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

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

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

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

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

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

Physical Channel (Cont’d) 2018/12/7 Prof. Huei-Wen Ferng

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

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

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

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

Pre-GPRS Systems 2018/12/7 Prof. Huei-Wen Ferng

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

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

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

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

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

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

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

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

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

GPRS Protocol Stack (Data Trans.) 2018/12/7 Prof. Huei-Wen Ferng

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

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

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

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

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

Access Delay 2018/12/7 Prof. Huei-Wen Ferng

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

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

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

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

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

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

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

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

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

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

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

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

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

2018/12/7 Prof. Huei-Wen Ferng

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