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First and Second Generation

First and Second Generation. Justin Champion Room C208 - Tel: 3273 www.staffs.ac.uk/personel/engineering_and_technology/jjc1. PCS – 1G to 2G technology. Contents Start of mobile devices TACS GSM Technlogy. PCS – 1G to 2G technology. History

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First and Second Generation

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  1. First and Second Generation Justin Champion Room C208 - Tel: 3273 www.staffs.ac.uk/personel/engineering_and_technology/jjc1

  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 • 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

  10. PCS – 1G to 2G technology • TDMA Time Frequency Frequencies 890 MHz - 960 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 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

  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/986334.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

  19. GSM SMS Infrastructure Base Station Base Station SMSC HLR 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 Centre HLR = Home Location Register

  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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