2001/10/19 Prof. Huei-Wen Ferng 1 Chapter 3 General Packet Radio Service (GPRS)

2001/10/19 Prof. Huei-Wen Ferng 2 GSM A Brief Introduction

2001/10/19 Prof. Huei-Wen Ferng 3 Architecture

2001/10/19 Prof. Huei-Wen Ferng 4 Components/ Elements Mobile Station (MS) Mobile Station (MS) Base Station Subsystem (BSS) Base Station Subsystem (BSS) Base Transceiver Station (BTS)Base Transceiver Station (BTS) Base Station Controller (BSC)Base Station Controller (BSC) Mobile Switching Center (MSC) Mobile Switching Center (MSC) Four databases Four databases Home Location Register (HLR)Home Location Register (HLR) Visitor Location Register (VLR)Visitor Location Register (VLR) Equipment Identity Register (EIR)Equipment Identity Register (EIR) Authentication Center (AUC)Authentication Center (AUC)

2001/10/19 Prof. Huei-Wen Ferng 5 Standard Interfaces U m :MS-BTS U m :MS-BTS Abis: BTS-BSC Abis: BTS-BSC A-interface: BSC-MSC A-interface: BSC-MSC SIM: SIM: Subscriber Identity Module Subscriber Identity Module

2001/10/19 Prof. Huei-Wen Ferng 6 Physical Channel

2001/10/19 Prof. Huei-Wen Ferng 7 Physical Channel (Cont’d)

2001/10/19 Prof. Huei-Wen Ferng 8 Logical Channel

2001/10/19 Prof. Huei-Wen Ferng 9 Logical Channel (Cont’d) TCH (Traffic Channel) TCH (Traffic Channel) TCH/FTCH/F TCH/HTCH/H Signaling channels Signaling channels BCH (Broadcast CH)->3 CHsBCH (Broadcast CH)->3 CHs CCCH (Common Control CH)->3 CHsCCCH (Common Control CH)->3 CHs DCCH (Dedicated Control CH)->3 CHsDCCH (Dedicated Control CH)->3 CHs

2001/10/19 Prof. Huei-Wen Ferng 10 GSM Data

2001/10/19 Prof. Huei-Wen Ferng 11 Evolution CSD:Circuit-Switched Data CSD:Circuit-Switched Data SMS: Short Message Service SMS: Short Message Service HSCSD: High-Speed CSD HSCSD: High-Speed CSD EDGE: Enhanced Data rate for GSM Evolution EDGE: Enhanced Data rate for GSM Evolution

2001/10/19 Prof. Huei-Wen Ferng 12 Pre-GPRS Systems

2001/10/19 Prof. Huei-Wen Ferng 13 SMS in GSM Two-way non-blocking packet-mode messaging service Two-way non-blocking packet-mode messaging service Allowing non-real-time (NRT) dialog between mobile terminalsAllowing non-real-time (NRT) dialog between mobile terminals Transmission on GSM ’ s signaling channel (e.g., SDCCH) Transmission on GSM ’ s signaling channel (e.g., SDCCH) Up to 160 bytes (PTP/broadcast)Up to 160 bytes (PTP/broadcast) Offered message categories Offered message categories SMS-mobile-terminated PTP (stored intermediately in the SMS service center (SMS-SC))SMS-mobile-terminated PTP (stored intermediately in the SMS service center (SMS-SC)) SMS-mobile-originated PTPSMS-mobile-originated PTP Cell broadcast SMSCell broadcast SMS

2001/10/19 Prof. Huei-Wen Ferng 14 HSCSD Aggregation of multiple slots in a GSM frame Aggregation of multiple slots in a GSM frame Speed ranges from 14.4 kbps to 64 KbpsSpeed ranges from 14.4 kbps to 64 Kbps Using the existing GSM infrastructure Using the existing GSM infrastructure Affects to GSM Affects to GSM Channel allocationChannel allocation Connection setupConnection setup Handoff proceduresHandoff procedures Access to the fixed networkAccess to the fixed network

2001/10/19 Prof. Huei-Wen Ferng 15 GPRS

2001/10/19 Prof. Huei-Wen Ferng 16 About GPRS Initiated in 1994 by ETSI Initiated in 1994 by ETSI Services offered: PTP and PTM Services offered: PTP and PTM Systems adopted: GSM and IS-136 Systems adopted: GSM and IS-136 Speed Speed Single slot->14.4 kbpsSingle slot->14.4 kbps Multiple slot->115.2 kbpsMultiple slot->115.2 kbps Web page browsing and Internet surfing Web page browsing and Internet surfing Channel allocation Channel allocation Fixed/Static or dynamicFixed/Static or dynamic

2001/10/19 Prof. Huei-Wen Ferng 17 GPRS Network Architecture

2001/10/19 Prof. Huei-Wen Ferng 18 Elements-SGSN Serving GPRS Support Node (SGSN) Serving GPRS Support Node (SGSN) Functions similar to MSC/VLRFunctions similar to MSC/VLR Monitors user locationMonitors user location Handles charging dataHandles charging data Provides security via A5 ciphering algorithmProvides security via A5 ciphering algorithm Manages sessions, mobility, and logical channelsManages sessions, mobility, and logical channels QoS management: policing and schedulingQoS management: policing and scheduling Network access controlNetwork access control

2001/10/19 Prof. Huei-Wen Ferng 19 Elements-GGSN Gateway GSN (GGSN) Gateway GSN (GGSN) Inter-works GPRS network with external packet-switched networksInter-works GPRS network with external packet-switched networks Data formattingData formatting Address translationAddress translation Protocol conversionProtocol conversion Routing of packetsRouting of packets Firewall, billing, and packet filteringFirewall, billing, and packet filtering

2001/10/19 Prof. Huei-Wen Ferng 20 GSN GSN includes SGSN and GGSN GSN includes SGSN and GGSN A GPRS network consists of multiple SGSNs but only one GGSN for internetworking A GPRS network consists of multiple SGSNs but only one GGSN for internetworking GTP (GPRS Tunnel Protocol) GTP (GPRS Tunnel Protocol) Communication protocol between two GSNsCommunication protocol between two GSNs User data is encapsulated and tunneled through the IP backbone networkUser data is encapsulated and tunneled through the IP backbone network

2001/10/19 Prof. Huei-Wen Ferng 21 GPRS Coding Schemes Four schemes: CS-1~CS-4 Four schemes: CS-1~CS-4 Convolutional Code Convolutional Code

2001/10/19 Prof. Huei-Wen Ferng 22 GPRS Protocol Stack (Data Trans.)

2001/10/19 Prof. Huei-Wen Ferng 23 Protocol Description Layer 1/ Physical layer Layer 1/ Physical layer PLL (Physical Link sub-Layer)PLL (Physical Link sub-Layer) Data unit framing Data unit framing Data coding Data coding Error detection and correction Error detection and correction RFL (Radio Frequency sub-Layer)RFL (Radio Frequency sub-Layer) Conforms to GSM 05 series recommendations Conforms to GSM 05 series recommendations Performs modulation and demodulation Performs modulation and demodulation Specifies carrier freq., radio channel structures, raw channel data rates, transceiver characteristics, performance requirements Specifies carrier freq., radio channel structures, raw channel data rates, transceiver characteristics, performance requirements

2001/10/19 Prof. Huei-Wen Ferng 24 Protocol Description (Cont’d) Layer 2/ Data link layer Layer 2/ Data link layer LLC (Logical Link Control)LLC (Logical Link Control) Supports PTM transmission Supports PTM transmission Provides secure logical pipe between MS and SGSN Provides secure logical pipe between MS and SGSN RLC (Radio Link Control)/ MAC (Medium Access Control)RLC (Radio Link Control)/ MAC (Medium Access Control) Provides access signaling Provides access signaling Resolves access contentions Resolves access contentions Provides link level ARQ Provides link level ARQ

2001/10/19 Prof. Huei-Wen Ferng 25 Protocol Description (Cont’d) Relay function Relay function In the BSS, relays LLC PDUs between the Um and Gb interfacesIn 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 interfacesIn the SGSN, it relays packet data protocol (PDP) PDUs between the Gb and Gn interfaces

2001/10/19 Prof. Huei-Wen Ferng 26 Protocol Description (Cont’d) SNDCP (Sub-Network-Dependent Convergence Protocol) SNDCP (Sub-Network-Dependent Convergence Protocol) Handles TCP/IP headers and data compressionHandles TCP/IP headers and data compression Deals with multiplexing, encryption, and segmentationDeals with multiplexing, encryption, and segmentation BSSGP (BSS GPRS Protocol) BSSGP (BSS GPRS Protocol) QoSQoS Routing between BSS and SGSNRouting between BSS and SGSN

2001/10/19 Prof. Huei-Wen Ferng 27 GPRS QoS Issues Access delay: 4 classes (Um~Gi) Access delay: 4 classes (Um~Gi) Priority: 3 classes Priority: 3 classes Reliability: 5 classes Reliability: 5 classes Mean throughput: 31 classes Mean throughput: 31 classes Peak throughput: 9 classes (Gi~R) Peak throughput: 9 classes (Gi~R)

2001/10/19 Prof. Huei-Wen Ferng 28 Access Delay

2001/10/19 Prof. Huei-Wen Ferng 29 The Others Priority classes: high, medium, and low Priority classes: high, medium, and low Reliability classes: relates to prob. Of corruption, loss, mis-sequencing, duplication of packets 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) Mean throughput classes: class 1 (0.22bps)~class 30 (111kbps), class 31 (best effort) Peak throughput classes: 8 kbps~2048 kbps Peak throughput classes: 8 kbps~2048 kbps : delay class and mean throughput are used by the SGSN for scheduling and admission control : delay class and mean throughput are used by the SGSN for scheduling and admission control

2001/10/19 Prof. Huei-Wen Ferng 30 MSDRA MAC Protocol MSDRA: Master-Slave Dynamic Rate Access MSDRA: Master-Slave Dynamic Rate Access Channel concept Channel concept PDCH (Packet Data CHannels)PDCH (Packet Data CHannels) Channels are dedicated to packet mode transfer Channels are dedicated to packet mode transfer Uplinks and downlinks are basically used as independent channel resources Uplinks and downlinks are basically used as independent channel resources Further divided into MPDCH (Master PDCH) and SPDCH (Slave PDCH) Further divided into MPDCH (Master PDCH) and SPDCH (Slave PDCH)

2001/10/19 Prof. Huei-Wen Ferng 31 Channel Concept (Cont’d) SPDCHs: the channels on which user data and signaling is transferred SPDCHs: the channels on which user data and signaling is transferred Packet Traffic Channels (PTCHs)Packet Traffic Channels (PTCHs) Dedicated to one MS or a group of MSs used for user data transfer Dedicated to one MS or a group of MSs used for user data transfer Packet-Associated Control Channels (PACCHs)Packet-Associated Control Channels (PACCHs) Transport signaling info related one MS Transport signaling info related one MS Packet Data Broadcast Channels (PDBCHs)Packet Data Broadcast Channels (PDBCHs) Downlink to broadcast user data Downlink to broadcast user data

2001/10/19 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 MPDCHs: accommodate Common Control Channels (CCHs) that carry the signaling information required to initiate packet transfer PRACH (Packet Random Access CH)PRACH (Packet Random Access CH) Uplink to initiate data transfer of the MS Uplink to initiate data transfer of the MS PPCH (Packet Paging CH)PPCH (Packet Paging CH) Downlink to inform MSs about incoming packets Downlink to inform MSs about incoming packets PPRCH (Packet Paging Response CH)PPRCH (Packet Paging Response CH) Uplink to respond to paging Uplink to respond to paging PAGCH (Packet Access Grant CH)PAGCH (Packet Access Grant CH) Downlink to send CH reservation info to an MS Downlink to send CH reservation info to an MS PBCCH (Packet Broadcast Control CH)PBCCH (Packet Broadcast Control CH) Downlink to broadcast all GPRS-specific info. Downlink to broadcast all GPRS-specific info.

2001/10/19 Prof. Huei-Wen Ferng 33 Phases of MAC MAC is based on a slotted ALOHA reservation protocol which has three phases on the uplink MAC is based on a slotted ALOHA reservation protocol which has three phases on the uplink Contention phaseContention phase NotificationNotification TransmissionTransmission Two phases on the downlink Two phases on the downlink NotificationNotification TransferTransfer

2001/10/19 Prof. Huei-Wen Ferng 34 PRACH Performance Analysis RACH and PRACH: slotted ALOHA with retransmission (# of max. retrx.=7) RACH and PRACH: slotted ALOHA with retransmission (# of max. retrx.=7) Assumption Assumption Equal new call arrival ratesEqual new call arrival rates System is memorylessSystem is memoryless Capture effect is consideredCapture effect is considered

2001/10/19 Prof. Huei-Wen Ferng 35 Performance Analysis (Cont’d) For infinite number of users, PDF of interfering packets is Poisson For infinite number of users, PDF of interfering packets is Poisson where G is total access attempts where G is total access attempts Pc(Su|n): the prob of success of a test packet given n interfering packets 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 PC(Su|n)=Pr(Pt>zPn), z is the capture ratio

2001/10/19 Prof. Huei-Wen Ferng 36 Performance Analysis (Cont’d) Pc(Su|n) is given by Pc(Su|n) is given by Pc(Su) is given by Pc(Su) is given by The access throughput is The access throughput is

2001/10/19 Prof. Huei-Wen Ferng 37 Performance Analysis (Cont’d) The prob that a packet will be successfully exactly k transmissions The prob that a packet will be successfully exactly k transmissions Average number of transmissions needed for a successful reception Average number of transmissions needed for a successful reception

2001/10/19 Prof. Huei-Wen Ferng 38 Performance Analysis (Cont’d)

2001/10/19 Prof. Huei-Wen Ferng 39 Channel Allocation for GPRS Packet Data Traffic CH (PDTCH) Packet Data Traffic CH (PDTCH) Packet Common Control CH (PCCCH) Packet Common Control CH (PCCCH) Packet Dedicated Control CH (PDCCH) Packet Dedicated Control CH (PDCCH)

2001/10/19 Prof. Huei-Wen Ferng 40 Allocation Algorithms Fixed resource allocation (FRA) Fixed resource allocation (FRA) Fixed resource allocation with queue capacity (FRAQ) Fixed resource allocation with queue capacity (FRAQ) Dynamic resource allocation (DRA) Dynamic resource allocation (DRA) Dynamic resource allocation with queue capacity (DRAQ) Dynamic resource allocation with queue capacity (DRAQ)

2001/10/19 Prof. Huei-Wen Ferng 41 EGPRS (EDGE) Initiated in 1997 Initiated in 1997 Using the GPRS core network but a new air interface with 8 coding schemes Using the GPRS core network but a new air interface with 8 coding schemes 8-PSK modulation 8-PSK modulation Max data rate: 384 kbps Max data rate: 384 kbps

2001/10/19 Prof. Huei-Wen Ferng 42

2001/10/19 Prof. Huei-Wen Ferng 43 References Book: Wireless Personal Communications Systems by D. J. Goodman 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: 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: 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. Paper: Channel allocation for GPRS by Phone Lin et al.