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CS8601 MOBILE COMPUTING

The document presents an overview of mobile telecommunications, specifically focusing on GSM (Global System for Mobile Communication). It discusses the architecture, services, and performance characteristics of GSM, as well as security features, bearer and tele services, and the role of mobile switching centers. Additionally, it highlights the disadvantages and complexities of GSM systems, along with the evolution of mobile communication standards from 1G to 3G and beyond.

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CS8601 MOBILE COMPUTING UNIT – II Dr.A.Kathirvel, Professor and Head, Dept of CSE Misrimal Navajee Munoth Jain Engineering College, Chennai
Unit - II MOBILE TELECOMMUNICATION SYSTEM Introduction to Cellular Systems - GSM – Services & Architecture – Protocols – Connection Establishment – Frequency Allocation – Routing – Mobility Management – Security – GPRS- UMTS – Architecture – Handover - Security TEXT BOOKS:Jochen Schiller, Mobile Communications, PHI, Second Edn, 2003. 2
Mobile phone subscribers worldwide 0 200 400 600 800 1000 1200 1996 1997 1998 1999 2000 2001 2002 year Subscribers[million] GSM total TDMA total CDMA total PDC total Analogue total Total wireless Prediction (1998) 3
Development of mobile telecommunication systems 1G 2G 3G2.5G IS-95 cdmaOne IS-136 TDMA D-AMPS GSM PDC GPRS IMT-DS UTRA FDD / W-CDMA EDGE IMT-TC UTRA TDD / TD-CDMA cdma2000 1X 1X EV-DV (3X) AMPS NMT IMT-SC IS-136HS UWC-136 IMT-TC TD-SCDMA CT0/1 CT2 IMT-FT DECT CDMATDMAFDMA IMT-MC cdma2000 1X EV-DO 4
GSM: Overview ❑ formerly: Groupe Spéciale Mobile (founded 1982) ❑ now: Global System for Mobile Communication ❑ Pan-European standard (ETSI, European Telecommunications Standardisation Institute) ❑ simultaneous introduction of essential services in three phases (1991, 1994, 1996) by the European telecommunication administrations (Germany: D1 and D2) ➔ seamless roaming within Europe possible ❑ today many providers all over the world use GSM (more than 184 countries in Asia, Africa, Europe, Australia, America) ❑ more than 747 million subscribers ❑ more than 70% of all digital mobile phones use GSM ❑ over 10 billion SMS per month in Germany, > 360 billion/year worldwide 5
Performance characteristics of GSM (wrt. analog sys.) Communication ❑ mobile, wireless communication; support for voice and data services Total mobility ❑ international access, chip-card enables use of access points of different providers Worldwide connectivity ❑ one number, the network handles localization High capacity ❑ better frequency efficiency, smaller cells, more customers per cell High transmission quality ❑ high audio quality and reliability for wireless, uninterrupted phone calls at higher speeds (e.g., from cars, trains) Security functions ❑ access control, authentication via chip-card and PIN 6
Disadvantages of GSM There is no perfect system!! ❑ no end-to-end encryption of user data ❑ no full ISDN bandwidth of 64 kbit/s to the user, no transparent B-channel ❑ reduced concentration while driving ❑ electromagnetic radiation ❑ abuse of private data possible ❑ roaming profiles accessible ❑ high complexity of the system ❑ several incompatibilities within the GSM standards 7
GSM: Mobile Services GSM offers ❑ several types of connections ⚫ voice connections, data connections, short message service ❑ multi-service options (combination of basic services) Three service domains ❑ Bearer Services ❑ Telematic Services ❑ Supplementary Services GSM-PLMN transit network (PSTN, ISDN) source/ destination network TE TE bearer services tele services R, S (U, S, R)Um MT MS 8
Bearer Services ❑ Telecommunication services to transfer data between access points ❑ Specification of services up to the terminal interface (OSI layers 1-3) ❑ Different data rates for voice and data (original standard) ❑ data service (circuit switched) ⚫ synchronous: 2.4, 4.8 or 9.6 kbit/s ⚫ asynchronous: 300 - 1200 bit/s ❑ data service (packet switched) ⚫ synchronous: 2.4, 4.8 or 9.6 kbit/s ⚫ asynchronous: 300 - 9600 bit/s Today: data rates of approx. 50 kbit/s possible – will be covered later! 9
Tele Services I ❑ Telecommunication services that enable voice communication via mobile phones ❑ All these basic services have to obey cellular functions, security measurements etc. ❑ Offered services ❑ mobile telephony primary goal of GSM was to enable mobile telephony offering the traditional bandwidth of 3.1 kHz ❑ Emergency number common number throughout Europe (112); mandatory for all service providers; free of charge; connection with the highest priority (preemption of other connections possible) ❑ Multinumbering several ISDN phone numbers per user possible 10
Tele Services II ❑ Additional services ❑Non-Voice-Teleservices ❑group 3 fax ❑voice mailbox (implemented in the fixed network supporting the mobile terminals) ❑electronic mail (MHS, Message Handling System, implemented in the fixed network) ❑... ❑Short Message Service (SMS) alphanumeric data transmission to/from the mobile terminal using the signaling channel, thus allowing simultaneous use of basic services and SMS 11
Supplementary services ❑ Services in addition to the basic services, cannot be offered stand-alone ❑ Similar to ISDN services besides lower bandwidth due to the radio link ❑ May differ between different service providers, countries and protocol versions ❑ Important services ❑ identification: forwarding of caller number ❑ suppression of number forwarding ❑ automatic call-back ❑ conferencing with up to 7 participants ❑ locking of the mobile terminal (incoming or outgoing calls) ❑ ... 12
Architecture of the GSM system GSM is a PLMN (Public Land Mobile Network) ❑ several providers setup mobile networks following the GSM standard within each country ❑ components ⚫ MS (mobile station) ⚫ BS (base station) ⚫ MSC (mobile switching center) ⚫ LR (location register) ❑ subsystems ⚫ RSS (radio subsystem): covers all radio aspects ⚫ NSS (network and switching subsystem): call forwarding, handover, switching ⚫ OSS (operation subsystem): management of the network 13
GSM: overview fixed network BSC BSC MSC MSC GMSC OMC, EIR, AUC VLR HLR NSS with OSS RSS VLR 14
GSM: elements and interfaces NSS MS MS BTS BSC GMSC IWF OMC BTS BSC MSC MSC Abis Um EIR HLR VLR VLR A BSS PDN ISDN, PSTN RSS radio cell radio cell MS AUCOSS signaling O 15
Um Abis A BS S radio subsystem MS MS BTS BSC BTS BTS BSC BTS network and switching subsystem MSC MSC fixed partner networks IWF ISDN PSTN PSPDN CSPDN SS7 EIR HLR VLR ISDN PST N GSM: system architecture 16
System architecture: radio subsystem Components ❑ MS (Mobile Station) ❑ BSS (Base Station Subsystem): consisting of ⚫ BTS (Base Transceiver Station): sender and receiver ⚫ BSC (Base Station Controller): controlling several transceivers Interfaces ❑ Um : radio interface ❑ Abis : standardized, open interface with 16 kbit/s user channels ❑ A: standardized, open interface with 64 kbit/s user channels Um Abis A BSS radio subsystem network and switching subsystem MS MS BTS BSC MS C BTS BTS BSC BTS MS C 17
System architecture: network and switching subsystem Components MSC (Mobile Services Switching Center): IWF (Interworking Functions) ISDN (Integrated Services Digital Network) PSTN (Public Switched Telephone Network) PSPDN (Packet Switched Public Data Net.) CSPDN (Circuit Switched Public Data Net.) Databases HLR (Home Location Register) VLR (Visitor Location Register) EIR (Equipment Identity Register) network subsystem MSC MSC fixed partner networks IWF ISDN PSTN PSPDN CSPDN SS7 EIR HLR VLR ISDN PSTN 18
Radio subsystem The Radio Subsystem (RSS) comprises the cellular mobile network up to the switching centers ❑ Components ❑ Base Station Subsystem (BSS): ⚫ Base Transceiver Station (BTS): radio components including sender, receiver, antenna - if directed antennas are used one BTS can cover several cells ⚫ Base Station Controller (BSC): switching between BTSs, controlling BTSs, managing of network resources, mapping of radio channels (Um) onto terrestrial channels (A interface) ⚫ BSS = BSC + sum(BTS) + interconnection ❑ Mobile Stations (MS) 19
possible radio coverage of the cell idealized shape of the cell cell segmentation of the area into cells GSM: cellular network ❑ use of several carrier frequencies ❑ not the same frequency in adjoining cells ❑ cell sizes vary from some 100 m up to 35 km depending on user density, geography, transceiver power etc. ❑ hexagonal shape of cells is idealized (cells overlap, shapes depend on geography) ❑ if a mobile user changes cells handover of the connection to the neighbor cell
Example coverage of GSM networks (www.gsmworld.com) e-plus (GSM-1800) T-Mobile (GSM-900/1800) Berlin O2 (GSM-1800) Vodafone (GSM-900/1800) 21
Base Transceiver Station and Base Station Controller Tasks of a BSS are distributed over BSC and BTS ❑ BTS comprises radio specific functions ❑ BSC is the switching center for radio channels Functions BTS BSC Management of radio channels X Frequency hopping (FH) X X Management of terrestrial channels X Mapping of terrestrial onto radio channels X Channel coding and decoding X Rate adaptation X Encryption and decryption X X Paging X X Uplink signal measurements X Traffic measurement X Authentication X Location registry, location update X Handover management X 22
Mobile station Terminal for the use of GSM services ❑ A mobile station (MS) comprises several functional groups ❑ MT (Mobile Terminal): ⚫ offers common functions used by all services the MS offers ⚫ corresponds to the network termination (NT) of an ISDN access ⚫ end-point of the radio interface (Um) ❑ TA (Terminal Adapter): ⚫ terminal adaptation, hides radio specific characteristics ❑ TE (Terminal Equipment): ⚫ peripheral device of the MS, offers services to a user ⚫ does not contain GSM specific functions ❑ SIM (Subscriber Identity Module): ⚫ personalization of the mobile terminal, stores user parameters R S Um TE TA MT 23
Network and switching subsystem NSS is the main component of the public mobile network GSM ❑ switching, mobility management, interconnection to other networks, system control ❑ Components ❑ Mobile Services Switching Center (MSC) controls all connections via a separated network to/from a mobile terminal within the domain of the MSC - several BSC can belong to a MSC ❑ Databases (important: scalability, high capacity, low delay) ⚫ Home Location Register (HLR) central master database containing user data, permanent and semi- permanent data of all subscribers assigned to the HLR (one provider can have several HLRs) ⚫ Visitor Location Register (VLR) local database for a subset of user data, including data about all user currently in the domain of the VLR 24
Mobile Services Switching Center The MSC (mobile switching center) plays a central role in GSM ❑ switching functions ❑ additional functions for mobility support ❑ management of network resources ❑ interworking functions via Gateway MSC (GMSC) ❑ integration of several databases ❑ Functions of a MSC ❑ specific functions for paging and call forwarding ❑ termination of SS7 (signaling system no. 7) ❑ mobility specific signaling ❑ location registration and forwarding of location information ❑ provision of new services (fax, data calls) ❑ support of short message service (SMS) ❑ generation and forwarding of accounting and billing information 25
Operation subsystem The OSS (Operation Subsystem) enables centralized operation, management, and maintenance of all GSM subsystems ❑ Components ❑ Authentication Center (AUC) ⚫ generates user specific authentication parameters on request of a VLR ⚫ authentication parameters used for authentication of mobile terminals and encryption of user data on the air interface within the GSM system ❑ Equipment Identity Register (EIR) ⚫ registers GSM mobile stations and user rights ⚫ stolen or malfunctioning mobile stations can be locked and sometimes even localized ❑ Operation and Maintenance Center (OMC) ⚫ different control capabilities for the radio subsystem and the network subsystem 26
1 2 3 4 5 6 7 8 higher GSM frame structures 935-960 MHz 124 channels (200 kHz) downlink 890-915 MHz 124 channels (200 kHz) uplink time GSM TDMA frame GSM time-slot (normal burst) 4.615 ms 546.5 µs 577 µs tail user data TrainingS guard space S user data tail guard space 3 bits 57 bits 26 bits 57 bits1 1 3 GSM - TDMA/FDMA 27
GSM hierarchy of frames 0 1 2 2045 2046 2047... hyperframe 0 1 2 48 49 50... 0 1 24 25... superframe 0 1 24 25... 0 1 2 48 49 50... 0 1 6 7... multiframe frame burst slot 577 µs 4.615 ms 120 ms 235.4 ms 6.12 s 3 h 28 min 53.76 s 28
GSM protocol layers for signaling CM MM RR MM LAPDm radio LAPDm radio LAPD PCM RR’ BTSM CM LAPD PCM RR’ BTSM 16/64 kbit/s Um Abis A SS7 PCM SS7 PCM 64 kbit/s / 2.048 Mbit/s MS BTS BSC MSC BSSAP BSSAP 29
Mobile Terminated Call PSTN calling station GMSC HLR VLR BSSBSSBSS MSC MS 1 2 3 4 5 6 7 8 9 10 11 12 13 16 10 10 11 11 11 14 15 17 1: calling a GSM subscriber 2: forwarding call to GMSC 3: signal call setup to HLR 4, 5: request MSRN from VLR 6: forward responsible MSC to GMSC 7: forward call to current MSC 8, 9: get current status of MS 10, 11: paging of MS 12, 13: MS answers 14, 15: security checks 16, 17: set up connection 30
Mobile Originated Call PSTN GMSC VLR BSS MSC MS 1 2 6 5 3 4 9 10 7 8 1, 2: connection request 3, 4: security check 5-8: check resources (free circuit) 9-10: set up call 31
MTC/MOC BTSMS paging request channel request immediate assignment paging response authentication request authentication response ciphering command ciphering complete setup call confirmed assignment command assignment complete alerting connect connect acknowledge data/speech exchange BTSMS channel request immediate assignment service request authentication request authentication response ciphering command ciphering complete setup call confirmed assignment command assignment complete alerting connect connect acknowledge data/speech exchange MTC MOC 32
4 types of handover MSC MSC BSC BSCBSC BTS BTS BTSBTS MS MS MS MS 1 2 3 4 33
Handover decision receive level BTSold receive level BTSold MS MS HO_MARGIN BTSold BTSnew 34
Handover procedure HO access BTSold BSCnew measurement result BSCold Link establishment MSCMS measurement report HO decision HO required BTSnew HO request resource allocation ch. activation ch. activation ackHO request ackHO commandHO commandHO command HO completeHO completeclear commandclear command clear complete clear complete 35
Security in GSM Security services ❑ access control/authentication ⚫ user SIM (Subscriber Identity Module): secret PIN (personal identification number) ⚫ SIM network: challenge response method ❑ confidentiality ⚫ voice and signaling encrypted on the wireless link (after successful authentication) ❑ anonymity ⚫ temporary identity TMSI (Temporary Mobile Subscriber Identity) ⚫ newly assigned at each new location update (LUP) ⚫ encrypted transmission 3 algorithms specified in GSM ❑ A3 for authentication (“secret”, open interface) ❑ A5 for encryption (standardized) ❑ A8 for key generation (“secret”, open interface) “secret”: • A3 and A8 available via the Internet • network providers can use stronger mechanisms 36
GSM - authentication A3 RANDKi 128 bit 128 bit SRES* 32 bit A3 RAND Ki 128 bit 128 bit SRES 32 bit SRES* =? SRES SRES RAND SRES 32 bit mobile network SIM AC MSC SIM Ki: individual subscriber authentication key SRES: signed response 37
GSM - key generation and encryption A8 RANDKi 128 bit 128 bit Kc 64 bit A8 RAND Ki 128 bit 128 bit SRES RAND encrypted data mobile network (BTS) MS with SIM AC BSS SIM A5 Kc 64 bit A5 MS data data cipher key 38
Data services in GSM I Data transmission standardized with only 9.6 kbit/s ❑ advanced coding allows 14,4 kbit/s ❑ not enough for Internet and multimedia applications HSCSD (High-Speed Circuit Switched Data) ❑ mainly software update ❑ bundling of several time-slots to get higher AIUR (Air Interface User Rate) (e.g., 115.2 kbit/s using 8 slots, 14.4 each) ❑ advantage: ready to use, constant quality, simple ❑ disadvantage: channels blocked for voice transmission AIUR [kbit/s] TCH/F4.8 TCH/F9.6 TCH/F14.4 4.8 1 9.6 2 1 14.4 3 1 19.2 4 2 28.8 3 2 38.4 4 43.2 3 57.6 4 39
Data services in GSM II GPRS (General Packet Radio Service) ❑ packet switching ❑ using free slots only if data packets ready to send (e.g., 115 kbit/s using 8 slots temporarily) ❑ standardization 1998, introduction 2001 ❑ advantage: one step towards UMTS, more flexible ❑ disadvantage: more investment needed (new hardware) GPRS network elements ❑ GSN (GPRS Support Nodes): GGSN and SGSN ❑ GGSN (Gateway GSN) ⚫ interworking unit between GPRS and PDN (Packet Data Network) ❑ SGSN (Serving GSN) ⚫ supports the MS (location, billing, security) ❑ GR (GPRS Register) ⚫ user addresses 40
GPRS quality of service Reliability class Lost SDU probability Duplicate SDU probability Out of sequence SDU probability Corrupt SDU probability 1 10-9 10-9 10-9 10-9 2 10-4 10-5 10-5 10-6 3 10-2 10-5 10-5 10-2 Delay SDU size 128 byte SDU size 1024 byte class mean 95 percentile mean 95 percentile 1 < 0.5 s < 1.5 s < 2 s < 7 s 2 < 5 s < 25 s < 15 s < 75 s 3 < 50 s < 250 s < 75 s < 375 s 4 unspecified 41
GPRS architecture and interfaces MS BSS GGSNSGSN MSC Um EIR HLR/ GR VLR PDN Gb Gn Gi SGSN Gn 42
GPRS protocol architecture apps. IP/X.25 LLC GTP MAC radio MAC radio FR RLC BSSGP IP/X.25 FR Um Gb Gn L1/L2 L1/L2 MS BSS SGSN GGSN UDP/TCP Gi SNDCP RLC BSSGP IP IP LLC UDP/TCP SNDCP GTP 43
DECT DECT (Digital European Cordless Telephone) standardized by ETSI (ETS 300.175-x) for cordless telephones ❑ standard describes air interface between base-station and mobile phone ❑ DECT has been renamed for international marketing reasons into „Digital Enhanced Cordless Telecommunication“ ❑ Characteristics ❑ frequency: 1880-1990 MHz ❑ channels: 120 full duplex ❑ duplex mechanism: TDD (Time Division Duplex) with 10 ms frame length ❑ multplexing scheme: FDMA with 10 carrier frequencies, TDMA with 2x 12 slots ❑ modulation: digital, Gaußian Minimum Shift Key (GMSK) ❑ power: 10 mW average (max. 250 mW) ❑ range: approx. 50 m in buildings, 300 m open space 44
DECT system architecture reference model global network local network local network FT FT PTPA PTPA VDB HDB D1 D2 D3D4 45
physical layer medium access control data link control data link control network layer OSI layer 1 OSI layer 2 OSI layer 3 U-PlaneC-Plane signaling, interworking application processes DECT reference model ❑ close to the OSI reference model ❑ management plane over all layers ❑ several services in C(ontrol)- and U(ser)- plane management 46
DECT layers I ❑ Physical layer ❑ modulation/demodulation ❑ generation of the physical channel structure with a guaranteed throughput ❑ controlling of radio transmission ⚫ channel assignment on request of the MAC layer ⚫ detection of incoming signals ⚫ sender/receiver synchronization ⚫ collecting status information for the management plane ❑ MAC layer ❑ maintaining basic services, activating/deactivating physical channels ❑ multiplexing of logical channels ⚫ e.g., C: signaling, I: user data, P: paging, Q: broadcast ❑ segmentation/reassembly ❑ error control/error correction 47
DECT time multiplex frame slot sync A field DATA DATA 64 C 16 DATA 64 C 16 DATA 64 C 16 DATA 64 C 16 B field D field 1 frame = 10 ms 12 down slots 12 up slots 0 419 0 31 0 387 0 63 0 319 protected mode unprotected mode simplex bearer 25.6 kbit/s 32 kbit/s 420 bit + 52 µs guard time („60 bit“) in 0.4167 ms guard X field 0 3 A: network control B: user data X: transmission quality 48
DECT layers II ❑ Data link control layer ❑ creation and keeping up reliable connections between the mobile terminal and basestation ❑ two DLC protocols for the control plane (C-Plane) ⚫ connectionless broadcast service: paging functionality ⚫ Lc+LAPC protocol: in-call signaling (similar to LAPD within ISDN), adapted to the underlying MAC service ❑ several services specified for the user plane (U-Plane) ⚫ null-service: offers unmodified MAC services ⚫ frame relay: simple packet transmission ⚫ frame switching: time-bounded packet transmission ⚫ error correcting transmission: uses FEC, for delay critical, time-bounded services ⚫ bandwidth adaptive transmission ⚫ „Escape“ service: for further enhancements of the standard 49
DECT layers III ❑ Network layer ❑ similar to ISDN (Q.931) and GSM (04.08) ❑ offers services to request, check, reserve, control, and release resources at the basestation and mobile terminal ❑ resources ⚫ necessary for a wireless connection ⚫ necessary for the connection of the DECT system to the fixed network ❑ main tasks ⚫ call control: setup, release, negotiation, control ⚫ call independent services: call forwarding, accounting, call redirecting ⚫ mobility management: identity management, authentication, management of the location register 50
Several „DECT Application Profiles“ in addition to the DECT specification ❑ GAP (Generic Access Profile) standardized by ETSI in 1997 ⚫ assures interoperability between DECT equipment of different manufacturers (minimal requirements for voice communication) ⚫ enhanced management capabilities through the fixed network: Cordless Terminal Mobility (CTM) ❑ DECT/GSM Interworking Profile (GIP): connection to GSM ❑ ISDN Interworking Profiles (IAP, IIP): connection to ISDN ❑ Radio Local Loop Access Profile (RAP): public telephone service ❑ CTM Access Profile (CAP): support for user mobility Enhancements of the standard DECT basestation GAP DECT Common Air Interface DECT Portable Part fixed network 51
TETRA - Terrestrial Trunked Radio Trunked radio systems ❑ many different radio carriers ❑ assign single carrier for a short period to one user/group of users ❑ taxi service, fleet management, rescue teams ❑ interfaces to public networks, voice and data services ❑ very reliable, fast call setup, local operation TETRA - ETSI standard ❑ formerly: Trans European Trunked Radio ❑ offers Voice+Data and Packet Data Optimized service ❑ point-to-point and point-to-multipoint ❑ ad-hoc and infrastructure networks ❑ several frequencies: 380-400 MHz, 410-430 MHz ❑ FDD, DQPSK ❑ group call, broadcast, sub-second group-call setup 52
TDMA structure of the voice+data system 0 1 2 57 58 59... hyperframe 0 1 2 15 16 17... multiframe 0 1 2 3 0 slot 509 frame 14.17 ms 56.67 ms 1.02 s 61.2 s CF Control Frame 53
UMTS and IMT-2000 Proposals for IMT-2000 (International Mobile Telecommunications) ❑ UWC-136, cdma2000, WP-CDMA ❑ UMTS (Universal Mobile Telecommunications System) from ETSI UMTS ❑ UTRA (was: UMTS, now: Universal Terrestrial Radio Access) ❑ enhancements of GSM ⚫ EDGE (Enhanced Data rates for GSM Evolution): GSM up to 384 kbit/s ⚫ CAMEL (Customized Application for Mobile Enhanced Logic) ⚫ VHE (virtual Home Environment) ❑ fits into GMM (Global Multimedia Mobility) initiative from ETSI ❑ requirements ⚫ min. 144 kbit/s rural (goal: 384 kbit/s) ⚫ min. 384 kbit/s suburban (goal: 512 kbit/s) ⚫ up to 2 Mbit/s urban 54
Frequencies for IMT-2000 IMT-2000 1850 1900 1950 2000 2050 2100 2150 2200 MHz MSS  ITU allocation (WRC 1992) IMT-2000 MSS  Europe China Japan North America UTRA FDD  UTRA FDD  T D D T D D MSS  MSS  DE CT GSM 1800 1850 1900 1950 2000 2050 2100 2150 2200 MHz IMT-2000 MSS  IMT-2000 MSS  GSM 1800 cdma2000 W-CDMA MSS  MSS  MSS  MSS  cdma2000 W-CDMA PHS PCS rsv. 55
IMT-2000 family IMT-DS (Direct Spread) UTRA FDD (W-CDMA) 3GPP IMT-TC (Time Code) UTRA TDD (TD-CDMA); TD-SCDMA 3GPP IMT-MC (Multi Carrier) cdma2000 3GPP2 IMT-SC (Single Carrier) UWC-136 (EDGE) UWCC/3GPP IMT-FT (Freq. Time) DECT ETSI GSM (MAP) ANSI-41 (IS-634) IP-Network IMT-2000 Core Network ITU-T IMT-2000 Radio Access ITU-R Interface for Internetworking Flexible assignment of Core Network and Radio Access Initial UMTS (R99 w/ FDD) 56
Licensing Example: UMTS in Germany, 18. August 2000 Sum: 50.81 billion € ❑ UTRA-FDD: ❑ Uplink 1920-1980 MHz ❑ Downlink 2110-2170 MHz ❑ duplex spacing 190 MHz ❑ 12 channels, each 5 MHz ❑ UTRA-TDD: ❑ 1900-1920 MHz, ❑ 2010-2025 MHz; ❑ 5 MHz channels ❑ Coverage: 25% of the population until 12/2003, 50% until 12/2005 57
UMTS architecture (Release 99 used here!) UTRANUE CN IuUu UTRAN (UTRA Network) ❑ Cell level mobility ❑ Radio Network Subsystem (RNS) ❑ Encapsulation of all radio specific tasks UE (User Equipment) CN (Core Network) ❑ Inter system handover ❑ Location management if there is no dedicated connection between UE and UTRAN 58
UMTS domains and interfaces I User Equipment Domain ❑ Assigned to a single user in order to access UMTS services Infrastructure Domain ❑ Shared among all users ❑ Offers UMTS services to all accepted users USIM Domain Mobile Equipment Domain Access Network Domain Serving Network Domain Transit Network Domain Home Network Domain Cu Uu Iu User Equipment Domain Zu Yu Core Network Domain Infrastructure Domain 59
UMTS domains and interfaces II Universal Subscriber Identity Module (USIM) ❑ Functions for encryption and authentication of users ❑ Located on a SIM inserted into a mobile device Mobile Equipment Domain ❑ Functions for radio transmission ❑ User interface for establishing/maintaining end-to-end connections Access Network Domain ❑ Access network dependent functions Core Network Domain ❑ Access network independent functions ❑ Serving Network Domain ⚫ Network currently responsible for communication ❑ Home Network Domain ⚫ Location and access network independent functions 60
Spreading and scrambling of user data Constant chipping rate of 3.84 Mchip/s Different user data rates supported via different spreading factors ❑ higher data rate: less chips per bit and vice versa User separation via unique, quasi orthogonal scrambling codes ❑ users are not separated via orthogonal spreading codes ❑ much simpler management of codes: each station can use the same orthogonal spreading codes ❑ precise synchronisation not necessary as the scrambling codes stay quasi- orthogonal data1 data2 data3 scrambling code1 spr. code3 spr. code2 spr. code1 data4 data5 scrambling code2 spr. code4 spr. code1 sender1 sender2 61
OSVF coding 1 1,1 1,-1 1,1,1,1 1,1,-1,-1 X X,X X,-X 1,-1,1,-1 1,-1,-1,1 1,-1,-1,1,1,-1,-1,1 1,-1,-1,1,-1,1,1,-1 1,-1,1,-1,1,-1,1,-1 1,-1,1,-1,-1,1,-1,1 1,1,-1,-1,1,1,-1,-1 1,1,-1,-1,-1,-1,1,1 1,1,1,1,1,1,1,1 1,1,1,1,-1,-1,-1,-1 SF=1 SF=2 SF=4 SF=8 SF=n SF=2n ... ... ... ... 62
UMTS FDD frame structure ❑W-CDMA ❑ 1920-1980 MHz uplink ❑ 2110-2170 MHz downlink ❑ chipping rate: 3.840 Mchip/s ❑ soft handover ❑ QPSK ❑ complex power control (1500 power control cycles/s) ❑ spreading: UL: 4-256; DL:4-512 666.7 µs 666.7 µs 666.7 µs 0 1 2 12 13 14... Radio frame Pilot FBI TPC Time slot 10 ms Data Data1 uplink DPDCH uplink DPCCH downlink DPCHTPC TFCI Pilot DPCCH DPDCH 2560 chips, 10 bits 2560 chips, 10*2k bits (k = 0...6) TFCI 2560 chips, 10*2k bits (k = 0...7) Data2 DPDCH DPCCH FBI: Feedback Information TPC: Transmit Power Control TFCI: Transport Format Combination Indicator DPCCH: Dedicated Physical Control Channel DPDCH: Dedicated Physical Data Channel DPCH: Dedicated Physical Channel Slot structure NOT for user separation but synchronisation for periodic functions! 63
UMTS TDD frame structure (burst type 2) ❑TD-CDMA ❑ 2560 chips per slot ❑ spreading: 1-16 ❑ symmetric or asymmetric slot assignment to UL/DL (min. 1 per direction) ❑ tight synchronisation needed ❑ simpler power control (100-800 power control cycles/s) 0 1 2 12 13 14... Radio frame Data 1104 chips Midample 256 chips Data 1104 chips Time slot 666.7 µs 10 ms Traffic burstGP GP: guard period 96 chips2560 chips 64
UTRAN architecture UTRAN comprises several RNSs Node B can support FDD or TDD or both RNC is responsible for handover decisions requiring signalingto the UE Cell offers FDD or TDD RNC: Radio Network Controller RNS: Radio Network Subsystem Node B Node B RNC Iub Node B UE1 RNS CN Node B Node B RNC Iub Node B RNS Iur Node B UE2 UE3 Iu 65
UTRAN architecture RNC Iub RNS CN RNC Iub RNS Iur Iu Node B Node BNode B Node BNode B Node B Node B UTRAN comprises several RNSs Node B can support FDD or TDD or both RNC is responsible for handover decisions requiring signaling to the UE Cell offers FDD or TDD RNC: Radio Network Controller RNS: Radio Network SubsystemUE 66
UTRAN functions ❑ Admission control ❑ Congestion control ❑ System information broadcasting ❑ Radio channel encryption ❑ Handover ❑ SRNS moving ❑ Radio network configuration ❑ Channel quality measurements ❑ Macro diversity ❑ Radio carrier control ❑ Radio resource control ❑ Data transmission over the radio interface ❑ Outer loop power control (FDD and TDD) ❑ Channel coding ❑ Access control 67
Core network: protocols MSC RNS SGSN GGSN GMSC HLR VLR RNS Layer 1: PDH, SDH, SONET Layer 2: ATM Layer 3: IP GPRS backbone (IP) SS 7 GSM-CS backbone PSTN/ ISDN PDN (X.25), Internet (IP) UTRAN CN 68
Core network: architecture BTS Node B BSC Abis BTS BSS MSC Node B Node B RNC Iub Node B RNS Node B SGSN GGSN GMSC HLR VLR IuPS IuCS Iu CN EIR Gn Gi PSTN AuC GR 69
Core network The Core Network (CN) and thus the Interface Iu, too, are separated into two logical domains: ❑ Circuit Switched Domain (CSD) ❑ Circuit switched service incl. signaling ❑ Resource reservation at connection setup ❑ GSM components (MSC, GMSC, VLR) ❑ IuCS ❑ Packet Switched Domain (PSD) ❑ GPRS components (SGSN, GGSN) ❑ IuPS ❑ Release 99 uses the GSM/GPRS network and adds a new radio access! ❑ Helps to save a lot of money … ❑ Much faster deployment ❑ Not as flexible as newer releases (5, 6) 70
UMTS protocol stacks (user plane) apps. & protocols MAC radio MAC radio RLC SAR Uu IuCSUE UTRAN 3G MSC RLC AAL2 ATM AAL2 ATM SAR apps. & protocols MAC radio MAC radio PDCP GTP Uu IuPSUE UTRAN 3G SGSN RLC AAL5 ATM AAL5 ATM UDP/IP PDCP RLC UDP/IP UDP/IP Gn GTP GTP L2 L1 UDP/IP L2 L1 GTP 3G GGSN IP, PPP, … IP, PPP, … IP tunnel Circuit switched Packet switched 71
Support of mobility: macro diversity Multicasting of data via several physical channels ❑ Enables soft handover ❑ FDD mode only Uplink ❑ simultaneous reception of UE data at several Node Bs ❑ Reconstruction of data at Node B, SRNC or DRNC Downlink ❑ Simultaneous transmission of data via different cells ❑ Different spreading codes in different cells CNNode B RNC Node BUE 72
Support of mobility: handover From and to other systems (e.g., UMTS to GSM) ❑ This is a must as UMTS coverage will be poor in the beginning RNS controlling the connection is called SRNS (Serving RNS) RNS offering additional resources (e.g., for soft handover) is called Drift RNS (DRNS) End-to-end connections between UE and CN only via Iu at the SRNS ❑ Change of SRNS requires change of Iu ❑ Initiated by the SRNS ❑ Controlled by the RNC and CN SRNC UE DRNC Iur CN Iu Node B Iub Node B Iub 73
Example handover types in UMTS/GSM RNC1 UE1 RNC2 Iur 3G MSC1 Iu Node B1 Iub Node B2 Node B3 3G MSC2 BSCBTS 2G MSC3 AAbis UE2 UE3 UE4 74
UMTS services (originally) Data transmission service profiles Virtual Home Environment (VHE) ❑ Enables access to personalized data independent of location, access network, and device ❑ Network operators may offer new services without changing the network ❑ Service providers may offer services based on components which allow the automatic adaptation to new networks and devices ❑ Integration of existing IN services Circuit switched16 kbit/sVoice SMS successor, E-MailPacket switched14.4 kbit/sSimple Messaging Circuit switched14.4 kbit/sSwitched Data asymmetrical, MM, downloadsCircuit switched384 kbit/sMedium MM Low coverage, max. 6 km/hPacket switched2 Mbit/sHigh MM Bidirectional, video telephoneCircuit switched128 kbit/sHigh Interactive MM Transport modeBandwidthService Profile 75
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CS8601 MOBILE COMPUTING

  • 1.
    CS8601 MOBILE COMPUTING UNIT– II Dr.A.Kathirvel, Professor and Head, Dept of CSE Misrimal Navajee Munoth Jain Engineering College, Chennai
  • 2.
    Unit - II MOBILETELECOMMUNICATION SYSTEM Introduction to Cellular Systems - GSM – Services & Architecture – Protocols – Connection Establishment – Frequency Allocation – Routing – Mobility Management – Security – GPRS- UMTS – Architecture – Handover - Security TEXT BOOKS:Jochen Schiller, Mobile Communications, PHI, Second Edn, 2003. 2
  • 3.
    Mobile phone subscribersworldwide 0 200 400 600 800 1000 1200 1996 1997 1998 1999 2000 2001 2002 year Subscribers[million] GSM total TDMA total CDMA total PDC total Analogue total Total wireless Prediction (1998) 3
  • 4.
    Development of mobiletelecommunication systems 1G 2G 3G2.5G IS-95 cdmaOne IS-136 TDMA D-AMPS GSM PDC GPRS IMT-DS UTRA FDD / W-CDMA EDGE IMT-TC UTRA TDD / TD-CDMA cdma2000 1X 1X EV-DV (3X) AMPS NMT IMT-SC IS-136HS UWC-136 IMT-TC TD-SCDMA CT0/1 CT2 IMT-FT DECT CDMATDMAFDMA IMT-MC cdma2000 1X EV-DO 4
  • 5.
    GSM: Overview ❑ formerly:Groupe Spéciale Mobile (founded 1982) ❑ now: Global System for Mobile Communication ❑ Pan-European standard (ETSI, European Telecommunications Standardisation Institute) ❑ simultaneous introduction of essential services in three phases (1991, 1994, 1996) by the European telecommunication administrations (Germany: D1 and D2) ➔ seamless roaming within Europe possible ❑ today many providers all over the world use GSM (more than 184 countries in Asia, Africa, Europe, Australia, America) ❑ more than 747 million subscribers ❑ more than 70% of all digital mobile phones use GSM ❑ over 10 billion SMS per month in Germany, > 360 billion/year worldwide 5
  • 6.
    Performance characteristics ofGSM (wrt. analog sys.) Communication ❑ mobile, wireless communication; support for voice and data services Total mobility ❑ international access, chip-card enables use of access points of different providers Worldwide connectivity ❑ one number, the network handles localization High capacity ❑ better frequency efficiency, smaller cells, more customers per cell High transmission quality ❑ high audio quality and reliability for wireless, uninterrupted phone calls at higher speeds (e.g., from cars, trains) Security functions ❑ access control, authentication via chip-card and PIN 6
  • 7.
    Disadvantages of GSM Thereis no perfect system!! ❑ no end-to-end encryption of user data ❑ no full ISDN bandwidth of 64 kbit/s to the user, no transparent B-channel ❑ reduced concentration while driving ❑ electromagnetic radiation ❑ abuse of private data possible ❑ roaming profiles accessible ❑ high complexity of the system ❑ several incompatibilities within the GSM standards 7
  • 8.
    GSM: Mobile Services GSMoffers ❑ several types of connections ⚫ voice connections, data connections, short message service ❑ multi-service options (combination of basic services) Three service domains ❑ Bearer Services ❑ Telematic Services ❑ Supplementary Services GSM-PLMN transit network (PSTN, ISDN) source/ destination network TE TE bearer services tele services R, S (U, S, R)Um MT MS 8
  • 9.
    Bearer Services ❑ Telecommunicationservices to transfer data between access points ❑ Specification of services up to the terminal interface (OSI layers 1-3) ❑ Different data rates for voice and data (original standard) ❑ data service (circuit switched) ⚫ synchronous: 2.4, 4.8 or 9.6 kbit/s ⚫ asynchronous: 300 - 1200 bit/s ❑ data service (packet switched) ⚫ synchronous: 2.4, 4.8 or 9.6 kbit/s ⚫ asynchronous: 300 - 9600 bit/s Today: data rates of approx. 50 kbit/s possible – will be covered later! 9
  • 10.
    Tele Services I ❑Telecommunication services that enable voice communication via mobile phones ❑ All these basic services have to obey cellular functions, security measurements etc. ❑ Offered services ❑ mobile telephony primary goal of GSM was to enable mobile telephony offering the traditional bandwidth of 3.1 kHz ❑ Emergency number common number throughout Europe (112); mandatory for all service providers; free of charge; connection with the highest priority (preemption of other connections possible) ❑ Multinumbering several ISDN phone numbers per user possible 10
  • 11.
    Tele Services II ❑Additional services ❑Non-Voice-Teleservices ❑group 3 fax ❑voice mailbox (implemented in the fixed network supporting the mobile terminals) ❑electronic mail (MHS, Message Handling System, implemented in the fixed network) ❑... ❑Short Message Service (SMS) alphanumeric data transmission to/from the mobile terminal using the signaling channel, thus allowing simultaneous use of basic services and SMS 11
  • 12.
    Supplementary services ❑ Servicesin addition to the basic services, cannot be offered stand-alone ❑ Similar to ISDN services besides lower bandwidth due to the radio link ❑ May differ between different service providers, countries and protocol versions ❑ Important services ❑ identification: forwarding of caller number ❑ suppression of number forwarding ❑ automatic call-back ❑ conferencing with up to 7 participants ❑ locking of the mobile terminal (incoming or outgoing calls) ❑ ... 12
  • 13.
    Architecture of theGSM system GSM is a PLMN (Public Land Mobile Network) ❑ several providers setup mobile networks following the GSM standard within each country ❑ components ⚫ MS (mobile station) ⚫ BS (base station) ⚫ MSC (mobile switching center) ⚫ LR (location register) ❑ subsystems ⚫ RSS (radio subsystem): covers all radio aspects ⚫ NSS (network and switching subsystem): call forwarding, handover, switching ⚫ OSS (operation subsystem): management of the network 13
  • 14.
    GSM: overview fixed network BSC BSC MSCMSC GMSC OMC, EIR, AUC VLR HLR NSS with OSS RSS VLR 14
  • 15.
    GSM: elements andinterfaces NSS MS MS BTS BSC GMSC IWF OMC BTS BSC MSC MSC Abis Um EIR HLR VLR VLR A BSS PDN ISDN, PSTN RSS radio cell radio cell MS AUCOSS signaling O 15
  • 16.
  • 17.
    System architecture: radiosubsystem Components ❑ MS (Mobile Station) ❑ BSS (Base Station Subsystem): consisting of ⚫ BTS (Base Transceiver Station): sender and receiver ⚫ BSC (Base Station Controller): controlling several transceivers Interfaces ❑ Um : radio interface ❑ Abis : standardized, open interface with 16 kbit/s user channels ❑ A: standardized, open interface with 64 kbit/s user channels Um Abis A BSS radio subsystem network and switching subsystem MS MS BTS BSC MS C BTS BTS BSC BTS MS C 17
  • 18.
    System architecture: networkand switching subsystem Components MSC (Mobile Services Switching Center): IWF (Interworking Functions) ISDN (Integrated Services Digital Network) PSTN (Public Switched Telephone Network) PSPDN (Packet Switched Public Data Net.) CSPDN (Circuit Switched Public Data Net.) Databases HLR (Home Location Register) VLR (Visitor Location Register) EIR (Equipment Identity Register) network subsystem MSC MSC fixed partner networks IWF ISDN PSTN PSPDN CSPDN SS7 EIR HLR VLR ISDN PSTN 18
  • 19.
    Radio subsystem The RadioSubsystem (RSS) comprises the cellular mobile network up to the switching centers ❑ Components ❑ Base Station Subsystem (BSS): ⚫ Base Transceiver Station (BTS): radio components including sender, receiver, antenna - if directed antennas are used one BTS can cover several cells ⚫ Base Station Controller (BSC): switching between BTSs, controlling BTSs, managing of network resources, mapping of radio channels (Um) onto terrestrial channels (A interface) ⚫ BSS = BSC + sum(BTS) + interconnection ❑ Mobile Stations (MS) 19
  • 20.
    possible radio coverageof the cell idealized shape of the cell cell segmentation of the area into cells GSM: cellular network ❑ use of several carrier frequencies ❑ not the same frequency in adjoining cells ❑ cell sizes vary from some 100 m up to 35 km depending on user density, geography, transceiver power etc. ❑ hexagonal shape of cells is idealized (cells overlap, shapes depend on geography) ❑ if a mobile user changes cells handover of the connection to the neighbor cell
  • 21.
    Example coverage ofGSM networks (www.gsmworld.com) e-plus (GSM-1800) T-Mobile (GSM-900/1800) Berlin O2 (GSM-1800) Vodafone (GSM-900/1800) 21
  • 22.
    Base Transceiver Stationand Base Station Controller Tasks of a BSS are distributed over BSC and BTS ❑ BTS comprises radio specific functions ❑ BSC is the switching center for radio channels Functions BTS BSC Management of radio channels X Frequency hopping (FH) X X Management of terrestrial channels X Mapping of terrestrial onto radio channels X Channel coding and decoding X Rate adaptation X Encryption and decryption X X Paging X X Uplink signal measurements X Traffic measurement X Authentication X Location registry, location update X Handover management X 22
  • 23.
    Mobile station Terminal forthe use of GSM services ❑ A mobile station (MS) comprises several functional groups ❑ MT (Mobile Terminal): ⚫ offers common functions used by all services the MS offers ⚫ corresponds to the network termination (NT) of an ISDN access ⚫ end-point of the radio interface (Um) ❑ TA (Terminal Adapter): ⚫ terminal adaptation, hides radio specific characteristics ❑ TE (Terminal Equipment): ⚫ peripheral device of the MS, offers services to a user ⚫ does not contain GSM specific functions ❑ SIM (Subscriber Identity Module): ⚫ personalization of the mobile terminal, stores user parameters R S Um TE TA MT 23
  • 24.
    Network and switchingsubsystem NSS is the main component of the public mobile network GSM ❑ switching, mobility management, interconnection to other networks, system control ❑ Components ❑ Mobile Services Switching Center (MSC) controls all connections via a separated network to/from a mobile terminal within the domain of the MSC - several BSC can belong to a MSC ❑ Databases (important: scalability, high capacity, low delay) ⚫ Home Location Register (HLR) central master database containing user data, permanent and semi- permanent data of all subscribers assigned to the HLR (one provider can have several HLRs) ⚫ Visitor Location Register (VLR) local database for a subset of user data, including data about all user currently in the domain of the VLR 24
  • 25.
    Mobile Services SwitchingCenter The MSC (mobile switching center) plays a central role in GSM ❑ switching functions ❑ additional functions for mobility support ❑ management of network resources ❑ interworking functions via Gateway MSC (GMSC) ❑ integration of several databases ❑ Functions of a MSC ❑ specific functions for paging and call forwarding ❑ termination of SS7 (signaling system no. 7) ❑ mobility specific signaling ❑ location registration and forwarding of location information ❑ provision of new services (fax, data calls) ❑ support of short message service (SMS) ❑ generation and forwarding of accounting and billing information 25
  • 26.
    Operation subsystem The OSS(Operation Subsystem) enables centralized operation, management, and maintenance of all GSM subsystems ❑ Components ❑ Authentication Center (AUC) ⚫ generates user specific authentication parameters on request of a VLR ⚫ authentication parameters used for authentication of mobile terminals and encryption of user data on the air interface within the GSM system ❑ Equipment Identity Register (EIR) ⚫ registers GSM mobile stations and user rights ⚫ stolen or malfunctioning mobile stations can be locked and sometimes even localized ❑ Operation and Maintenance Center (OMC) ⚫ different control capabilities for the radio subsystem and the network subsystem 26
  • 27.
    1 2 34 5 6 7 8 higher GSM frame structures 935-960 MHz 124 channels (200 kHz) downlink 890-915 MHz 124 channels (200 kHz) uplink time GSM TDMA frame GSM time-slot (normal burst) 4.615 ms 546.5 µs 577 µs tail user data TrainingS guard space S user data tail guard space 3 bits 57 bits 26 bits 57 bits1 1 3 GSM - TDMA/FDMA 27
  • 28.
    GSM hierarchy offrames 0 1 2 2045 2046 2047... hyperframe 0 1 2 48 49 50... 0 1 24 25... superframe 0 1 24 25... 0 1 2 48 49 50... 0 1 6 7... multiframe frame burst slot 577 µs 4.615 ms 120 ms 235.4 ms 6.12 s 3 h 28 min 53.76 s 28
  • 29.
    GSM protocol layersfor signaling CM MM RR MM LAPDm radio LAPDm radio LAPD PCM RR’ BTSM CM LAPD PCM RR’ BTSM 16/64 kbit/s Um Abis A SS7 PCM SS7 PCM 64 kbit/s / 2.048 Mbit/s MS BTS BSC MSC BSSAP BSSAP 29
  • 30.
    Mobile Terminated Call PSTN calling station GMSC HLRVLR BSSBSSBSS MSC MS 1 2 3 4 5 6 7 8 9 10 11 12 13 16 10 10 11 11 11 14 15 17 1: calling a GSM subscriber 2: forwarding call to GMSC 3: signal call setup to HLR 4, 5: request MSRN from VLR 6: forward responsible MSC to GMSC 7: forward call to current MSC 8, 9: get current status of MS 10, 11: paging of MS 12, 13: MS answers 14, 15: security checks 16, 17: set up connection 30
  • 31.
    Mobile Originated Call PSTNGMSC VLR BSS MSC MS 1 2 6 5 3 4 9 10 7 8 1, 2: connection request 3, 4: security check 5-8: check resources (free circuit) 9-10: set up call 31
  • 32.
    MTC/MOC BTSMS paging request channel request immediateassignment paging response authentication request authentication response ciphering command ciphering complete setup call confirmed assignment command assignment complete alerting connect connect acknowledge data/speech exchange BTSMS channel request immediate assignment service request authentication request authentication response ciphering command ciphering complete setup call confirmed assignment command assignment complete alerting connect connect acknowledge data/speech exchange MTC MOC 32
  • 33.
    4 types ofhandover MSC MSC BSC BSCBSC BTS BTS BTSBTS MS MS MS MS 1 2 3 4 33
  • 34.
    Handover decision receive level BTSold receivelevel BTSold MS MS HO_MARGIN BTSold BTSnew 34
  • 35.
    Handover procedure HO access BTSoldBSCnew measurement result BSCold Link establishment MSCMS measurement report HO decision HO required BTSnew HO request resource allocation ch. activation ch. activation ackHO request ackHO commandHO commandHO command HO completeHO completeclear commandclear command clear complete clear complete 35
  • 36.
    Security in GSM Securityservices ❑ access control/authentication ⚫ user SIM (Subscriber Identity Module): secret PIN (personal identification number) ⚫ SIM network: challenge response method ❑ confidentiality ⚫ voice and signaling encrypted on the wireless link (after successful authentication) ❑ anonymity ⚫ temporary identity TMSI (Temporary Mobile Subscriber Identity) ⚫ newly assigned at each new location update (LUP) ⚫ encrypted transmission 3 algorithms specified in GSM ❑ A3 for authentication (“secret”, open interface) ❑ A5 for encryption (standardized) ❑ A8 for key generation (“secret”, open interface) “secret”: • A3 and A8 available via the Internet • network providers can use stronger mechanisms 36
  • 37.
    GSM - authentication A3 RANDKi 128bit 128 bit SRES* 32 bit A3 RAND Ki 128 bit 128 bit SRES 32 bit SRES* =? SRES SRES RAND SRES 32 bit mobile network SIM AC MSC SIM Ki: individual subscriber authentication key SRES: signed response 37
  • 38.
    GSM - keygeneration and encryption A8 RANDKi 128 bit 128 bit Kc 64 bit A8 RAND Ki 128 bit 128 bit SRES RAND encrypted data mobile network (BTS) MS with SIM AC BSS SIM A5 Kc 64 bit A5 MS data data cipher key 38
  • 39.
    Data services inGSM I Data transmission standardized with only 9.6 kbit/s ❑ advanced coding allows 14,4 kbit/s ❑ not enough for Internet and multimedia applications HSCSD (High-Speed Circuit Switched Data) ❑ mainly software update ❑ bundling of several time-slots to get higher AIUR (Air Interface User Rate) (e.g., 115.2 kbit/s using 8 slots, 14.4 each) ❑ advantage: ready to use, constant quality, simple ❑ disadvantage: channels blocked for voice transmission AIUR [kbit/s] TCH/F4.8 TCH/F9.6 TCH/F14.4 4.8 1 9.6 2 1 14.4 3 1 19.2 4 2 28.8 3 2 38.4 4 43.2 3 57.6 4 39
  • 40.
    Data services inGSM II GPRS (General Packet Radio Service) ❑ packet switching ❑ using free slots only if data packets ready to send (e.g., 115 kbit/s using 8 slots temporarily) ❑ standardization 1998, introduction 2001 ❑ advantage: one step towards UMTS, more flexible ❑ disadvantage: more investment needed (new hardware) GPRS network elements ❑ GSN (GPRS Support Nodes): GGSN and SGSN ❑ GGSN (Gateway GSN) ⚫ interworking unit between GPRS and PDN (Packet Data Network) ❑ SGSN (Serving GSN) ⚫ supports the MS (location, billing, security) ❑ GR (GPRS Register) ⚫ user addresses 40
  • 41.
    GPRS quality ofservice Reliability class Lost SDU probability Duplicate SDU probability Out of sequence SDU probability Corrupt SDU probability 1 10-9 10-9 10-9 10-9 2 10-4 10-5 10-5 10-6 3 10-2 10-5 10-5 10-2 Delay SDU size 128 byte SDU size 1024 byte class mean 95 percentile mean 95 percentile 1 < 0.5 s < 1.5 s < 2 s < 7 s 2 < 5 s < 25 s < 15 s < 75 s 3 < 50 s < 250 s < 75 s < 375 s 4 unspecified 41
  • 42.
    GPRS architecture andinterfaces MS BSS GGSNSGSN MSC Um EIR HLR/ GR VLR PDN Gb Gn Gi SGSN Gn 42
  • 43.
    GPRS protocol architecture apps. IP/X.25 LLC GTP MAC radio MAC radio FR RLCBSSGP IP/X.25 FR Um Gb Gn L1/L2 L1/L2 MS BSS SGSN GGSN UDP/TCP Gi SNDCP RLC BSSGP IP IP LLC UDP/TCP SNDCP GTP 43
  • 44.
    DECT DECT (Digital EuropeanCordless Telephone) standardized by ETSI (ETS 300.175-x) for cordless telephones ❑ standard describes air interface between base-station and mobile phone ❑ DECT has been renamed for international marketing reasons into „Digital Enhanced Cordless Telecommunication“ ❑ Characteristics ❑ frequency: 1880-1990 MHz ❑ channels: 120 full duplex ❑ duplex mechanism: TDD (Time Division Duplex) with 10 ms frame length ❑ multplexing scheme: FDMA with 10 carrier frequencies, TDMA with 2x 12 slots ❑ modulation: digital, Gaußian Minimum Shift Key (GMSK) ❑ power: 10 mW average (max. 250 mW) ❑ range: approx. 50 m in buildings, 300 m open space 44
  • 45.
    DECT system architecturereference model global network local network local network FT FT PTPA PTPA VDB HDB D1 D2 D3D4 45
  • 46.
    physical layer medium accesscontrol data link control data link control network layer OSI layer 1 OSI layer 2 OSI layer 3 U-PlaneC-Plane signaling, interworking application processes DECT reference model ❑ close to the OSI reference model ❑ management plane over all layers ❑ several services in C(ontrol)- and U(ser)- plane management 46
  • 47.
    DECT layers I ❑Physical layer ❑ modulation/demodulation ❑ generation of the physical channel structure with a guaranteed throughput ❑ controlling of radio transmission ⚫ channel assignment on request of the MAC layer ⚫ detection of incoming signals ⚫ sender/receiver synchronization ⚫ collecting status information for the management plane ❑ MAC layer ❑ maintaining basic services, activating/deactivating physical channels ❑ multiplexing of logical channels ⚫ e.g., C: signaling, I: user data, P: paging, Q: broadcast ❑ segmentation/reassembly ❑ error control/error correction 47
  • 48.
    DECT time multiplexframe slot sync A field DATA DATA 64 C 16 DATA 64 C 16 DATA 64 C 16 DATA 64 C 16 B field D field 1 frame = 10 ms 12 down slots 12 up slots 0 419 0 31 0 387 0 63 0 319 protected mode unprotected mode simplex bearer 25.6 kbit/s 32 kbit/s 420 bit + 52 µs guard time („60 bit“) in 0.4167 ms guard X field 0 3 A: network control B: user data X: transmission quality 48
  • 49.
    DECT layers II ❑Data link control layer ❑ creation and keeping up reliable connections between the mobile terminal and basestation ❑ two DLC protocols for the control plane (C-Plane) ⚫ connectionless broadcast service: paging functionality ⚫ Lc+LAPC protocol: in-call signaling (similar to LAPD within ISDN), adapted to the underlying MAC service ❑ several services specified for the user plane (U-Plane) ⚫ null-service: offers unmodified MAC services ⚫ frame relay: simple packet transmission ⚫ frame switching: time-bounded packet transmission ⚫ error correcting transmission: uses FEC, for delay critical, time-bounded services ⚫ bandwidth adaptive transmission ⚫ „Escape“ service: for further enhancements of the standard 49
  • 50.
    DECT layers III ❑Network layer ❑ similar to ISDN (Q.931) and GSM (04.08) ❑ offers services to request, check, reserve, control, and release resources at the basestation and mobile terminal ❑ resources ⚫ necessary for a wireless connection ⚫ necessary for the connection of the DECT system to the fixed network ❑ main tasks ⚫ call control: setup, release, negotiation, control ⚫ call independent services: call forwarding, accounting, call redirecting ⚫ mobility management: identity management, authentication, management of the location register 50
  • 51.
    Several „DECT ApplicationProfiles“ in addition to the DECT specification ❑ GAP (Generic Access Profile) standardized by ETSI in 1997 ⚫ assures interoperability between DECT equipment of different manufacturers (minimal requirements for voice communication) ⚫ enhanced management capabilities through the fixed network: Cordless Terminal Mobility (CTM) ❑ DECT/GSM Interworking Profile (GIP): connection to GSM ❑ ISDN Interworking Profiles (IAP, IIP): connection to ISDN ❑ Radio Local Loop Access Profile (RAP): public telephone service ❑ CTM Access Profile (CAP): support for user mobility Enhancements of the standard DECT basestation GAP DECT Common Air Interface DECT Portable Part fixed network 51
  • 52.
    TETRA - TerrestrialTrunked Radio Trunked radio systems ❑ many different radio carriers ❑ assign single carrier for a short period to one user/group of users ❑ taxi service, fleet management, rescue teams ❑ interfaces to public networks, voice and data services ❑ very reliable, fast call setup, local operation TETRA - ETSI standard ❑ formerly: Trans European Trunked Radio ❑ offers Voice+Data and Packet Data Optimized service ❑ point-to-point and point-to-multipoint ❑ ad-hoc and infrastructure networks ❑ several frequencies: 380-400 MHz, 410-430 MHz ❑ FDD, DQPSK ❑ group call, broadcast, sub-second group-call setup 52
  • 53.
    TDMA structure ofthe voice+data system 0 1 2 57 58 59... hyperframe 0 1 2 15 16 17... multiframe 0 1 2 3 0 slot 509 frame 14.17 ms 56.67 ms 1.02 s 61.2 s CF Control Frame 53
  • 54.
    UMTS and IMT-2000 Proposalsfor IMT-2000 (International Mobile Telecommunications) ❑ UWC-136, cdma2000, WP-CDMA ❑ UMTS (Universal Mobile Telecommunications System) from ETSI UMTS ❑ UTRA (was: UMTS, now: Universal Terrestrial Radio Access) ❑ enhancements of GSM ⚫ EDGE (Enhanced Data rates for GSM Evolution): GSM up to 384 kbit/s ⚫ CAMEL (Customized Application for Mobile Enhanced Logic) ⚫ VHE (virtual Home Environment) ❑ fits into GMM (Global Multimedia Mobility) initiative from ETSI ❑ requirements ⚫ min. 144 kbit/s rural (goal: 384 kbit/s) ⚫ min. 384 kbit/s suburban (goal: 512 kbit/s) ⚫ up to 2 Mbit/s urban 54
  • 55.
    Frequencies for IMT-2000 IMT-2000 18501900 1950 2000 2050 2100 2150 2200 MHz MSS  ITU allocation (WRC 1992) IMT-2000 MSS  Europe China Japan North America UTRA FDD  UTRA FDD  T D D T D D MSS  MSS  DE CT GSM 1800 1850 1900 1950 2000 2050 2100 2150 2200 MHz IMT-2000 MSS  IMT-2000 MSS  GSM 1800 cdma2000 W-CDMA MSS  MSS  MSS  MSS  cdma2000 W-CDMA PHS PCS rsv. 55
  • 56.
    IMT-2000 family IMT-DS (Direct Spread) UTRAFDD (W-CDMA) 3GPP IMT-TC (Time Code) UTRA TDD (TD-CDMA); TD-SCDMA 3GPP IMT-MC (Multi Carrier) cdma2000 3GPP2 IMT-SC (Single Carrier) UWC-136 (EDGE) UWCC/3GPP IMT-FT (Freq. Time) DECT ETSI GSM (MAP) ANSI-41 (IS-634) IP-Network IMT-2000 Core Network ITU-T IMT-2000 Radio Access ITU-R Interface for Internetworking Flexible assignment of Core Network and Radio Access Initial UMTS (R99 w/ FDD) 56
  • 57.
    Licensing Example: UMTSin Germany, 18. August 2000 Sum: 50.81 billion € ❑ UTRA-FDD: ❑ Uplink 1920-1980 MHz ❑ Downlink 2110-2170 MHz ❑ duplex spacing 190 MHz ❑ 12 channels, each 5 MHz ❑ UTRA-TDD: ❑ 1900-1920 MHz, ❑ 2010-2025 MHz; ❑ 5 MHz channels ❑ Coverage: 25% of the population until 12/2003, 50% until 12/2005 57
  • 58.
    UMTS architecture (Release99 used here!) UTRANUE CN IuUu UTRAN (UTRA Network) ❑ Cell level mobility ❑ Radio Network Subsystem (RNS) ❑ Encapsulation of all radio specific tasks UE (User Equipment) CN (Core Network) ❑ Inter system handover ❑ Location management if there is no dedicated connection between UE and UTRAN 58
  • 59.
    UMTS domains andinterfaces I User Equipment Domain ❑ Assigned to a single user in order to access UMTS services Infrastructure Domain ❑ Shared among all users ❑ Offers UMTS services to all accepted users USIM Domain Mobile Equipment Domain Access Network Domain Serving Network Domain Transit Network Domain Home Network Domain Cu Uu Iu User Equipment Domain Zu Yu Core Network Domain Infrastructure Domain 59
  • 60.
    UMTS domains andinterfaces II Universal Subscriber Identity Module (USIM) ❑ Functions for encryption and authentication of users ❑ Located on a SIM inserted into a mobile device Mobile Equipment Domain ❑ Functions for radio transmission ❑ User interface for establishing/maintaining end-to-end connections Access Network Domain ❑ Access network dependent functions Core Network Domain ❑ Access network independent functions ❑ Serving Network Domain ⚫ Network currently responsible for communication ❑ Home Network Domain ⚫ Location and access network independent functions 60
  • 61.
    Spreading and scramblingof user data Constant chipping rate of 3.84 Mchip/s Different user data rates supported via different spreading factors ❑ higher data rate: less chips per bit and vice versa User separation via unique, quasi orthogonal scrambling codes ❑ users are not separated via orthogonal spreading codes ❑ much simpler management of codes: each station can use the same orthogonal spreading codes ❑ precise synchronisation not necessary as the scrambling codes stay quasi- orthogonal data1 data2 data3 scrambling code1 spr. code3 spr. code2 spr. code1 data4 data5 scrambling code2 spr. code4 spr. code1 sender1 sender2 61
  • 62.
  • 63.
    UMTS FDD framestructure ❑W-CDMA ❑ 1920-1980 MHz uplink ❑ 2110-2170 MHz downlink ❑ chipping rate: 3.840 Mchip/s ❑ soft handover ❑ QPSK ❑ complex power control (1500 power control cycles/s) ❑ spreading: UL: 4-256; DL:4-512 666.7 µs 666.7 µs 666.7 µs 0 1 2 12 13 14... Radio frame Pilot FBI TPC Time slot 10 ms Data Data1 uplink DPDCH uplink DPCCH downlink DPCHTPC TFCI Pilot DPCCH DPDCH 2560 chips, 10 bits 2560 chips, 10*2k bits (k = 0...6) TFCI 2560 chips, 10*2k bits (k = 0...7) Data2 DPDCH DPCCH FBI: Feedback Information TPC: Transmit Power Control TFCI: Transport Format Combination Indicator DPCCH: Dedicated Physical Control Channel DPDCH: Dedicated Physical Data Channel DPCH: Dedicated Physical Channel Slot structure NOT for user separation but synchronisation for periodic functions! 63
  • 64.
    UMTS TDD framestructure (burst type 2) ❑TD-CDMA ❑ 2560 chips per slot ❑ spreading: 1-16 ❑ symmetric or asymmetric slot assignment to UL/DL (min. 1 per direction) ❑ tight synchronisation needed ❑ simpler power control (100-800 power control cycles/s) 0 1 2 12 13 14... Radio frame Data 1104 chips Midample 256 chips Data 1104 chips Time slot 666.7 µs 10 ms Traffic burstGP GP: guard period 96 chips2560 chips 64
  • 65.
    UTRAN architecture UTRAN comprisesseveral RNSs Node B can support FDD or TDD or both RNC is responsible for handover decisions requiring signalingto the UE Cell offers FDD or TDD RNC: Radio Network Controller RNS: Radio Network Subsystem Node B Node B RNC Iub Node B UE1 RNS CN Node B Node B RNC Iub Node B RNS Iur Node B UE2 UE3 Iu 65
  • 66.
    UTRAN architecture RNC Iub RNS CN RNC Iub RNS Iur Iu Node B NodeBNode B Node BNode B Node B Node B UTRAN comprises several RNSs Node B can support FDD or TDD or both RNC is responsible for handover decisions requiring signaling to the UE Cell offers FDD or TDD RNC: Radio Network Controller RNS: Radio Network SubsystemUE 66
  • 67.
    UTRAN functions ❑ Admissioncontrol ❑ Congestion control ❑ System information broadcasting ❑ Radio channel encryption ❑ Handover ❑ SRNS moving ❑ Radio network configuration ❑ Channel quality measurements ❑ Macro diversity ❑ Radio carrier control ❑ Radio resource control ❑ Data transmission over the radio interface ❑ Outer loop power control (FDD and TDD) ❑ Channel coding ❑ Access control 67
  • 68.
    Core network: protocols MSC RNS SGSNGGSN GMSC HLR VLR RNS Layer 1: PDH, SDH, SONET Layer 2: ATM Layer 3: IP GPRS backbone (IP) SS 7 GSM-CS backbone PSTN/ ISDN PDN (X.25), Internet (IP) UTRAN CN 68
  • 69.
    Core network: architecture BTS NodeB BSC Abis BTS BSS MSC Node B Node B RNC Iub Node B RNS Node B SGSN GGSN GMSC HLR VLR IuPS IuCS Iu CN EIR Gn Gi PSTN AuC GR 69
  • 70.
    Core network The CoreNetwork (CN) and thus the Interface Iu, too, are separated into two logical domains: ❑ Circuit Switched Domain (CSD) ❑ Circuit switched service incl. signaling ❑ Resource reservation at connection setup ❑ GSM components (MSC, GMSC, VLR) ❑ IuCS ❑ Packet Switched Domain (PSD) ❑ GPRS components (SGSN, GGSN) ❑ IuPS ❑ Release 99 uses the GSM/GPRS network and adds a new radio access! ❑ Helps to save a lot of money … ❑ Much faster deployment ❑ Not as flexible as newer releases (5, 6) 70
  • 71.
    UMTS protocol stacks(user plane) apps. & protocols MAC radio MAC radio RLC SAR Uu IuCSUE UTRAN 3G MSC RLC AAL2 ATM AAL2 ATM SAR apps. & protocols MAC radio MAC radio PDCP GTP Uu IuPSUE UTRAN 3G SGSN RLC AAL5 ATM AAL5 ATM UDP/IP PDCP RLC UDP/IP UDP/IP Gn GTP GTP L2 L1 UDP/IP L2 L1 GTP 3G GGSN IP, PPP, … IP, PPP, … IP tunnel Circuit switched Packet switched 71
  • 72.
    Support of mobility:macro diversity Multicasting of data via several physical channels ❑ Enables soft handover ❑ FDD mode only Uplink ❑ simultaneous reception of UE data at several Node Bs ❑ Reconstruction of data at Node B, SRNC or DRNC Downlink ❑ Simultaneous transmission of data via different cells ❑ Different spreading codes in different cells CNNode B RNC Node BUE 72
  • 73.
    Support of mobility:handover From and to other systems (e.g., UMTS to GSM) ❑ This is a must as UMTS coverage will be poor in the beginning RNS controlling the connection is called SRNS (Serving RNS) RNS offering additional resources (e.g., for soft handover) is called Drift RNS (DRNS) End-to-end connections between UE and CN only via Iu at the SRNS ❑ Change of SRNS requires change of Iu ❑ Initiated by the SRNS ❑ Controlled by the RNC and CN SRNC UE DRNC Iur CN Iu Node B Iub Node B Iub 73
  • 74.
    Example handover typesin UMTS/GSM RNC1 UE1 RNC2 Iur 3G MSC1 Iu Node B1 Iub Node B2 Node B3 3G MSC2 BSCBTS 2G MSC3 AAbis UE2 UE3 UE4 74
  • 75.
    UMTS services (originally) Datatransmission service profiles Virtual Home Environment (VHE) ❑ Enables access to personalized data independent of location, access network, and device ❑ Network operators may offer new services without changing the network ❑ Service providers may offer services based on components which allow the automatic adaptation to new networks and devices ❑ Integration of existing IN services Circuit switched16 kbit/sVoice SMS successor, E-MailPacket switched14.4 kbit/sSimple Messaging Circuit switched14.4 kbit/sSwitched Data asymmetrical, MM, downloadsCircuit switched384 kbit/sMedium MM Low coverage, max. 6 km/hPacket switched2 Mbit/sHigh MM Bidirectional, video telephoneCircuit switched128 kbit/sHigh Interactive MM Transport modeBandwidthService Profile 75
  • 76.