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)
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 Base Station VLR MSC VLR MSC HLR MSC Mobile Switching Center VLR Visitor Location Register HLR Home Location Register land link Radio link
12 GSM Architecture Databases Switches Radio Systems BTS BSC MS MSC GMSC SSP PSTN BSS HLRVLR EIR SSP AuC NSS PLMN 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
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
27 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
28 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
29 System overview Logical control channels –BCCH, SCH, … Sub Layers –Sublayer resource management –Sublayer mobility management and –Sublayer connection management Procedures Messages format
30 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
31 + sublayers layers Supplementary Services - SS –… Short Message Service - SMS –… SIM manager - SIM –…
32 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
34 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
35 MM Messages 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
36 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
37 CC messages 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
38 E.g. the IEs in Alerting IEIInformation elementType / ReferencePresenceFormatLength Call controlProtocol discriminator M V ½ protocol discriminator(RR, MM, CM) Transaction identifierTransaction identifier M V ½ (Voir norme) AlertingMessage type M V 1 message type(Ciphering, Handover) 1CFacilityFacility O TLV 2 ‑ ? 10.5.4.15 1EProgress indicatorProgress indicator O TLV 4 10.5.4.21 7EUser ‑ userUser ‑ user O TLV 3 ‑ 35 10.5.4.25
39 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 –TType only –VValue only –TVType and Value –LVLength and Value –TLVType, Length and Value
43 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 cellular phone indicates the home exchage. The handy works with a provision number
44 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.
55 E.g. http Encapsulation Overhead of 88 bytes !!!
56 GPRS Data Transmission Speeds The supported data transmission speed per channel is 13.4Kbits. Depending on the type of phone, the following data transmission speeds are theoretically possible: Type 2+1: Receive 26.8Kbits & send 13.4Kbits. Type 3+1: Receive 40.2Kbits &send 13.4Kbits. Type 4+1: Receive 53.6Kbits &send 13.4Kbits
57 GPRS vs HSCSD Stay connected all the time (+) Higher Transfer Speed (=) IP Support (+) APN (-) –Access Point Name –GPRS can be only connected to the ISP GPRS WAP –Much confortable (Speed & Connection)
59 Is GSM Data-Ready? SMS (Short Message Services) –160 ASCII characters Direct IP (starting with 9.6 kbps) –bypass PSTN 14.4 kbps per time slot –new channel coding GPRS (General Packet Radio Services) –packet mode –fractional & multiple time slots (0.8 to 128 kbps) HSCSD (High-Speed Circuit Switch Data) –38.4 kbps (4 time slots) Yes, the technology is ready and it can (and will) be improved
60 Evolution of GSM EDGE (Enhanced Data rate for GSM Evolution) –2.5 G –new modulation scheme but still 200kHz –384 kbps is the maximum data rate –designed for service providers that may or may not migrate to UMTS UMTS (Universal Mobile Telecommunications Systems) –3G –384 kbps for wide-area coverage –2 Mbps for local coverage –WCDMA (wideband CDMA) (BW=5MHz @ 2GHz) –Adopted by Europe and Japan