Mobile Computing-wireless Telecommunication Systems
- 2. GSM: Overview • GSM • 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
- 3. Performance characteristics of GSM • 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
- 4. 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
- 5. GSM: Mobile Services GSM-PLMN transit network (PSTN, ISDN) source/ destination network TE TE bearer services tele services R, S (U, S, R) Um MT MS • 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
- 6. 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!
- 7. 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
- 8. 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
- 9. 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) • ...
- 10. 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
- 11. GSM: overview fixed network BSC BSC MSC MSC GMSC OMC, EIR, AUC VLR HLR NSS with OSS RSS VLR
- 12. 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 AUC OSS signaling O
- 13. Um Abis A BSS 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 PSTN GSM: system architecture
- 14. 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 MSC BTS BTS BSC BTS MSC
- 15. 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
- 16. 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)
- 17. 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
- 18. Base Transceiver Station and Base Station Controller 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 • Tasks of a BSS are distributed over BSC and BTS BTS comprises radio specific functions BSC is the switching center for radio channels
- 19. 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
- 20. 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
- 21. 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
- 22. 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
- 23. 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 f r e q u e n c y time GSM TDMA frame GSM time-slot (normal burst) 4.615 ms 546.5 µs 577 µs tail user data Training S guard space S user data tail guard space 3 bits 57 bits 26 bits 57 bits 1 1 3 GSM - TDMA/FDMA
- 24. 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
- 25. 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
- 26. Mobile Terminated Call •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 PSTN calling station GMSC HLR VLR BSS BSS BSS MSC MS 1 2 3 4 5 6 7 8 9 10 11 12 13 16 10 10 11 11 11 14 15 17
- 27. Mobile Originated Call •1, 2: connection request •3, 4: security check •5-8: check resources (free circuit) •9-10: set up call • PSTN GMSC VLR BSS MSC MS 1 2 6 5 3 4 9 10 7 8
- 28. MTC/MOC BTS MS 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 BTS MS 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
- 29. 4 types of handover MSC MSC BSC BSC BSC BTS BTS BTS BTS MS MS MS MS 1 2 3 4
- 30. Handover decision receive level BTSold receive level BTSold MS MS HO_MARGIN BTSold BTSnew
- 31. Handover procedure HO access BTSold BSCnew measurement result BSCold Link establishment MSC MS measurement report HO decision HO required BTSnew HO request resource allocation ch. activation ch. activation ack HO request ack HO command HO command HO command HO complete HO complete clear command clear command clear complete clear complete
- 32. 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
- 33. GSM - authentication A3 RAND Ki 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
- 34. GSM - key generation and encryption A8 RAND Ki 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
- 35. 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
- 36. 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
- 37. GPRS architecture and interfaces MS BSS GGSN SGSN MSC Um EIR HLR/ GR VLR PDN Gb Gn Gi SGSN Gn
- 38. 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
- 39. 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
- 40. DECT system architecture reference model global network local network local network FT FT PT PA PT PA VDB HDB D1 D2 D3 D4
- 41. physical layer medium access control data link control data link control network layer OSI layer 1 OSI layer 2 OSI layer 3 U-Plane C-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
- 42. 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
- 43. 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
- 44. 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
- 45. 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
- 46. Enhancements of the standard • 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 DECT basestation GAP DECT Common Air Interface DECT Portable Part fixed network
- 47. 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
- 48. 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
- 49. 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
- 50. 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)
- 51. UMTS architecture • 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 UTRAN UE CN Iu Uu
- 52. 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
- 53. 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
- 54. 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
- 55. 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 burst GP GP: guard period 96 chips 2560 chips
- 56. 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
- 57. UTRAN architecture RNC Iub RNS CN RNC Iub RNS Iur Iu Node B Node B Node B Node B Node 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 Subsystem UE
- 58. 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
- 59. 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
- 60. 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
- 61. 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)
- 62. UMTS protocol stacks (user plane) apps. & protocols MAC radio MAC radio RLC SAR Uu IuCS UE UTRAN 3G MSC RLC AAL2 ATM AAL2 ATM SAR apps. & protocols MAC radio MAC radio PDCP GTP Uu IuPS UE 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
- 63. 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 CN Node B RNC Node B UE
- 64. 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
- 65. Example handover types in UMTS/GSM RNC1 UE1 RNC2 Iur 3G MSC1 Iu Node B1 Iub Node B2 Node B3 3G MSC2 BSC BTS 2G MSC3 A Abis UE2 UE3 UE4
- 66. 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 switched 16 kbit/s Voice SMS successor, E-Mail Packet switched 14.4 kbit/s Simple Messaging Circuit switched 14.4 kbit/s Switched Data asymmetrical, MM, downloads Circuit sitched 384 kbit/s Medium MM Low coverage, max. 6 km/h Packet switched 2 Mbit/s High MM Bidirectional, video telephone Circuit switched 128 kbit/s High Interactive MM Transport mode Bandwidth Service Profile