1. Shourya Roy Pradeep Bhatt Gururaja K.
An Overview of GPRS
Shourya Roy
Pradeep Bhatt
Gururaja K.

2. What is GPRS?
A new bearer service for GSM that greatly improves and simplifies wireless access to packet data networks,e.g to the internet.

3. Motivation Speed Immediacy New and better applications
User friendly billing

4. GSM Architecture PSTN PDN ISDN GMSC BSC BTS MS MSC BTS BSC EIR MS AUC
HLR
BTS MS
VLR

5. GPRS Architecture Other GPRS PLMN Gp GGSN Gn SGSN Gb Gf BSC Gr Gs Gi
BTS Gc
GGSN
PDN
EIR D
BTS
HLR MS
MSC/VLR

6. Protocol Architechture
Transmission Plane
GPRS specifies a tunnel mechanism to transfer user data packets .
Signalling Plane
GTP specifies a tunnel control management protocol.The signalling is used to create modify and delete tunnels.

7. Registration of a Mobile Node
A mobile station must register itself with GPRS network.
GPRS attach
GPRS detach
GPRS detach can be initiated by the MS or the network.

8. Session Management
After Successful attach a MS gets one or more Packet Data Protocol(PDP) address.This address is unique only for a particular session.
It consists of,
PDP type
PDP address assigned to MS
Requested QoS
Address of the corresponding GGSN

9. Session Management(Contd.)
PDP-Address allocation:
Static:Assigned by network operator of User’s home PLMN.
Dynamic:Assigned by Corresponding GGSN.

10. PDP Context Activation
MS SGSN GGSN
Activate PDP Context Request
PDP type,PDP Address
QoS Requested,Access Point,…
Security Functions
Create PDP Context Request
PDP type,PDP Address
QoS Negotiated,Access Point,…
Create PDP Context Response
Activate PDP Context Accept
PDP type,QoS Negotiated,…
PDP type,PDP Address
QoS Negotiated,…

11. Packet Data Network(PDN)
Routing
BSC
BTS
BSC
BTS
SGSN
SGSN MS
Inter-PLMN
GPRS Backbone Gn
Intra-PLMN
GPRS Backbone Gp
Intra-PLMN
GPRS Backbone
PLMN1
PLMN2
Border
Gateway Gn
Border Gateway Gn
GGSN
SGSN
Packet Data Network(PDN)
Eg.Internet,Intranet Gi
GGSN
Router
Host
LAN

12. Location Management
MS frequently sends location update messages to inform the SGSN where it is.
Determining frequency of update messages is non-trivial.
The location update frequency is dependent on the state of the MS.

13. Location Management(Contd.)
A MS can be in 3 states:
IDLE
READY
STANDBY

14. Protocol Architechture
Transmission Plane
The protocols provide transmission of user data and its associated signalling
Signalling Plane
Comprises protocols for the control and support of functions of the transmission plane

15. Transmission Plane GPRS Backbone:SGSN GGSN
GTP tunnels the user packets and related signalling information between the GPRS support nodes.
Subnetwork dependent convergence protocol
It is used to transfer packets between SGSN and MS
Data link layer
LLC(MS-SGSN)
RLC/MAC(MS-BSS)
Physical layer
PLL:channel coding,detection of errors, forward error correction, interleaving, detection of physical link congestion
RFL:modulation and demodulation

16. Transmission Plane Gi Network Layer (IP or X.25) Relay SNDCP GTP GTP
LLC TCP/UDP
TCP/UDP
Relay
RLC BSSP
BSSGP IP IP
MAC Network
Service
Network Data Link
Service Service
Data Link
Layer
PLL
RFL Phy Layer
Phy Layer Phy Layer
Phy layer Gm Gb
BSS
SGSN
GGSN Gi
RLC :Radio link control BSSGP:BSS GPRS Application protocol
PLL :Physical link layer GTP :GPRS tunneling protocol
RFL :Physical RF layer TCP :Transmission control protocol
MAC:Medium access control UDP :user datagram protocol
IP :Internet Protocol
Transmission Plane

17. SNDCP:Subnetwork dependent convergence protocol MS
BSS
Application
Network Layer
SNDCP
LLC
RLC
Relay
RLC BSSGP
MAC
MAC Network
Service
PLL
RFL
PLL
PHY
RFL Layer Um
SNDCP:Subnetwork dependent convergence protocol
LLC :Logical link control
RLC :Radio link control

18. SGSN BSS MS GMM/SM GMM/SM LLC Application LLC Relay RLC BSSGP BSSGP
MAC
Network
layer
MAC Network service
GSM/RF
GSM RF Physical layer
Phy Layer Um Gb
GMM/SM:GPRS Mobilty Management and session Management Protocol
GSM/RF:GSM physical layer(radio interface) I.e.PLL and RFL
Signalling Plane:MSSGSN

19. SGSN
MSC/VLR
BSSAP
BSSAP
SCCP
SCCP
MTP3
MTP3
MTP2
MTP2
Phy Layer
Phy Layer Gs
Signalling Plane SGSN
MSC/VLR

20. Signalling Plane SGSNHLR/SGSNEIR
HLR(and EIR)
MAP
MAP
TCAP
TCAP
SCCP
SCCP
MTP3
MTP3
MTP2
MTP2
Phy Layer
Phy Layer Gr
MAP :Mobile Application Part
TCAP :Transaction capabilities and application part
SCCP :Signalling connection control part
MTP :Message transfer part
Signalling Plane SGSNHLR/SGSNEIR

21. GSM TDMA Frame Slots and Bursts
960 MHz
959.8 MHz
124
Time Slot
123
. . .
200 KHz
. . .
Downlink 1 2 3 4 5 6 7 1 8 2
TDMA Frame
935.2 MHz 1
935 MHz
915 MHz
Data Burst = bit periods
914.8 MHz
124
123
. . .
200 KHz
. . . 1 2 3 4 5 6 7 1 8
Uplink 2
TDMA Frame
890.2 MHz 1
890 MHz

22. GPRS Air Inteface Uplink Downlink Time Slot Number Carrier Frequency1 1 2 2 3 3 4 4 5 5 6 6 7 7 1 1 2 2 3 3 4 4 F1
Uplink F2 F3 F4
Carrier
Frequency 1 1 2 2 3 3 4 4 5 5 6 6 7 7 1 1 2 2 3 3 4 4 F1 F2
Downlink F3 F4
Voice User1
GPRS User1
GPRS User3
Voice User2
GPRS User2

23. GPRS Air Interface Master slave concept Capacity on demand
One PDCH acts as Master
Master holds all PCCCH channels
The rest of channels act as Slaves
Capacity on demand
PDCH(s) are increased or decreased according to demand
Load supervision is done in MAC Layer

24. GPRS Logical Channels Group Channel Function Direction Packet data
Traffic channel
PDTCH
Data Traffic
MS BSS
Packet broadcast
control channel
PBCCH
Broadcast Control
MS BSS
PRACH
Random Access
MS BSS
Packet common
Control Channel
(PCCCH)
PAGCH
Access Grant
MS BSS
PPCH
Paging
MS BSS
PNCH
Notification
MS BSS
PACCH
Associated Control
MS BSS
Packet Dedicated
Control Channels
PTCCH
Timing Advance Control
MS BSS

25. Uplink Data Transfer MS BSS Packet channel Request
PRACH or RACH
Packet Immediate assignment
PAGCH or AGCH
Packet resource Request
PACCH
Packet resource assignment
PACCH
Random Access
Frame Transmission
Transmission
PDTCH
Negative Acknowledgement
PACCH
Retransmission of blocks in error
PDTCH
Acknowledgement
PACCH

26. Downlink Data TransferMS
BSS
Packet paging request
PPCH or PCH
Packet channel Request
PRACH or RACH
Packet Immediate assignment
PAGCH or AGCH
Packet paging response
PACCH
Packet resource assignment
PACCH or PAGCH
Paging
Frame Transmission
Transmission
PDTCH
Negative Acknowledgement
PACCH
Retransmission of blocks in error
PDTCH
Acknowledgement
PACCH

27. Multi Slot Operation
GPRS allows a mobile to transmit data in up to 8 PDCHs (eight-slot operation)
3-bit USF at beginning of each radio block in downlink points to next uplink radio block
Comparison with single-slot GSM
Higher delay at higher load
Low blocking rate
Improved Throughput

28. Conclusion GPRS provides efficient access to Packet Data Networks.
Multislot operation in GPRS leads to efficient channel utilization.
GPRS is more effective for long data packet transmission than short ones.

29. References
“General Packet Radio Service in GSM”, Jian Cai and David J. Goodman, Rutgers University, IEEE Communications Magazine, Oct 1997
“Wireless Internet Access based on GPRS”, IEEE Personal Comm. April 2000.