General Packet Radio Service (GPRS)

Mobile Computing and Broadband Networking Laboratory

CIS, NCTU

Outline Introduction GSM System Circuit-Switch Packet-Switch GPRS Compare GPRS with GSM The functions of SGSN and GGSN The future of GPRS Conclusions

Introduction Internet is developed rapidly and includes more

and more information in recent years Peoples’ activity areas are not limited Cell phones are more convenient There are plenty of powerful information in the

Internet Using the mobility of the cell phone and those

valuable information in the Internet

GSM System

GSM System Voice communication Using Short Message Service (SMS) to transmit

data Using Circuit-Switch Disadvantages:

The transmit speed is too slow (9.6 Kbps or 14.4 Kbps) No support of multimedia data: audio and video Low efficiency for bandwidth Too expensive to support multimedia services

Circuit-Switch

Packet-Switch

Burstiness comparison

GPRS (General Packed Radio Service)

GPRS (cont.) Advantages

High bit rates 4 code schemes (9.05Kbps ~ 21.4Kbps) 8 channels (171.2Kbps)

Using packet-switching and is more suitable for bursty traffic

Fast call setup time (always connected) Coexistence with GSM systems Using radio resource and network more flexible Counting the fees by the amount of data An important step to 3G

GPRS (cont.) GPRS provides two types of services:

PTP (Point-To-Point) Connectionless: IP Connection-oriented: X.25

PTM (Point-To-Multipoint) Multicast Service (PTM-M) Group Call Service (PTM-G)

Compare GPRS with GSM High-speed circuit-switch data (HSCSD)

Giving a single user simultaneous access to multiple channels

The highest speed is up to 115.2 Kbps

Enhanced Data for GSM Evolution (EDGE) Eight-phase-shift (8 PSK) modulation Every time slot can support up to 48 Kbps The highest speed is up to 384 Kbps 40 times of GSM and 3 times of GPRS

Data Services Comparison

The Architecture of GSM

The Architecture of GPRS (cont.)

The Functions of SGSN and GGSN

Serving GPRS Support Node (SGSN) Admission control Mobility management Receiving and delivering the packets Address translation and mapping Encapsulation

Gateway GPRS Support Node (GGSN) The interface between GPRS network and packet

data network

Protocol Architecture

Protocol Architecture (cont.) Physical layer:

RFL (Physical RF Layer) – modulation/demodulation PLL (Physical Link Layer) – error

control、 congestion detect

Data link layer: MAC (Medium Access Control) – slotted ALOHA RLC (Radio Link Control) – error correction LLC (Logical Link Control) – always connected

Protocol Architecture (cont.) GPRS supports interworking of MSs with X.25-, I

P-based networks by encapsulation and decapsulation

Between SGSN and MS, further encapsulation is performed by SNDCP (SubNetwork-Dependent Convergence Protocols) including: multiplexing、 compression、 segmentati

on The MAC is derived from a slotted reservation AL

OHA protocol, and operate between MS and BTS

Three Kinds of Routing Examples

Applications of GPRS

The Future of GPRS

The Future of GPRS (cont.)

Conclusions GPRS is economical for the operators It is more popular in Europe People demand more mobile data access Its data rate is limited by the availability of

time slots The development of cell phones is slow The problem of junk mails

Reference A.A Samjani, “General Packet Radio Service (GPRS),”

IEEE Potentials, Volume: 21, April-May 2002. Internet Network Communication (Chinese), June 2001. www.3g-generation.com/gprs_and _edge.htm Michael Clever, “Mass Market Solution for Mobile Dat

a,” Telecommunications, June 1999. David Tade, “Evolving Wireless System: Choosing a

Migration Path,” Telecommunication, February 1999.