1. General Packet Radio Service (GPRS)
Chapter 3
General Packet Radio Service (GPRS)
2018/12/7
Prof. Huei-Wen Ferng

2. GSM
A Brief Introduction
2018/12/7
Prof. Huei-Wen Ferng

3. Architecture
2018/12/7
Prof. Huei-Wen Ferng

4. Components/ Elements Mobile Station (MS) Base Station Subsystem (BSS)
Base Transceiver Station (BTS)
Base Station Controller (BSC)
Mobile Switching Center (MSC)
Four databases
Home Location Register (HLR)
Visitor Location Register (VLR)
Equipment Identity Register (EIR)
Authentication Center (AUC)
2018/12/7
Prof. Huei-Wen Ferng

5. Standard Interfaces Um:MS-BTS Abis: BTS-BSC A-interface: BSC-MSC SIM:
Subscriber Identity Module
2018/12/7
Prof. Huei-Wen Ferng

6. Physical Channel
2018/12/7
Prof. Huei-Wen Ferng

7. Physical Channel (Cont’d)
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Prof. Huei-Wen Ferng

8. Logical Channel
2018/12/7
Prof. Huei-Wen Ferng

9. Logical Channel (Cont’d)
TCH (Traffic Channel)
TCH/F
TCH/H
Signaling channels
BCH (Broadcast CH)->3 CHs
CCCH (Common Control CH)->3 CHs
DCCH (Dedicated Control CH)->3 CHs
2018/12/7
Prof. Huei-Wen Ferng

10. GSM Data
2018/12/7
Prof. Huei-Wen Ferng

11. Evolution CSD:Circuit-Switched Data SMS: Short Message Service
HSCSD: High-Speed CSD
EDGE: Enhanced Data rate for GSM Evolution
2018/12/7
Prof. Huei-Wen Ferng

12. Pre-GPRS Systems
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Prof. Huei-Wen Ferng

13. SMS in GSM Two-way non-blocking packet-mode messaging service
Allowing non-real-time (NRT) dialog between mobile terminals
Transmission on GSM’s signaling channel (e.g., SDCCH)
Up to 160 bytes (PTP/broadcast)
Offered message categories
SMS-mobile-terminated PTP (stored intermediately in the SMS service center (SMS-SC))
SMS-mobile-originated PTP
Cell broadcast SMS
2018/12/7
Prof. Huei-Wen Ferng

14. HSCSD Aggregation of multiple slots in a GSM frame
Speed ranges from 14.4 kbps to 64 Kbps
Using the existing GSM infrastructure
Affects to GSM
Channel allocation
Connection setup
Handoff procedures
Access to the fixed network
2018/12/7
Prof. Huei-Wen Ferng

15. GPRS
2018/12/7
Prof. Huei-Wen Ferng

16. About GPRS Initiated in 1994 by ETSI Services offered: PTP and PTM
Systems adopted: GSM and IS-136
Speed
Single slot->14.4 kbps
Multiple slot->115.2 kbps
Web page browsing and Internet surfing
Channel allocation
Fixed/Static or dynamic
2018/12/7
Prof. Huei-Wen Ferng

17. GPRS Network Architecture
2018/12/7
Prof. Huei-Wen Ferng

18. Elements-SGSN Serving GPRS Support Node (SGSN)
Functions similar to MSC/VLR
Monitors user location
Handles charging data
Provides security via A5 ciphering algorithm
Manages sessions, mobility, and logical channels
QoS management: policing and scheduling
Network access control
2018/12/7
Prof. Huei-Wen Ferng

19. Elements-GGSN Gateway GSN (GGSN)
Inter-works GPRS network with external packet-switched networks
Data formatting
Address translation
Protocol conversion
Routing of packets
Firewall, billing, and packet filtering
2018/12/7
Prof. Huei-Wen Ferng

20. GSN GSN includes SGSN and GGSN
A GPRS network consists of multiple SGSNs but only one GGSN for internetworking
GTP (GPRS Tunnel Protocol)
Communication protocol between two GSNs
User data is encapsulated and tunneled through the IP backbone network
2018/12/7
Prof. Huei-Wen Ferng

21. GPRS Coding Schemes Four schemes: CS-1~CS-4 Convolutional Code
2018/12/7
Prof. Huei-Wen Ferng

22. GPRS Protocol Stack (Data Trans.)
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Prof. Huei-Wen Ferng

23. Protocol Description Layer 1/ Physical layer
PLL (Physical Link sub-Layer)
Data unit framing
Data coding
Error detection and correction
RFL (Radio Frequency sub-Layer)
Conforms to GSM 05 series recommendations
Performs modulation and demodulation
Specifies carrier freq., radio channel structures, raw channel data rates, transceiver characteristics, performance requirements
2018/12/7
Prof. Huei-Wen Ferng

24. Protocol Description (Cont’d)
Layer 2/ Data link layer
LLC (Logical Link Control)
Supports PTM transmission
Provides secure logical pipe between MS and SGSN
RLC (Radio Link Control)/ MAC (Medium Access Control)
Provides access signaling
Resolves access contentions
Provides link level ARQ
2018/12/7
Prof. Huei-Wen Ferng

25. Protocol Description (Cont’d)
Relay function
In the BSS, relays LLC PDUs between the Um and Gb interfaces
In the SGSN, it relays packet data protocol (PDP) PDUs between the Gb and Gn interfaces
2018/12/7
Prof. Huei-Wen Ferng

26. Protocol Description (Cont’d)
SNDCP (Sub-Network-Dependent Convergence Protocol)
Handles TCP/IP headers and data compression
Deals with multiplexing, encryption, and segmentation
BSSGP (BSS GPRS Protocol)
QoS
Routing between BSS and SGSN
2018/12/7
Prof. Huei-Wen Ferng

27. GPRS QoS Issues Access delay: 4 classes (Um~Gi) Priority: 3 classes
Reliability: 5 classes
Mean throughput: 31 classes
Peak throughput: 9 classes (Gi~R)
2018/12/7
Prof. Huei-Wen Ferng

28. Access Delay
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29. The Others Priority classes: high, medium, and low
Reliability classes: relates to prob. Of corruption, loss, mis-sequencing, duplication of packets
Mean throughput classes: class 1 (0.22bps)~class 30 (111kbps), class 31 (best effort)
Peak throughput classes: 8 kbps~2048 kbps
<Remark>: delay class and mean throughput are used by the SGSN for scheduling and admission control
2018/12/7
Prof. Huei-Wen Ferng

30. MSDRA MAC Protocol MSDRA: Master-Slave Dynamic Rate Access
Channel concept
PDCH (Packet Data CHannels)
Channels are dedicated to packet mode transfer
Uplinks and downlinks are basically used as independent channel resources
Further divided into MPDCH (Master PDCH) and SPDCH (Slave PDCH)
2018/12/7
Prof. Huei-Wen Ferng

31. Channel Concept (Cont’d)
SPDCHs: the channels on which user data and signaling is transferred
Packet Traffic Channels (PTCHs)
Dedicated to one MS or a group of MSs used for user data transfer
Packet-Associated Control Channels (PACCHs)
Transport signaling info related one MS
Packet Data Broadcast Channels (PDBCHs)
Downlink to broadcast user data
2018/12/7
Prof. Huei-Wen Ferng

32. Channel Concept (Cont’d)
MPDCHs: accommodate Common Control Channels (CCHs) that carry the signaling information required to initiate packet transfer
PRACH (Packet Random Access CH)
Uplink to initiate data transfer of the MS
PPCH (Packet Paging CH)
Downlink to inform MSs about incoming packets
PPRCH (Packet Paging Response CH)
Uplink to respond to paging
PAGCH (Packet Access Grant CH)
Downlink to send CH reservation info to an MS
PBCCH (Packet Broadcast Control CH)
Downlink to broadcast all GPRS-specific info.
2018/12/7
Prof. Huei-Wen Ferng

33. Phases of MAC
MAC is based on a slotted ALOHA reservation protocol which has three phases on the uplink
Contention phase
Notification
Transmission
Two phases on the downlink
Transfer
2018/12/7
Prof. Huei-Wen Ferng

34. PRACH Performance Analysis
RACH and PRACH: slotted ALOHA with retransmission (# of max. retrx.=7)
Assumption
Equal new call arrival rates
System is memoryless
Capture effect is considered
2018/12/7
Prof. Huei-Wen Ferng

35. Performance Analysis (Cont’d)
For infinite number of users, PDF of interfering packets is Poisson
where G is total access attempts
Pc(Su|n): the prob of success of a test packet given n interfering packets
PC(Su|n)=Pr(Pt>zPn), z is the capture ratio
2018/12/7
Prof. Huei-Wen Ferng

36. Performance Analysis (Cont’d)
Pc(Su|n) is given by
Pc(Su) is given by
The access throughput is
2018/12/7
Prof. Huei-Wen Ferng

37. Performance Analysis (Cont’d)
The prob that a packet will be successfully exactly k transmissions
Average number of transmissions needed for a successful reception
2018/12/7
Prof. Huei-Wen Ferng

38. Performance Analysis (Cont’d)
2018/12/7
Prof. Huei-Wen Ferng

39. Channel Allocation for GPRS
Packet Data Traffic CH (PDTCH)
Packet Common Control CH (PCCCH)
Packet Dedicated Control CH (PDCCH)
2018/12/7
Prof. Huei-Wen Ferng

40. Allocation Algorithms
Fixed resource allocation (FRA)
Fixed resource allocation with queue capacity (FRAQ)
Dynamic resource allocation (DRA)
Dynamic resource allocation with queue capacity (DRAQ)
2018/12/7
Prof. Huei-Wen Ferng

41. EGPRS (EDGE) Initiated in 1997
Using the GPRS core network but a new air interface with 8 coding schemes
8-PSK modulation
Max data rate: 384 kbps
2018/12/7
Prof. Huei-Wen Ferng

42. 2018/12/7
Prof. Huei-Wen Ferng

43. References
Book: Wireless Personal Communications Systems by D. J. Goodman
Paper: GPRS-features and packet random access channel performance analysis by A. Gyasi-Agyei et al.
Paper: Concepts, services, and protocols of new GSM phase 2+ General Packet Radio Service by G. Brasche et al.
Paper: Channel allocation for GPRS by Phone Lin et al.
2018/12/7
Prof. Huei-Wen Ferng