First and Second Generation

Justin Champion

Room C208 - Tel: 3273www.staffs.ac.uk/personel/engineering_and_technology/jjc1

PCS – 1G to 2G technology

ContentsStart of mobile devicesTACSGSMTechnlogy

PCS – 1G to 2G technology History

Earliest Wireless Communications was Morse Code Then came radio Now we are able to carry our personal radios in the form of

mobile devices First Generation mobile devices

Based on Analogue communications First started in the UK in Jan 1985, with BT Cellnet & Vodafone

Transmission in the UK and Italy was called Total Access Cellular System (TACS) and was based on an American design (AMPS)

Germany adopted C-Net France adopted Nordic Mobile Telephone (NMT)

PCS – 1G to 2G technology TACS

Operated in the 900 MHz rangeWorks by the use of multiplex the traffic by the

use of Frequency Division Multiple Access (FDMA)

The signal from these devices was not secure Anyone could listen into them, remember the “Squidgy

Tapes”?

PCS – 1G to 2G technology FDMA

Breaks up the available frequency into 30 KHz channels Allocates a single channel to each phone call The channel is agreed with the Base station before transmission

takes place on agreed and reserved channel The device can then transmit and receive on this channel

No other device can share this channel even if the person is not talking at the time!

The voice/sound is transmitted as analogue data, which means that a large than required channel has to be allocated.

PCS – 1G to 2G technology

FDMA Frequency

PCS – 1G to 2G technology Second Generation (2G) Technology

Mobile phones became popular and requirements changed

Users wanted more from the phones The frequency for the phones to use was limited and better

use of this frequency was required Guarantee that a call was possible when needed Privacy was needed as the phones may be used for business

or personal conversations. The phones needed to be smaller for ease of carrying Improved battery life

PCS – 1G to 2G technology Global System for Mobile Communications

(GSM)1982 the European Commission requested that

900 MHz be reserved for the use of GSM Before the use of TACS and NMT !!!!

1989 ETSI defined the standard which was GSM Originally called “Groupe Spéciale Mobile” later

changed to English

PCS – 1G to 2G technology GSM Operates

Using Time Division Multiplex Access (TDMA) This allow the frequency to be broken up into slots

The frequencies used are GSM 900 , GSM 1800 and GSM 1900 Separate frequencies are used for the uplink and downlink

890-915MHz uplink, 935-960MHz downlink for example 200KHz spacing on the frequency 124 channels per frequency band

These slots are then divided into time slices For GSM each slice is 0.577 ms

This means that there is eight times the capacity as before in one part of the frequency

PCS – 1G to 2G technology

TDMA

Frequency

Time

Frequencies890 MHz - 960 MHz – Europe1710 – 1880 MHz - Europe1850 MHz – 1950 MHz - America

PCS – 1G to 2G technology GSM Operates

Using Time Division Multiplex Access (TDMA) This allow the frequency to be broken up into slots These slots are then divided into time slices

For GSM each slice is 0.577 ms

To allow this to happen all voice communications needs to be converted to binary

Synchronisation is required for the use of TDMA

Time Division Multiple Access (TDMA)

Guard Time: Interval between bursts used to avoid overlapping Preamble: First part of the burst Message: Part of burst that includes user data Postamble: Last part of burst – used to initialise following burst

Slot 1 Slot 2 Slot 8 Slot 8Slot 1

Frame 1 Frame N

Multiframe

Guard Time Preamble Message Postamble Guard Time

Slot

Slot i ……..

GSM System – Multiple Access

PCS – 1G to 2G technology GSM Operates

Using Time Division Multiplex Access (TDMA)The voice is sampled using a ADC

8KHz / second, with an 8 bit result

PCS – 1G to 2G technology GSM Features

Uses encryption to make phone calls more secure Data networking Group III facsimile services

9600 bps transmission speed Short Message Service (SMS) for text messages and

paging Call forwarding Caller ID Call waiting Multi-party conferencing

PCS – 1G to 2G technology Subscriber Identity Module (SIM) Card

Essential for the GSM networkContains

Subscriber Authentication key 128 bit encryption key

International Mobile Subscriber Identity Temporary Mobile Subscriber Identity Mobile Station International Service Digital Network PIN to secure the card SMS messages Personal data, phone numbers, Phone settings etc

PCS – 1G to 2G technology SIM continued

Each one is unique e-commerce

Purchasing items from your phone, with certainty that your device bought the item

Authentication encryption is used called the A3/A8 This is used to authenticate your device

A random number is sent The A3/A8 algorithm then works on the number and returns a 32-

bit response. If this matches the one which the network has calculated the

device is authenticated A5 Encryption is used for the voice calls Virgin Cola, has a vending machine where you pay via the phone

(news.bbc.co.uk/1/hi/sci/tech/986334.stm, 2000)

PCS – 1G to 2G technology Short Message Service (SMS)

Also known as “Simple message service” ETSI standard for SMS is detailed in “GSM 03.40” Intended to allow user to replace pagers with GSM devices Allows the transmission of 160 Characters 7 bit characters

using a western alphabet The character numbers are reduce for other alphabets

Extremely successful This was never expected or planned for 1985 Vodafone in the UK was the first use of the system

PCS – 1G to 2G technology SMS Continued

Transfers the SMS message in a single packet Octet = 8 Bytes

SCA Service Centre Address

MR Message Reference PID Protocol Identifier

PDU Type Protocol Data Unit Type

DA Destination Address DCS Data Coding Scheme

VP Validity Period UDL User Data Length UD User Data

PCS – 1G to 2G technology

SMS Continued Example SMS transmission packet saying “Hallo World”

018011000A8143372890550000A70BC82093F9045D9F522611(www.spallared.com/nokia/smspdu/smspdu.htm#_Toc485435709, 2003)

SMSC = Short Message Service CentreHLR = Home Location Register

SMSC

GSM SMS InfrastructureBaseStation

BaseStation

HLR

PCS – 1G to 2G technology

SMS Continued SMS is not delay sensitive It is best effort to deliver the message The HLR for the device is requested to see if it is turned on If the device is turned off the SMSC will store the message for a period of

time This time can be defined in the PDU in the VP section or more commonly the

SMSC has a defined period to store messages for. When the device is turned on again the HLR is informed and this then

requests the SMS message from the SMSC

GSM System – Location Management GSM consists of three major systems:

The Switching System (SS) Base-station System (BSS) Operation and Support System (OSS)

The Switching System performs call processing and subscriber related functions The system contains the following functional units

Home Location Register (HLR) Mobile Switching Center (MSC) Visitor Location Register (VLR) Authentication Center (AUC) Equipment Identity Register (EIR)

HLR is the most important database Storage and management of subscriptions Permanent data includes:

Subscribers‘s service profile Subscribers‘s location information Subscriber‘s activity status

Subscribing to a particular provider‘s service registers you in the HLR of that provider

The MSC performs the telephony switching functions of the network Controlls call to and from other telephone and data systems Also performs functions such as

Toll ticketing Network interfacing Common Channel signalling

GSM System – Location Management

VLR contains data on visiting (roaming) subscribers Integrated with the MSC When a roamer enters the service area the VLR queries the appropriate HLR If a roamer makes a call the VLR will already have the information it needs for call setup

The AUC verifies the identity of the user and ensures and ensures the confidentiality of each call By provide authenticity and encryption parameters for every call Protects network operators from fraud Assures a certain level of security for the content of each call

The EIR is a database that includes info solely about the identity mobile equipment Prevents calls from stolen, unauthorised or defective mobile devices

GSM System – Location Management

PCS – 1G to 2G technology

GSM Infrastructure The specifications created by ETSI do not require any of the

following infrastructure but recommends it ! All mobile operators have it

VLRMSC

VLR MSC

HLR

MSC Mobile Switching Center

VLR Visitor Location Register

HLR Home Location Register

PCS – 1G to 2G technology Summary

1G Communications2G GSM Communications

Physical Transmissions SMS Messages GSM Infrastructure