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GSM

GSM. Mohamed Mokdad Ecole d’Ingénieurs de Bienne. Agenda. GSM Architecture, Interface, … Enhancements HSCSD GPRS SIM Architecture Protocoles. Why GSM in 1982?. Good subjective speech quality Low terminal and service cost Support for international roaming

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GSM

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  1. GSM Mohamed Mokdad Ecole d’Ingénieurs de Bienne

  2. Agenda • GSM • Architecture, Interface, … • Enhancements • HSCSD • GPRS • SIM • Architecture • Protocoles

  3. Why GSM in 1982? • Good subjective speech quality • Low terminal and service cost • Support for international roaming • Ability to support handheld terminals • Support for range of new services and facilities • Spectral efficiency • ISDN compatibility

  4. Phased GSM Approach 1 • GSM Phase 1 features • Call Forwarding • All Calls • No Answer • Engaged • Unreachable • Call Barring • Outgoing - Bar certain outgoing calls (e.g. ISD) • Incoming - Bar certain incoming calls (Useful if in another country) • Global roaming - Visit any other country with GSM and a roaming agreement and use your phone and existing number

  5. Phased GSM Approach 2 • GSM Phase 2 features • SMS - Short Message Service - Allows you to send text messages too and from phones • Multi Party Calling - Talk to five other parties as well as yourself at the same time • Call Holding - Place a call on Hold • Call Waiting - Notifies you of another call whilst on a call • Mobile Data Services - Allows handsets to communicate with computers • Mobile Fax Service - Allows handsets to send, retrieve and receive faxes • Calling Line Identity Service - This facility allows you to see the telephone number of the incoming caller on our handset before answering • Advice of Charge - Allows you to keep track of call costs • Cell Broadcast - Allows you to subscribe to local news channels • Mobile Terminating Fax - Another number you are issued with that receives faxes that you can then download to the nearest fax machine.

  6. Phased GSM Approach 3 • GSM Phase 2 + features • Available by 1998 • Upgrade and improvements to existing services • Majority of the upgrade concerns data transmission, including bearer services and packet switched data at 64 kbps and above • DECT access to GSM • PMR/Public Access Mobile Radio (PAMR)-like capabilities • GSM in the local loop • Virtual Private Networks • Packet Radio • SIM enhancements • Premium rate services (e.g. Stock prices sent to your phone)

  7. Requirements Service aspects Technical realization Signalling protocols (user equipment to network) Radio aspects CODECs Data Signalling protocols (RSS-CN) Signalling protocols (intra-fixed-network) Programme management User Identity Module (SIM / USIM) O&M Access requirements and test specifications Requirements Service aspects Technical realization Signalling protocols (user equipment to network) Radio aspects CODECs Data Signalling protocols (RSS-CN) Signalling protocols (intra-fixed-network) Programme management User Identity Module (SIM / USIM) O&M Security aspects Test specifications Security algorithms Requirements Service aspects Technical realization Signalling protocols (user equipment to network) Radio aspects CODECs Data Signalling protocols (RSS-CN) Signalling protocols (intra-fixed-network) Programme management User Identity Module (SIM / USIM) O&M 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 GSM & UMTS numbering

  8. Phased GSM Approach 3 • GSM-R • Future Railway control platform • UMTS • In the context of IMT 2000 families • Releases 4, 5 and 6 • Each release is a complete setand a system can be build on it

  9. GSM Evolution review

  10. Reference Configuration ISDN/PSTN

  11. Cellular System • The geographic area is divided into cells • Each cell has a Base Station managing the communications • A set of cells managed by a single MSC is called Location Area land link MSC VLR HLR land link VLR MSC BaseStation Radio link MSC Mobile Switching Center VLR Visitor Location Register HLR Home Location Register

  12. GSM Architecture PLMN Databases NSS Network and Switching Subsystem EIR Equipment Identity Register AuC Authentication Center GMSC Gateway MSC BSS Base Station System BSC Base Station Controller BTS Base Transceiver Station MS Mobile Station SSP Service Switching Point EIR VLR VLR HLR AuC PSTN MSC MSC GMSC SSP NSS Switches SSP BSC BSS BSS MS BTS Radio Systems

  13. The GSM Interfaces 1 R S Um MT0 BS/MSC TE1 MT1 BS/MSC TE2 TA MT1 BS/MSC TE2 MT2 BS/MSC

  14. The GSM Interfaces 2 + B, C, D, E, F, G, H et I to HLR, VLR, MCS, …

  15. The GSM Interfaces 3

  16. GSM Radio Interface • Spectrum • 900 MHz (and 1800 MHz) • 890-915 MHz Uplink - 935-960 MHz Downlink • FDMA • 124 carriers under 900 MHz • TDMA • 8 Time Slots per carrier • 1 (physical) channel per Time Slot • 1 channel = 1 communication = 15/26 ms

  17. GSM Radio Interface bis 123 0 1 2 3 4 5 6 7 122 0 1 2 3 4 5 6 7 3 0 1 2 3 4 5 6 7 1 0 1 2 3 4 5 6 7 0 0 1 2 3 4 5 6 7

  18. E.g. 2G Mobile telephony Spectrum

  19. Channels: Logical & Physical

  20. Les canaux GSM

  21. Logical control channels Broadcast Control CHannel (BCCH)downlink only, used to broadcast Cell specific information; Synchronization CHannel (SCH)downlink only, used to broadcast synchronization and BSS identification information; Paging CHannel (PCH)downlink only, used to send page requests to Mobile Stations; Random Access CHannel (RACH)uplink only, used to request a Dedicated Control CHannel; Access Grant CHannel (AGCH)downlink only, used to allocate a Dedicated Control CHANNEL; Stand Alone Dedicated Control CHannel (SDCCH)bi‑directional; Fast Associated Control CHannel (FACCH)bi‑directional, associated with a Traffic CHannel; Slow Associated Control CHannel (SACCH)bi‑directional, associated with a SDCCH or a Traffic CHannel; Cell Broadcast CHannel (CBCH)downlink only used for general (not point to point) short message information.

  22. GSM Frames • Hyperframes • i.e. 2048 Superframes • Superframes • 1326 frames: • i.e. 51 x 26 Multiframes for signalling • i.e. 26 x 51 Multiframes for traffic • Multiframes • i.e 51 TDMA frames for signalling channels • i.e. 24 TDMA frames for traffic channels + 2

  23. Speech Coding

  24. GSM Speech Coding • 8 bit samples • i.e. 256 values • @ 8 kHz sampling rate • Implies 64 kbps • i.e. Normal ISDN • Then Compressed • i.e. 13 kbps FR (Full Rate Coding)

  25. GSM Speech Coding

  26. GSM Layers • Layer 1 • Enables physical transmission (TDMA, FDMA, etc.) • Assessment of channel quality • Layer 2 • Multiplexing of 1 or more layer 2 connections • Routing, flow control, a.o. • Layer 3 • Connection management (air interface) • Management of location data • Subscriber identification

  27. Layer 3 • Radio resource management • Cell Selection, Handover, etc. • Mobility management • Authentication, Location management, etc. • Connection management • Call control • Supplementary service support • Short message service support

  28. System overview • Logical control channels • BCCH, SCH, … • Sub Layers • Sublayer resource management • Sublayer mobility management and • Sublayer connection management • Procedures • Messages format

  29. Sublayers in layer 3 • Sublayer radio resource mgmt - RR • Radio Resource management procedures • Establish, maintain & release R connections • Cell selection/reselection and the handover • Sublayer mobility management - MM • Management of the radio interface (Um) • In cooperation with RR • Sublayer connection management - CC • Call control (CC) protocol

  30. + sublayers layers • Supplementary Services - SS • … • Short Message Service - SMS • … • SIM manager - SIM • …

  31. Sublayer RR • Idle mode • MS available ready for signalling (e.g. paging) • BSS sends system information (e.g. cell info) • Establishment & release of RR connection • Physical point‑to‑point bi‑directional • RR connection transfer • RR connected mode • Automatic cell reselection • Indication of temporary unavailability

  32. Channel establishment messages: ADDITIONAL ASSIGNMENT IMMEDIATE ASSIGNMENT IMMEDIATE ASSIGNMENT EXTENDED IMMEDIATE ASSIGNMENT REJECT Handover messages: ASSIGNMENT COMMAND ASSIGNMENT COMPLETE ASSIGNMENT FAILURE HANDOVER ACCESS HANDOVER COMMAND HANDOVER COMPLETE HANDOVER FAILURE PHYSICAL INFORMATION Ciphering messages: CIPHERING MODE COMMAND CIPHERING MODE COMPLETE Channel release messages: CHANNEL RELEASE PARTIAL RELEASE PARTIAL RELEASE COMPLETE Paging messages: PAGING REQUEST TYPE 1 PAGING REQUEST TYPE 2 PAGING REQUEST TYPE 3 PAGING RESPONSE RR Messages

  33. Sublayer MM • MM common procedures • TMSI reallocation procedure • Temporary Mobile Subscriber Identity • MM specific procedures • IMSI attach procedure • International Mobile Subscriber Identity • Location updating • Authentication, Ciphering

  34. Registration messages: IMSI DETACH INDICATION LOCATION UPDATING ACCEPT LOCATION UPDATING REJECT LOCATION UPDATING REQUEST Security messages: AUTHENTICATION REJECT AUTHENTICATION REQUEST AUTHENTICATION RESPONSE IDENTITY REQUEST IDENTITY RESPONSE TMSI REALLOCATION COMMAND TMSI REALLOCATION COMPLETE Connection management messages: CM SERVICE ACCEPT CM SERVICE REJECT CM SERVICE ABORT CM SERVICE REQUEST CM RE-ESTABLISHMENT REQUEST ABORT Miscellaneous message: MM STATUS MM Messages

  35. Sublayer CC • Call establishment procedures • From MS or Network • Signalling procedures during active state • Notifications & connection rearrangement • Call clearing • Call release • Miscellaneous procedures • In‑band tones and announcements

  36. Call establishment messages: ALERTING CALL CONFIRMED CALL PROCEEDING CONNECT CONNECT ACKNOWLEDGE EMERGENCY SETUP PROGRESS SETUP Call information phase messages: MODIFY MODIFY COMPLETE MODIFY REJECT USER INFORMATION Call clearing messages: DISCONNECT RELEASE RELEASE COMPLETE Messages for supplementary service control FACILITY HOLD HOLD ACKNOWLEDGE HOLD REJECT RETRIEVE RETRIEVE ACKNOWLEDGE RETRIEVE REJECT Miscellaneous messages: CONGESTION CONTROL NOTIFY START DTMF START DTMF ACKNOWLEDGE START DTMF REJECT STATUS STATUS ENQUIRY STOP DTMF STOP DTMF ACKNOWLEDGE CC messages

  37. E.g. the IEs in Alerting IEI Information element Type / Reference Presence Format Length Call control Protocol discriminator M V ½ protocol discriminator (RR, MM, CM) Transaction identifier Transaction identifier M V ½ (Voir norme) Alerting Message type M V 1 message type (Ciphering, Handover) 1C Facility Facility O TLV 2‑? 10.5.4.15 1E Progress indicator Progress indicator O TLV 4 10.5.4.21 7E User‑user User‑user O TLV 3‑35 10.5.4.25

  38. Some indications • Protocol discriminator • 0 0 1 1 Call Control; call related SS messages • 0 1 0 1 Mobility Management messages • 0 1 1 0 Radio Resource management messages • Presence • Mandatory • Optional • Format • T Type only • V Value only • TV Type and Value • LV Length and Value • TLV Type, Length and Value

  39. CC IEs • 0 : : : : : : : : : Type 3 & 4 info elements • 0 0 0 0 1 0 0 Bearer capability • 0 0 0 1 0 0 0 Cause • 0 0 1 0 1 0 0 Note • 0 0 1 0 1 0 1 Call Control Capabilities • 0 0 1 1 1 0 0 Facility • 0 0 1 1 1 1 0 Progress indicator • 0 1 0 1 1 0 0 Keypad facility • 0 1 1 0 1 0 0 Signal • 1 0 0 1 1 0 0 Connected number • 1 0 0 1 1 0 1 Connected subaddress • 1 0 1 1 1 0 1 Calling party subad • 1 0 1 1 1 1 0 Called party BCD number • 1 1 0 1 1 0 1 Called party subad • 1 1 1 1 1 0 0 Low layer compatibility • 1 1 1 1 1 0 1 High layer compatibility • 1 1 1 1 1 1 0 User-user • 1 1 1 1 1 1 1 SS version indicator

  40. Capability IEs • Bearer capability • Synchronous • V.110, X.30 • Low layer compatibility • Unrestricted digital information transfer • 3.1 kHz audio • High layer compatibility • Telephony • Facsimile G2/G3

  41. Incoming GSM Call 2

  42. Where is the cellular phone? • Handset Switched ON > "here I am" • Location update • The radio station relays the information to the nearest exchange: The VLR • The VLR updates the HLR • This way, the home exchange always knows where the phone is • The telephone number of the cellularphone indicates the home exchage. • The handy works with a provision number

  43. Roaming (# Handover) • Roaming is the ability to use your own GSM phone number in another GSM network. • A roaming agreement is a business agreement between two network operators to transfer items such as call charges and subscription information back and forth, as their subscribers roam into each others areas.

  44. Location Based Services

  45. GPRS - HSCSD Mohamed Mokdad Ecole d’Ingénieurs de Bienne

  46. HSCSD High Speed Circuit Switched Data

  47. GPRS Global Packet Radio Service

  48. GPRS time slots

  49. Coding schemes

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