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2G Cellular Networks


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2G Cellular Networks

  1. 1. Second Generation Dr Alison Griffiths Room C203 - Tel: 3292 [email_address] Original Credit to J Champion
  2. 2. MCCS – 2nd Gen <ul><li>Contents </li></ul><ul><ul><li>Why was this needed </li></ul></ul><ul><ul><li>GSM </li></ul></ul><ul><ul><li>Technology </li></ul></ul>
  3. 3. MCCS – 2nd Gen <ul><li>Why was 2G needed </li></ul><ul><ul><li>The number of phones & users increased </li></ul></ul><ul><ul><ul><li>The user base which was originally mostly business related started to change to include other groups </li></ul></ul></ul><ul><ul><ul><ul><li>This increased the number of users which were on the networks </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Became a supply and demand problem </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>If current providers could not provide for the demand users would move away from the technology. </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>As the user base increased in size users in peak areas would find that they could not connect to the network </li></ul></ul></ul></ul>
  4. 4. MCCS – 2nd Gen <ul><li>Second Generation (2G) Technology </li></ul><ul><ul><li>Mobile phones became popular and requirements changed </li></ul></ul><ul><ul><ul><li>Users wanted more from the phones </li></ul></ul></ul><ul><ul><ul><ul><li>The frequency for the phones to use was limited and better use of this frequency was required </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Guarantee that a call was possible when needed </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Privacy was needed as the phones may be used for business or personal conversations. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>The phones needed to be smaller for ease of carrying </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Improved battery life </li></ul></ul></ul></ul>
  5. 5. MCCS – 2nd Gen <ul><li>Global System for Mobile Communications (GSM) </li></ul><ul><ul><li>1982 the European Commission requested that 900 MHz be reserved for the use of GSM </li></ul></ul><ul><ul><ul><li>Before the use of TACS and NMT !!!! </li></ul></ul></ul><ul><ul><li>1989 ETSI defined the standard which was GSM </li></ul></ul><ul><ul><ul><li>Originally called “Groupe Spéciale Mobile” later changed to English </li></ul></ul></ul>
  6. 6. MCCS – 2nd Generation World <ul><li>There was a recognition of the problems with 1G and compatibility issues </li></ul><ul><ul><li>To deal with this 2 approaches were taken </li></ul></ul><ul><ul><ul><li>Force adoption of a standard </li></ul></ul></ul><ul><ul><ul><ul><li>European Commission decided that all member countries should use one system GSM </li></ul></ul></ul></ul><ul><ul><ul><li>Market forces dictating </li></ul></ul></ul><ul><ul><ul><ul><li>United States of America adopted this approach </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>In the US the 2G system had to use the same spectrum as 1G </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>AMPS – became DAMPS – Digital AMPS </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Code division Multiple access (CDMA) (also know as IS-95) was introduced </li></ul></ul></ul></ul></ul>
  7. 7. MCCS – 2nd Generation World <ul><li>In Japan </li></ul><ul><ul><li>Personal Digital Cellular </li></ul></ul><ul><ul><li>Introduced by NTT Do Como </li></ul></ul><ul><ul><li>Operating in 800 and 1500 MHz band </li></ul></ul><ul><ul><li>NTT Do Como introduced i-mode to the world with PDC </li></ul></ul>
  8. 8. MCCS – 2nd Generation World <ul><li>GSM due to its standards based approach </li></ul><ul><ul><li>Now dominates the cellular market </li></ul></ul><ul><ul><li>73% of all mobile phones operate on the GSM standards </li></ul></ul><ul><ul><ul><li>Over 1 Billion users </li></ul></ul></ul><ul><ul><ul><ul><li> </li></ul></ul></ul></ul><ul><ul><ul><li>In some countries there are now more phones than people </li></ul></ul></ul><ul><ul><ul><ul><li>Users having more than one phone for each of there roles </li></ul></ul></ul></ul><ul><ul><ul><ul><li> </li></ul></ul></ul></ul>
  9. 9. MCCS – 2nd Generation World Taken from the report at GSM world for quarter 2, 2004
  10. 10. MCCS – 2nd Gen <ul><li>GSM Services </li></ul><ul><ul><li>Intended primarily as a voice service </li></ul></ul><ul><ul><ul><li>Although now we can see the benefit of data, the increasing use of voice calls was the issue addressed by this standard </li></ul></ul></ul><ul><ul><ul><li>GSM does support some limited data services </li></ul></ul></ul><ul><ul><li>Three services are offered by GSM </li></ul></ul><ul><ul><ul><li>Teleservices </li></ul></ul></ul><ul><ul><ul><li>Bearer Services </li></ul></ul></ul><ul><ul><ul><li>Supplementary Service </li></ul></ul></ul>
  11. 11. MCCS – GSM <ul><li>Teleservices </li></ul><ul><ul><li>Telephony </li></ul></ul><ul><ul><ul><li>Codecs for voice and data </li></ul></ul></ul><ul><ul><ul><li>Encryption of voice data </li></ul></ul></ul><ul><ul><li>Emergency Calls </li></ul></ul><ul><ul><ul><li>These calls must have the highest priority </li></ul></ul></ul><ul><ul><ul><li>Directing you to the nearest connection point </li></ul></ul></ul><ul><ul><li>Voice Mail </li></ul></ul><ul><ul><li>Fax Mail </li></ul></ul><ul><ul><li>Facsimile Group 3 </li></ul></ul><ul><ul><li>Short Messaging Service (SMS) </li></ul></ul><ul><ul><ul><li>Including the SMS – Cell Broadcast (SMS-CB) </li></ul></ul></ul>
  12. 12. MCCS – GSM <ul><li>Bearer Services </li></ul><ul><ul><li>Bearer services are for the transport of data </li></ul></ul><ul><ul><ul><li>9600 bits per second maximum </li></ul></ul></ul><ul><ul><ul><ul><li>Synchronous and asynchronous </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Alternate data and speech </li></ul></ul></ul></ul><ul><ul><ul><li>Transparent </li></ul></ul></ul><ul><ul><ul><ul><li>Fixed delay in data transfer </li></ul></ul></ul></ul><ul><ul><ul><ul><li>No guarantees of data integrity </li></ul></ul></ul></ul><ul><ul><ul><li>Non transparent </li></ul></ul></ul><ul><ul><ul><ul><li>Variable Delay </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Guaranteed data integrity via Automatic repeat request (ARQ) </li></ul></ul></ul></ul>
  13. 13. MCCS – GSM <ul><li>Supplementary Services </li></ul><ul><ul><li>User Identification </li></ul></ul><ul><ul><li>Call Redirection </li></ul></ul><ul><ul><li>Call Hold </li></ul></ul><ul><ul><li>Advice of Charge </li></ul></ul><ul><ul><li>Call Barring </li></ul></ul><ul><ul><li>Call Forwarding </li></ul></ul><ul><ul><li>Multiparty calls </li></ul></ul>
  14. 14. MCCS – 2nd Gen <ul><li>GSM Operates </li></ul><ul><ul><li>Using Time Division Multiplex Access (TDMA) & FDMA </li></ul></ul><ul><ul><ul><li>This allow the frequency to be broken up into slots </li></ul></ul></ul><ul><ul><ul><ul><li>The frequencies used are GSM 900 , GSM 1800 and GSM 1900 </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Separate frequencies are used for the uplink and downlink </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>890-915MHz uplink, 935-960MHz downlink for example </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Uplink and Downlink are 45 MHz apart </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>200KHz spacing on the frequency </li></ul></ul></ul></ul><ul><ul><ul><ul><li>124 pairs of channels </li></ul></ul></ul></ul><ul><ul><ul><ul><li>These channels are then divided into 8 time slices </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>For GSM each slice is 0.577 ms </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>Total channels available is 8 * 124 = 992 (in a theoretical context) </li></ul></ul></ul></ul><ul><ul><ul><li>This means that there is eight times the capacity as before in one part of the frequency </li></ul></ul></ul><ul><ul><ul><ul><li>Assuming the same rate is used </li></ul></ul></ul></ul>
  15. 15. MCCS – 2nd Gen <ul><li>TDMA </li></ul>Frequency Time Frequencies 890 MHz - 960 MHz – Europe 1710 – 1880 MHz - Europe 1850 MHz – 1950 MHz - America
  16. 16. MCCS – 2nd Gen <ul><li>GSM Operates </li></ul><ul><ul><li>One of the features which allowed the increase in the number of users is digitisation of voice </li></ul></ul><ul><ul><ul><li>The voice is sampled using a (analogue to Digital Converter) ADC </li></ul></ul></ul><ul><ul><ul><ul><li>8KHz / second, with an 8 bit result </li></ul></ul></ul></ul><ul><ul><ul><li>The voice information is then transferred using one of these methods </li></ul></ul></ul><ul><ul><ul><ul><li>Enhanced Full Rate </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Best quality speech </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Uses a full slot </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Marginal increase in processor overhead </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>Full Rate </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Improved speech quality </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Takes a full slot to transfer </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>Half Rate </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>This mode allows for a doubling of capacity to a base station </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Loss in speech quality, but not significant </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Half a slot to transfer </li></ul></ul></ul></ul></ul>
  17. 17. MCCS – 2nd Gen <ul><li>Digitisation </li></ul><ul><ul><li>Of voice allows for a number of features </li></ul></ul><ul><ul><ul><li>Takes less bandwidth to transfer the voice </li></ul></ul></ul><ul><ul><ul><li>The data once digital </li></ul></ul></ul><ul><ul><ul><ul><li>Can be encrypted </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Can be recovered even with the attenuation effects </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Additional bits can be added to allow for errors within transport </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Without the need for retransmission – Forward Error Checking (FEC) </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>The digital voice data can then be place inside of a packet for transport </li></ul></ul></ul></ul>
  18. 18. <ul><li>Time Division Multiple Access (TDMA) </li></ul><ul><ul><li>Guard Time: Interval between bursts used to avoid overlapping </li></ul></ul><ul><ul><li>Preamble: First part of the burst </li></ul></ul><ul><ul><li>Message: Part of burst that includes user data </li></ul></ul><ul><ul><li>Postamble: Last part of burst – used to initialise following burst </li></ul></ul>Slot 1 Slot 2 Slot 8 Slot 8 Slot 1 Frame 1 Frame N Multiframe Guard Time Preamble Message Postamble Guard Time Slot Slot i …… .. GSM System – Multiple Access
  19. 19. MCCS – 2nd Gen - SIM <ul><li>Subscriber Identity Module (SIM) Card </li></ul><ul><ul><li>Essential for the GSM network </li></ul></ul><ul><ul><li>The SIM is located within the Mobile station (MS) </li></ul></ul><ul><ul><ul><li>Basically the phone handset you use </li></ul></ul></ul><ul><ul><li>Contains </li></ul></ul><ul><ul><ul><li>Subscriber Authentication key </li></ul></ul></ul><ul><ul><ul><ul><li>128 bit encryption key </li></ul></ul></ul></ul><ul><ul><ul><li>International Mobile Subscriber Identity (IMSI) </li></ul></ul></ul><ul><ul><ul><ul><li>A unique international none dialable number which is attached to your device </li></ul></ul></ul></ul><ul><ul><ul><li>Temporary Mobile Subscriber Identity </li></ul></ul></ul><ul><ul><ul><li>Mobile Station Integrated Service Digital Network (MSISDN) </li></ul></ul></ul><ul><ul><ul><ul><li>Basically this is YOUR phone number </li></ul></ul></ul></ul><ul><ul><ul><li>PIN to secure the card </li></ul></ul></ul><ul><ul><ul><li>SMS messages </li></ul></ul></ul><ul><ul><ul><li>Personal data, phone numbers, Phone settings etc </li></ul></ul></ul>
  20. 20. MCCS – 2nd Gen <ul><li>SIM continued </li></ul><ul><ul><li>Each one is unique </li></ul></ul><ul><ul><ul><li>e-commerce </li></ul></ul></ul><ul><ul><ul><ul><li>Purchasing items from your phone, with certainty that your device bought the item </li></ul></ul></ul></ul><ul><ul><ul><li>Authentication encryption is used called the A3/A8 </li></ul></ul></ul><ul><ul><ul><ul><li>This is used to authenticate your device using challenge/response </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>A random number is sent </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>The A3/A8 algorithm then works on the number and returns a 32-bit response. </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>If this matches the one which the network has calculated the device is authenticated </li></ul></ul></ul></ul></ul><ul><ul><ul><li>A5 Encryption is used for the voice calls </li></ul></ul></ul><ul><ul><ul><li>Virgin Cola, has a vending machine where you pay via the phone </li></ul></ul></ul><ul><ul><ul><ul><li>(, 2000) </li></ul></ul></ul></ul>
  21. 21. MCCS – Location <ul><li>GSM consists of three major systems: </li></ul><ul><ul><ul><li>Base-Station System (BSS) </li></ul></ul></ul><ul><ul><ul><li>Network Switiching Sub-System (NSS) </li></ul></ul></ul><ul><ul><ul><li>Operation and Support System (OSS) </li></ul></ul></ul><ul><ul><li>The Switching System performs call processing and subscriber related functions </li></ul></ul><ul><ul><li>The system contains the following functional units </li></ul></ul><ul><ul><ul><li>Home Location Register (HLR) </li></ul></ul></ul><ul><ul><ul><li>Mobile Switching Center (MSC) </li></ul></ul></ul><ul><ul><ul><li>Visitor Location Register (VLR) </li></ul></ul></ul><ul><ul><ul><li>Authentication Center (AUC) </li></ul></ul></ul><ul><ul><ul><li>Equipment Identity Register (EIR) </li></ul></ul></ul>
  22. 22. MCCS – BSS <ul><li>Base Station System (BSS) </li></ul><ul><ul><li>This is the part of the network which connects the MS to the network via the radio interface </li></ul></ul><ul><ul><ul><li>Base Station (BS) </li></ul></ul></ul><ul><ul><ul><ul><li>Know as (Base Transceiver Station(BTS) ) in official GSM documentation </li></ul></ul></ul></ul><ul><ul><ul><ul><li>This is the radio transceiver the area of transmission is referred to as the cell </li></ul></ul></ul></ul>BS Theory BS Reality Transmission distance
  23. 23. MCCS – 2nd Gen <ul><li>Base station controller </li></ul><ul><ul><li>This node takes overall control of a number of base stations a point of control for the BS </li></ul></ul><ul><ul><ul><li>Other functionality </li></ul></ul></ul><ul><ul><ul><ul><li>Traffic concentration </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Switching operations </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Data based and voice </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>Network management to all BS attached </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Radio channel management for all BS attached </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Conversion of air interface rates to network applicable rates </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>13 Kbps to 64 Kbps </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>Handover control </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>This is for base stations which it has control of </li></ul></ul></ul></ul></ul>
  24. 24. MCCS – BSS <ul><li>Base station Controller </li></ul>Base Station Controller BS BS BS BS
  25. 25. MCCS – GSM - NSS <ul><li>Network Switching Sub-System (NSS) </li></ul><ul><ul><li>Responsible for the transfer of information from the handsets to the correct part of the infrastructure </li></ul></ul><ul><ul><li>Functions </li></ul></ul><ul><ul><ul><li>Handovers between BSC’s </li></ul></ul></ul><ul><ul><ul><li>Allow communication between mobile and PSTN networks </li></ul></ul></ul><ul><ul><ul><li>Allows for roaming between networks </li></ul></ul></ul><ul><ul><ul><li>A number of nodes are a part of the NSS </li></ul></ul></ul>
  26. 26. MCCS – GSM - NSS <ul><li>NSS nodes consist of </li></ul><ul><ul><li>Mobile Switching Centre (MSC) </li></ul></ul><ul><ul><li>Home Location Register (HLR) </li></ul></ul><ul><ul><li>Visitor Location Centre (VLR) </li></ul></ul><ul><ul><li>Authentication Centre (AuC) </li></ul></ul><ul><ul><li>Equipment Identity Register (EIR) </li></ul></ul>
  27. 27. MCCS – GSM - NSS <ul><li>HLR is the most important database </li></ul><ul><ul><li>Storage and management of subscriptions </li></ul></ul><ul><ul><li>Permanent data includes: </li></ul></ul><ul><ul><ul><li>Subscriber's service profile </li></ul></ul></ul><ul><ul><ul><li>Subscriber's location information </li></ul></ul></ul><ul><ul><ul><li>Subscriber‘s activity status </li></ul></ul></ul><ul><ul><li>Subscribing to a particular provider‘s service registers you in the HLR of that provider </li></ul></ul><ul><li>The MSC performs the telephony switching functions of the network </li></ul><ul><ul><li>Controls call to and from other telephone and data systems </li></ul></ul><ul><ul><ul><li>Also performs functions such as </li></ul></ul></ul><ul><ul><ul><ul><li>Toll ticketing </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Network interfacing </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Common Channel signalling </li></ul></ul></ul></ul>
  28. 28. MCCS – GSM - NSS <ul><li>VLR contains data on visiting (roaming) subscribers </li></ul><ul><ul><li>Integrated with the MSC </li></ul></ul><ul><ul><li>When a roamer enters the service area the VLR queries the appropriate HLR </li></ul></ul><ul><ul><li>If a roamer makes a call the VLR will already have the information it needs for call setup </li></ul></ul><ul><li>The AUC verifies the identity of the user and ensures and ensures the confidentiality of each call </li></ul><ul><ul><li>By provide authenticity and encryption parameters for every call </li></ul></ul><ul><ul><li>Protects network operators from fraud </li></ul></ul><ul><ul><li>Assures a certain level of security for the content of each call </li></ul></ul><ul><li>The EIR is a database that includes info solely about the identity mobile equipment </li></ul><ul><ul><li>Prevents calls from stolen, unauthorised or defective mobile devices </li></ul></ul><ul><ul><ul><li>Since 2002 all UK based operators have shared the contents of the EIR database </li></ul></ul></ul><ul><ul><ul><li>This is also true for countries which have roaming agreements with UK operators </li></ul></ul></ul><ul><ul><ul><li>If a phone is stolen anywhere in the world, it can now be registered as stolen and traced within 24 hours </li></ul></ul></ul>
  29. 29. MCCS – GSM - OSS <ul><li>Operation and Support System </li></ul><ul><ul><li>This part of the network allows monitoring of the network </li></ul></ul><ul><ul><li>Ensures the smooth running and involves management tasks </li></ul></ul><ul><ul><ul><li>Accounting and Billing </li></ul></ul></ul><ul><ul><ul><li>Status Reports </li></ul></ul></ul><ul><ul><ul><li>Traffic monitoring </li></ul></ul></ul><ul><ul><ul><li>In addition if a BSC can not carry out all of its tasks the OSS will take control of the BSC’s tasks </li></ul></ul></ul><ul><ul><li>The OSS is logically connected to all equipment in the infrastructure </li></ul></ul>
  30. 30. MCCS – 2nd Gen <ul><li>GSM Infrastructure </li></ul><ul><ul><li>The specifications created by ETSI do not require any of the following infrastructure but recommends it ! </li></ul></ul><ul><ul><ul><li>All mobile operators have it </li></ul></ul></ul>VLR MSC VLR MSC HLR MSC Mobile Switching Center VLR Visitor Location Register HLR Home Location Register OSS AUC
  31. 31. MCCS – GSM Roaming <ul><li>At the moment what we have discussed is a single company using a single infrastructure </li></ul><ul><ul><li>The issue of incompatible systems has been discussed as a problems for 1G </li></ul></ul><ul><ul><ul><li>By a large majority of companies using the same technology the availability to communicate across the infrastructures can be achieved </li></ul></ul></ul><ul><ul><ul><ul><li>This is a similar concept to how the Internet operates </li></ul></ul></ul></ul><ul><ul><ul><li>This is referred to as “GSM Roaming” </li></ul></ul></ul><ul><ul><ul><ul><li>A full list of countries that allow roaming with companies and other countries listed </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li> </li></ul></ul></ul></ul></ul>
  32. 32. MCCS – GSM Roaming <ul><li>In theory you can take your phone and use it abroad </li></ul><ul><ul><li>In reality you may need a tri-band phone </li></ul></ul><ul><ul><ul><li>This is a phone which can receive and send on all of the frequencies which are used by GSM worldwide </li></ul></ul></ul><ul><ul><li>You can not just connect to another GSM network </li></ul></ul><ul><ul><ul><li>There has to be a roaming agreement between your operator and the one you wish to connect to </li></ul></ul></ul>
  33. 33. MCCS – GSM Roaming <ul><li>When you turn on your phone abroad </li></ul><ul><ul><li>Your HLR of your operator will be informed where the device is located </li></ul></ul><ul><ul><li>The device itself will be attached to the VLR of the operator whom you are connected </li></ul></ul><ul><ul><ul><li>Your device will be given </li></ul></ul></ul><ul><ul><ul><ul><li>Mobile Station Roaming Number </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>This is a unique number – a virtual number </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Any calls then made to your number will be forwarded to you virtual number </li></ul></ul></ul></ul></ul>
  34. 34. MCCS – GSM Roaming <ul><li>The operator of the VLR </li></ul><ul><ul><li>Will request information from your HLR </li></ul></ul><ul><ul><ul><li>Information like </li></ul></ul></ul><ul><ul><ul><ul><li>Is the device allowed to roam </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Confirmation you are allowed to connect to the network </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Subscriber information </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Services which the handset can provide </li></ul></ul></ul></ul>
  35. 35. MCCS – GSM Roaming VLR MSC VLR MSC HLR MSC Mobile Switching Center VLR Visitor Location Register HLR Home Location Register AUC AUC
  36. 36. MCCS – GSM Roaming <ul><li>All calls then to your number will be directed using SS7 </li></ul><ul><ul><li>These calls will be direct to the device anywhere on the planet </li></ul></ul><ul><ul><li>The HLR of your operator, where the call will go first will have your current location for re-direction </li></ul></ul><ul><ul><ul><li>All of this will take place transparently without user intervention </li></ul></ul></ul>
  37. 37. MCCS – GSM <ul><li>The infrastructure which has been discussed </li></ul><ul><ul><li>Is ever expanding </li></ul></ul><ul><ul><li>As new functionality is required this is built into the infrastructure </li></ul></ul><ul><ul><ul><li>This gives GSM the ability to remain future proof without large investment in new infrastructure when new technology becomes available </li></ul></ul></ul><ul><ul><ul><li>This will be seen more in the future lectures when we can see that new technology uses GSM as a basis and essential part </li></ul></ul></ul><ul><ul><ul><ul><li>Even for 3G/4G communications </li></ul></ul></ul></ul>
  38. 38. MCCS – 2nd Gen <ul><li>Summary </li></ul><ul><ul><li>2G GSM Communications </li></ul></ul><ul><ul><ul><li>Physical Transmissions </li></ul></ul></ul><ul><ul><ul><li>GSM Infrastructure </li></ul></ul></ul><ul><ul><ul><li>Roaming Agreements </li></ul></ul></ul>