General Packet Radio Service
(GPRS)
Petteri Lappalainen
23.11.1998
IP Tech School
Seminar Presentation
Based on the material by
Tuomas Niemelä (-97), Hannu H. Kari (-98) and ETSI
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 1
Wireless roadmap
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 2
Contents
1. Introduction to GPRS
What is GPRS ?
GPRS characteristics
Applications
2. GPRS architecture
Network elements
3. GPRS Operations
Radio interface
resource reservation
Security operations
Connecting to GPRS
Data transfer
Mobility management
Interworking with GSM
services
•
•
•
•
•
•
•
•
•
•
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 3
4. Special issues
SMS
Charging
O&M
Supplementary services
QoS
Performance
5. GPRS business view
• What must be invested…
• How to make money with
GPRS
• Users' benefits of GPRS
• Business model
•
•
•
•
•
•
6. GPRS specifications
1. Introduction to GPRS
1.1. What is GPRS ?
1.2. GPRS access interfaces and reference points
1.3. How is GPRS seen by external networks and GPRS users
1.4. Air interface resources
1.5. GPRS characteristics
1.6. Applications
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 4
1.1. What is GPRS ?
• Part of GSM phase 2+
• General Packet Radio Service
• General -> not restricted to GSM use (DECT ?, 3rd
•
•
generation systems ?)
Packet Radio -> enables packet mode communication
over air
Service, not System -> existing BSS (partially also NSS)
infrastructure is used
• Requires many new network elements into NSS
• Provides connections to external packet data networks
(Internet, X.25)
• Main benefits
• Resources are reserved only when needed and charged
•
•
accordingly
Connection setup times are reduced
Enables new service opportunities
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 5
1.2. GPRS access interfaces and
reference points
R reference point
TE
Um
MT
MS
Gi reference point
GPRS network 1
PDNs or
other networks
Gp
GPRS network 2
• GPRS provides packet switched connections from MS
to packet data networks (PDN)
• Different operator’s GPRS networks are connected
through Gp interface
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 6
1.3. How is GPRS seen by external
networks and GPRS users?
HOST
155.222.33.55
GPRS
SUBNETWORK
SUBNETWORK
155.222.33.XXX
"Router"
SUBNETWORK
131.44.15.XXX
SUBNETWORK
191.200.44.XXX
Corporate 1
Router
HOST
191.200.44.21
Local
area
network
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 7
Packet
Data
network
network
Router
Corporate 2
(Internet)
Local
area
network
HOST
131.44.15.3
1.4. Air interface resources
An example of occupied TCH
capacity by CS traffic during
busy hour with n% blocking
GPRS "steals" any TCH
capacity not used by CS
traffic
14
Free
Capacity
12
10
8
TCH
6
4
14
2
12
Capacity occupied by CS traffic
TCH
10
8
0
6
1:00 PM
4
2
0
3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 8
1:15 PM
1:30 PM
1:45 PM
1.5. GPRS characteristics
GPRS uses packet switched resource allocation
• resources allocated only when data is to be
sent/received
Flexible channel allocation
• one to eight time slots
• available resources shared by active users
• up and down link channels reserved separately
• GPRS and circuit switched GSM services can use
same time slots alternatively
Traffic characteristics suitable for GPRS
• Intermittent, bursty data transmissions
• Frequent transmissions of small volumes of data
• Infrequent transmission of larger volumes of data
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 9
1.6. Applications
•
Standard data network protocol based
•
GPRS specific protocol based
•
SMS delivery (GPRS as a bearer for SMS)
• IP based applications
– WWW, FTP, Telnet, ...
– Any conventional TCP/IP based applications
• X.25 based applications
– Packet Assembly/Disassembly (PAD) type approach
• Point-to-point applications
– Toll road system, UIC train control system
• Point-to-multipoint applications
– Weather info, road traffic info, news, fleet management
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 10
2. GPRS architecture
2.1. Interfaces, reference points and network elements
2.2. Functional view on GPRS
2.3. Subscription of GPRS service
2.4. New network elements
2.4.1. GGSN
2.4.2. SGSN
2.4.3. Other elements
2.4.4. GPRS backbones
2.5. GPRS Mobile classes
2.6. MS multislot capabilities
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 11
2.1. Interfaces, reference points and
network elements
SMS-GMSC
SMS-IWMSC
MAP-H
SM-SC
MAP-C
Gd
MSC/VLR
Gs
A
TE
MT
R
HLR
MAP-D
Gb
BSS
Um
Gc
Gr
SGSN
Gp
Gi
PDN
GGSN
Gn
MAP-F
EIR
GGSN
Other PLMN
Signalling Interface
Signalling and Data Transfer Interface
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 12
TE
2.2. Functional view on GPRS
BTS
R/S
Um
Packet
network
PSTN
BSC
MSC
HLR/AuC
Gb
Packet
Inter-PLMN
network
Backbone
network
Serving GPRS
Support Node
Gn
(SGSN)
Border
Gateway (BG)
Intra-PLMN
backbone
network
(IP based)
Gp
Firewall Point-ToMultipoint
Service
Center
(PTM SC)
Gn
Gr
Gs
IP TECH SCHOOL seminar / 23.11.1998 / slide 13
Gd
Gd
Packet
SS7
network
Network
Gs
GPRS
INFRASTRUCTURE
EIR
Corporate 1
Server
MAP-F
Router
Gateway GPRS
Support Node
(GGSN)
Firewall
Gi.IP
Gi.X.25
Firewall
NOKIA TELECOMMUNICATIONS
Gr
Data
Packet
network
network
(X.25)
SMS-GMSC
Data
Packet
network
network
(Internet)
Local
area
network
Corporate 2
Server
Router
Local
area
network
Assignment of functions to general
logical architecture
Function
Network Access Control:
Registration
Authentication and Authorisation
Admission Control
Message Screening
Packet Terminal Adaptation
Charging Data Collection
MS
X
X
BSS
SGSN
X
X
X
GGSN
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Mobility Management:
X
X
X
Logical Link Management:
Logical Link Establishment
Logical Link Maintenance
Logical Link Release
X
X
X
X
X
X
Packet Routeing & Transfer:
Relay
Routeing
Address Translation and Mapping
Encapsulation
Tunnelling
Compression
Ciphering
Radio Resource Management:
Um Management
Cell Selection
Um-Tranx
Path Management
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 14
HLR
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
2.3. Subscription of GPRS
service (1/2)
Subscription storage: HLR
Supports Multiple Subscriber Profile (MSP)
Mobile identification: IMSI
One or several PDP addresses per user
• Each subscribed configuration contains
• PDP type
(e.g., IP, X.25)
• PDP address (static, e.g. 128.200.192.64)
• Subscribed QoS (level 1…4)
• Dynamic address allowed
• VPLMN address allowed
• GGSN address
• Screening information (optional)
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 15
2.3. Subscription of GPRS
service (2/2)
Subscription is copied from HLR to SGSN during GPRS
Attach
Part of PDP context is copied to relevant GGSNs when a
PDP address is activated
Possible PDP address allocation alternatives
• Static address allocated from HPLMN
• Dynamic address allocated from HPLMN
• Dynamic address allocated from VPLMN
HPLMN operator specifies which alternatives are possible
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 16
2.4.1. Gateway GPRS Support Node
GGSN
• Typically located at one of the MSC sites
One (or few) per operator
• Main functions
• Interface to external data networks
• Resembles to a data network router
• Forwards end user data to right SGSN
• Routes mobile originated packets to right destination
• Filters end user traffic
• Collects charging information for data network usage
• Data packets are not sent to MS unless the user has
activated the PDP address
•
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 17
2.4.2. Serving GPRS Support Node
SGSN
• Functionally connected with BSC, physically can be at
MSC or BSC site
• One for few BSCs or one (or few) per every BSC
• One SGSN can support BSCs of several MSC sites
• Main functions
• Authenticates GPRS mobiles
• Handles mobile’s registration in GPRS network
• Handles mobile’s mobility management
• Relays MO and MT data traffic
• TCP/IP header compression, V.42bis data
•
compression, error control MS- SGSN (ARQ)
Collect charging information of air interface usage
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 18
2.4.3. Other elements
BG (Border Gateway)
• (Not defined within GPRS)
• Routes packets from SGSN/GGSN of one operator to a SGSN/GGSN of an
other operator
• Provides protection against intruders from external networks
DNS (Domain Name Server)
• Translates addresses from ggsn1.oper1.fi -format to 123.45.67.89 format
(i.e. as used in Internet)
Charging Gateway
• Collects charging information from SGSNs and GGSNs
PTM-SC (Point to Multipoint -Service Center)
• PTM Multicast (PTM-M): Downlink broadcast; no subscription; no ciphering
PTM Group call (PTM-G): Closed or open groups; Down/up -link; ciphered
• Geographical area limitation
•
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 19
2.4.4. GPRS backbones
Enables communication between GPRS Support Nodes
Based on private IP network
• IPv6 is the ultimate protocol
• IPV4 can be used as an intermediate solution
Intra-PLMN backbone
• Connects GPRS Support Nodes of one operator
• Operator decides the network architecture
• LAN, point-to-point links, ATM, ISDN, ...
Inter-PLMN backbone
• Connects GPRS operators via BGs
• Provides international GPRS roaming
• Operators decide the backbone in the roaming agreement
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 20
2.5. GPRS mobile types
Class A:
• Simultaneous GPRS and conventional GSM operation
• Supports simultaneous circuit switched and GPRS data transfer
Class B:
• Can be attached to both GPRS and conventional GSM services
simultaneously
• Can listen circuit switched and GPRS pages (via GPRS)
• Supports either circuit switched calls or GPRS data transfer but
not simultaneous communication
Class C:
• Alternatively attached in GPRS or conventional GSM
• No simultaneous operation
• ‘GPRS only’ mobiles also possible (e.g. for telemetric
applications)
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 21
2.6. GPRS multislot capabilities
1-slot
MS RX
0
1
MS TX
5
6
MS RX
0
1
MS TX
5
6
MS RX
0
1
MS TX
5
6
2
3
7
4
0
5
6
7
0
1
1 2
3
4
5
6
Monitor
2-slot
2
7
3
4
0
5
6
7
0
1
1 2
3
4
5
6
Monitor
3-8 -slot
2
7
3
4
0
1
5
2
6
7
0
1
3
4
5
6
Monitor
3 slots:
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 22
4th slot:
5th slot:
3. GPRS operations
3.1 Security: Basic security rules
• Authentication, key management, ciphering
3.2 GPRS attach
3.3 Data transmission
• MO, MT, MO+MT
3.4 Mobility management
3.5 Interworking with GSM services
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 23
3.1. Security: Based on GSM phase 2
Authentication
• SGSN uses same principle as MSC/VLR:
•
•
Get triplet, send RAND to MS, wait for SRES from MS, use Kc
MS can’t authenticate the network
Key management in MS
• Kc generated same way from RAND using Ki as in GSM
Ciphering
• Ciphering algorithm is optimized for GPRS traffic (‘GPRS - A5’)
• Ciphering is done between MS and SGSN
User confidentiality
• IMSI is only used if a temporary identity is not available
• Temporary identity (TLLI) is exchanged over ciphered link
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 24
3.2. GPRS Attach
GPRS Attach function is similar to IMSI attach
• Authenticate the mobile
• Generate the ciphering key
• Enable the ciphering
• Allocate temporary identity (TLLI)
• Copy subscriber profile from HLR to SGSN
After GPRS attach
• The location of the mobile is tracked
• Communication between MS and SGSN is secured
• Charging information is collected
• SGSN knows what the subscriber is allowed to do
• HLR knows the location of the MS in accuracy of SGSN
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 25
3.3. Data transfer: Basic rules (1/4)
• SGSN:
• Does not interpret user data, except
•
•
•
• SGSN may perform TCP/IP header compression
Does not interpret source or destination addresses
Sends all packets to specified GGSN that handles
the PDP context
GGSN:
• Performs optional filtering
• Decides where and how to route the packet
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 26
3.3. Data transfer (2/4)
Mobile originated (left when MS in HPLMN, right when in
VPLMN, no filtering/screening)
BTS
BSC
BSC
Packet
SGSN
BG
HPLMN
SGSN
Inter-PLMN
backbone
network
network
BG
Intra-PLMN
backbone
network
(IP based)
Intra-PLMN
backbone
network
(IP based)
GGSN
GGSN
Data
Packet
network
network
(Internet)
Corporate
Server
Router
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 27
BTS
Local
area
network
VPLMN
3.3. Data transfer (3/4)
Mobile terminated (left when MS in HPLMN, right when in
VPLMN, with/without filtering/screening)
BTS
BSC
BSC
Packet
SGSN
BG
HPLMN
SGSN
Inter-PLMN
backbone
network
network
BG
Intra-PLMN
backbone
network
(IP based)
Intra-PLMN
backbone
network
(IP based)
GGSN
GGSN
Data
Packet
network
network
(Internet)
Corporate
Server
Router
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 28
BTS
Local
area
network
VPLMN
3.3. Data transfer (4/4)
Mobile originated and terminated (left MSs in same
PLMN, right MSs in different PLMN)
BTS
BSC
BSC
Packet
SGSN
BG
HPLMN
SGSN
SGSN
Inter-PLMN
backbone
network
network
BG
Intra-PLMN
backbone
network
(IP based)
Intra-PLMN
backbone
network
(IP based)
GGSN
GGSN
Data
Packet
network
network
(Internet)
BTS
BSC
Corporate
Server
Router
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 29
BTS
Local
area
network
VPLMN
3.4. Mobility management (1/3)
Instead of Location Area, GPRS uses Routing Areas to
group cells. RA is a subset of LA.
• IDLE:
• MS is not known by the network (SGSN)
• STANDBY:
• MS’s location is known in accuracy of Routing Area
• MS can utilize DRX (to save battery)
• MS must inform its location after every Routing
•
•
Area change (no need to inform if MS changes
from one cell to another within same Routing Area)
Before the network can perform MT data transfer
MS must be paged within the Routing Area
MS may initiate MO data transfer at any time
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 30
3.4. Mobility management (2/3)
• READY:
• MS’s location is known in accuracy of cell
• MS must inform its location after every cell change
• MS can initiate MO data transfer at any time
• SGSN does not need to page the MS before MT
•
data transfer
MS listens continuously GPRS PCCCH channel
• DRX in READY state is optional
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 31
3.4. Mobility management (3/3)
Mobility management messages:
• Cell update (implicit, with any message)
• When MS changes the cell within a Routing Area in
•
READY state
Routing Area update
• When MS changes the cell between two Routing
•
•
Areas in READY or STANDBY state
Two types of Routing Area Updates (from MS’s point
of view only one type)
– Intra-SGSN Routing Area Update
– Inter-SGSN Routing Area Update
Periodic Routing Area updates are applicable
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 32
3.5. Interworking with GSM services (1/3)
• GPRS can interwork with GSM services through Gsinterface
• If no Gs interface exists:
• Type of the location update procedure is indicated
by the network in the response message to MS
• Effects on different MS classes if Gs does not exist:
• A-class mobiles must use conventional GSM
services via normal GSM channels
• B-class mobiles won’t get simultaneous support
from the network. Depending on MS design
• MS can try listen both paging channels
•
•
simultaneously by themselves
MS does IMSI detach and use only GPRS service
No effect on C-class mobiles as simultaneous
services are not supported
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 33
3.5. Interworking with GSM services (2/3)
Combined GPRS and IMSI attach
• To save radio resources
• MS indicates its request for combined attach
• MS sends combined GPRS and IMSI attach to SGSN
• SGSN may authenticate the MS
• SGSN informs MSC/VLR about the new MS
Combined Location and Routing Area update
• To save radio resources
• MS indicates its request for combined update
• This is done when both Location Area and Routing Area
changes at the same time
• Combined Location and Routing Area update is not done if
MS has CS connection
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 34
3.5. Interworking with GSM services (3/3)
Paging CS services via GPRS network
• MSC/VLR gets MT call or SMS
In VLR, presence of SGSN address tells that the MS is
in GPRS attached state
• MSC/VLR sends the paging request to SGSN address
(not to BSC)
SGSN checks the location of MS (identified by IMSI)
• SGSN pages the MS via GPRS channels indicating “CS
page” status
• MS replies to the page using normal GSM channels
•
•
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 35
4. Special issues
4.1. SMS
4.2. Charging
4.3. O&M
4.4. Supplementary services
4.5. Quality of Service
4.6. Performance
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 36
4.1 Special issues: SMS support
MO and MT SMSs can be carried via GPRS network
HLR stores and returns two SS7 addresses to GMSC:
• SGSN address
• MSC/VLR address
Primary route:
• Via SGSN, if available
Secondary route:
• Via MSC/VLR, if available and primary failed
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 37
4.2 Special issues:
GPRS charging of PTP (1/2)
SGSN gathers charging:
• usage of radio resources (packets, bits)
• usage of packet data protocols (time)
• usage of general GPRS resources
• e.g. signaling messages, GPRS backbone
GGSN gathers charging :
• based on destination/source of data packets
• usage of external data networks (packets, bits)
• usage of general GPRS resources
Operator selects what information is used for billing
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 38
4.2 Special issues:
GPRS charging of PTM (2/2)
SGSN gathers usage of:
• usage of radio resources
•
• amount of data
• geographical areas
• number of repetition
usage of general GPRS resources
PTM Service Center gathers charging :
• usage of general GPRS resource
• usage of PTM-G groups
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 39
4.3 Special issues:
Operation and management
GSM related parts can be handled with Q3
GPRS backbone network is based on IP network
• IP network uses Simple Network Management
Protocol (SNMP)
GPRS/GSM OMC
BTS
BSC
Inter-operator's GPRS
backbone management
Packet
Inter-operator
network
backbone
network
SGSN
GPRS
backbone
network
(IP based)
IP
ROUTER
Operator B's GPRS
backbone management
GGSN
Operator A's GPRS
backbone management
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 40
Data network
management
Data
Packet
network
network
(Internet)
4.4 Special issues:
Supplementary services
Most of the conventional GSM supplementary services
are not applicable for GPRS
• E.g., Call forwarding when busy, Calling line
identification, Call waiting
Some supplementary services may be applicable
• Advice of charge (can be difficult to realize)
• Closed user group (can be implemented as part of
external data network)
GPRS has its own supplementary services
• Barring of GPRS Interworking Profile(s)
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 41
4.5 Quality of Service
• Precedence class (1,2,3)
• Delay class (1-4)
• Reliability class
• Peak throughput class; and
• Mean throughput class.
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 42
4.5.1 Reliability Class
• Data reliability is defined in terms of the residual error
rates for the following cases (see GSM 02.60):
• Probability of data loss
• Probability of data delivered out of sequence
• Probability of duplicate data delivery
• Probability of corrupted data
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 43
4.5.2 Throughput classes
Peak Throughput Class
1
2
3
4
5
6
7
8
9
Mean Throughput Class
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 44
Peak Throughput in octets per second
Up to 1 000 (8 kbit/s).
Up to 2 000 (16 kbit/s).
Up to 4 000 (32 kbit/s).
Up to 8 000 (64 kbit/s).
Up to 16 000 (128 kbit/s).
Up to 32 000 (256 kbit/s).
Up to 64 000 (512 kbit/s).
Up to 128 000 (1 024 kbit/s).
Up to 256 000 (2 048 kbit/s).
Mean Throughput in octets per hour
Best effort.
100 (~0.22 bit/s).
200 (~0.44 bit/s).
500 (~1.11 bit/s).
1 000 (~2.2 bit/s).
2 000 (~4.4 bit/s).
5 000 (~11.1 bit/s).
10 000 (~22 bit/s).
20 000 (~44 bit/s).
50 000 (~111 bit/s).
100 000 (~0.22 kbit/s).
200 000 (~0.44 kbit/s).
500 000 (~1.11 kbit/s).
1 000 000 (~2.2 kbit/s).
2 000 000 (~4.4 kbit/s).
5 000 000 (~11.1 kbit/s).
10 000 000 (~22 kbit/s).
20 000 000 (~44 kbit/s).
50 000 000 (~111 kbit/s).
4.6 Performance 1/3
Example
• SGSN that handles 2 Mbps up and downlink traffic
– Average packet size 500 octets (4000 bits)
– => Each packet must be processed totally every 1 milliseconds
• IP stack in backbone
• possible UDP (de)fragmentation, IP checksums
• GTP header processing, finding the right context
• possible paging of the MS
• compression in SNDCP level, possible segmentation
• LLC CRC, LLC acknowledges, LLC timers
• handle GPRS ciphering/deciphering
• BSSGP protocol
• Frame relay protocol
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 45
4.6 Performance 2/3
Example continued
• Background tasks
– Ensuring the QoS for every mobile
• Scheduling pending packets to time horizon
• Rescheduling everything after MS has changed the cell
– Handling charging data collection
– Performance monitoring
– Handle SGSN operating system, task switching, etc.
– Handle diagnostics of the network element
• If SGSN handles 65 Mbps, instead of 2 Mbps?
– => SGSN has just about 30 micro seconds to do all
above
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 46
4.6 Performance 3/3
Solution to the example
• Each network element has limited capacity (x
packets/second)
• If operator needs more capacity (e.g. 50x)
– use 50 parallel boxes
– for example,
• every GGSN boxes are really independent of each other
• each SGSN handles its own area (list of cells)
• Capacity grows linearly but complexity in each box
remains the same
• Reliability? Configuration?
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 47
5. GPRS Business View
5.1. What must be invested to get GPRS up and running?
5.2. How to launch GPRS with minimised incremental cost
5.3. How to make money with GPRS?
5.4. Users' benefits of GPRS
5.5. Business model
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 48
5.1 What must be invested to get GPRS
up and running?
• Updates on existing network elements
– BTS, BSC, MSC/HLR, O&M, billing system, network
planning
• New network elements
– Totally new network for GPRS backbone, based on IP
– New packet network nodes
– A lot of Internet "stuff" (routers, DNS servers, firewalls, …)
• Totally new skills needed
– "Internet way" of thinking
• New mobiles and new type of users
• New type of business thinking
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 49
5.2 How to launch GPRS with minimised
incremental cost
• A single SGSN/GGSN combined functional unit
• BTSs support basic GPRS services with software
update only, BSCs need HW upgrade to add connection
to SGSN
• Use existing paging and control channels for GPRS
• Limit the number of radio channels available for GPRS
• Gs interface can be deleted => no MSC developments
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 50
5.3. How to make money with
GPRS?
• New users
– More subsribers
• New services
– New ways to get money from users
– New intances to pay instead of the users (e.g. advertisers)
• New applications
– New ways to get money from users
• More data traffic
– More data traffic
– Small payments per packet, but huge number of packets
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 51
5.4. Users' benefits of GPRS
• GPRS Selling arguments:
– Higher capacity Internet access
• Up to 171,2 kbps in theory, 40 kbps in practice
– Quicker access to Internet
• No set up time, Iternet access all the time available
– Lower cost
• Flat rate or volume based billing
– Or no cost
• via anonymous access (somebody else pays the bill)
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 52
5.5. Business model
1/2
• If the users are paying little (or nothing), how does this
make profit to the operator?
– Not the high cost per time but the large number of packets
– Somebody else may pay the bill (e.g. anonymous access)
Example business model
# subscribers
Business users
100000
"Normal" users
1000000
Web surfers
1000000
Computers
100000
Total
2200000
QoS level Monthly Cost/kB Volume/ Monthly Total annual Total data
fee (FIM) FIM
day (FIM) cost/subs cost (MFIM) volume (GB)
High
50
0,02
1000
650
780
36500
Normal
25
0,01
20
31
372
7300
Best effort
50
0
250
50
600
91250
High
50
0,1
20
110
132
730
1884
135780
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 53
5.5. Business model 2/2
Volume calculations
Average data
volume
per day
per hour
per sec
per sec
372
15,5
4,3
34,3
GB/d
GB/h
MB/s
Mbps
Peak hour data
volume
per year
per day
per hour
per sec
per sec
43800
120
30
8,3
66,7
GB/a
GB/d
GB/h
MB/s
Mbps
Number of time
slots needed
6667 TSs
Carrier
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 54
833 Carriers
all data in 4 busy hours
average 10 kbps/TS
6. GPRS Standardization
GPRS Phase 1: Release 97
• Basic set of GPRS functionality
• Optional features
GPRS Phase 2: GPRS for UMTS
• Certain issues defined in stage 1 documents are not
included in the first release of the GPRS standard
• New requirements have been pointed out for UMTS
Standard was approved March/June 1998
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 55
6.1 List of participants
The following companies and organizations have been
participating in GPRS work in last 3 years
Some of the manufacturers, operators and others
participating GPRS standardization:
• Alcatel, BT, CNET, CSELT, Detemobil, Eplus,
Ericsson, France Telecom, IBM, Inmarsat, Lucent,
Mannesmann, Motorola, NEC, Nokia, Nortel/Matra,
Omnipoint, OPI, Philips, SFR, Siemens, Telecom
Finland, Telia, UIC, Vodafone
EU sponsored project team PT8OV to expedite GPRS
standardization
Support of PT12
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 56
6.2 GPRS Specifications
GPRS document structure
Doc.
Title
01.60
Requirements Specification of GPRS
Stage 1
02.60
General GPRS Overview
10.60
GPRS standarsisation status and overview
Stage 2
03.60
03.64
03.61
03.62
General System Description and Newtwork Architecture
Radio Architecture Description
Point to Multipoint – Multicast (very draft)
Point to Multipoint – Group Call (non existing)
New Stage 3
04.60
Radio stage 3: RLC/MAC Radio Protocol
04.61
PTM-M Services (not existing yet)
04.62
PTM-G Services (not existing yet)
04.64
LLC
04.65
SNDCP
07.60
User Interworking
08.18
BSSGP: The Gb Interface
08.16
Gb Network Service
08.14
Gb Layer 1
09.16
Gs Layer 2
09.18
Gs Layer 3
09.60
GPRS Tunnelling Protocol (GTP): Gn & Gp Interface
09.61
External Interworking Networks
NOKIA TELECOMMUNICATIONS
IP TECH SCHOOL seminar / 23.11.1998 / slide 57