Introduction to GSM - an Overview of Global System for Mobile Communication

ALTHOSSimpl if ying Know l edge(t m)

Introduction to GSM

This slideshow describes the basic components, technologies used, and operation of Global System for Mobile Communication - GSM -

systems. You will discover the evolution of GSM; 1st generation analog systems, 2nd generation GSM systems (digital voice), 3rd generation multimedia, and 4th generation wideband ultra broadband systems.


Introduction to GSM © Althos, 2009-2013 page 2

Introduction to GSM

Lawrence [email protected]:

www.linkedin.com/in/lharte/

Lawrence Harte is a mobile communication expert who has developed, designed, and managed many types of communication products and services since 1985.

Mr. Harte is the publisher and editor of Mobile Video magazine and author of over 112 books with over 53 on wireless communication. As a magazine editor, he has interviewed over 2100 companies in the mobile communication industry to discover the key issues and solutions of the wireless industry.

Mr. Harte has worked for Ericsson/General Electric, Audiovox/Toshiba and Westinghouse and has consulted for hundreds of other companies. He is the inventor of several patents on communication technology.

Mr. Harte Holds many degrees and certificates including an Executive MBA and a BSET.



GSM Topics

Global System for Mobile Communication GSM Services GSM Products (Mobile Devices) GSM Radio Technology Digital Audio and Baseband Radio Channels Logical Channels GSM Network GSM System Operation GSM Evolution



What is GSM?

Mobile Communication System

Digital Media Formats

Functional Sections- Mobile Stations (MS)- Base Station Subsystem (BSS)- Network and Switching System (NSS)



GSM Services

Voice Services - Circuit Switched Data Services - Low to Medium Speed Short Messaging Services - Location Multicast Service

- Group Call - Voice Broadcast

Packet Data - Internet Browsing



GSM Devices

Subscriber Identity Module (SIM)

Mobile Telephones PCMCIA Air Cards Embedded Radio

Modules External Radio Modems



Subscriber Identity Module (SIM)

Holds User Identification Data

Microprocessor Memory Software



GSM Radio Technology

Frequency Reuse Time Division

Multiple Access (TDMA)

RF Power Control



Digital Audio and Baseband

Analog to Digital Conversion Digital Speech Compression Channel Coding



Analog to Digital Conversion

Voice Coding- 13 kbps Full Rate- 6.5 kbps Half Rate



Digital Speech Compression

Analyze Voice

Use Code Book to Identify Human Sounds



Channel Coding

Error Protection- CRC- Block- Convolutional

Signaling Commands- Fast- Slow

Time Slot Allocation



Echo Cancellation

Audio Analysis Time Shifting Echo Modeling

- delay- amplitude

Signal Subtraction



GSM Radio Channels

Radio Channel Structure

Time Slot Structure Frame Structure Dynamic Time

Alignment

A GSM radio channel is a 200 kHz communications channel that transfer digital information from a source to a destination. The GSM radio channel is

divided into time slots and frames to allow multiple communication paths (logical channels) to share a single radio transmission channel.



Radio Channel Structure

200 kHz RF Channel Bandwidth

Frequency Duplex Channels- Downlink- Uplink

Time Offset



Time Slot Structure

Normal Burst Random Access Burst (Shortened Burst) Frequency Correction Burst Synchronization Burst



Frame Structure

GSM Frame- 4.615 msec

Multiframes- Traffic- Control

Superframes



Logical Channels

Traffic Channels - User Data Control Channels - Signaling

- Broadcast - System Information- Common Control - Paging and Access- Dedicated Control - On an Assigned Channel

The GSM system divides up the RF communications channel into logical channels that serve different purposes. Traffic channels carry user data (voice

and data). Control channel transport signaling messages.



Traffic Channels

Full Rate (TCH/F) Half Rate (TCH/H) Eighth Rate (TCH/8)



Control Channels

Beacon (Broadcast) Channels (BCH) Common Control Channels (CCCH) Dedicated Control Chanels



GSM Network

Base Stations Repeaters Switching Centers Network Databases Wireless Network

System Interconnection



Base Stations

Radio Antenna Towers

Radio Equipment- Transmitters- Combiners- Multicouplers- Receivers- Controllers

Communication Links Power Supplies



GSM Switching Systems

Mobile Switching Center (MSC)- circuit switching

Packet Nodes (SGSN)- packet data



Network Databases

Home Location Register (HLR)- Registered with Operator

Visitor Location Register (VLR)- Operating in System (including home subscribers)

Equipment Identity Register (EIR)- Identifies Stolen Equipment

Authentication Center (AuC)- Security Validation

SMS Center (SMSC)- Message Reception and Routing

Group Call Register (GCR)- Dispatch Type Services



GSM System Operation

Mobile Telephone Initialization

Updating Location Waiting for Calls (Idle) Cell Reselection System Access Mobile Call Origination Mobile Assisted Handoff

Transferring Calls Between Call Sites

Receiving a Call on a Mobile Telephone

Conversation Mode Connected Mode Authentication



System Access

Randomly Attempt Access

Receive RF Channel and Time Slot Assignment



Mobile Call Origination

Request Access- random attempts

Assign Traffic Channel- frequency- time slot

Setup Audio Connection

Open Audio Path- hear ringing



Receiving a Call

Send Page Alert Message to Last Known Mobile Location- start ringing

Mobile Request Access

Assign Traffic Channel

Open Audio Path



Mobile Assisted Handoff (MAHO)

Signal Quality Fall Below Allowable Level

System Sends List of Channels for Mobile to Monitor

Mobile Periodically Returns Measurements



GSM Evolution

General Packet Radio Service (GPRS) Enhanced Data for Global Evolution (EDGE) Wideband Code Division Multiple Access (WCDMA) UMTS Long Term Evolution (UMTS LTE)



Wireless Resources

Wireless Dictionary (17,000+ Definitions) – www.WirelessDictionary.com

Intro to GSM Book (by Lawrence Harte) – http://www.althosbooks.com/intogsm.html - Also Available from Amazon and Barnes & Noble

Mobile Video Magazine – www.mVideoMagazine.com

Wireless Trade Shows - http://www.mvideomagazine.com/events.asp

More Detailed GSM Tutorial (with notes):

http://www.tvdictionary.com/tutorial/gsm-tutorial-title-slide.html



Summary

GSM Continues to Evolve over Time

GSM - Worldwide Mobile Wireless System Can Provide, Voice, Messaging, and Data Services Many Types of Mobile Devices - Voice, Data Only 200 kHz Digital RF Channel - 8 Slots per Frame Mix of Logical Channels - Traffic and Control GSM Network - Base Stations, Switches, and Databases Evolved into GPRS, EDGE, WCDMA, UMTS LTE

Introduction to GSM - an Overview of Global System for Mobile Communication

Documents

visitor location

home location

embedded radio

external radio

mobile assisted

radio coverage

continuously

rf communications