gprs
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Abstract
The general packet radio service is being operated by gsm operator’s world wide used to offer services on data access at bandwidths comparable to that of fixed telephone modem which is used for providing fast and inexpensive internet links .
GPRS offers packet based radio services and allow data information to be sent and received across
mobile networks The main benefits of GPRS are that it reserves radio
resources efficiently and sends data when ever user need and also reduces wastage of bandwidth.
ContentsContents
Overview of GSM
What is GPRS? Network Architecture Protocol Stack Air Interface
Page 2
Overview of GSMOverview of GSM Second Generation
Technology Groups Special Mobile Developed by ETSI International wireless
standard Based on the cellular
concept Frequency reuse
implementation Over 480 million
subscribers
Page 3
Introduction to GPRS
F1
F2
F3
F4
F1
F2
F3
F4
F2
F1
F2
N=4 Frequency Reuse Concept
100 200 300 400 5000
GSM
IS-95
IS-136
PDC (Japan)
Analog
Millions of subscribers (Feb 2001)source: EMC
ContentsContents Overview of GSM
What is GPRS? Network Architecture Protocol Stack Air Interface HSCSD, EDGE, and 3G Growth Path
Page 4
Introduction to GPRS
What is GPRS? - Circuit vs What is GPRS? - Circuit vs Packet SwitchPacket Switch
2G technologies are circuit switched
Dial-up type connections A single user occupies a
channel for the entire transmission
Requires time-oriented billing GSM transmissions are bursty Bursty nature favors data
services
Page 5
• GPRS is packet switched technology
• More appropriate for data services
• Continuous flow is not required
• Access is based on demand only
• Several users can be multiplexed
• Billing based on negotiated QoS and usage
Introduction to GPRS
What is GPRS? - Types of What is GPRS? - Types of Data ServicesData Services
Most popular Internet data applications include:
E-mail Web browsing File transfers Real time audio Streaming video
Different services have different throughput requirements
GSM evolution is expected to provide services at throughputs similar to their landline counterparts
Page 6
Introduction to GPRS
ContentsContents Overview of GSM What is GPRS?
Network Architecture SGSN, GGSN GR, PCU Mobile Station
Protocol Stack Air Interface
Page 7
Introduction to GPRS
GPRS Network GPRS Network ArchitectureArchitecture GPRS introduces new entities to support data packet transmissions
New entities are PCU, GSN, Border Gateway, and GPRS register
Page 8
GPRS Network Architecture
ForeignPLMNBG
M S
BSC
DATA-BASESUBSYSTEM
Other SGSNBG
VLR H LRG R
EXTERNALNETW ORKS
BTS
BTS
GSMRADIOSUBSYSTEM
GPRSSUBSYSTEM
PDNGGSNSGSNPCU
AirInterface
GbInterface
GnInterface
GnInterface
GpInterface
GiInterface
GcInterface
GrInterface
GsInterface
AbisInterface
BTS - Base Transceiver StationBSC - Base Station ControllerPCU - Packet Control UnitSGSN - Service GPRS Support NodeGGSN - Gateway GPRS Support NodeBG - Border GatewayHLR - HomeLocation RegisterVLR - Visitor Location RegisterGR - GPRS RegisterPDN- Packet Data Netw ork
Introduction to GPRS
GPRS Network Architecture - GPRS Network Architecture - SGSNSGSN
Serving GPRS support nodeDelivers data packets to
the mobile stationsEach SGSN is assigned to a
specific service areaAllows for very little
change in the BTS and BSC
Page 9
SGSNPCU
BSS
BSS
BSS
SGSNPCU
SGSNPCU
GGSN
• All mobile stations communicate to the SGSN in the area
• Provides authentication
• Handles mobility management
• Introduction of the routing area - RA
• Also responsible for billing over the air interface
Introduction to GPRS
GPRS Network Architecture - GPRS Network Architecture - GGSNGGSN
Gateway GPRS support node Allows the GPRS network to
communicate with external PDNs
Routes all packet data units through the corresponding SGSN
Whereas the SGSNs can change during cell reselections, the GGSN remains the same during an on going packet transaction
Responsible for billing related to connections with external PDNs
Page 10
GGSN
GGSN GGSN
PDNPDN
PLMN
PDN
Introduction to GPRS
GPRSGPRSGPRS standard defines three mobile station
classesClass A supports simultaneous circuit and packet
switched communicationsClass B supports packet and circuit switched
sequentially Currently only Class B mobiles being developed
Class C does not support parallel operationOperates in either packet or circuit mode only
Page 11
Introduction to GPRS
GPRS Network Architecture - GPRS Network Architecture - GSM and GPRSGSM and GPRS
Page 12
GMSC
M S
ForeignPLMNBG
BSC
BSC
Other MSC
DATA-BASESUBSYSTEM
Other SGSNBG
VLRH LRG R
EXTERNALNETW ORKS
BTS
BTS
BTS
GSMRADIOSUBSYSTEM
GSMSW ITCHINGSUBSYSTEM
GPRSSUBSYSTEM
PDN
ISDN
MSCTRAU
GGSNSGSNPCU
AirInterface
AbisInterface
GbInterface
GnInterface
GnInterface
GpInterface
GiInterface
GcInterface
GrInterface
GsInterface
AInterface
BInterface
CInterface
EInterface
DInterface
AbisInterface
AirInterface
PSTNBTS
M S
Introduction to GPRS
ContentsContents What is GPRS? Network Architecture
Protocol Stack OSI/ISO Model GPRS Protocol Stack GTP SNDCP and BSSGP RLC/MAC and LLC
Air Interface
Page 13
Introduction to GPRS
GPRS Protocol Stack - GPRS Protocol Stack - ISO/OSI ModelISO/OSI Model
International Telecommunications Union (ITU) and International Standardization Organization (ISO) developed Open Systems Interconnect (OSI)
Allows for compatibility between different equipment manufacturers
Page 14
Session Layer
Transport Layer
Netw ork Layer
Data Link Layer
PresentationLayer
Physical Layer
ApplicationLayer
1
2
3
4
5
6
7
Session Layer
Transport Layer
Netw ork Layer
Data Link Layer
PresentationLayer
Physical Layer
ApplicationLayer
1
2
3
4
5
6
7
Netw ork Layer
Data Link Layer
Physical Layer
Node A Node B Node C
peer-to-peer protocol
Introduction to GPRS
GPRS Protocol Stack - GPRS Protocol Stack - ISO/OSI ModelISO/OSI Model
Each layer adds its own header to the message
Same layer at destination node removes its corresponding header
Physical layer delivers message from one node to the next
In GSM, layer 1 corresponds to the air interface
GPRS layers fall between OSI layers 2 and 3
Page 15
Node A Node C
Application Layer
Presentation Layer
Session Layer
Transport Layer
Netw ork Layer
Data Link Layer
Physical Layer
234567Info
Info
2
3
4
5
6 7
7 Info
Info
6 7 Info
5 6 7 Info
4 5 6 7 Info
5 4 5 6 7 Info
6 5 4 5 6 7 Info 1
2
3
4
5
6
7
2
3
4
5
67
7Info
Info
67Info
567Info
4567Info
34567Info
234567Info1
2
3
4
5
6
7
Info
Introduction to GPRS
GPRS Protocol StackGPRS Protocol Stack
Page 16
M SBTS
BSC PCU SGSN GGSN
RFL PhysicalLayer
PhysicalLayer
PhysicalLayer
PhysicalLayer
PhysicalLayer
PhysicalLayer
PhysicalLayer
PhysicalLayer
MACNSFR
RLC BSSGP
NSFR
L2
BSSGP IP
LLC UDP
SNDCP GTP
L2
IP
UDP
GTP
RFL
MAC
RLC
LLC
SNDCP
Netw orkLayer
Netw orkLayer
AbisInterface
AirInterface
InternalInterface
GbInterface
GnInterface
OSILayer 1
OSILayer 2
OSILayer 3
Introduction to GPRS
GPRS Protocol Stack - GTPGPRS Protocol Stack - GTP GPRS Tunneling protocol
Allows communication between the GGSN and SGSN Data transfer is done via encapsulation and tunneling GTP header includes such as PDU type, QoS parameters, and
tunnel identifier (TID) TID differentiates PTP from PTM transactions
Page 17
Introduction to GPRS
GTP PDU
N PDUTCP/IPHeader
User Data
Netw ork Layer
GTP Layer
GTPHeader
TID User Data
GPRS Protocol Stack - SNDCP GPRS Protocol Stack - SNDCP & BSSGP& BSSGP
Sub network Dependent Convergence Protocol
Makes GPRS network transparent to the common subscriber regardless of what application is running
Responsible for converting network packet data units into GPRS suitable format Multiplexing of SN packet data units over the LLC layer Segmentation and Desegmentation of SN packets into LLC packets Compression of the IP header information
Page 18
• Base Station Subsystem GPRS Protocol
– Routing between SGSN and PCU
– Provide radio related info for RLC/MAC
– Routing goes via Network Relay
– Transparent transfer of LLC frames
– Convey QoS information
Introduction to GPRS
TCP/IPHeader
User Data
Netw ork Layer
SNDCP Layer
SN-PDUHeader
Com pressed Inform ation TailSN-PDUHeader
Com pressed Inform ation Tail
GPRS Protocol Stack - LLCGPRS Protocol Stack - LLC Logical Link Control
Provides a logical reliable link between MS and SGSN Designed as independent as possible from the radio interface
layers Encapsulation of SNDCP packet data units Detection and recovery of lost LLC packet data units Responsible for acknowledged/unacknowledged operation
Page 19
Introduction to GPRS
Fram eHeader
Radio Blocks
SNDCP Layer
SN-PDUHeader
Compressed Inform ation TailSN-PDUHeader
Compressed Inform ation Tail
FCS
LLC Layer
Fram eHeader
Radio Blocks FCS Fram eHeader
Radio Blocks FCS
GPRS Protocol Stack - RLC / GPRS Protocol Stack - RLC / MACMAC
RLC sublayer Transmission of data blocks across the air interface Retransmission of error data blocks using ARQ
Page 20
• MAC sublayer
– Provides access to a given transmission medium
– Controls access signaling, medium sharing by multiple users
– Release operations over the radio channel
– Access is based on slotted ALOHA
– Performs mapping of RLC blocks onto the GSM physical channels
Introduction to GPRS
PC PCT TRLC
HeaderRLC/MAC Signaling
Inform ationUSF BCS USF BCS
RLC/MACLayer
RLC Data
RLC Data B lock RLC/MAC S ignaling B lock
Fram eHeader Radio Blocks FCS
LLC Layer
Fram eHeader Radio Blocks FCS Fram e
Header Radio Blocks FCS
ContentsContents Network Architecture Protocol Stack
Air Interface GPRS Logical Channels The Master Slave Concept The 52-Multiframe Timing Advance
Mobility Management HSCSD, EDGE, and 3G Growth Path
Page 21
Introduction to GPRS
GPRS Air InterfaceGPRS Air Interface Air interface continues to be
limiting factor in terms of capacity
GPRS shares the same interface with GSM
Recall GSM has 200 kHz and eight TS
GPRS utilizes multiplexing and dynamic channel allocation to use the air interface more efficiently
Some channels can be configured for data traffic and others for voice traffic
Channels are reconfigured accordingly based on demand
Page 22
GPRS Air Interface
Introduction to GPRS
PhysicalLayer
MAC
RLC
RFL
MAC
RLC
MS BSS
RLC - Radio Link ControlM AC - M edium Access ControlRFL - Radio Frequency LinkM S - M obile StationBSS - Base Station Subsystem
GPRS Logical ChannelsGPRS Logical Channels Signaling and traffic channels are also required for GPRS A new family of packet data channels PDCHs has been
defined Some of the existing GSM signaling channels can still be
used for GPRS The GPRS mobile still requires to listen to the GSM
broadcast channel for GPRS channel information
Page 23
Introduction to GPRS
GPRS 52-MultiframeGPRS 52-Multiframe Each radio block is transmitted over 4 TDMA
frames Resource allocation is done in terms of
blocks for both uplink and downlink A 52-Multiframe consists of:
twelve blocks for PDCHs signaling and traffic two timing advance frames two idle frames (for neighbor list and power control) 12 x 4 +2 + 2 = 52 frames
Page 24
0
Block 0 Block 1 Block 2TA
1 2 3 4 5 6 7 8 9 10 11 12 13
Block 3 Block 4 Block 5 I
14 15 16 17 18 19 20 21 22 23 24 25 26
Block 6 Block 7 Block 8TA
27 28 29 30 31 32 33 34 35 36 37 38 39
Block 9 Block 10 Block 11 I
40 41 42 43 44 45 46 47 48 49 50 51
TA - T im ing A lignm ent F ram eI - Id le F ram e
Introduction to GPRS
GPRS 52-MultiframeGPRS 52-Multiframe The PDCHs are mapped and organized into a 52-Multiframe
Page 25
0 1 2 3 4 5 6 7 21 22 23 24 25.5
0 1 2 3 4 49 50 51
0 1 2 3 4 5 6 7 21 22 23 24 25
1 TDM A Frame4.615 ms
26 M ultiframe120 ms
51 M ultiframe235.4 ms
Hyperframe3 h 28 min 53 s 760 ms
0 1 2 3 4 48 49 50
0 1 2 3 4 5 6 7 2043 2044 2045 2046 2047
0 1 2 3 4 5 6 7 46 47 48 49 50
0 1 2 3 4 23 24 25
52 M ultiframe240 ms
51 x 26 Superframe or 26 x 51 Superframe or 25.5 x 52 Superframe6s 120 ms
0 1 2 3 4 5 6 7
Introduction to GPRS
GPRS Timing Advance - GPRS Timing Advance - UplinkUplink
The PTCCH/U is divided into 16 subchannels with eight 52-multiframes
The 16 subchannels can be assigned to 16 different active mobile stations
Every PTCCH/U has a cycle of 1.92 s
Active mobile stations will transmit one access burst with TA=0 to the BTS once per eight 52-multiframes within their subchannel
Based on the PTCCH/U message, the BTS can recalculate the timing advance value Pa
ge 26
0 1
2 3
4 5
6 7
8 9
10 11
12 13
14 15
8 x 52-multiframe = 416 framesTAI = 0 - 15
Introduction to GPRS
GPRS Timing Advance - GPRS Timing Advance - DownlinkDownlink
Each mobile is assigned a timing advance index (TAI) value via the PTCCH/D
The TA message sent on the downlink can convey timing advance information for up to 16 mobile stations
The timing advance message contains the TAI values associated with each mobile station
Since the message requires 4 frames, it is carried within four consecutive TA frames
Page 27
One TA message in 4 normal burstsfor up to 16 MS
0 1
3 4
Introduction to GPRS
ContentsContents Network Architecture Protocol Stack Air Interface
Mobility Management Mobility Management States GPRS Attach
HSCSD, EDGE, and 3G Growth Path
Page 28
Introduction to GPRS
GPRS Mobility Management GPRS Mobility Management StatesStates
Mobility management states apply for both the mobile and the SGSN
Idle: Mobile is powered on but not attached to GPRS
Standby: Mobile is powered on and attached to GPRS. No packet transfer is in progress. Routing area updates are sent as needed.
Ready: The mobile is currently engaged in packet transfer or recently terminated a packet transfer. The Ready state is determined by a timer. No need to page a mobile in Ready state
Page 29
GPRS Mobility Management States for MS
Introduction to GPRS
Idle
Ready
Standby
Ready-TimerExpiry
PDUTransfer
GPRSDetach
GPRSAttach
PDUTransfer
GPRS Attach ProcessGPRS Attach Process Process of registration of the mobile into the GPRS
network Occurs when mobile is first powered on and can occur
afterwards based on network settings Mobile registers directly with the SGSN
Page 30
M S BTS
BSC SGSN
AirInterface
GbInterface
GsInterface
VLRH LRG R
DInterface
Attach Request
Authentication and Ciphering Authentication and Ciphering
Routing Area Update
Location Area Update
Attach Acknow ledged
For GPRS
For GSM
• Information Exchanged
– IMSI or P-TMSI
– TLLI
– RA, LA
– Power class mark
– Type of registration (GSM, GPRS)
– Authentication
– Ciphering
Introduction to GPRS
GPRS PDP Context GPRS PDP Context ActivationActivation
Page 31
M S BTS
BSC SGSN
AirInterface
GbInterface
GnInterface
Request PDP Context Create PDP Context
PDP Context ActivatedPDP Context Granted
GGSN
Message Includes:§ IP Address (Static of Dynamic)§ Access Point-AP(ie yahoo.com)§ QoS§ NSAPI
Message Includes:§ IP Address (Static of Dynamic)§ Access Point-AP(ie yahoo.com)§ QoS§ Tunneling ID (TID)
Message Includes:§ IP Address (Static of Dynamic)§ UPD Protocol Header§ QoS§ Tunneling ID (TID)
Message Includes:§ IP Address (Static of Dynamic)§ Priority Level§ QoS§ Tunneling ID (TID)§ NSAPI§ GGSN Address
• The mobile need to activate a packet data protocol context before it can transmit or receive information
Introduction to GPRS
GPRS Measurements - End-GPRS Measurements - End-to-End Processto-End Process
End-to-end test process is best approach towards measuring performance at the application layer
Client - Server configuration On the uplink, the mobile sends packets over the
GPRS network. A test server measures the performance and reports results back to the mobile
On the downlink, the test server sends packets over the GPRS network. The test mobile measures performance and stores the results
Page 32
Test Server
GPRS Netw ork
GiInterface
M SDrive Test System
Introduction to GPRS
HSCSD, EDGE and 3G HSCSD, EDGE and 3G Growth PathGrowth Path
Page 33
EDGE
SMS, Data (9.6Kbit/s)
UMTS
2 Mbit/s
GPRS
171.2 kbit/s
HSCSD
60 kbit/s
Bandwidth
Technology
384 kbit/s
9.6 kbit/s
1997 1998 1999 2000 2001 2002 2003
Introduction to GPRS
Conclusion An understanding of the above
technology and changes it brings will be a vital for successful deployment of gprs and full realization of benefits to mobile network
Any queries
Thank you
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