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Mobile Network

Mobile Network. What is GSM ?. Global System for Mobile (GSM) is a second generation cellular standard developed to cater voice services and data delivery using digital modulation. GSM Services. Tele-services Bearer or Data Services Supplementary services. Tele Services.

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Mobile Network

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  1. Mobile Network

  2. What is GSM ? Global System for Mobile (GSM) is a second generation cellular standard developed to cater voice services and data delivery using digital modulation

  3. GSM Services Tele-services Bearer or Data Services Supplementary services

  4. Tele Services • Telecommunication services that enable voice communication via mobile phones • Offered services - Mobile telephony - Emergency calling

  5. Bearer Services • Include various data services for information transfer between GSM and other networks like PSTN, ISDN etc at rates from 300 to 9600 bps • Short Message Service (SMS) • up to 160 character alphanumeric data transmission to/from the mobile terminal • Unified Messaging Services(UMS) • Group 3 fax • Voice mailbox • Electronic mail

  6. Supplementary Services • Call related services : • Call Waiting- Notification of an incoming call while on the handset • Call Hold- Put a caller on hold to take another call • Call Barring- All calls, outgoing calls, or incoming calls • Call Forwarding- Calls can be sent to various numbers defined by the user • Multi Party Call Conferencing - Link multiple calls together • CLIP – Caller line identification presentation • CLIR – Caller line identification restriction • CUG – Closed user group

  7. PSTN ISDN PDN GSM System Architecture BSC MS BTS MSC GMSC BTS BSC VLR MS EIR BTS AUC MS HLR

  8. GSM System Architecture-I • Mobile Station (MS) Mobile Equipment (ME) Subscriber Identity Module (SIM) • Base Station Subsystem (BSS) Base Transceiver Station (BTS) Base Station Controller (BSC) • Network Switching Subsystem(NSS) Mobile Switching Center (MSC) Home Location Register (HLR) Visitor Location Register (VLR) Authentication Center (AUC) Equipment Identity Register (EIR)

  9. System ArchitectureMobile Station (MS) • In 2G it is known as MS. • In 3G systems, It is referred as User Equipment (UE). • The Mobile Station is made up of two entities: • Mobile Equipment (ME) • Subscriber Identity Module (SIM)

  10. System Architecture- Mobil Station (MS) • In GSM, the Mobile Station consists of four main components: • Mobile Terminal (MT)- offers common functions that are used by all the service the Mobile Station offers. It is equivalent to the network termination of an ISDN access and is also the end-point of the radio interface. • Terminal Equipment (TE) - is a peripheral device of the Mobile Station and offers services to the user. It does not contain any functions specific to GSM. • Terminal Adapter (TA) - hides radio-specific characteristics. • Subscriber Identity Module (SIM) - is a personalization of the Mobile Station and stores user specific parameters (such as mobile number, contacts etc).

  11. System ArchitectureMobile Station (MS) -Mobile Equipment • Portable,vehicle mounted, hand held device • Uniquely identified by an IMEI (International Mobile Equipment Identity) • IMEI can be displayed on most phones by dialing the code *# 06 #. • It is not stored in SIM. It is stored in the phone • If a mobile handset is lost or stolen, CEIR (Central Equipment Identity Register) can be contacted. • CERI will blacklist the device in all currently operating switches. • This makes the lost or stolen handset unusable. • Blacklisting stolen mobile handsets is seen as a deterrent to crime. • It is possible, however, to change an IMEI with special tools. • Certain mobile networks that do not automatically blacklist handsets registered with the CEIR. • Approximately 10% of IMEI's in use today are not unique or have been reprogrammed (hacked).

  12. Format of IMEI • Mainly two types • 15 Digits or 17 Digits • The IMEI (14 decimal digits plus a check digit) or IMEISV (16 digits) • The structure of the IMEI/SV are specified in 3GPP TS 23.003 • The model and origin comprise the initial 8-digit portion of the IMEI/SV, known as the Type Allocation Code (TAC). • Format of the IMEI is AA-BBBBBB-CCCCCC-D • AA: Reporting Body Identifier, indicating the GSMA-approved group that allocated the model TAC. • BBBBBB: The remainder of the TAC (Type Approval Code) • CCCCCC: Serial sequence of the model • D: Luhn check digit of the entire number (or zero) • EE: Software Version Number (SVN)

  13. Example: Format of IMEI • 35-209900-176148-1 • What is the meaning of it. • 352099 so it was issued by the BABT (British Approvals Board for Telecommunications) and has the allocation number 2099. • The Reporting Body Identifier is allocated by the Global Decimal Administrator; • FAC (Finally Assembly Code): 00 so it was numbered during the transition phase from the old format to the new format • SNR: 176148 - uniquely identifying a unit of this modelCD: 1 so it is a GSM Phase 2 or higher

  14. Mobile Equipment Identifier • There are two administrators: • the Global Decimal Administrator (GDA) for IMEIs • Global Hexadecimal Administrator (GHA).

  15. CDMA Format An MEID is 56 bits long (14 hex digits). It consists of three fields, including an 8-bit regional code (RR), a 24-bit manufacturer code, and a 24-bit manufacturer-assigned serial number. The check digit (CD) is not considered part of the MEID. As of August 2006, the TIA acts as the Global Hexadecimal Administrator (GHA) to assign MEID, and the GSM Association acts as the Global Decimal Administrator

  16. Luhn algorithm • The check digit is validated in three steps: • Starting from the right, double a digit every two digits (e.g., 7 → 14). • Sum the digits (e.g., 14 → 1 + 4). • Check if the sum is divisible by 10. • Conversely, one can calculate the IMEI by choosing the check digit that would give a sum divisible by 10. For the example IMEI 49015420323751?,

  17. Luhn algorithm To make the sum divisible by 10, we set ? = 8, so the IMEI is 490154203237518

  18. CEIR Classification of Handsets

  19. System ArchitectureMobile Station (MS) - Mobile Equipment • Voice and data transmission • Monitoring power and signal quality of surrounding cells for optimum handover • Power level : 0.8W – 20 W • 160 character long SMS.

  20. What is an IMSI? • The IMSI (International Mobile Subscriber Identity) is a unique 15-digit code used to identify an individual user on a GSM network. • The IMSI consists of three components: • Mobile Country Code (MCC) • Mobile Network Code (MNC) • Mobile Subscriber Identity Number (MSIN) • The IMSI is stored in the Subscriber Identity Module (SIM).

  21. System ArchitectureMobile Station (MS) contd. Subscriber Identity Module (SIM) • Smart card contains the International Mobile Subscriber Identity (IMSI) • Allows user to send and receive calls and receive other subscribed services • Encoded network identification details - Key Ki,Kc and A3,A5 and A8 algorithms • Protected by a password or PIN • Can be moved from phone to phone – contains key information to activate the phone

  22. New Trends • In random order Mega-trends of Mobile Industry are: • The threat and possibilities of the Discount Mobile Service Providers, • Falling profit margins on basic mobile services (voice, SMS) as a result of competition, • The use of outsourcing - to minimize OPEX, • Controlled investment in infrastructure - to reduce CAPEX, • The use of micro-segmentation (Mobile operators will use sub-brands and producers of mobile terminals will introduce a wide range of different terminal models), • Higher marketing expenses – partly because of the use of micro-segmentation, • Stock Rotation Risk – the result of the terminal producers larger product portfolio, • New business models in the mobile value chain – the existing business models are an impediment on economic growth, • A more complex value chain – a growing number of different players seek the place in the mobile value chain, • Mobile penetration vs. SIM-penetration – there is an important difference.

  23. Issues • Environmental Related • About 1.2 billion mobile handsets were sold worldwide. To put that into context, it means that, on average, more than 3 million new handsets were sold every day last year. • How to reduce power consumption • How to use solar power • How to reduce CO2 emission. • How to take care of large number of chargers lying with subscribers. • It should be done through regulation • It should be done through Innovation • Or combination of both • Reduction of Hazardous Substances (RoHS) directive • Waste Electrical and Electronic Equipment (WEEE) Directive

  24. Statistics

  25. Indian Statistics

  26. System ArchitectureBase Station Subsystem (BSS) Base Station Subsystem is composed of two parts that communicate across the standardized Abis interface allowing operation between components made by different suppliers • Base Transceiver Station (BTS) • Base Station Controller (BSC)

  27. BSS interfaces • Um: The air interface between the mobile station (MS) and the BTS. • Abis: The interface between the BTS and BSC. • A: The interface between the BSC and MSC. • Ater: The interface between the BSC and transcoder. • Gb: Connects the BSS to the SGSN in the GPRS core network

  28. System ArchitectureBase Station Subsystem (BSS) Base Transceiver Station (BTS): • Encodes,encrypts,multiplexes,modulates and feeds the RF signals to the antenna. • Frequency hopping • Communicates with Mobile station and BSC • Consists of Transceivers (TRX) units

  29. System ArchitectureBase Station Subsystem (BSS) Base Station Controller (BSC) • Manages Radio resources for BTS • Assigns Frequency and time slots for all MS’s in its area • Handles call set up • Transcoding and rate adaptation functionality • Handover for each MS • Radio Power control • It communicates with MSC and BTS

  30. System ArchitectureNetwork Switching Subsystem(NSS) Mobile Switching Center (MSC) • Heart of the network • Manages communication between GSM and other networks • Call setup function and basic switching • Call routing • Billing information and collection • Mobility management - Registration - Location Updating - Inter BSS and inter MSC call handoff • MSC does gateway function while its customer roams to other network by using HLR/VLR.

  31. System ArchitectureNetwork Switching Subsystem • Home Location Registers (HLR) - permanent database about mobile subscribers in a large service area(generally one per GSM network operator) • database contains IMSI,MSISDN,prepaid/postpaid,roaming restrictions,supplementary services. • Visitor Location Registers (VLR) • Temporary database which updates whenever new MS enters its area, by HLR database • Controls those mobiles roaming in its area • Reduces number of queries to HLR • Database contains IMSI,TMSI,MSISDN,MSRN,Location Area,authentication key

  32. System ArchitectureNetwork Switching Subsystem • Authentication Center (AUC) • Protects against intruders in air interface • Maintains authentication keys and algorithms and provides security triplets ( RAND,SRES,Kc) • Generally associated with HLR • Equipment Identity Register (EIR) - Database that is used to track handsets using the IMEI (International Mobile Equipment Identity) • Made up of three sub-classes: The White List, The Black List and the Gray List • Only one EIR per PLMN

  33. GSM Specifications-1 • RF Spectrum GSM 900 Mobile to BTS (uplink): 890-915 Mhz BTS to Mobile(downlink):935-960 Mhz Bandwidth : 2* 25 Mhz GSM 1800 Mobile to BTS (uplink): 1710-1785 Mhz BTS to Mobile(downlink) 1805-1880 Mhz Bandwidth : 2* 75 Mhz

  34. GSM Specification-II • Carrier Separation : 200 Khz • Duplex Distance : 45 Mhz • No. of RF carriers : 124 • Access Method : TDMA/FDMA • Modulation Method : GMSK • Modulation data rate : 270.833 Kbps

  35. Speech Speech Speechdecoding Speech coding 13 Kbps Channel Coding Channeldecoding 22.8 Kbps Interleaving De-interleaving 22.8 Kbps BurstFormatting Burst Formatting 33.6 Kbps Ciphering De-ciphering 33.6 Kbps Radio Interface Modulation Demodulation 270.83 Kbps GSM Operation

  36. Call Routing • Call Originating from MS • Call termination to MS

  37. MS sends dialled number to BSS BSS sends dialled number to MSC 3,4 MSC checks VLR if MS is allowed the requested service.If so,MSC asks BSS to allocate resources for call. MSC routes the call to GMSC GMSC routes the call to local exchange of called user 7, 8, 9,10 Answer back(ring back) tone is routed from called user to MS via GMSC,MSC,BSS Outgoing Call

  38. Calling a GSM subscribers Forwarding call to GSMC Signal Setup to HLR 5. Request MSRN from VLR Forward responsible MSC to GMSC Forward Call to current MSC 9. Get current status of MS 11. Paging of MS 13. MS answers 15. Security checks 17. Set up connection Incoming Call

  39. Between 1 and 2 – Inter BTS / Intra BSC Between 1 and 3 – Inter BSC/ Intra MSC Between 1 and 4 – Inter MSC Handovers

  40. Security in GSM • On air interface, GSM uses encryption and TMSI instead of IMSI. • SIM is provided 4-8 digit PIN to validate the ownership of SIM • 3 algorithms are specified : - A3 algorithm for authentication - A5 algorithm for encryption - A8 algorithm for key generation

  41. Authentication in GSM

  42. Key generation and Encryption

  43. Characteristics of GSM Standard • Fully digital system using 900,1800 MHz frequency band. • TDMA over radio carriers(200 KHz carrier spacing. • 8 full rate or 16 half rate TDMA channels per carrier. • User/terminal authentication for fraud control. • Encryption of speech and data transmission over the radio path. • Full international roaming capability. • Low speed data services (upto 9.6 Kb/s). • Compatibility with ISDN. • Support of Short Message Service (SMS).

  44. Advantages of GSM over Analog system • Capacity increases • Reduced RF transmission power and longer battery life. • International roaming capability. • Better security against fraud (through terminal validation and user authentication). • Encryption capability for information security and privacy. • Compatibility with ISDN,leading to wider range of services

  45. GSM Applications • Mobile telephony • GSM-R • Telemetry System - Fleet management - Automatic meter reading - Toll Collection - Remote control and fault reporting of DG sets • Value Added Services

  46. Future Of GSM 2nd Generation • GSM -9.6 Kbps (data rate) 2.5 Generation ( Future of GSM) • HSCSD (High Speed ckt Switched data) • Data rate : 76.8 Kbps (9.6 x 8 kbps) • GPRS (General Packet Radio service) • Data rate: 14.4 - 115.2 Kbps • EDGE (Enhanced data rate for GSM Evolution) • Data rate: 547.2 Kbps (max) 3 Generation • WCDMA(Wide band CDMA) • Data rate : 0.348 – 2.0 Mbps

  47. Questions ?

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