1. First and Second Generation
Justin Champion
Room C208 - Tel: 3273

2. PCS – 1G to 2G technology Contents Start of mobile devices TACS GSM
Technlogy

3. 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)

4. PCS – 1G to 2G technology TACS Operated in the 900 MHz range
Works 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”?

5. 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.

6. PCS – 1G to 2G technology
FDMA
Frequency

7. 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

8. 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

9. 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
MHz uplink, MHz 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 ms
This means that there is eight times the capacity as before in one part of the frequency

10. PCS – 1G to 2G technology TDMA Frequencies 890 MHz - 960 MHz – Europe
Time
Frequency
Frequencies
890 MHz MHz – Europe
1710 – 1880 MHz - Europe
1850 MHz – 1950 MHz - America

11. 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 ms
To allow this to happen all voice communications needs to be converted to binary
Synchronisation is required for the use of TDMA

12. GSM System – Multiple Access
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
Multiframe
Frame 1
Frame N
……..
Slot 1
Slot 2
Slot i
Slot 8
Slot 1
Slot 8
Slot
Guard Time
Preamble
Message
Postamble
Guard Time

13. 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

14. 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

15. PCS – 1G to 2G technology Subscriber Identity Module (SIM) Card
Essential for the GSM network
Contains
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

16. 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/ stm, 2000)

17. 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

18. 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

19. PCS – 1G to 2G technology SMS Continued
Example SMS transmission packet saying “Hallo World”
A A70BC82093F9045D9F522611
( 2003)
SMSC = Short Message Service Centre
HLR = Home Location Register
SMSC
GSM SMS Infrastructure
Base
Station
HLR

20. 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

21. 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)

22. GSM System – Location Management
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

23. 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

24. 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
MSC
VLR
HLR
VLR
MSC
MSC Mobile Switching Center
VLR Visitor Location Register
HLR Home Location Register

25. PCS – 1G to 2G technology Summary 1G Communications
2G GSM Communications
Physical Transmissions
SMS Messages
GSM Infrastructure