Data Services in GSM HSCSD GPRS. GPRS Infrastructure Components

Transcription

1 4 4 Data Services in Data transmission in with only 9.6 kbit/s Advanced channel coding allows 14.4 kbit/s Still not enough for Internet access or even multimedia applications Thus: UMTS as 3G network : Integration of data and voice in one network But: new network infrastructure, new software, new devices, Development of other enhancements of as interim solutions 2.5G networks as interim solution HSCSD as software solution GPRS as hardware solution EDGE as 3G solution in a 2G network HSCSD HSCSD (High-Speed Circuit Switched Data) Put together several time for one AIUR (Air Interface User Rate, up to 57.6 kbit/s with 4 Slots of 14.4 kbit/s) Symmetrical (2 time channels each for up- and downlink) and asymmetrical (3 + 1 channels) communication are supported Mainly software update for the realization of the putting together Advantage: fast availability, continuous quality, simple Disadvantage: connection-oriented, 4 channels are blocked the whole time, signaling for several channels necessary AIUR [kbit/s] TCH/F4.8 TCH/F9.6 TCH/F GPRS GPRS Infrastructure Components GPRS (General Packet Radio Service) Packet-oriented transmission, usable also for multicast Usage of up to 8 time of a TDMA frame on demand Usage of time only when data are available for sending (e.g. 50 kbit/s with short usage of 4 ) Advantage: step towards UMTS, flexible Disadvantage: expensive because some new infrastructure is needed to handle the new transmission mechanism, wireless transmission becomes a bottleneck for high traffic amount Needed infrastructure: GSN (GPRS Support Nodes) - GGSN and SGSN - GGSN (Gateway GSN): translation between GPRS und PDN (Packet Data Network) - SGSN (Serving GSN): support of the MS (location, accounting, security) - GR (GPRS Register): Management of user addresses 40 PCU BSC AUC: Authentication Center BSC: Base Station Controller EIR: Equipment Identity Register GMSC: Gateway Mobile Switching Center HLR: Home Location Register MSC: Mobile Switching Center VLR: Visitor Location Register SGSN MSC GGSN GMSC PSTN ISDN EIR AUC HLR 4 NSS GR VLR RSS GPRS PDN GGSN: Gateway GPRS Support Node GR: GPRS Register PCU: Packet Control Unit SGSN: Serving GPRS Support Node OSS 41

2 GPRS Data Rates [kbit/s] Advantages of GPRS (error-) coding CS-1 CS-2 CS-3 CS-4 Data rate 1 time slot 9,05 13,4 15,6 21,4 CS-4 2 time 18,2 26,8 31,2 42,8 CS-3 CS-2 3 time 27,15 40,2 46,8 64,2 CS-1 Position 4 time 36,2 53,6 62,4 85,6 5 time 45, time 54,3 80,4 93,6 128,4 7 time 63,35 93,8 109,2 149,8 8 time 72,4 107,2 124,8 171,2 CS-1 to CS-4: decreasing error protection Dynamic choice of coding Basing on measurements of signal quality (and the needed QoS) The user is assigned the highest possible data rate 42 Always connected Long duration for connection establishment are eliminated Transmission of data on demand Accounting by data volume, not by connection duration Robust connection Coding of data bases on current signal quality Even the BSS checks the data correctness and initiates if necessary a transmission repeat 43 EDGE UMTS und EDGE (Enhanced Data Rates for Evolution) Up to 384 kbit/s by enhanced modulation (8PSK instead of GMSK) Transmission repeat: Change of coding to adapt to the current channel quality Is build upon the existing /GPRS system: New transceiver are needed (hardware upgrade in the BSS) Software-Upgrade BSS und BSC New devices (8PSK) No changes in the core network! Cheap alternative to UMTS? Proposals for (International Mobile Telecommunications) as world-wide standardized 3G communication system: UWC-136, cdma2000, WP-CDMA UMTS (Universal Mobile Telecommunications System, ETSI) UMTS bases on UTRA: Universal Terrestrial Radio Access Integration of different mobile, cordless and pager systems into only one radio access network supporting world-wide roaming Integration von voice, data, and multimedia data services Enhancement of : higher data rates, enhanced service concept, global roaming Data rates: 144 kbit/s up to 2 MBit/s min. 144 kbit/s rural (target: 384 kbit/s) min. 384 kbit/s suburban (target: 512 kbit/s) up to 2 MBit/s urban Compatibility to, ATM, ISDN and IP 44 45

3 Frequencies for Family ITU allocation MHz UMTS UMTS Interface for networking Europe China DE CT T D D UTRA FDD T D D UTRA FDD core network ITU-T ANSI-41 (IS-634) IP network Japan cdma2000 PHS W-CDMA cdma2000 W-CDMA Initial UMTS (Release99 with FDD) Flexible assignment of core network and radio access North America PCS MHz : Mobile satellite services DECT: Digital Enhanced Cordless Telecommunications PHS: Personal Handyphone System PCS: Personal Communications Service (1900) rsv. 46 radio access ITU-R IMT-DS (Direct Spread) UTRA FDD (W-CDMA) IMT-TC (Time Code) UTRA TDD (TD-CDMA); TD-SCDMA IMT-MC (Multi Carrier) cdma2000 IMT-SC (Single Carrier) UWC-136 (EDGE) IMT-FT (Freq. Time) DECT 47 Licensing of UMTS in Germany, UTRA-FDD: Uplink MHz Downlink MHz Duplex spacing 190 MHz 12 channels, 5 MHz each UTRA-TDD: MHz MHz 5 MHz channels Planned coverage: 25% of the population till 12/2003, 50% till 12/2005 Sum: 50,81 billion UMTS Architektur (Release 99) UTRAN (UTRA Network) Cell level mobility Comprises several Radio Network Subsystems (RNS) Encapsulation of all radio specific tasks UE (User Equipment) CN (Core Network) Handover between systems Gateways to other systems Location management, if there is no dedicated connection between UE and UTRAN Usage of existing /GPRS infrastructure, change to an IP-based core network? UE U u UTRAN CN 48 49

4 UMTS s and Interfaces UMTS s and Interfaces Home Network Universal Subscriber Identity Module (USIM) Functions for encryption and authentication of users Located on the SIM USIM C u Mobile U u Access Equipment Network Serving Network Z u Y u Transit Network Mobile Equipment Functions for radio transmission User interface for establishing/maintaining end-to-end connections User Equipment Infrastructure Core Network User Equipment Assigned to a single user in order to access UMTS services Infrastructure Shared among all users Offers UMTS services to all accepted users Access Network Access network dependent functions Core Network Access network independent functions Serving Network Network currently responsible for communication Home Network Location and access network independent functions Spreading and Scrambling of User Data OSVF Coding Constant chipping rate of 3.84 million chip/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 synchronization not necessary as the scrambling codes stay quasiorthogonal data 1 data 2 data 3 data 4 data 5 code 1 code 2 scrambling code 1 code 3 code 1 scrambling code 2 code 4 OSVF: Orthogonal Variable Spreading Factors Simple generation of orthogonal chip sequences Thus: simple user management 1,1,1,1,1,1,1,1 Further simplification: codes are 1,1,1,1 only used within one station, 1,1,1,1,-1,-1,-1,-1 no coordination between stations 1,1 1,1,-1,-1,1,1,-1,-1 1,1,-1,-1 X,X 1,1,-1,-1,-1,-1,1,1 X 1 1,-1,1,-1,1,-1,1,-1 X,-X 1,-1,1,-1 1,-1,1,-1,-1,1,-1,1 SF=n SF=2n 1,-1 1,-1,-1,1,1,-1,-1,1 1,-1,-1,1 1,-1,-1,1,-1,1,1, sender 1 sender 2 SF=1 SF=2 SF=4 SF=

5 UMTS FDD Frame Structure UMTS TDD Frame Structure 10 ms 666,7 µs 666,7 µs 666,7 µs Radio frame Time slot Pilot TFCI FBI TPC Data Chips, 10 Bits Data 2560 Chips, 10*2 k Bits (k = 0...6) TPC TFCI Data 2 Pilot Uplink DPCCH Uplink DPDCH Downlink DPCH W (Wideband)-CDMA MHz Uplink MHz Downlink Chipping rate: 3,840 MChip/s Soft handover QPSK Complex power control (1500 power control cycles/s) Spreading factor: UL: 4-256; DL: DPDCH DPCCH DPDCHDPCCH FBI: Feedback Information TPC: Transmit Power Control 2560 Chips, 10*2 k Bits (k = 0...7) TFCI: Transport Format Combination Indicator DPCCH: Dedicated Physical Control Channel DPDCH: Dedicated Physical Data Channel DPCH: Dedicated Physical Channel 10 ms 666,7 µs Radio Frame Data 1104 Chips Time slot Midample 256 Chips 2560 Chips Data 1104 Chips Traffic burst GP: guard period 96 Chips TD-CDMA 2560 Chips per slot Spreading factor: 1-16 Symmetric or asymmetric slot assignment to UL/DL (min. 1 per direction) Tight synchronization needed Simpler power control ( power control cycles/s) GP Slot structure not for user separation but synchronization for periodic functions! UTRAN Architecture UTRAN Functions UE 1 UE 3 UE 2 b b RNS RNC r RNC RNC: Radio Network Controller RNS: Radio Network Subsystem CN UTRAN comprises several RNSs can support both, FDD or TDD RNC is responsible for handover decisions requiring signaling to the UE Cell offers FDD or TDD Admission Control Congestion Control System Information Broadcasting Radio Channel Encryption Handover Radio Network Configuration Channel Quality Measurements Macro Diversity Radio Carrier Control Radio Resource Control Data Transmission over the Radio Interface Power Control Channel Coding Access Control RNS 56 57

6 Core Network: Protocols Core Network VLR RNS MSC -CS Backbone HLR GMSC PSTN/ ISDN The Core Network and thus also the interface are separated into two logical domains: Circuit Switched (CSD) Circuit switched service inclusive signaling Resource reservation at connection setup components (MSC, GMSC, VLR) RNS Packet Switched (PSD) GPRS components (SGSN, GGSN) Layer 3: IP Layer 2: ATM Layer 1: PDH, SDH, SONET SGSN GPRS Backbone (IP) SS 7 GGSN PDN (X.25), Internet (IP) Release 99 uses the /GPRS network and just adds a new radio access Lower costs, faster deployment Not as flexible as newer releases 4, 5, 6 (change to IP based functions, ) UTRAN CN RNS can be UMTS RNS or BSS Support of Mobility: Macro Diversity Support of Mobility: Handover UE RNC CN A device can receive signals over 3 antennas in parallel Multicast of data via several physical channels Enables soft handover only in FDD mode Uplink Simultaneous reception of UE data at several s Reconstruction of data at Node B, SRNC or DRNC From and to other systems (e.g. UMTS to ) A must for the beginning when UMTS coverage is poor RNS controlling the connection is called SRNS (Serving RNS) RNS offering additional resources (e.g.. for soft handover) is called DRNS (Drift RNS) End-to-end connections between UE and CN only via at the SRNS Change of SRNS requires change of Initiated by SRNS Controlled by the RNC and CN Downlink Simultaneous transmission of data via different cells Different spreading codes in different cells UE b b SRNC DRNC r CN 60 61

7 Example Handover Types in in UMTS/ Cell Breathing UE 1 UE 2 UE 3 UE b RNC 1 3 RNC 2 3G MSC 2 r 3G MSC 1 BTS BSC 2G MSC 3 A bis A Device gets full power from the base station Number of connected devices has no influence on the cell size UMTS Cell size and capacity are tightly correlated Capacity is determined at the Signal-to-Noise-Ratio Noise is increased by interference with other cells with other participants Devices at the cell border are not able to increase their signal strength (power limitation) for too high noise no communication is possible Restriction of simultaneous number of users necessary Cell breathing makes cell planning complicated Cell Breathing: Example UMTS Services Data Transmission Service Profiles Service Profile Bandbreite Transportmodus High Interactive MM 128 kbit/s circuit switched High MM 2 Mbit/s packet switched Medium MM 384 kbit/s circuit switched Switched Data 14,4 kbit/s circuit switched Simple Messaging 14,4 kbit/s packet switched Sprache 16 kbit/s circuit switched bidirectional, video telephone low coverage, max. 6 km/h asymmetrical, MM, downloads SMS successor, 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 64 65

8 What is Next? Overlay Networks the global Goal 1981: NMT : NMT 900 Cellular phones 1992: 1994: DCS : CDMA 1983: AMPS 1991: D-AMPS 1993: PDC Satellites 1982: Inmarsat-A 1988: Inmarsat-C 1992: Inmarsat-B Inmarsat-M 1998: Iridium Cordless phones 1980: CT0 1984: CT1 Wireless LANs 1987: CT : CT : DECT 199x: proprietary 1997: IEEE : b, Bluetooth Integration of heterogeneous fixed and mobile networks with different transmission characteristics vertical handover urban area region analog digital 4G Fourth Generation when and where? 2000: GPRS 2001: 200?: Fourth Generation (Internet-based?) 2000: IEEE a 66 company car, house, personal range horizontal handover 67 Characteristics of Future Networks (?) Exemplarily IP-based 4G/Next G/ Network Improved radio techniques and antennas Intelligent antennas, direction, MIMO (multiple-input-multiple-output) antennas Space multiplex for higher capacity, usage of multipath signal propagation Software defined radios (SDR) Usage of different radio interfaces, download of new modulation and coding technologies Needs high computing power (UMTS RF: GIPS) Dynamic frequency allocation Dynamic assignment of frequencies improves capacity Convergence of core networks IP-based, Quality of Service, Mobile IP Ad-hoc techniques Spontaneous communication, power management, redundancies Simple and open service platform Intelligence a network borders, not in the network (as in IN) Thus: more service providers, not only the network providers PSTN, CS-Core MSC BSC UMTS SS7-Signaling IP-based core network SGSN Router RNC Gateways public WLAN or WMAN Server-Farm, Gateways, Proxies Firewall, GGSN, Gateway Internet access points private WPAN private WLAN Radio/TV broadcast 68 69

9 Possible Problems Quality of Service The Internet provides best effort data transfer Integrated Services has bad scalability, Differentiated Services have still to be proofed Simplicity of the Internets? DoS attacks auf QoS? Internet Protocols are well-known also for attackers, hackers, Reliability, maintenance Still an open question if Internet technology is cheaper, when a high reliability is needed ( %) and all demanded services are integrated Missing accounting technology Accounting based of technical parameters (data volume, time) makes no sense A content- or application-based accounting is much better Killer Application! There is no single killer application: The selection of provided services and the seamless access to the services using different access technologies is important 70