding schemes, FEC, and redundancy
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2.2 GPRS Subscriber Profile
The GPRS Subscriber Profile is the description of the services a subscriber is al-lowed to use. Essentially, it contains the description of the packet data protocol used.
A subscriber may also use different packet data protocols (PDPs), or one PDP withdifferent addresses. The following parameters are available for each PDP:
The packet network addressis necessary to identify the subscriber in the publicdata net. Either dynamically assigned (temporary) addresses or (in the future) staticaddresses are used in case of IP. The problem of the dynamic addresses will beovercome with the change from Ipv4 to IPv6. In GPRS is two layer 2 protocols are al-lowed, X.25 or IP.
The quality of service QoS: QoS describes various parameters. The subscriber pro-file defines the highest values of the QoS parameters that can be used by the sub-scriber.
The screening profile: This profile depends on the PDP used and on the capacity ofthe GPRS nodes. It serves to restrict acceptance during transmission/reception ofpacket data. For example, a subscriber can be restricted with respect to his possiblelocation, or with respect to certain specific applications.
The GGSN address: The GGSN address indicates which GGSN is used by the sub-scriber. In this way the point of access to external packet data networks PDN is de-fined. The internal routing of the data is done by IP protocol; the GSNs will have IPaddresses. A DNS function is needed to find the destination of the data packets (ad-
dress translating: e.g. www.gsn-xxx.com129.64.39.123)
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GPRS Subscriber Profile
Subscription profileused Packet Data Protocols PDP
possible: 1 Subscriber - different PDPs / 1 PDP with different addresses
PDPParameter
Packet
network addressstatic/dynamic
IP address
QoS
Quality of Servicehighest QoS-
parameter values inSubscriber Profile
Screening
Profilelimits receiving / emission
of data packets
GGSN addressAccess to external PDN
Fig. 6 Part of the GPRS subscriber profile are the PDPs and their parameters
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2.3 Quality of Service (QoS) Profiles
The different applications that will make use of packet-oriented data transmission viaGPRS require different qualities of transmission. GPRS can meet these different re-quirements because it can vary the quality of service (QoS) over a wide range of at-tributes. The quality of service profile (Rec. 02.60, 03.60) permits selection of the fol-lowing attributes:
Precedence class
Delay class
Reliability class
Peak throughput class
Mean throughput class.
By combining the variation possibilities of the individual attributes a large number ofQoS profiles can be achieved. Only a limited proportion of the possible QoS profilesneed PLMN-specific support.
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Quality of Service QoS - Profile
Different requirements for different applicationsmultiple GPRS QoS profiles
precedence class
delay class
reliability class
Peak
throughputclass
mean throughput
class
PLMN must support onlylimited QoS service profile
Fig. 7 Quality of service parameters
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Precedence Class
Three different classes have been defined to allow assessment of the importance of
the data packets, in case of limited resources or overload:1. High precedence
2. Normal precedence
3. Low precedence
Delay Class
GSM Rec.02.60 defines 4 delay classes (1 to 4). However, a PLMN only needs to re-alize part of these. The minimum requirement is the support of the so-called best ef-fort delay class (Class 4). Delay requirements (maximum delay) concern the delay oftransported data through the entire GPRS network (the first two columns refer to datapackets 128 bytes in length, while the last two columns apply to packets 1024 bytesin length).
Delay Class mean transferdelay (sec)
95% delay(sec)
mean transferdelay (sec)
95% delay(sec)
1 < 0,5 < 1,5 < 2 < 7
2 < 5 < 25 < 15 < 75
3 < 50 < 250 < 75 < 375
4 (Best Effort) unspecified unspecified unspecified unspecified
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Reliability Class
Transmission reliability is defined with respect to the probability of data loss, data de-livery beyond/outside the sequence, twofold data delivery, and data falsification(probabilities 10-2 to 10-9):. 5 reliability classes (1 to 5) have been defined, 1 guaran-teeing the highest and 5 the lowest degree of reliability. Highest reliability (Class 1) isrequired for error-sensitive, non-real-time applications, which have no possibility ofcompensating for data loss; lowest reliability (Class 5) is needed for real-time applica-tions which can get over data loss.
Peak Throughput Class
The peak throughput class defines the maximum data rate to be expected (inbytes/s). However, there is no guarantee that this data rate/throughput can beachieved over a certain period of time. This depends on the capacity of the MS andthe availability of radio resources. 9 throughput classes have been defined, rangingfrom Class 1 with 1000 bytes/s (8 kbit/s) to 256,000 bytes (2048 kbit/s). The maxi-mum data rate doubles from one class to the next.
Mean Throughput Class
The mean throughput class represents the mean data rate /throughput to be ex-pected for data transport via the GPRS network during an activated link. A total of 19classes have been defined. Class 1 is best effort and means that the data rate forthe MS is made available on the basis of demand and availability of resources.
Class 2 stands for 100 bytes/h (0.22 bit/s), class 3 for 200 bytes/h, class 4 for 500bytes/h and class 5 for 1000 bytes/h, etc. till Class 19 which stands for 50000000bytes/h (111 kbit/s).
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Quality of Service QoS - Profile
Reliability Class
1 - 5 (lowest):
data loss probability
out of sequence probability
duplicate probability
corrupt data probability
probabilities 10 -9 - 10 -2peak throughput Class
1 - 9: > 8 kbit /s - >2048 kbit /s
maximum data rateno guarantee for this data rates
over a longer period of time
mean throughput Classmedium, guaranteed data rate; Class 1-19
1: best effort
100 Byte/h (0,22 bit/s) / 200 / 500 / 1000 / ... /
50 Mio. Byte/h (111 kbit/s)
Fig. 9 QoS is an assumption of several parameters, which are defined in the recommendations
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3 GPRS-Architecture
Architecture
GPRSGeneral Packet Radio Services
Fig. 10
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3.1 GPRS Architecture
For introducing GPRS, the logical GSM architecture is extended by two functionalunits:
The Serving GPRS Support Node SGSNis on the same hierarchic level as MSCand has functions comparable to those of a Visited MSC (VMSC).
The Gateway GPRS Support Node GGSNhas functions comparable with those of aGateway MSC (GMSC) and offers interworking functions for establishing contact be-tween the GSM/GPRS-PLMN and external packet data networks PDN
A GPRS Support Node GSNincludes the central functions required to support the
GPRS. One PLMN can contain one or more GSNs.In addition to GSN, extensions of functions in other GSM functional units are neces-sary:
In the BSS a Packet Control Unit PCUensures the reception/adaptation of packetdata from SGSN into BSS and vice versa.
GPRS subscriber data are added to the HLR. On the following pages of this scriptthis extension will be termed GPRS Register GR.
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Channel Codec Unit CCUin BTS
for channel coding
Mobile
DTE
SGSNServing GPRS
Support Node
PSTN
InternetIntranet
X.25
GGSNGateway GPRS
Support Node
VMSC /
VLR GMSC
HLR
New network entities:SGSN
(access toBSS)GGSN
(access to PDN)
GPRS - Architecture
ISDNPCU
BSS
GPRS subscription data(GPRS Register GR)
Packet Control Unit PCUfor
protocol conversion &
radio resourcemanagement
Fig. 11 Outline of the GPRS architecture
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3.2 GSM Phase 2+, Interfaces
Integration of functions GGSN and SGSN (which are necessary for GPRS) into aGSM-PLMN makes it necessary to provide names for a series of new interfaces inaddition to interfaces A-G already defined in the GSM-PLMN:
Gb- between an SGSN and a BSS; Gb allows the exchange of signaling and userdata: Unlike the A-interface, in which a user is assigned a certain physical resourcefor the entire/full duration of a connection, on Gb a resource is only assigned in caseof activity (i. e. when data are being transmitted/received). A large number of sub-scribers use the same physical resources. The same holds for interfaces Gi, Gn andGp.
Gc - between a GGSN and an HLR
Gd- between an SMS-GMSC / SMS-IWMSC and an SGSN
Gf- between an SGSN and an EIR
Gi - between GPRS and an external packet data network PDN
Gn- between two GPRS support nodes GSN within the same PLMN
Gp- between two GSN located in different PLMNs. The Gp interface allows the sup-porting of GPRS services over an area of cooperating GPRS PLMNs.
Gr- between an SGSN and an HLR
Gs- between an SGSN and an MSC/VLR; serves to support an MS using both
GPRS and circuit switched services (e.g. update of location information).
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PSTN
X.25
Common GSM/GPRS/UMTS Network:
Interfaces, Network Elements
ISDN
IP
IWF/TC: Interworking Function / Transcoder
IWF/
TC
A
Gb
Iu(PS)
Gi
GMSC
GGSN
GSM Phase 2+
Core Network
MSC
SGSN
HLR/ACEIRCSE
Iu(CS)
A
Gn
T
R
A
U
B
S
C
BTS
BTS
Abis
UE(USIM)
Uu
Um
MS(SIM)
E
SMS-GMSC
SMS-IWMSC
E Gd
GSM BSS
Asub
Gs
Gr Gc
UMTS
Terrestrial
Radio
Access
Network
Gf
VLR
SLR
Fig. 12 Common GSM/GPRS/UMTS core network, coexistence of two radio access networks (GSM BSS/UTRAN)
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3.3 New Network Elements for GPRS
3.3.1 Serving GPRS Support Node (SGSN) Functions
SGSN realizes a large number of functions for performing GPRS services.
SGSN is on the same hierarchic level as an MSC and handles many functions com-parable to a Visited MSC (VMSC).
SGSN
is the node serving GPRS mobile stations in a region assigned to it;
traces the location of the respective GPRS MSs (Mobility Management functions);
is responsible for the paging of MS;performs security functions and access control (authentication/cipher setting proce-dures,...) Procedures are based on the same algorithm, ciphers and criteria as in theformer GSM. Ciphering algorithms have been optimized for the transmission ofpacket data;
has routing/traffic-management functions;
collects data connected with fees/charges;
realizes the interfaces to GGSN (Gn), PCU (Gb), other PLMNs (Gp), HLR (Gr),VLR (Gs), SMS-GMSC (Gd), EIR (Gf).
3.3.2 Gateway GPRS Support Node (GGSN) Functions
GGSN realizes functions comparable to those of a gateway MSC.
GGSN
is the node allowing contact/interworking between a GSM PLMN and a packetdata network PDN (realization Gi-interface);
contains the routing information for GPRS subscribers available in the PLMN.Routing information serves to contact the respective SGSN in the providing area of
which an MS is momentarily located;
has a screening function;
can inquire about location informations from the HLR via the optional Gc interface
transfers data/signaling to SGSN via Gn interface.
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GGSN
SGSN & GGSN
SGSN
Serving GPRS Support Node SGSN serves MSs in SGSN area
Mobility Management functions, e.g
Update Location, Attach, Paging,..
Security and access control:
Authentication, Cipher setting, IMEI Check...
New cipher algorithm
Routing / Traffic-Management
collecting charging data
realises Interfaces: Gn, Gb, Gd, Gp, Gr, Gs, Gf
controls subscribers in its service area (SLR)
Gateway GPRS Support Node GGSN Gi-,Gn-Interface: Interworking PLMN PDN Routing Information for attached GPRS user
Screening / Filtering
collecting charging data
optional Gc interface
Fig. 13 Tasks of GGSN and SGSN
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3.3.3 Physical Realization SGSN/GGSN
SGSN and GGSN functions, respectively, can be located within the same physicalunit or at different locations in different physical units. SGSN and GGSN include theinternet protocol (IP) routing function and can be linked together/Interconnected withIP routers (IP-based GPRS backbone network for Gn). The same holds for the Gp in-terface (SGSN and GGSN in different PLMNs); in addition there are safety functionsfor inter-PLMN communication.
HLR (GPRS Register GR)
HLR includes the GPRS subscriber information (GPRS Register GR) and routing in-
formation. Access to HLR is possible from SGSN via Gr and from GGSN via Gc inter-face.
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SGSN & GGSN:
physical location
External
IP Network
GGSN
SGSN
HLR (GR)
BSS PCU
GPRS-MS
MSC/VLR
BSS PCU
HLR: GPRS subscriber data
(GPRS Register GR) Routing information
Gb
Gb
Gi
GrGs
SGSN & GGSNin same
physical entity
SGSN
GGSN
SGSN
GGSN
GGSN
BSS PCU
GPRS-MS
BSS PCU
External
X.25 Network
IP-based
Backbone
Network
Gn
Gp
Security functions
for I nter-PLMN
communication
otherPLMN
SGSN & GGSNin different
physical entities /location
External
IP Network
Fig. 14 Different physical locations of SGSN and GGSN
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CCU
CCU PCU
BTS BSC site GSN site
CCU
CCU
BTS BSC site GSN site
CCU
CCU
BTS BSC site GSN site
PCU
PCU
A
B
C
optional:
PCU-locationPCU, CCU, GPRS - MS
Um Abis
Gb
MS
MS
MS
Packet Control Unit PCU Channel Access Control functions Radio Channel Management functions(Power Control, Congestion Control,...)
scheduling data transmission (UL/DL) protocol conversion (Gb Um)
Gb
Channel Codec Unit CCU Channel Coding (FEC, Interleaving,..) Radio Channel Measurementfuncions(received quality & signal level, TA,..)
Fig. 15 Positioning of the new network elements in the GSM BSS
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3.3.6 GPRS Mobile Stations MS
A GPRS MS can work in three different operational modes. The operational modedepends on the service an MS is attached to (GPRS or GPRS and other GSM ser-vices) and on the mobile stations capacity of simultaneously handling GPRS andother GSM services.
Class A operational mode: The MS is attached to GPRS and other GMS servicesand the MS supports the simultaneous handling of GPRS and other GSM services.
Class B operational mode: The MS is attached to GPRS and other GMS services,but the MS cannot handle them simultaneously.
Class C operational mode: The MS is attached exclusively to GPRS services.
Note: Various GSM specifications use the terms GPRS Class-A MS, GPRS Class-BMS, GPRS Class-C MS.
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GPRS-Mobile Station
Class A
Simultaneously handlingof GPRS and otherGSM services
Class B
GPRS and GSMservices but notsimultaneously
Class C
Only GPRS services
Fig. 16 GPRS mobile stations
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4 Logical Functions
Logical Functions
GPRSGeneral Packet Radio Services
Fig. 17
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Logical functions
in GPRS networksNetwork Access
ControlFunctions
MobilityManagement
Functions
Radio ResourceManagement
Functions
Packet Routeing
& TransferFunctions
Logical Link
ManagementFunctions
NetworkManagement
Functions
Fig. 18 Logical functions of the GPRS network
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4.1.1 Network Access Control Functions
Network access means the way or manner in which a subscriber gains access to atelecommunication network to make use of the services this network provides. Anaccess protocol consists of a defined set of procedures, which makes access to thenetwork possible. Network access can be obtained both from the MS and from thefixed network part of the GPRS network. Depending on the provider, the interface toexternal data networks can support various access protocols, e.g. IP or X.25. The fol-lowing functions have been defined for access to the GPRS network:
Registration function: Registration stands for linking the identity of the mobile radiosubscriber to his packet data protocol (or protocols), the PLMN-internal addressesand the point of access of the user to external data Protocol (PDP) networks. Thislink can be static (HLR entry), or it can be effected on demand.
Authentication and authorization function: This function stands for the identifica-tion of the subscriber and for access legitimacy when a service is demanded. In addi-tion, the legitimacy of the use of this particular service is controlled. The authentica-tion function is carried out in conjunction with the mobility management functions.
Admission control function: Admission control is intended for determining the net-work resources required for performing the desired service (QoS). It also decideswhether these resources are available, and lastly it is used for reserving resources.Admission control is effected in conjunction with the radio resource managementfunctions to enable assessment of radio resources requirements in each individualcell.
Message screening function: A "screening" function is combined with the filtering ofunauthorized or undesirable information/messages. In the introduction stage ofGPRS a network-controlled screening function is supported. Subscription-controlledand user-controlled screening may be additionally provided at a later stage.
Packet terminal adaptation function: This function adapts data packets re-ceived/transmitted from/to the terminal equipment TE to a form suited for transportthrough the GPRS network.
Charging data collection function: This function is used for collecting data requiredfor billing
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Packet Routing & Transfer Function
Relayforward data packets Routing
next hop
Address Mapping&Translation
Encapsulation
Tunneling
Compression
Ciphering Domain NameServer
Fig. 20 Packet routing and transfer functions in the GPRS network
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4.1.3 Mobility Management Functions
Mobility management functions are used to enable tracing the actual location of amobile station in either the home-PLMN or a Visited-PLMN.
4.1.4 Logical Link Management Functions
Logical link management functions concern maintenance of a communication chan-nel between an MS and the PLMN via the radio interface Um. These functions in-clude the coordination of link state information between the MS and the PLMN andthe monitoring of data transfer activities via the logical link.
Logical link establishment function: Building up a logical link by during GPRS at-tach.
Logical link maintenance function: Monitoring of the state of the logical link andstate modification control.
Logical link release function: De-allocation of resources associated with the logicallink.
4.1.5 Radio Resource Management Functions
Radio resource management functions include allocation and maintenance of com-munication channels via the radio interface. The GSM radio resources must be di-
vided /distributed between circuit switched services and GPRS.Um management function: Managing available physical channels of cells and de-termining the share of radio resources allocated for use in the GPRS. This share mayvary from cell to cell.
Cell selection function: Allows the MS to select the optimal cell for a communicationpath. This includes measurement and evaluation of the signal quality of neighboringcells and detection and avoidance of overload in the eligible cells.
Um-tranx function: Offers capacity for packet data transfer via Um. The function in-cludes a. o. procedures for multiplexing packets via shared physical channels, for re-taining packets in the MS, for error detection and correction, and for flow control.
Path management function: Management of packet data communication betweenBSS and serving GSN node. Establishing and canceling these paths can be effectedeither dynamically (amount of traffic data) or statically (maximum load to be expectedfor each cell).
4.1.6 Network Management Functions
Network management functions provide mechanisms for the support of GPRS-related operation & maintenance functions.
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Maintenance of communication channel,co-ordination Link state information & supervision ofdata transfer activity over the logical link MS - SGSNLogical Link Establishment
Logical Link Maintenance
Logical Link Release
Keep track of current MS-location
Mobility Management Functions
Allocation & maintenance of radio communication pathUm Management:manage resources GPRS / non GPRS
Cell Selection:select optimal cell (by MS)Um-tranx: MAC via Um, user multiplexing, packet discriminationwithin MS, error detection & correction, flow control procedures
Path Management:manages packet data communicationBSSSGSN(dynamic data traffic or static)
Radio Resource
Management Functions
mechanism to support O&Mfunctions related to GPRS
Network ManagementFunctions
Logical LinkManagement Functions
Fig. 21 Mobility management, logical link, radio resource and network management functions
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4.2 Allocation of Logical Functions
The tasks described in the logical functions can be allocated to various functionalunits of the GSM-/GPRS network. The mobile station MS, the base station subsys-tem BSS (with the packet control unit PCU and channel codec unit CCU), the servingGPRS support node SGSN and the gateway GPRS support node GGSN participatein handling the following functions:
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Function MS BSS SGSN GGSN HLR
Network Access Control:
Registration XAuthentication & Authorization X X X
Admission Control X X X
Message Screening X
Packet Terminal Adaptation X
Charging Data Collection X X
Packet Routing & Transfer:
Relay X X X X
Routing X X X X
Address Translation & Mapping X X X
Encapsulation X X X
Tunneling X X
Compression X X
Ciphering X X X
Domain Name Server X
Mobility Management X X X X
Logical Link Management:
Logical Link Establishment X X
Logical Link Maintenance X X
Logical Link Release X X
Radio Resource Management:
Um Management X X
Cell Selection X X
Um-Tranx X X
Path Management X X
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5 Exercises
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Exercise
Title:GPRS-General Packet Radio Service
Task
Please tick one answer. More than one answer can be correct
Query
1. Advantages of GPRS are:
transmission of higher data rates
volume dependent charging
direct access to the IP-network
resource efficiency
all above
2. GPRS subscriber profile contains:
packet network address
IMSI
P-TMSI
routing area
3. True/False
The packet network address is necessary to identify the subscriber's location
area The packet network address is necessary to identify the cell of one subscriber
The screening profile limits reception of data packets
The GGSN address identifies verify the access to the correct SSGN
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4. The QoS-Profile consist of:
delay class
IP-address
throughput class
IMSI
5. True/False
With GPRS it is also possible to transport real time data
With GPRS you can only transmit speech data
With GPRS it is only possible to transmit non real time data
With GPRS it is only possible to transmit data
6. Delay class 1 means:
95% of the data have a shorter delay than 2 s
95% of the data have a shorter delay than 7 s
the mean transfer delay is shorter than 7 s
the mean transfer delay is unspecified
7. Which new HW-elements have to be implemented for GPRS?
PCU, CCU and SGSN
CCU, PCU GGSN
PCU, SGSN, GGSN
SGSN, GGSN, CAP
8. The PCU is responsible for:
charging
ciphering
radio resource management
access to the Internet
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9. Which of the following paths are correct considering "element-interface-element"?
BSC - A - SGSN
BSC - Gb - SGSN
SGSN - Gi - GGSN
SGSN - Gs - GGSN
SGSN - Gn - GGSN
10. A routing area
is a part of the cell
is a part of the location area
consists of several location areas
consists of several VLR-areas
11. Which of the following is not a task of the GGSN:
collecting charging data
ciphering
interworking PLNM - PDN
screening/filtering
12. True/False
To use GPRS a GPRS mobile phone is needed
GPRS can be also implemented virtually, in the HLR only as GR
The only major difference between HSCSD and GPRS is the number of codingschemes
GRPS is a necessary step for operators who want to keep the GSM NSS whenintroducing UMTS
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13. Which one is not correct:
The CCU is only a SW-modification
The CCU is a new HW-element
The CCU is responsible for the new coding schemes
The CCU is implemented in the BTS
14. Logical function in the GPRS network are:
packet routing and transfer functions
QoS-function
network access control functions
mobility management function
all of the answers are correct
15. Tunneling means
transfer of decapsulated data
transfer of data over the air interface
transfer of encapsulated data
transfer of data inside IP-network
16. Routing function means:
transfer of data from one node to another node
transfer of data on the air interface
determining the transmission path for the next "hop"
none of the above is correct
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17. Network access control function contains:
registration
compressing of data
Um-management
path management
admission control
routing
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6 Solutions
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Solution
Title:GPRS-General Packet Radio Services
1. Advantages of GPRS are:
transmission of higher data rates
volume dependent charging
direct access to the IP-network
resource efficiency
all above
2. GPRS subscriber profile contains:
packet network address
IMSI
P-TMSI
routing area
3. True/False
The packet network address is necessary to identify the subscriber's locationarea
The packet network address is necessary to identify the cell of one subscriber
The screening profile limits reception of data packets
The GGSN address identifies verify the access to the correct SSGN
4. The QoS-Profile consist of:
delay class
IP-address
throughput class
IMSI
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9. Which of the following paths are correct considering "element-interface-element"?
BSC - A - SGSN
BSC - Gb - SGSN
SGSN - Gi - GGSN
SGSN - Gs - GGSN
SGSN - Gn - GGSN
10. A routing area
is a part of the cell
is a part of the location area
consists of several location areas
consists of several VLR-areas
11. Which of the following is not a task of the GGSN:
collecting charging data
ciphering
interworking PLNM - PDN
screening/filtering
12. 12.True/False
To use GPRS a GPRS mobile phone is needed
GPRS can be also implemented virtually, in the HLR only as GR
The only major difference between HSCSD and GPRS is the number of codingschemes
GRPS is a necessary step for operators who want to keep the GSM NSS whenintroducing UMTS
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13. Which one is not correct:
The CCU is only a SW-modification
The CCU is a new HW-element
The CCU is responsible for the new coding schemes
The CCU is implemented in the BTS
14. Logical function in the GPRS network are:
packet routing and transfer functions
QoS-function
network access control functions
mobility management function
all of the answers are correct
15. Tunneling means
transfer of decapsulated data
transfer of data over the air interface
transfer of encapsulated data
transfer of data inside IP-network
16. Routing function means:
transfer of data from one node to another node
transfer of data on the air interface
determining the transmission path for the next "hop"
none of the answer is correct
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17. Network access control function contains:
registration
compressing of data
Um-management
path management
admission control
routing
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