GPRS.ppt

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


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

• • • • •

• • • • •


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


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


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


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


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


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


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


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

Gi

SGSN Gp

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


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)


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


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

•


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


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

•


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


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

2

MS TX

5

6

7

MS RX

0

1

2

MS TX

5

6

MS RX

0

1

MS TX

5

6

3

4 0

5

6

7

0

1

1 2

3

4

5

6

Monitor

2-slot

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:


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


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


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


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


3.3. Data transfer (2/4) Mobile originated (left when MS in HPLMN, right when in VPLMN, no filtering/screening) BTS

BSC

BSC

SGSN BG HPLMN

Packet Inter-PLMN backbone network network

SGSN BG

Intra-PLMN backbone network (IP based)


GGSN

GGSN Data Packet network network (Internet)

Corporate Server

Router


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



GGSN


Corporate Server

Router


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

SGSN BG HPLMN

SGSN

Packet Inter-PLMN backbone network network

SGSN BG



GGSN


BTS

BSC

Corporate Server

Router


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


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


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


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


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

• •


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


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


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


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


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


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)


4.5 Quality of Service • Precedence class (1,2,3) • Delay class (1-4) • Reliability class • Peak throughput class; and • Mean throughput class.


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


4.5.2 Throughput classes Peak Throughput Class 1 2 3 4 5 6 7 8 9

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 Class 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

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


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


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?


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


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


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


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


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)


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


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


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


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


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


GPRS.ppt

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