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First and Second Generation

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Presentation on theme: "First and Second Generation"— Presentation transcript:

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

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

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 ( 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

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