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.
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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
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
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
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
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