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Mobile Communication and Mobile Computing1 Prof. Dr. Alexander Schill TU Dresden, Computer Networks Dept.

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Presentation on theme: "Mobile Communication and Mobile Computing1 Prof. Dr. Alexander Schill TU Dresden, Computer Networks Dept."— Presentation transcript:

1 Mobile Communication and Mobile Computing1 Prof. Dr. Alexander Schill TU Dresden, Computer Networks Dept.

2 Mobile Communication and Mobile Computing2 Contents 1. Motivation 2. Mobile Communication –History –Principles –Media Access Methods –Mobile Radio Networks: Overview –GSM –HSCSD, GPRS –UMTS

3 Mobile Communication and Mobile Computing3 Contents 2. Mobile Communication (Continuation) –Broadband-Radio Systems –Wireless Local-area Networks (IEEE 802.11, Bluetooth etc.) –Satellite-based Systems

4 Mobile Communication and Mobile Computing4 Contents 3. Mobile Computing –Layer 3 MobileIP v4 & v6 DHCP –Layer 4 –Higher Layers and Services WAP, XML Mobile RPC CODA, Databases Mobile Agents Middleware for spontaneous networking Services and system support for Mobile Computing

5 Mobile Communication and Mobile Computing5 Roth, J.: Mobile Computing, dpunkt-Verlag, 2002 Very good overview to mobile communication and mobile computing Schiller, J., Mobilkommunikation, Techniken für das allgegenwärtige Internet, Addison-Wesley, 2000 Mobile Communication principles and Mobile Computing Bernhard, Walke: Mobilfunknetze und ihre Protokolle, 2 Bände. Teubner, 2000 Principles, GSM, UMTS and other cellular Mobile Radio Networks [Vol.1] Circuit Switched Radio, Cordless Phone Systems, W-ATM, HIPERLAN, Satellite Radio, UPT [Vol.2] Schumny, Harald: Signalübertragung, Friedrich Vieweg & Sohn, Braunschweig/Wiesbaden 1987; Wave propagation and wireless transmission A.S. Tanenbaum: Computernetzwerke, 4. Aufl., Prentice Hall, 1998 Protocols, ISO/OSI, standards, fixed networks Principles Literature

6 Mobile Communication and Mobile Computing6 1. Motivation and Examples

7 Mobile Communication and Mobile Computing7 Speech- and Data Communication location independent and mobile New application areas, flexibility, improved workflows Requirements: - Mobile end-devices - Radio transmission - Localization and signalization/management - Standards - Application Concepts for mobile end-devices in distributed systems - Control of heterogeneous, dynamic infrastructures Mobile Computing Motivation

8 Mobile Communication and Mobile Computing8 Building site Architect Building of enterprise A (main office) Building of enterprise B Construction supervisor X.25 ISDN ATM ISDN GSM Selected drafts, Videoconferences Material data, status data, dates Large archives, Videoconferences Drafts, urgent modification Building of enterprise A (branch office) Application example: Civil Engineering, Field Service

9 Mobile Communication and Mobile Computing9 WAP-Example: Order processing Order book Status of bond transactions. Executed and deleted orders are indicated in the order book for some days more. Partial execution of some order is presented as one open and one executed partial order in the order book. Details to an order could be indicated via dial-up of correspondent Links.

10 Mobile Communication and Mobile Computing10 Product Data Main office Caching Client LAN-Access Maintenance technician - very different performance and charges: radio networks versus fixed networks Software-technical, automatic adaptation to concrete system environment Example: Access to picture data/compressed picture data/graphics/text Mobile Access Local Resources, Error Protocols Perspective: Mobile Multimedia Systems

11 Mobile Communication and Mobile Computing11 Ethernet E-Fax-Order Management DB-Access Firm Branch office Client X GSM xDSL Application Resource Mobile Station Communication path DB Distributed Database Distributed Database Cache Application Structure

12 Mobile Communication and Mobile Computing12 Internet Content Provider Main Office Infrastructure GSM Radio/Infrared ATM GSM, RDS/TMC, DAB... Beam Radio, ISDN GSM Traffic Telematics Systems Content Provider DAB: Digital Audio Broadcast RDS/TMC: Radio Data System/ Traffic Message Channel

13 Mobile Communication and Mobile Computing13 GSM (Global System for Mobile Communications): worldwide standard for digital, cellular Mobile Radio Networks UMTS (Universal Mobile Telecommunications System): European Standard for future digital Mobile Radio Networks AMPS (Advanced Mobile Phone System): analog Mobile Radio Networks in USA DECT (Digital Enhanced Cordless Telecommunications): European standard for cordless phones TETRA (Terrestrial Trunked Radio): European standard for circuit switched radio networks ERMES (European Radio Message System): European standard for radio paging systems (Pager) 802.11: International standard for Wireless Local Networks Bluetooth: wireless networking in close/local area Inmarsat: geostationary satellite systems Teledesic: planned satellite system on a non-geostationary orbit Mobile Communication Networks: Examples

14 Mobile Communication and Mobile Computing14 Mobile Communication: Development 2005 200019951990 D (GSM900) C Cordless Telephony Mobile Phone Networks Packet Networks Circuit Switched Networks Satellite Networks Local Networks Modacom Mobitex Tetra Inmarsat IR-LAN MBS IMT2000/ UMTS IEEE 802.11/ Hiperlan Radio-LAN Iridium/ Globalstar E (GSM1800) EDGE HSCSD GPRS CT2DECT

15 Mobile Communication and Mobile Computing15 Used Acronyms CT2: Cordless Telephone 2. Generation HSCSD: High Speed Circuit Switched Data GPRS: General Packet Radio Service EDGE: Enhanced Data Rates for GSM Evolution IMT2000: International Mobile Telecommunications by the year 2000 MBS: Mobile Broadband System

16 Mobile Communication and Mobile Computing16 2. Mobile Communication

17 Mobile Communication and Mobile Computing17 Principles

18 Mobile Communication and Mobile Computing18 Mobile Communication Tied to electro-magnetic radio transmission radio transmission terrestrial orbital (satellite) beam radio broadcast radio equatorial orbit non-equatorial orbit cellularnon-cellular Principles: – Propagation and reception of electro-magnetic waves – Modulation methods and their properties – Multiplex methods – Satellite orbits/Sight- and overlap areas

19 Mobile Communication and Mobile Computing19 Cellular Networks: Principles Supply- (radius R) and interference areas (5 R) 7-Cell-Cluster (repeat sample of the same radio-channels) Interference Zone R Channels 801-1600 Channels 1-800 Channels 1-800 5R 1 5 6 6 3 7 4 4 2 7 5 3 4 1 1 5 2 7 7 3 2 6 4 5 63 5 1 5 6 6 3 7 4 4 2 1 7 2 5 3 2 1 42 4 1 2 R

20 Mobile Communication and Mobile Computing20 Cell structure: Example Reference cell Cell in the interference area of the reference cell Further cells, whose channel distribution should be known to the reference cell Cellular Networks: Principles

21 Mobile Communication and Mobile Computing21 Kinds of antennas: directional & sectored Energy is radiated in definite directions, for instance x- Direction So called main propagation directions, for instance Satellite Antennas Often also used in Mobile Radio Systems, such as GSM, for creation of sectored cells Seamless radio supply via partial/overlay of sectors x y x z Directional AntennaSectored Antenna

22 Mobile Communication and Mobile Computing22 Media Access Methods

23 Mobile Communication and Mobile Computing23 Principles Multiplex –Multiple-shift usage of the medium without interference –4 multiplex methods: Space Time Frequency Code Media Access Methods –controls user access to medium

24 Mobile Communication and Mobile Computing24 SDMA (Space Division Multiple Access) based on SDM (Space Division Multiplexing, Space Multiplex) communication channel obtains definite Space for definite Time on the definite Frequency with definite Code Space Multiplex for instance in the Analog Phone Systems (for each participant one line) and for Broadcasting Stations Problem: secure distance (interferences) between transmitting stations is required (using one frequency) and by pure Space Multiplex each communication channel would require an own transmitting station Space Multiplex is only reasonable in combination with other multiplex methods SDMA for instance by base station dedication to an end-device via Media Access Methods or respectively by segmentation of a Mobile Radio Network to several areas

25 Mobile Communication and Mobile Computing25 SDMA: Example k1k2 s s – secure distance k3k4k5k6 SDMA finds selection f1

26 Mobile Communication and Mobile Computing26 FDMA (Frequency Division Multiple Access) Based on FDM (Frequency Division Multiplexing, Frequency Multiplex) i.e. to transmission channels several frequencies are permanently assigned, for instance radio transmitting stations k1k2k3k4k5k6 f1 f2 f3 f4 f5 f6 s – secure distance s FDMA finds selection t f k1 k2 k3 k4 k5 k6

27 Mobile Communication and Mobile Computing27 TDMA (Time Division Multiple Access) Based on TDM (Time Division Multiplexing, Time Multiplex) i.e. to transmission channels is the transmission medium is slot assigned for certain time, is often used in LANs Synchronization (timing, static or dynamic) between transmitting and receiving stations is required k1k2k3k4k5k6 f1 t f k1k2k3k4k5k6k1 TDMA finds selection

28 Mobile Communication and Mobile Computing28 Combination: FDMA and TDMA, for instance GSM GSM uses combination of FDMA and TDMA for better use of narrow resources the used band width for each carrier is 200 kHz t f in MHz TS0TS1TS2TS3TS4TS5TS6TS7TS0 TS1TS2TS3TS4TS5TS6TS7TS0 TS1TS2TS3TS4TS5TS6TS7TS0 TS1TS2TS3TS4TS5TS6TS7TS0 TS1TS2TS3TS4TS5TS6TS7TS0 TS1TS2TS3TS4TS5TS6TS7TS0 890,2 915 200 kHz 935,2 960 25 MHz 45 MHz 25 MHz uplink downlink

29 Mobile Communication and Mobile Computing29 CDMA (Code Division Multiple Access) based on CDM (Code Division Multiplexing, Code multiplex) i.e. to transmission channels the definite Code is assigned, this can be on the same Frequency for the same Time transmitted derivates from military area via development of cost-efficient VLSI components via spread spectrum techniques a good communication security and tiny fault sensitivity but: exact synchronization is required, code of transmitting station must be known to receiving station, complex receivers for signal separation are required Noise should not be very high

30 Mobile Communication and Mobile Computing30 CDMA k1k2k3k4k5k6 f1 CDMA decoded

31 Mobile Communication and Mobile Computing31 The Principle of CDMA can be good illustrated by the example of some party: communication partners stand closely to each other, each transmission station (Sender) is only so loud, that it does not interfere to neighbored groups transmission stations (Senders) use certain Codes (for instance, just other languages), they can be just separately received by other transmission stations receiving station (Listener) attunes to this language (Code), all other Senders are realizing this only as background noise if receiving station (Listener) cannot understand this language (Code), then it can just receive the data, but it cannot do anything with them if two communication partners would like to have some secure communication line, then they should simply use a secret language (Code) Potential Problems: –security distance is too tiny: interferences (i.e. Polish und Czech) CDMA illustrated by example

32 Mobile Communication and Mobile Computing32 Sender A Sends A d =1, Key A k = 010011 (set: 0= -1, 1= +1) Transmit signal A s =A d *A k = (-1, +1, -1, -1, +1, +1) Sender B sends B d =0, Key B k = 110101 (set: 0= -1, 1= +1) Transmit signal B s =B d *B k = (-1, -1, +1, -1, +1, -1) Both signals superpose additively in air Faults are ignored here (noises etc.) C = A s + B s =(-2,0,0,-2,+2,0) Receiver will listen to Sender A uses Key A k bitwise (internal product) –A e = C * A k =2 +0+0 +2 +2+0 = 6 –Result is greater than 0, so sent bit was 1 analog B –B e = C * B k =-2 +0 +0 -2 -2 +0 = -6, also 0 CDMA-Example in the theory

33 Mobile Communication and Mobile Computing33 Spread Spectrum Techniques Signal is spread by the Sender before the transmission (overblown) dP/df value corresponds with so called Power Density, Energy is constant (in the Figure: the filled areas) Objective: Increase of robustness against small band-width faults listening security: power density of spread-spectrum signals can be lower than that of background noise

34 Mobile Communication and Mobile Computing34 Spread Spectrum Techniques small band-width faults are spread by de-spreading in receiving station band-pass deletes redundant frequency parts t

35 Mobile Communication and Mobile Computing35 Mobile Radio Networks: Overview

36 Mobile Communication and Mobile Computing36 General technological development in mobile telephony before 19701970198020002005 Analog Networks...150Mhz 1990 Anal. cellular Networks...450 Mhz Anal. cellular Networks...900 Mhz Digital cellular Networks...900 Mhz Digital cellular Networks...1800 Mhz GSM Phase II+ UMTS Satellite Systems (LEO) Prognoses Development of Mobile Radio

37 Mobile Communication and Mobile Computing37 Correspondent data rates (GEO)Satellites (GEO)

38 Mobile Communication and Mobile Computing38 Participant quantities in Mobile Radio – world-wide November 2002: 1148 Mio. participants world-wide (1119 Mio. digital & 29 Mio analog) 1... Europe: Western 4... Americas (thereof 15.4 Mio. analog) 2... Asia Pacific5... USA/Canada (thereof 5.4 Mio. analog) 3... Middle East6... Africa 7… Europe: Eastern (Source:

39 Mobile Communication and Mobile Computing39 Frequency Assignment TETRA 380-400 410-430 NMT 453-457 463-467 CT2 864-868 CT1+ 885-887890-915 GSM900CT1+ 930-932 GSM900 935-960 TFTS (Pager, aircraft phones)GSM1800 1670-16751710-17851800-1805 TFTS 1805-1880 GSM1800DECT 1880-1900(1885-2025 2110-2200) TETRA 450-470 (nationally different) UMTS IEEE 802.11b 2400-2483 HIPERLAN1 5176-5270 MHz Bluetooth 2402-2480 HIPERLAN2 (ca.5200,5600) WLAN 2412-2472 HomeRF...(approx.2400) Circuit Switched Radio Mobile Phones Cordless Phones Wireless LANs Notes:- 2,4 GHz license free, nationally different - () written : Prognoses! - today speech over license free frequencies up to 61Ghz -> interesting for high data rates (ca.17000) HIPER-Link 1GHz500Mhz TFTS - Terrestrial Flight Telephone System IEEE 802.11a: 5,15-5,25; 5,25-5,35; 5,725-5,825

40 Mobile Communication and Mobile Computing40 Broadcast/multicast networks several carrier frequencies but participant obtains carrier for short time only often in use by taxi- und logistics enterprises etc., each own separated frequency reaches can use the same frequency packs with FDM- and TDM- techniques, i.e. more efficient handling with narrow resource frequency spectrum improves transition to fixed network, speech- and data services not for public access very reliable, cost-efficient

41 Mobile Communication and Mobile Computing41 TETRA (Terrestrial Trunked Radio) former name: Trans-European Trunked Radio frequencies: 380-390, 410-420 MHz Uplink; 390-400, 420-430 MHz Downlink bandwidth of each channel: 25 kHz 1991 started by ETSI replace of national networks like MODACOM, MOBITEX or COGNITO Services: –Voice + Data (V+D)- Service: Speech and Data, channel-oriented, uni-, multi- and broadcast possible –Packet Data Optimized (PDO)- Service: packet-oriented, improves connection-oriented or connectionless service, as well as point-to-point and point-to-multipoint communication carrier services with data rate up to 28,8 kbit/s unprotected; 9,6 kbit/s - protected

42 Mobile Communication and Mobile Computing42 TETRA, advantages compared with GSM, UMTS confirmed and/or non-confirmed Group Call (however its already possible with GSM today: up to 16 participants) Group call listening is possible (so called open-channel mode) very reliable fast dialing: approx. 300 ms (so called push to talk), GSM: several seconds certain independence of infrastructure (so called direct mode between end-devices) cost-efficient, especially for limited user quantity, because of the large cells x 10 km also especially suitable for emergency teams (fire department, ambulance etc.)

43 Mobile Communication and Mobile Computing43 Cordless Telephony - DECT (Digital Enhanced Cordless Telecommunications) frequency reach: 1880 - 1990 MHz other than GSM limited to short reaches (1km) in buildings particularly under 50m is not designed for use at high rates mobile phones with GSM and DECT are available in the market 120 full duplex channels TDD (Time Division Duplex) for directional separation with 10ms frame length frequency reach is divided into 10 carrier frequencies using FDMA each station 10mW averaged, max. 250mW of transmitting power, GSM – radio phones transmit at 1 to 2W, fixed car phones up to 8W

44 Mobile Communication and Mobile Computing44 PA PT FT D4D4 D3D3 D2D2 Local Networks HDB VDB Global Networks D1D1 FT..Fixed Radio Termination PT..Portable Radio Termination PA...Portable Terminations HDB..Home Data Base VDB..Visitor Data Base DECT – system architecture

45 Mobile Communication and Mobile Computing45 64 bit8 bit160 bit48 bit32 bit Synchronization Signalization Used Data (Speech) CRC Used Data (Speech) CRCSecure marker 160 bit8 bit 0,417 ms DECT-timeslot structure Transmission reach of fixed part (downlink)Transmission reach of mobile part (uplink) carrier frequency 1: 1 2 3 4 5 6.... 11 121' 2' 3' 4' 5' 6'.... 11' 12' 1 2 3 4 5 6.... 11 12 1' 2' 3' 4' 5' 6'.... 11' 12' 1 2 3 4 5 6.... 11 12 1' 2' 3' 4' 5' 6'.... 11' 12'......... 1728 kHz Transmission principle of DECT-system Channel 1Channel 2Channel 12Channel 1Channel 2'Channel 12'... fixed part to mobile partmobile part to fixed part Time duplex with 10 ms frame length Structure of DECT-time multiplex frame DECT - Multiplex carrier frequency 2: carrier frequency 10:

46 Mobile Communication and Mobile Computing46 Eurosignal –to each participant 4 different audio signals using 4 diverse call numbers are assigned. Meaning must be agreed. Receiving stations are at a size of a cigarette packet –85 senders in the 87 MHz-reach (ultra short waves) –called person location must be approximately known: 3 area codes: North 0509, Middle 0279, South 0709 Cityruf (city call) –additionally to 4 audio- or respectively optical signals transmission of short numerical (15 digitals) or alpha-numerical messages (80 characters) exists optionally, receiving station is smaller than with Eurosignal PEP (Pan European Paging) –preparation for coupling of national services for ERMES –D: Cityruf, F: Alphapage, GB: Europage, I: SIP ERMES (European Radio Message System) –ETSI-Standard for pan-European radio service, similar to PEP but in 169 MHz- reach with 60 Mio. addresses Pager systems: overview

47 Mobile Communication and Mobile Computing47 GSM: Global System for Mobile Communications

48 Mobile Communication and Mobile Computing48 GSM: Properties cellular radio network (2nd Generation) digital transmission, data communication up to 9600 Bit/s Roaming (mobility between different net operators, international) good transmission quality (error detection and -correction) scalable (large number of participants possible) Security mechanisms (authentication, authorization, encryption) good resource use (frequency and time division multiplexing) integration within ISDN and fixed network standard (ETSI, European Telecommunications Standards Institute)

49 Mobile Communication and Mobile Computing49 Providers in Germany (1) D1 T-Mobile –subscribers: 24,6 Mio (Stand 2003) Vodafone D2 –old name: Mannesmann Mobilfunk D2 –subscribers: 22,7 Mio (Stand 2003) E-plus O2 –old name: VIAG Interkom

50 Mobile Communication and Mobile Computing50 Providers in Germany (2) ProvidersSubscribers, millions 200120022003World-wide by 2003 D1 T-Mobile22,623,124,682 Vodafone D221,9-22,7112,5 E-Plus-7,5-- O2 VIAG Interkom -3,66--

51 Mobile Communication and Mobile Computing51 AuCAuthentication Centre BSS Base Station Subsystem BSCBase Station Controller BTSBase Transceiver Station EIREquipment Identity Register HLRHome Location Register MSMobile Station (G)MSC(Gateway) Mobile Switching Centre OMCOperation and Maintenance Centre PSTN Public Switched Telephone Network VLRVisitor Location Register ISDNIntegrated Services Digital Network Fixed network Switching Subsystems VLR Radio Subsystems HLRAuCEIR (G)MSC OMC BTS BSC BSS MS Network Management Call Management Data networks PSTN/ ISDN MS GSM: structure

52 Mobile Communication and Mobile Computing52 GSM: Structure Operation and Maintenance Centre (OMC) logical, central structure with HLR, AuC und EIR Authentication Centre (AuC) authentication, storage of symmetrical keys, generation of encryption keys Equipment Identity Register (EIR) storage of device attributes of allowed, faulty and jammed devices (white, grey, black list) Mobile Switching Centre (MSC) arrangement centre, partial as gateways to other nets, assigned to one VLR each Base Station Subsystem (BSS): technical radio centre Base Station Controller (BSC): control centre Base Transceiver Station (BTS): radio tower / antenna

53 Mobile Communication and Mobile Computing53 1 TDMA-Frame, 144 Bit in 4,615 ms 8 TDMA-channels, together 271 kBit/s inclusive error protection information 124 radio frequency channels (carrier), each 200 kHz 2 frequency wavebands, for each 25 MHz, divided into radio cells 890 935 915 MHz 960 MHz downlink uplink Radio technical structure One or several carrier frequencies per BSC Physical channels defined by number and position of time slots

54 Mobile Communication and Mobile Computing54 GSM: protocols, incoming call VLR BSS MSCGMSC HLRBSS (4) (2) (4) (5) (3) (10) (6) (11) (7) (8) (9) (12) (8) (1) (12) (9) (8) PSTN/ ISDN (1) Call from fixed network was switched via GMSC (2) GMSC finds out HLR from phone number and transmits need of conversation (3) HLR checks whether participant for a corresponding service is authorized and asks for MSRN at the responsible VLR (4) MSRN will be returned to GMSC, can now contact responsible MSC

55 Mobile Communication and Mobile Computing55 GSM: protocols, incoming call VLR BSS MSCGMSC HLRBSS (4) (2) (4) (5) (3) (10) (6) (11) (7) (8) (9) (12) (8) (1) (12) (9) (8) PSTN/ ISDN (5) GMSC transmits call to current MSC (6) ask for the state of the mobile station (7) Information whether end terminal is active (8) Call to all cells of the Location Area (LA) (9) Answer from end terminal (10 - 12) security check and connection construction

56 Mobile Communication and Mobile Computing56 GSM: protocols, outgoing call VLR BSS MSCGMSC HLR BSS (5) (3)(4) (2)(1) (1) Demand on connection (2) Transfer by BSS (3-4) Control for authorization (5) Switching of the call demand to fixed net

57 Mobile Communication and Mobile Computing57 GSM: channel strucure Traffic Channel speech- / data channel (13 kbit/s brutto; differential encoding) units of 26 TDMA - Frames Half-rate traffic channel: for more efficient speech encoding with 7 kbit/s Control Channel Signal information Monitoring of the BSCs for reconnaissance of Handover Broadcast Control Channel BSC to MS (identity, frequency order etc.) Random Access Channel Steering of channel entry with Aloha-procedure Paging Channel signalize incoming calls

58 Mobile Communication and Mobile Computing58 Databases Home Location Register (HLR), stores data of participants, which are reported in an HLR-area –Semi-permanent data: Call number (Mobile Subscriber International ISDN Number) - MSISDN, e.g. +49/171/333 4444 (country, net, call number) identity (International Mobile Subscriber Identity) - IMSI: MCC = Mobile Country Code (262 + MNC = Mobile Network Code (01-D1, 02- Vodafone-D2, 03-eplus, 07-O2) + MSIN = Mobile Subscriber Identification Number Personal data (name, address, mode of payment) Service profile ( call transfer, Roaming-limits etc.) –Temporary data: MSRN (Mobile Subscriber Roaming Number) (country, net, MSC) VLR-address, MSC-address Authentication Sets of AuC (RAND (128 Bit), SRES (128 Bit), K C (64Bit)) charge data

59 Mobile Communication and Mobile Computing59 Databases Visitor Location Register (VLR) local database of each MSC with following data: –IMSI, MSISDN –service profile –accounting information –TMSI (Temporary Mobile Subscriber Identity) - pseudonym for data security –MSRN –LAI (Location Area Identity) –MSC-address, HLR-address

60 Mobile Communication and Mobile Computing60 MSC-area = VLR-area radio- cell with BTS Location Area (LA) LA = smallest addressable unit Handover GSM: mobile telephone areas

61 Mobile Communication and Mobile Computing61 MSC-area HLR VLR Location area advantage of the architecture: Location Update at limited mobility, as a rule only at VLR, rarely at (perhaps far remote) HLR Connection HLR, VLR

62 Mobile Communication and Mobile Computing62 LA 5 LA 3 LA 2 LA 3 VLR 10 VLR 9 IMSILA 2 HLR 26 32311VLR 9 IMSI participant call number in HLR country code number net-entry code Provider +49 0177-26 32311 0x62F22001E5 z.B. Localization at GSM

63 Mobile Communication and Mobile Computing63 Data transmission each GSM-channel configurable as a data channel; similar structure like ISDN-B and -D-channels data rates up to 9600 bit/s now delay approximately 200 ms speech channels have as a rule higher priority as data channels kinds of channels: –transparent (without error correction; however FEC; fixed data rate; error rate 10 -3 up to 10 -4 ) –non-transparent (repeat of faulty data frames; very low error rate, but also less throughput) Short-Message-Service (SMS) –connectionless transmission (up to 160 Byte) on signal channel Cell Broadcast (CB) –connectionless transmission (up to 80 Byte) on signal channel to all participants, e.g. one cell

64 Mobile Communication and Mobile Computing64 MSC BSC UDI BTS IWF TA ISDN Modem PSTN Internet Modem IWF - Inter Working Function UDI - Unspecified Digital TA - Terminal Adapter Data transmission - structure

65 Mobile Communication and Mobile Computing65 Chip-card (Smart Cart) to personalize a mobile subscriber (MS): IMSI (International Mobile Subscriber Identity) participant special symmetric key K i, stored also at AuC algorithm A3 for Challenge-Response-Authentication algorithm A8 for key generation of K c for content data PIN (Personal Identification Number) for entry control Temporary data: TMSI (Temporary Mobile Subscriber Identity) LAI (Location Area Identification) Encryption key K c Security aspects: Subscriber Identity Module (SIM)

66 Mobile Communication and Mobile Computing66 Security in GSM-networks SIM Entry control and cryptographic algorithms Single-sided authentication (participant against network) Challenge-Response-method (cryptographic algorithm: A3) Pseudonyms of participants at the Radio interface Temporary Mobile Subscriber Identity (TMSI) Connection encoding on the Radio interface Key generation: A8 Encryption: A5

67 Mobile Communication and Mobile Computing67 Security aspects: Authentication MSC, VLR, AuC MS Authentication Request RAND (128 Bit) Random number generator A3 SRES SRES (32 Bit) A3 Authentication Response = Location Registration Location Update with VLR-change Call setup (in both directions) SMS (Short Message Service) max. 128 Bit

68 Mobile Communication and Mobile Computing68 Security aspects: Session Key Netz MS Authentication Request RAND (128 Bit) Random number generator A8 64 Bit Key generation: Algorithm A8 –Stored on SIM and in AuC –with K i parametric one way function –no (Europe, world wide) standard –can be determined by net operator –Interfaces are standardized –combination A3/A8 known as COMP128

69 Mobile Communication and Mobile Computing69 Security aspects: encryption at the Radio interface NetMS Ciphering Mode Command A5 Data encryption through algorithm A5: –stored in the Mobile Station –standardized in Europe and world wide –weaker algorithm A5* or A5/2 for specific countries TDMA-frame- number Key block + Plain text block + Ciphering Mode Complete Encrypted Text 114 Bit

70 Mobile Communication and Mobile Computing70 GSM-Security: assessment cryptographic methods secret, so they are not well examined symmetric procedure –consequence: storage of user special secret keys with net operators required low key length K i with max. 128 Bit (could be hacked by using Brute Force Attack in 8-12 hours) no mutual authentication intended –consequence: Attacker can pretend a GSM-Net no end-to-end encryption no end-to-end authentication Key generation and -administration not controlled by the participants

71 Mobile Communication and Mobile Computing71 GSM Phase II+ HSCSD, GPRS

72 Mobile Communication and Mobile Computing72 HSCSD: High Speed Circuit Switched Data

73 Mobile Communication and Mobile Computing73 higher data rate because of channel bundling parallel usage of several time slots (TCH) of one frequency on U m more efficient channel encoding (14,4 kbit/s per TCH) Data rates from 9,6 up to 53,8 kbit/s asymmetric transmission (1TCH Uplink / 3TCH Downlink) Properties

74 Mobile Communication and Mobile Computing74 HSCSD data rates transparent non transparent up- / downlink100% coverage95% coverage100% coverage95% coverage 1 + 19,614,49,613,2 2 + 219,228,819,226,4 1 + 3-------28,839,6 1 + 4-------38,453,8

75 Mobile Communication and Mobile Computing75 MSC BSC UDI BTS IWF TA ISDN Modem PSTN Internet Modem IWF - Inter Working Function UDI - Unspecified Digital TA - Terminal Adapter n time slots (TCH) of each TDMA frame (theoretically max. 8) HSCSD: structure

76 Mobile Communication and Mobile Computing76 UmUm A bis A MSCBSCBTS n time slots (TCH) of each TDMA frame (theoretically max. 8) multiplex of the time slots on each 64 kBit/s channel certain changes are necessary at the component several changes at the software/firmware minimal changes at the software/firmware HSCSD: changes

77 Mobile Communication and Mobile Computing77 parallel usage of several time slots limited to one frequency Cost factor limits number of used TCHs to (2+2) or (1+3, uplink, downlink) Required time for setting to receiving standby 7654321076543210 4321076543210765 Required time for setting to transmission standby Required time for signal strength measure and setting to receiving standby MS RECEIVE MS TRANSMIT MS MONITOR HSCSD radio interface

78 Mobile Communication and Mobile Computing78 Assessment of HSCSD +existing net structure and accounting model maintained +in comparison to GPRS only around1/5 of investment necessary +HSCSD is still circuit switched +has defined QoS- settings (data rate, delay) –one logical channel will be switched on all interfaces for the time of the connection –Non-efficient for burst-like traffic (Internet) or Flat Rate billing (Logistics) –no international acceptance (Roaming!) uses also more resources on the radio interface –problems with handover into a new cell

79 Mobile Communication and Mobile Computing79 GPRS: General Packet Radio Service

80 Mobile Communication and Mobile Computing80 Properties Packet switching service (end- to- end) Data rates up to 171,2 kbit/s (theoretical) Effective and flexible administration of the radio interface adaptive channel encoding Internetworking with IP- and X.25 nets standardized dynamic sharing of resources with classical GSM speech services Advantage: Billing and Accounting according to data volume Disadvantage: cost intensive additional net hardware necessary

81 Mobile Communication and Mobile Computing81 Properties –point-to-point-Packet transfer service PTP-CONS (PTP Connection oriented Network Service) –connection oriented, similar to X.25 PTP- CLNS (PTP Connectionless Network Service) –connectionless, similar to IP –point- to- multipoint - group communication

82 Mobile Communication and Mobile Computing82 MSC BSC BTS Internet GPRS: Structure HLR GSM GPRS Backbone Frame Relay / ATM GGSN SGSN Border Gateway GPRS Nets other operators other packet switching networks SGSN - Serving GPRS Support Node GGSN - Gateway GPRS Support Node signalization data user data

83 Mobile Communication and Mobile Computing83 GMSC Circuit switched traffic HLR/AuC GPRS register MAP A GGSN GPRS: Changes A bis GbGb GnGn GiGi other packet switching networks public remote fixed nets Packet arranged traffic GsGs UmUm n time slots (TCH) per TDMA frame (theoretically max. 8) per packet! modified network components new components or extensively modified components Existing components PCU - Packet Control Unit SGSN MSC BSC BTS PCU

84 Mobile Communication and Mobile Computing84 SGSN: - mobility management - session management - QoS - security External Data Domain Intranet SGSN HLR Internet MAP Signalization (SGSN) Tasks: SGSN, GGSN BSS PCU BSS PCU BSS PCU Client GGSN Client Server MAP Signalization (GGSN) SGSN, GGSN: - Routing - Signalization - Resource management SGSN

85 Mobile Communication and Mobile Computing85 Tasks of the SGSN Packet delivery mobility management –apply/ sign off of terminals –localization LLC (Logical Link Control) management authentication billing

86 Mobile Communication and Mobile Computing86 Tasks of the GGSN mediator between GPRS backbone and external data networks (Internet, X-25 etc.) converts GPRS packets, data Protocol (PDP) into the corresponding structure also converts PDP addresses of incoming packets into GSM address of the receiver saves current data for the SGSN address of the participant as well as their profile and data for authentication and invoice

87 Mobile Communication and Mobile Computing87 Radio Link Control (RLC) Segmentation of the LLC-Frames in RLC blocks Block size dependent on short-term channel conditions Backward error correction and data flow control by Automatic Repeat Request (ARQ) protocol –repeating not repairable RLC blocks selectively Medium Access Control ( MAC) Channel reservation contains: -one/several time slots (Packet Data Channels PDCH) of one frequency –one uplink status flag (USF) per Packet Data Channel (PDCH), channel partition of up to 8 ms GPRS: air interface

88 Mobile Communication and Mobile Computing88 Medium Access Control ( MAC) Reservation in the uplink (MS to BSS): MS sends reservation request on a Random Access Channel (Slotted ALOHA) –BTS allocates a (split) channel and sends packet assignment –MS sends data depending on the current priority (USF flag) Reservation in the Downlink (BSS to MS): –BTS displays transmitting request and informs about the reserved channel –MS supervises the reserved channel and receives GPRS: air interface

89 Mobile Communication and Mobile Computing89 Physical Link Control adaptive forward error correction (FEC) dependent on short- term channel conditions temporal scrambling (Interleaving) of the bursts and Mapping on reserved PDCH (Packet Data Channel) procedure to recognize overbooking situations on the physical channel GPRS: air interface GPRS Channel Encoding

90 Mobile Communication and Mobile Computing90 Quality of Service QoS profile agrees service parameters inside the whole network Agreed for the duration of one PDP (Packet Data Protocol) context (session, end terminal is obtainable for the duration of the context, e.g. obtainable over Internet ) : –temporary address (IP) for mobile station –tunneling information, among others GGSN, which is used for access to corresponding packet arranged network –type of the connection –QoS profile QoS profile commits: –precedence class, priority against other services (high, normal, low) –packet delay class, times are valid for traffic inside the GPRS- network –reliability class –peak throughput class –mean throughput class

91 Mobile Communication and Mobile Computing91 Quality of Service Packet delay classes Security classes

92 Mobile Communication and Mobile Computing92 Quality of Service GPRS- using data rates CS 3 and CS 4 are only reasonable in the second phase of GPRS introduction They will be used adaptively at corresponding good quality of radio connection CS 4 does not comprise error correction, code rate = 1!

93 Mobile Communication and Mobile Computing93 Assessment of GPRS +An up to 4 times higher data rate in comparison to ordinary GSM- data services +better resource management through packet arranged service +always on data service (email, etc.) +GPRS is a more suitable carrier for services like WAP -IP-derivate, no true guaranties (QoS) -development of the network infrastructure is relatively expensive, particularly regarding introduction to UMTS (return of investment) -GPRS doesnt give such data rates like advertising has sometimes promised

94 Mobile Communication and Mobile Computing94 9.6 kbit/s Data rate 26.4 kbit/s 13.2 kbit/s HSCSD Channel packing, NT HSCSD Channel packing, NT 39.6 kbit/s CS 1 GPRS Packet arranged GPRS Packet arranged 9 kbit/s 18.1 kbit/s 27.2 kbit/s 13.4 kbit/s 26.8 kbit/s 40.2 kbit/s CS 2 Development of the GSM-data services flow

95 Mobile Communication and Mobile Computing95 Enhanced Services - EMS (enhanced message service) Uses widespread existing infrastructure (SMS) new Mobile telephones necessary allows sending and receiving of messages with formatted texts, melodies, graphics (32 x 32 Pixel) and animations (16 x 16 Pixel) – e.g. NOKIA new applications like Mobile Ticketing tickets will be transferred to mobile phone like a bar code and checked at the admission EMS enables transition to MMS (multimedia messaging service), which allows transmission of multimedia enriched messages over UMTS-Network (photos, parts of videos) MMS requires new network elements in the Infrastructure of the operators

96 Mobile Communication and Mobile Computing96 MMS - architecture... MMS Relay MMS User Agent MMS User Databases MMS Server (e.g. E-Mail) MMS Server (other service) alien MMS Relay SMTP LDAP GSM-MAP or IS-41-MAP or TCP/IP SMTP, HTTP, POP3, IMAPv4 WAP or MExE (e.g. Java and TCP/IP) HLR MMS Server (e.g. Fax) Based on materials from 3GPP, http://www.3gpp.org

97 Mobile Communication and Mobile Computing97 UMTS: Universal Mobile Telecommunications System, 3G, 3rd generation of mobile radio

98 Mobile Communication and Mobile Computing98 IMT-2000 - structure source: 3 systems - UMTS - CDMA2000 - UWC-136 2 core technologies - TDMA - CDMA satellite- supported network expansion: - SW-CDMA: Satellite Wideband CMDA - SW-CDTMA: Satellite Wideband CDMA/TDMA (Hybride procedure) - SAT-CDMA: Satellite CDMA - ICO RTT: ICO Radio Transmission Technology IMT-2000 family of radio interfaces : –IMT-DS (Direct Spread) UTRA-FDD (UMTS) –IMT-MC (Multi Carrier) CDMA2000, USA –IMT-TC (Time Code) UTRA-TDD (UMTS), TD- SCDMA (Synchronous Code Division Multiple Access, China) –IMT-SC (Single Carrier) UWC-136, USA –IMT-FT (Frequency time) DECT IMT-2000 TDMA CDMA individual carrier multiple carrier IMT-SC IMT-FT TDD IMT-DS IMT-MC UWC-136 (EDGE) DECT UTRA-FDD CDMA2000 UTRA-TDD TD-SCDMA FDD IMT-TC ICO RTT... Standard by ICO Global Communications IMT... International Mobile Telecommunications UTRA... Universal Terrestrial Radio Access UWC... Universal Wireless Communications In europe UMTS

99 Mobile Communication and Mobile Computing99 Worldwide frequency assignment for IMT-200 developed by ITU PCS... Personal Communication System MSS...Mobile Satellite Service PHS... Personal Handy-Phone System

100 Mobile Communication and Mobile Computing100 UMTS - Facts consideration: early 90ies Universal Mobile Telecommunications System, developed in the EU (ETSI: European Telecommunication Standards Institute) UMTS is the European implementation of IMT-2000 (International Mobile Telecommunications by the year 2000) Start of network expansion: –in Europe: 2003 (some trials, e.g. British Telecom on Isle of Man, 2002) –in the USA: 2005 –in Japan since 2000 : NTT DOCOMO

101 Mobile Communication and Mobile Computing101 1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200 GSM1800 Uplink GSM1800 Downlink DECT FDD Uplink FDD Downlink TDD MSS 230 MHz frequency range for IMT-2000 at FDD symmetrical spectrum is necessary, not at TDD (time slots at same frequency) gradual new assignment of wavebands depending on development of the need up to 300-500 MHz frequency range in 2008 Frequency award in Europe source: MSS…Satellite- based

102 Mobile Communication and Mobile Computing102 system general, worldwide roaming high data rates: 144 kbit/s mobile, up to 2 Mbit/s at local area fusion of different mobile radio communications-, wireless- and pager-systems into one common system speech-, data-, and multimedia- information services independent of used network access support of different carrier services: –real-time capable/not real-time capable –circuit switched/ packet switched Roaming also between UMTS and GSM and satellite networks Asymmetrical data rates in up-/downlink Characteristics

103 Mobile Communication and Mobile Computing103 UMTS- Disadvantages Technology not yet perfect rent ability of pico cells (Hotspots) not yet analyzed strong contention by WLAN increased radiation exposure high data rate only obtainable sometimes (High-Tech-network expansion, stationary and exclusive usage necessary!) because of high license costs high charges necessary (around double GSM- costs)

104 Mobile Communication and Mobile Computing104 UMTS - Performance TransmissionReal- time (Video)Not Real-time (SMS etc.) Bit error rate10 -3 … 10 -7 10 -5 … 10 -8 Permitted delay20ms … 300ms> 150 ms ~ 0 sec10 sec1 min10 min1 h UMTS GPRS ISDN PSTN GSM Web Photo Mail Report Video Report Video Report Video Report source: Mobilkom Austria

105 Mobile Communication and Mobile Computing105 UMTS - Hardware big color displays high resolution True Color

106 Mobile Communication and Mobile Computing106 UMTS- cell structure Quelle: Mobilkom Austria Gateway Mobile Switching Centre 3G Mobile Switching Centre Home Location Register Gateway GPRS Support Node Internet customer Intranet packet- switched BTS GSM - BSSUTRAN- UMTS Terrestrial Radio Access Network Base Station Controller Radio Network Controller Radio access network PSTN/ ISDN UMTS-Core Network Visitor Location Register circuit switched 3G- Serving GPRS Support Node

107 Mobile Communication and Mobile Computing107 Zone1: In-building Pico cell Zone 2: Neighborhood Micro cell Zone 3: Suburban Macro cell Zone 4: Global Satellite Integration with the fixed network Basic terminal PDA terminal Audio/visual terminal UMTS: cell structure World cell

108 Mobile Communication and Mobile Computing108 Global Lokal Regional Home/ Office World Macro Micro Pico UMTS: hierarchical cell structure principle: - all neighbor cells use same frequency channel - only one waveband is necessary for cellular construction - further wavebands are necessary for hierarchical structure expansionData rate (kbit/s) Max. velocity (mph) Special features World Cellglobal-no UTRAN, other technology! Macro CellUp to 1,24 miles144310complete national UMTS support Micro CellUp to 0,62 miles38474Greater cities, commonly used Pico Cell> 60miles20006,2!Hotspots – e.g. airport, station

109 Mobile Communication and Mobile Computing109 Classification

110 Mobile Communication and Mobile Computing110 Virtual Home Environment (VHE): offered services are freely configurable, configuration still exists in the whole network choose of service quality and also arising costs behave at bottlenecks (data rates, etc.) configurable dynamic customization to connection Service concept

111 Mobile Communication and Mobile Computing111 one phone number for several devices (Call- Management) subscriber localization e.g. with SIM-card call passing virtual mobility of fixed networks UPT: Universal Personal Telecommunication Service

112 Mobile Communication and Mobile Computing112 Intelligent networks Implementation of basic services like subscriber localization billing etc. supply of value added service (Voice-Mailbox, etc.) –possibility of easy, fast introduction of new services –flexible service administration –usage of services also from foreign network possible –better control of service parameters through subscriber

113 Mobile Communication and Mobile Computing113 UMTS: basic network structure Access Network: base stations, responsible for radio contact to mobile end devices Core Network (Fixed Network): responsible for structure of connections Intelligent Network (IN): responsible for billing, subscriber localization, Roaming, Handover Intelligent Network Core Network Access Network User Equipment (UE)

114 Mobile Communication and Mobile Computing114 General reference architecture UEUTRAN UuUu IuIu CN UTRA: UMTS Terrestrial Radio Access –UTRAN (UTRA- Network) contains several radio subsystems, so called Radio Network Subsystems (RNS) and contains functions for mobility management –RNS controls handover at cell change, capacitates functions for the encoding and administrates the resources of the radio interface –U u connects UTRAN with mobile end devices, so called User Equipment (UE), is comparable with U m in GSM –UTRAN is connected over I u with the Core Network, comparable with the A interface in GSM between BSC and MSC –CN contains the interfaces to other networks and mechanisms for connection handover to other systems

115 Mobile Communication and Mobile Computing115 The UMTS-radio interface UTRA (UMTS Terrestrial Radio Access) Two modes defined: –UTRA/FDD (Frequency Division Duplex) mainly in suburban areas for symmetrical transmission of speech and video data rates up to 384 kbit/s, supra-regional roaming for circuit- and packet switched services in urban areas –UTRA/TDD (Time Division Duplex) mainly in households and other restricted areas (company's premises, similar to DECT) for broadcast of speech and video, both symmetrical: up to 384 kbit/s also asymmetrical: up to 2 Mbit/s

116 Mobile Communication and Mobile Computing116 UTRA/FDD t f in MHz 190 MHz uplink downlink 1920,9 1979,7 carrier 1 5 MHz carrier 12...... 2110,9 2169,7 carrier 1 carrier 12...... puts wide- band- CDMA (W-CDMA) together with DSSS (Direct Sequence Spread Spectrum) as spread spectrum technique channel separation by carrier frequencies, spreading code and phase position (only uplink) ca. 250 channels for used data, data rates up to 2 Mbit/s complex performance control necessary

117 Mobile Communication and Mobile Computing117 UTRA/TDD puts wideband- TDMA/CDMA together with DSSS sends and receives on same carrier (TDD) ca. 120 channels for used data, data rates up to 2 Mbit/s channel separation by spread code and time slots less spreading than at FDD precise synchronization necessary lower demand for performance control t f in MHz 1900,1 1920,1 carrier 1 5 MHz carrier 4...... 2010,1 2020,1 carrier 5 carrier 6 uplink downlink

118 Mobile Communication and Mobile Computing118 Extension Band 1 (worldwide similar) – partly terrestrial, partly satellite- based Extension Bands (for a future market potential..from 2005) 25202670MHz4708622290230027002900 Existing Nets 8801885MHz GSM, DECT 16751710 MHz satellite-based 1885 1980 1920 201020252110217060 GHzMHz MBSterrestrial satellite- based Frequency award for UMTS

119 Mobile Communication and Mobile Computing119 UMTS-licenses in Germany E-Plus Hutchison 8.394.492.363 Group 3G 8.408.706.278 Vodafone (Mannesmann Mobilfunk) 8.422.920.192 MobilCom Multimedia 8.369.848.095 T-Mobil 8.478.344.232 O2 (VIAG Interkom) 8.445.008.001 17.08.2000: each license got 2 x 5 MHz packets, 60 MHz have been given away altogether, 150 MHz are available altogether RegTP determined: - till end of 2003 25 % network coverage - till end of 2005 50 % network coverage

120 Mobile Communication and Mobile Computing120 Summary introduced variants are the proposals, which will be supported by Europe, Japan and partly by the USA worldwide accessibility can be realized only with multimode end devices even in Europe combined UTRA-FDD/UTRA- TDD/GSM- devices are necessary (those are realized by the identical frame time of 10ms at relatively low costs)

121 Mobile Communication and Mobile Computing121 Wireless Local Networks, WLAN

122 Mobile Communication and Mobile Computing122 Why do we need wireless LANs? Advantages flexibility Ad-hoc-network realizable with less expenditure No problems with cables Disadvantages high error vulnerability on the transmission link in comparison to Standard-LANs National restrictions, no international standards at used frequency bands (Industrial Scientific Medical (ISM)- Band) security, costs

123 Mobile Communication and Mobile Computing123 Application areas networks in exhibition halls hospitals warehouses airports structure of networks in historic buildings extension of existing wired local area networks in offices, universities etc.

124 Mobile Communication and Mobile Computing124 Problems with the use of WLANs –physical problems interference: band spreading echo: use of special antennas Hidden Terminal problem: use CSMA/CA –data security Wired Equivalent Privacy (WEP) service further development WiFi (Wireless Fidelity), WPA (WiFi Protected Access)

125 Mobile Communication and Mobile Computing125 Standards IEEE 802.11 (a,b,g ; optional e,h,i) –frequency band 2,4 GHz, also in the 5GHz - band –data rates: 1 bis 11 Mbit/s (at present, later up to 20 (2,4 GHz) or 54 Mbit/s (5,4 GHz)) –WiFi: Wireless Fidelity, certificate from the WECA (Wireless Compatibility Allicance), secures the interoperability between the Radio- LANs and contains improved security mechanisms HomeRF Bluetooth (IEEE 802.15) –Frequency band: 2,4 GHz –Data rate: 1 Mbit/s; in the future also 20 Mbit/s –connection of peripherals HIPERLAN (ETSI) / Wireless ATM –frequency bands 5,15 / 5,30 GHz and 17,1 / 17,3 GHz –data rates: 24 Mbit/s or 155 Mbit/s –however no practical relevance

126 Mobile Communication and Mobile Computing126 IEEE 802.11b frequency: –2,4 GHz frequency band, also called ISM (= Industrial Scientific Medical Band), not regulated –850 - 950 nm at infrared transmission power: –min. 1mW –max. 100mW in Europe (1W in the USA) reach: –of 10m (IR) to 30km or more with the help of special antennas (directional antennas)

127 Mobile Communication and Mobile Computing127 Basic WLAN- structure Ad-hoc-network: AP STA4STA5 3 connected infrastructure networks: AP - Access Point

128 Mobile Communication and Mobile Computing128 System architecture IEEE 802.11 Distribution System 802.x LAN 802.11 LAN STA 1 Access Point Portal BSS 1 Access Point STA 2 STA 3 802.11 LAN BSS 2 ESS

129 Mobile Communication and Mobile Computing129 System architecture IEEE 802.11, concepts Station (STA) –device with 802.11- concurring interface Access Point –allows the access to the distribution system for registered stations and secures accessibility of the stations also beyond the BSS Coordination Function (CF) –logical functional unit, which decides when a station can send Basic Service Set (BSS) –consists of several stations, that were controlled by an CF, e.g. BSS 2 and STA 2, STA 3

130 Mobile Communication and Mobile Computing130 System architecture IEEE 802.11, concepts Distribution System –connects several BSS over access points and forms a logically larger net Extended Service Set (ESS) –Radio networks, which are connected over Distribution System Portal –allows transition into other networks

131 Mobile Communication and Mobile Computing131 Overview 802.11 is the most frequently used solution for wireless connection; very strong distribution on the market interesting future option: Seamless Handover between GSM and IEEE 802.11; supported by Cisco, Intel etc. (alternative to UMTS?) higher data rates already standardized or in use –802.11a: physical layer at 5 GHz – Band, data rates up to 54 MBit/s –802.11b: extension to physical layer for the 2,4 GHz – band, data rates up to 11 MBit/s, products available –802.11g: at present the industry works on an extension, shall allow the up to 54Mbit/s in the frequency band around 2.4 GHz –Study Group 5GSG: examines the harmonization between IEEE 802.11 and ETSI HiperLAN –Task Group e: MAC functions for QoS-Management and to refine improved safety functions, introduction of service classes etc.

132 Mobile Communication and Mobile Computing132 802.11 – Norms for WLAN 802.11Since end of 1990; RadioLAN; B=1-2 MBit/s; ISM-Band F=2,4GHz; low Interoperability and bit rate! 802.11b11MBit/s, actual Standard, existed NICs and APs; ISM-Band F=2,4GHz; possesses further sub-standards 802.11aSince 2000; competition with 802.11b; up to 54 MBit/s; F=5,1 GHz, correspond. national restrictions: in the buildings 802.11gRatification March, 2003; first pre-standard products; ISM-Band 2,4GHz; up to 54 MBit/s; 802.11eSub-standard; planed for end 2003; use of QoS-approaches; realization of multimedia applications/ Voice over IP over WLAN 802.11hSub-standard / method for 802.11a; optional functionality – transmission power control of radio interface by national via RegTP prescribed norms; correspond. especially for Germany 802.11a or h 802.11iSub-standard; security approaches for WLAN (encryption, authentication) WPAWiFi Protected Access; Substandard; competition with 802.11i 802.11cSub-standard; Method of Wireless-Bridging 802.11dSub-standard; country specifics for 802.11b 802.11fSub-standard; Routing between radio cells of different vendors by IAPP (Inter-Access- Point Protocol)

133 Mobile Communication and Mobile Computing133 ParametersStandards 802.11 802.11802.11b802.11a / h802.11g Frequency band, GHz 2,4 (ISM-Band) 5,12,4 (ISM-Band) Bit rate, MBit/s1-111154 Use fieldbuilding, territory in the buildingsbuilding, territory DeploymentEnd 1990actuallySince 2000Since March 2003 Available Hardware Marketable NICs and APs Experimental operation Pre-standard Products Data securityWEP64/128/256 bit WEP 802.11i - security approaches for WLAN (encryption, authentication); WPA - WiFi Protected Access (competition with 802.11i) QoS for multimedia- transmission none 802.11e (Ende 2003): use of QoS- approaches; realization of multimedia applications/ Voice over IP Problematiclow bit rate low interoperability low bit rateNational restrictions Pre-standard

134 Mobile Communication and Mobile Computing134 Example: Lucent Wavelan 802.11b WLAN Card Wireless connection that acts just like a conventional Ethernet link Technical specifications: –11 Mbps wireless connection –40-bit WEP or 104-bit RC4 link layer encryption –Interoperability with other cards of IEEE 802.11b (i.e. Cisco Aironet or the Apple Airport Card) –Tiny size - a PCMCIA card less than 1 inch –Cross-platform support (Linux, Mac, and Win*) –Very low cost (comparable to a PCMCIA 10/100 Ethernet card)

135 Mobile Communication and Mobile Computing135 Example: Globalsuntech 802.11b products Bit rates: 22/11/5.5/2/1 MBit/s per channel WEP 64/128/256 Bit Available devices: –Card Bus –PCMCIA Card –PCI Card –Mini USB DSSS; selectable channels: –USA, Canada - 11 channels –Europe - 13 channels –Japan - 14 channels Sensitivity, range: –80dBm for 22MBit/s –92dBm for 1MBit/s Cross-platform support (Linux, Win*)

136 Mobile Communication and Mobile Computing136 Further Scenarios (1) Wireless Access Point (Hub Type) Wireless PC PCs Scenario 1: Wireless Access LAN WLAN

137 Mobile Communication and Mobile Computing137 Ethernet Hub Wireless Access Point (Bridge Type) Wireless PCs Scenario 2: Wireless Bridging Further Scenarios (2) WLAN LAN

138 Mobile Communication and Mobile Computing138 Further Scenarios (3) Wireless Access Point (Router Type) Scenario 3: Share Wireless AP Cable/DSL-Modem Internet WAN WLAN Wireless PCs

139 Mobile Communication and Mobile Computing139 Cable/DSL- Wireless/ Wired Router Wireless PCs Scenario 4: Wireless/Wired Routing Further Scenarios (4) Cable/DSL-Modem Internet WAN LAN WLAN

140 Mobile Communication and Mobile Computing140 UMTS vs WLAN

141 Mobile Communication and Mobile Computing141 Mobility and data rates mobility Data rate [Mbit/s] Source: Bluetooth 0,1 110100 2G 3G – UMTS WLAN LAN Fixed Walk Vehicle UMTS: better mobility, connectivity WLAN: higher data rates, more cheap, but no telephone 0,4 2,0 5,5 65,5 WLAN UMTS (best support) TDSL ISDN in minutes, trailer, 30 MB Source: Focus, 34/2002

142 Mobile Communication and Mobile Computing142 520056005900570058005500540053005100 HIPERLAN High Speed wireless access U-NII Frequency [MHz] License exempt. 455 MHz Sharing rules 100 MHz Unlicensed 300 MHz U-NII... Unlicensed national information infrastructure source:, WLAN- Spectrum Allocation

143 Mobile Communication and Mobile Computing143 Interworking UMTS/WLAN - User should be notified of any possible degradation - subscriber database could be shared, or separated in HLR/HSS (3GPP) or AAA (IETF) format Three classes: - no coupling - loose coupling - tight coupling UMTS/WLAN as completely independent Contra: Pro: - Rapid introduction - no impact on GSN nodes - poor handover - no common database, billing no couplingloose couplingtight coupling UMTS/WLAN use same database in AAA format AAA... Authentication, authorization, accounting - poor handover - good handling - no impact on GSN nodes - improved handover performance - HIPERLAN/2 have to support complete UMTS interface - feasible if operator have both networks HIPERLAN/2 is connected through UTRAN to UMTS, using special interface

144 Mobile Communication and Mobile Computing144 Data security in WLAN and UMTS Data security for WLAN: 802.11i -new, additionally standards 802.11a/h and 802.11g -complex solution for security -packet encryption -key distribution via RADIUS -Remote Access Dial-In User Service -packet authentication -partial compatibility with IPsec -relevant against all attacks WPA - WiFi Protected Access preliminary to 802.11i properties similar to 802.11i competition to 802.11i WEP - Wired Equivalent Privacy -additionally to standard 802.11b, partially obsolete!!! -users mobility between several Access- Points, without re-configuration (roaming) -disadvantages: -short key of 64 / 128 bit -different, partially contradictory statements to offered security Data security for UMTS: IPsec -Client/Server based, Clients and IPsec-Servers negotiate dynamic keys -tolerant, relevant for key assignment to IP-subnets and against all Internet-attacks -secrecy on the network layer: IP-datagrams TCP/UDP-segments ICMP/SNMP-messages -Encryption via DES, 3DES and 40- bit-DES -authentication via -IP Encapsulating Security Payload" (RFC 2406, 1998) -IP Authentication Header (RFC 2402, 1998)

145 Mobile Communication and Mobile Computing145 HomeRF (Radio Frequency) competitive standard to IEEE 802.11 Up to 128 network nodes Frequency jump in separations of 3MHz or 5MHz Low costs and support of synchronous services: DECT speech support 2,4 GHz (FHSS), transition power max. 100 mW, Shared Wireless Access Protocol (SWAP): –hybrid protocol of DECT (TDMA) and CSMA according to IEEE802.11 (modified) up to 6 wireless fixed network connections however sinking market shares in comparison with IEEE 802.11

146 Mobile Communication and Mobile Computing146 HomeRF data rate 1-2 Mbit/s 50 m reach within buildings Supplier: e.g. Intel with ANYPOINT (wireless home network) future: –HomeRF + Bluetooth: DUAL MODE SYSTEM (Symbionics) +ad-hoc possibly +voice transmission - today only few manufactures

147 Mobile Communication and Mobile Computing147 Wireless City Networking via 802.16 IEEE Wireless MAN/ ETSI Hiper MAN

148 Mobile Communication and Mobile Computing148 Wireless City Networking: scenarios new IEEE 802.16 standards can provide great regions with fast Internet services Use fields: –office materials shops –cafes –at the railway stations –to surf at the parks

149 Mobile Communication and Mobile Computing149 USA: Wireless MAN Wireless MAN: 802.16-version in USA Backgrounds: –competition to T-Mobile USA - mobile radio network provider –great number of 802.11-Internet service providers (ISP via Wireless LAN) –wide spread 802.11x – networks in the country –via 802.11 provided approx. 2500 regions

150 Mobile Communication and Mobile Computing150 Europa: Hiper MAN ETSI (European Telecommunications Standard Institute): –activities in the range of 802.16 – development of Hiper MAN new marketable products: since July 2004 (according to announcement of Fujitsu Europe)

151 Mobile Communication and Mobile Computing151 802.16 / 802.16a Wireless MAN Standard 802.16 –developed end of month January 2003 –frequency bandwidth: 10 up to 66 GHz –reach: up to 50 km (30 miles) –data rate: up to 134 MBit/s –new 802.16x standards can provide great regions with fast Internet service, momentary trial operation in Boston/USA (ISP via Wireless MAN) Start-Standard 802.16a –frequency bandwidth: 2-11 GHz –reach: up to 50 km (30 miles) –data rate: up to 70 MBit/s only –predominantly conceptualized for fast links of hotspots –can be used to establishment of private DSL-links –final operation inset: January 2005

152 Mobile Communication and Mobile Computing152 802.16a-Forum Members: –Airspan Networks, Alvarion, Aperto Networks, Ensemble Communication, Fujitsu of America, Intel, Nokia, Proxim, Wi-LAN Aims: –to provide compatibility of 802.16a-products among each other

153 Mobile Communication and Mobile Computing153 Conclusion: 802.16 vs 802.11 802.11 +advantage: –in spite of sharp competition to Mobile Radio (IMT2000/UMTS) 802.11x gained the mass market –well-elaborated 802.11x (x = a, b, c, d, e, f, g, h, i, WPA) disadvantage: –existing bandwidth problems (at most up to 54 Mbit/s) –reach at most up to 100m without directional antennas 802.16 +advantage: –covers approx. 50km (30 miles) –substitution via 802.16 as access techniques possible –in future cost-efficient in comparison to 802.11 disadvantage: –averaged investment for leased circuits amounting to 1000$ per location necessary –sharp competition to Mobile Radio (IMT2000/UMTS): to occupy the market is for Wireless Networks more important as for Mobile Radio! –final operation inset: planned January 2005 only

154 Mobile Communication and Mobile Computing154 (2) via Wireless MAN Access Point Wireless PCs Scenario: fast Internet Better than UMTS: future use scenarios of 802.16 (1) via ISDN, Modem, DSL Internet WAN Wireless MAN 802.16 WAN PC/LAN WWW- Server/ Intranet- Firewall up to 50 Km (30 miles) 70-134 Mbit/s ISP via Wireless MAN

155 Mobile Communication and Mobile Computing155 Bluetooth

156 Mobile Communication and Mobile Computing156 Bluetooth - Facts Harald Bluetooth was the King of Denmark in the 10th century 1998 started from Ericsson, Intel, IBM, Nokia, Toshiba Open Standard: IEEE 802.15.1 Generally for wireless Ad-hoc- piconets (Range < 10m) Goal: not expensive One-Chip-Decision for radio/ wireless communication networks Use fields: –Connection of peripheral devices –Support of Ad-Hoc-Nets –Connection of different networks Frequency band in IMS-Range of 2,4 GHz

157 Mobile Communication and Mobile Computing157 Bluetooth Pico nets with up to 8 participants (ad-hoc) (one master, slaves) Scatter nets as an association of different pico nets frequency hopping is used for improving of interception safety and system robustness

158 Mobile Communication and Mobile Computing158 Bluetooth - properties Range: - 10 cm up to 10 m at 1 mW transmitting power - up to 100m at 100mW Data rates: –433,9 kBit/s asynchronous-symmetrical –723,2 kBit/s / 57,6 kbit/s asynchronous- asymmetrical –64 kBit/s synchronous, voice service –In future up to 20 Mbit/s (IEEE 802.15.3) Basic set-up Bluetooth 2,4-Ghz- HF Bluetooth- Baseband- Controller Host- System

159 Mobile Communication and Mobile Computing159 Bluetooth-comparison Source: FUNCTIONBluetooth v1.1IrDA Data 1.1IEEE802.11 (WLAN) Range w/o PA:10 meter max.1 meter max.50 meter max. Angle:omni-directionalca 30°omni-directional RF Frequency Band: ISM Band, 2.4 GHzInfrared RadiationISM Band, 2.4 GHz Mobility:mobilestationarymobile Data rate:721kBit/s4MBit/s2MBit/s Security level:HighLowHigh

160 Mobile Communication and Mobile Computing160 Bluetooth- functionality Standby Inquiry after unknown Address Page after unknown Address Send dataconnected PARKHOLDSNIFF MAC-Address resigned MAC-Address available t =2 ms t =2 s t =0,6 s Not connected Standby connection- status active states Low-Power- states

161 Mobile Communication and Mobile Computing161 Bluetooth – architecture (1) Physical connection interface connection between end devices In hardware implemented ! connection between Hardware and upper protocol (only necessary, if L2CAP not implemented in Hardware!) Applications TCS,SDP,RFCOMM L2CAP LMP Baseband Radio Data HCL TCS …Telephony Control Protocol Specification SDP … Service discovery protocol RFCOMM … RF communication protocol (cable replacement protocol) LMP … Link Manager Protocol HCL … Host Controller L2CAP … Logical Link Control and Adaptation Protocol

162 Mobile Communication and Mobile Computing162 Bluetooth- architecture (2) Radio Layer - work area: ISM-Band (2,4 Ghz) - Spread Spectrum Communication - Frequency Hopping- Technology - high error rate acceptability through CVSD-encoding at heavy micro wave load Baseband - controls Radio- Layer 2 Modes: - Synchronous, connection-oriented transfer (SCO) voice connections need symmetrical, circuit-switched point-to-point-connections, Master reserves two successive time slots (up- and downstream) - Asynchronous, connectionless transfer (ACL) data transfers need symmetrical or asymmetrical, packet-switched point-to-point/multipoint- transfers, master uses polling CVSD… Continuously Variable Slop Delta (Sprachkodierung)

163 Mobile Communication and Mobile Computing163 Bluetooth- architecture Link Manager Protocol 3 Functions - Piconet management - link configuration - security functions Logical Link Control and Adaption Protocol Functions: - Mutiplexing (different applications can use connection between 2 devices simultaneously) - Reduzierung der Paketgröße der Anwendungen auf akzeptable Baseband- Paket- Größe - Quality of Service

164 Mobile Communication and Mobile Computing164 Possible configurations Master Slave PiconetScatter net

165 Mobile Communication and Mobile Computing165 GSM Bluetooth possible configurations association of different pico nets frequency hopping : jumps in k steps (k = 0…22 or 79) with Δf distances in ISM-band a) Peer to Peer (or 1 Master and 1 Slave) b) Multi-slave (up to 7 "slaves" with 1 Master) ScatternetPiconet Master Slave 4 Master Slave 3 Slave 1 Slave 2 Slave 5 Piconet 1 Piconet 2 Scatternet

166 Mobile Communication and Mobile Computing166 Bluetooth - Frequencies Source: - different frequencies around the world Goal: Harmonization of wavebands CountryFrequency range [MHz] RF channelsMultiplier Spain2445 – 2475 f k = 2449 + k Δf k = 0,…,22 France2446,5 – 2483,5 f k = 2454 + k Δf k = 0,…,22 Japan2471 – 2497 f k = 2473 + k Δf k = 0,…,22 other Europe / USA2446,5 – 2483,5 f k = 2402 + k Δf k = 0,…,78 Δf… frequency distance between channels

167 Mobile Communication and Mobile Computing167 Bluetooth - Framestructure Single slot frame Multi slot frame source: one Slot Packet Frame fkfk f k+1 one Slot Packet Master Slave 625 µs one slot three slot Packets fkfk f k+1 one Slot Packet Master Slave 3- Slot-packets 625 µs one slot Frame

168 Mobile Communication and Mobile Computing168 Bluetooth – security source: PIN E2E2 E2E2 Link Key E3E3 E3E3 Encryption KeyEncyption Key Authentication Encryption user input (Initialization) (possible) permanent storage temporary storage - 128 Bit Key encryption and authentication - every device has own 48 Bit- address - over 281. 10 12 devices can keep apart - low range (manipulation only local!)

169 Mobile Communication and Mobile Computing169 Bluetooth – security Generic access: Three modes - non-secure - service level enforced security - link level enforced security For Devices: two modes - trusted - untrusted for Services: three modes: - services that require authorization and authentication - services that require authentication only - services that are open to all devices Bluetooth device initiates security procedures before the channel is established Sources:, Müller T., Bluetooth Security Architecture Bluetooth is not secure enough for critical transmissions (billing etc.)

170 Mobile Communication and Mobile Computing170 Bluetooth – applications (1) replaces perhaps infrared in the area of the coupling of peripherals completely Intelligent Shop –shop informs the buyer about special offers by mobile phone or handles inquiries for offers in the individual halls Bluetooth-capable ticket machine –Payment over mobile telephone is carried out without contacts control of home appliances by mobile telephone lower layers are developed further in the context of the IEEE 802.15 working group (WPAN - Wireless Personal Area Networks) –higher data rates, further frequencies, but possible interferences with other systems

171 Mobile Communication and Mobile Computing171 Bluetooth - applications wireless connection Headset Handy

172 Mobile Communication and Mobile Computing172 HIPERLAN HIPERLAN/1wireless LAN (as extension to conventional LANs) 5,15 - 5,25 GHz, ca. 20 Mbps, reach > 50 m, mobility < 10m/s decentralized Ad-hoc net, no QoS-guarantee HIPERLAN/2wireless ATM-LAN (as extension to ATM and IP nets) 5,15 - 5,25 GHz, ca. 20 Mbps, reach 50 m, mobility<10m/s cellular structure with base stations, ATM service classes HIPERACCESSpoint-to-multipoint ATM connections 5,15 - 5,25 GHz, ca. 25 Mbps, reach 5000 m, stationary/quasi-stationary, point-to-multipoint, ATM service classes HIPERLINKpoint-to-point ATM connection 17,1 - 17,3 GHz, 155 MBit/s, reach 150 m, stationary/quasi-stationary, point-to-point, ATM source: ETSI RES 10, BRAN

173 Mobile Communication and Mobile Computing173 Assessment of HIPERLAN despite of some unique characteristics there are no products available yet, only single prototypes is planned as one of the alternatives for BRAN (Broadband Radio Access Network) in the Wireless ATM planned frequencies are originally not worldwide available (5,1-53GHz)

174 Mobile Communication and Mobile Computing174 Requirements : wireless connection of mobile terminals to ATM-networks compatibility to existing standards existing networks should be easily upgradeable guaranteed service quality properties which other wireless nets don't offer UMTS and WLANs dont offer any data rates >50 Mbit/s Problems: ATM is conceived for high data rates ATM is optimized on reliable media applications should notice nothing of the wireless mode Wireless ATM

175 Mobile Communication and Mobile Computing175 Wireless ATM: review WATM still is standardization endeavors, no definite standards approved the WATM forum has tried to standardize as much as possible, the WATM standard is relatively complex WATM supports relatively many configurations: –wireless Ad-hoc networks –wireless mobile end-devices: access to the network via radio subsystem, similar to access-points –mobile end-devices: seamless handover between connected terminals –mobile ATM-Switches (for planes, ships, trains etc.) –fixed ATM-terminals: conventional ATM –fixed terminals with radio access: comparable with line-of-sight radio links It is not arranged completely for which configuration also products will exist

176 Mobile Communication and Mobile Computing176 Satellite-based systems

177 Mobile Communication and Mobile Computing177 Sample system Inter-Satellite Link (ISL) Gateway Link (GWL) Mobile User Link (MUL) Spot beams Footprint Gateway Ground Station User PSTN, ISDN, GSM,... Internet

178 Mobile Communication and Mobile Computing178 Basics (1) satellites describe elliptical or circular orbit around the earth distance to the earth remains constant: - Appeal of the Earth - Centrifugal force - Mass of the satellite - Earth radius, 6.370km - Distance of the satellite to the Earths center - Grounding acceleration, g = 9,81 m/s 2 - Angular frequency: - Cycle frequency of the satellite (1)

179 Mobile Communication and Mobile Computing179 Basics (2) Formulae transformation: F = m. a(by Newton) F grav = k. M. m / r 2 (Gravitation between 2 point masses) mg = k. M. m / R 2 (Appeal on the Earth surface = Gravitation) k. M = gR 2 F G = gR 2 m/r 2 = gm(R/r) 2 (transformed) δt = 2. (r-R) / c Signal propagation delay Satellite Downlink r-R Uplink

180 Mobile Communication and Mobile Computing180 Basics (3) (1) resolved to r gives: that means, the distance of a satellite to the earth's surface depends only on its cycle duration (special case T = 24h - > synchronous distance r=35.786 km) (2) Cycle duration [h] 10 2030 40 x 10 6 m 4 12 20 velocity [x1000km/h] Synchronous distance 35.786 km

181 Mobile Communication and Mobile Computing181 GEO (Geostationary Earth Orbit) ca. 36 000 km MEO (Medium Earth Orbit) ca. 6000 - 12 000 km Van-Allen-belts 2000 - 6000 km 15 000 - 30 000 km (no satellite use possible) LEO (Low Earth Orbit) ca. 500 - 1500 km HEO (Highly Elliptical Orbit) Satellite system classes

182 Mobile Communication and Mobile Computing182 Base for Inmarsat Principle: Satellit Uplink Downlink Geostationary Satellite systems Constant position to the Earth, 3 satellites cover complete earth (with the exception of the polar caps), satellites move synchronously to the Earth Simple solution, however large distance (36000 km), therefore high signal propagation delay, long life time of the satellites: ~ 15 years low data rates, large transmission power required problems: –on the other side of the 60th degree of latitude reception problems (elevation) –because of a high transmission power unfavorable for mobile telephones –signal propagation delay too high (0.25 s)

183 Mobile Communication and Mobile Computing183 LEO- Systems non-stationary satellites (LEO - Low Earth Orbit) distance to the earth ~ 500 - 2000 km shorter signal runtimes (5-10 ms), lower transmission power of the mobile stations sufficing however more satellites necessary, frequent handover between satellites, approximately all 10 min. examples: Teledesic, Globalstar only low transmission power necessary, suitable for mobile phone networks Disadvantages: –large number is necessary (50 - 200, or more) –fast handovers within satellites are necessary –short life time of the satellites because of atmospheric friction (5-8 years)

184 Mobile Communication and Mobile Computing184 MEO- Systems ~ 10000km, lower number of satellites necessary : ~12 slow movement: handover between satellites is hardly necessary cycle duration: 6h high elevation enables coverage large, highly-populated areas Problems: –signal propagation delay: 70 to 80 ms –higher transmission power is necessary –special antennas for small cells are necessary

185 Mobile Communication and Mobile Computing185 Service transitions in Inmarsat-C-service Terrestrial station Buffer memory X.25 Interface Phone-Interface Telefax- Interface Fixed network Internet X.25 Net Email System modem PAD data + maps laptop fax data + maps Email desktop laptop Inmarsat - C – End-Terminal Graphic table Fax- Interface Mail Box text 600 bit/s Inmarsat Satellite L-Band 1,5/1,6 GHz Rx/Tx (GPS)

186 Mobile Communication and Mobile Computing186 Satellites HeightData rate Teledesic (planned) 288 (?)~ 700 km64 Mbit/s 2 / 64 Mbit/s Iridium 66 (+6)~ 780 km2,4 / 4,8 kbit/s Globalstar 48 (+4)~ 1400 km9,6 kbit/s ICO 10 (+2)~ 10 000 km4,8 kbit/s Inmarsat 5geostationary2,4 kbit/s Orbcomm 35LEO-stationary 57,6 kbit/s Examples of satellite-based systems Globalstar can transfer bi-directionally up to 144 Kbit/s, through combination of channels Orbcomm - first commercial LEO–service worldwide

187 Mobile Communication and Mobile Computing187 Comparison of satellite-based systems Satellite-based system GEOMEOLEO Distance, kmr = 35.786 kmr-R=6000 – 12000 km r-R= 500 – 2000 km Cycle duration, T24 h6 h95 – 120 min Signal propagation delay, t 0.25 s70-80 ms10 ms Transmission power, W 1051 Use examplesNumerous systems, approx. 2000: Sputnik (1957) Intelsat 1-3 (1965, 1967, 1969) Marisat (1976) Inmarsat-A (1982) Inmarsat-C (1988) ICO 10+2Iridium (bankrupt, 2000) 66+6 Globalstar, 48+4/ 144 kBit/s Teledesic (2003), 288/ 2-64 MBit/s Orbcomm, 35 Data rate, kBit/s0.1 – 1101 – 64000 Life time, years15105-8

188 Mobile Communication and Mobile Computing188 Global Positioning System, GPS

189 Mobile Communication and Mobile Computing189 Overview 24 satellites on the 6 orbits (20200 km, time of circulation = 12h) 5 earth stations (Hawaii, Ascension Island, Diego Garcia, Kwajalein, Colorado Springs) Accuracy: –so called P-Code for military applications: on ~6m accurately, partially 2,8m –so called Selective Availability Mode, SAM (artificial degradation) for civil applications: < 100m (1.5.2000 disestablished) Functionality principle: Triangulation GPS-receiver calculates distance to the satellite on the base of Time of Arrival of the received signals distances to at least three satellites enables the calculation of position, a fourth satellite can be used for determination of elevation over zero official initiation 1995, testing since 1978

190 Mobile Communication and Mobile Computing190 Principle: TOA (Time of Arrival) / TDOA (Time Difference of Arrival) Distance d, Signal Delay T Mobile Object synchronized clocks measurement of signal delay by speed of light between satellite and receiver, for instance T = 100 ms hence calculation of distance: d = T c = 1 10 -1 s 3 10 8 m/s = 3 10 7 m = 30.000 km calculation of spheres around each satellite the position is on the intersection point of three spheres

191 Mobile Communication and Mobile Computing191 Principles satellites send a signal composed of three components 50 times per second: –identification component: PRC (Pseudo Random Code), provides satellite recognition and status information –position component: exact position of satellite –time component: time point, when signal is transmitted the time offset measured by the receiver is corresponding to the Time of Arrival, from TOA the distance is calculated for measurement of TOA of signals very accurate clocks are required the exact position of the satellites must be known

192 Mobile Communication and Mobile Computing192 Sources of errors Clocks highly accurate atom clocks in the satellites simple clocks in the receivers are calibrated via measurement of a fourth satellite Satellite position satellite orbits are relatively stable and forecastable deviations are measured by US DoD deviations are transmitted as correction factor to the satellites using the PRC Miscellaneous error sources atmospheric faults multi-path propagation

193 Mobile Communication and Mobile Computing193 Differential GPS, DGPS use of a stationary receiver as reference position of this receiver is exactly known the stationary receiver carries out position determination and calculates correction factor from the actually obtained position on the base of deviations correction factor is delivered to the mobile receiver

194 Mobile Communication and Mobile Computing194 DGPS accuracy grades Accuracy under 10cm: –professional applications, for instance is interesting in meterology and respectively for user of well- engineered software decisions (machine control systems etc.) Accuracy under 1m: –events mapping, control of machines, traffic control systems, agriculture Guaranteed accuracy under 10m: –agriculture/ forestry, railway (wagon search service), car navigation (private/commercial)

195 Mobile Communication and Mobile Computing195 Galileo EU-Project for installation of European satellite navigation system initiation: prospective 2008 positioning accuracy: 45cm 30 satellites Approx. costs: 3,2 Billion

196 Mobile Communication and Mobile Computing196 A system that both competes with and complements the American GPS system Galileo ITS (Intelligent Transport System) based on a constellation of 30 MEO-satellites ground stations providing information concerning the positioning of users in many sectors usable: transport (vehicle location, route searching, speed control, etc.) social services (e.g. aid for the disabled or elderly) the justice system ( border controls) public works (geographical information systems)

197 Mobile Communication and Mobile Computing197 Galileo - architecture Service centres GALILEO GLOBAL CONTENT MEO Constellation OSS Network TTC Navigation control & constellation management OSS Network... User segment UHF- S&R I-Band- NAV Local Components Local MS. Data link UMTS External complementary systems Regional Components BSS network. COSPAS-SARSAT ground segment BSS network RMS network GEO EGNOS i-band Integrity determination &dissemination s-band

198 Mobile Communication and Mobile Computing198 Broadcast Systems, Distribution Networks

199 Mobile Communication and Mobile Computing199 Overview special variants of asymmetric communication systems HSCSD supports for instance asymmetric connections regarding to data rate, also ADSL WWW is the biggest representative of asymmetric communication: –data volume of uplink (URLs) is much lower than downlink (complete HTML-pages) Problem of distribution systems: Sender can be optimized for a large quantity of receivers only, for instance videostreaming Examples: –DVB, Digital Video Broadcast –DAB, Digital Audio Broadcast

200 Mobile Communication and Mobile Computing200 Principle of Distribution Systems ACBAA AABBBCCCC Time information sequence is optimized for expected access behavior of all consumers t Individual access sample of diverse consumers can more or less deviate from expected access behavior

201 Mobile Communication and Mobile Computing201 Digital Audio Broadcast, DAB Audio-transmission in CD-Quality Non-sensible towards interferences of multi-path-propagation Use of SFN (Single Frequency Network) – i.e. all senders of some broadcast-program are working on the same frequency as a rule Frequencies: UHF,VHF, for instance: 174-230 MHz, 1452-1492 MHz Modulation methods: DQPSK (Differential Quadrature Phase Shift Keying) Optionally COFDM (Coded Orthogonal Frequency Division Multiplexing) is used with several carrier frequencies inside some DAB-channel (its quantity is between 192 and 1536), 1,5MHz bandwidth for each channel FEC (Forward Error Correction)-mechanism for fault correction Up to 6 stereo-programs by 192 kbit/s in the same frequency band are transmittable alternatively data can be transmitted with up to 1,5 Mbit/s (responding to the used code rate etc.)

202 Mobile Communication and Mobile Computing202 Digital Audio Broadcast, DAB 2 Transport Mechanisms Main Service Channel (MSC): –Data, Audio, Multimedia –2 Transport Modes: Stream Mode, Packet Mode Fast Information Channel (FIC): –Transport of Fast Information Blocks (FIB, 32 Byte) – control data for interpretation of Data in the MSC, can be also used for services such as Traffic Dispatches, Paging etc. Audio-converting: PCM 48 kHz & MPEG2-Audiocompression High transmission rates by high velocities, up to 250 km/h, responding to distance from sender and error security class, use for instance in high- speed train MOT (Multimedia Object Transfer) protocol for data transmission Cyclic repeat and caching of data blocks

203 Mobile Communication and Mobile Computing203 Dynamic channel reconfiguration for DAB Ensemble-Configuration Temporarily changed Ensemble-Configuration Audio 2 192 KBit/s PAD Audio 3 192 KBit/s PAD Audio 4 160 KBit/s PAD Audio 5 160 KBit/s PAD Audio 6 128 KBit/s PAD Audio 1 192 KBit/s PAD Data D2 Data D3 Data D1 Data D6 Data D7 Data D4 Data D8 Data D5 Audio 2 192 KBit/s PAD Audio 4 160 KBit/s PAD Audio 5 160 KBit/s PAD Audio 1 192 KBit/s PAD Audio 3 128 KBit/s PAD Data D10 Data D11 Data D2 Data D3 Data D1 Data D6 Data D7 Data D4 Data D8 Data D5 Audio 7 96 KBit/s PAD Audio 8 96 KBit/s PAD

204 Mobile Communication and Mobile Computing204 DVB - Digital Video Broadcasting 1991 ELR (European Launching Group) founded Goal: joint digital Television System for Europe Specifications: DVB-S, DVB-T, DVB-C Frequency reaches: 200, 550, 700 MHz Cell size: up to 60 km Used data rate: ~38,5 Mbit/s Velocity of mobile stations: up to 200 km/h Central Unit: combined DVB-Receiver-Decoder (set-top-box) –can receive DVB-Data via satellites, B-ISDN, ADSL… –some transmission systems offer a feedback channel for Video on Demand etc.

205 Mobile Communication and Mobile Computing205 DVB - Digital Video Broadcasting Different Quality Levels defined: –SDTV (Standard Definition TV) –EDTV (Enhanced DTV) –HDTV (High DTV) Data transport: –User Data: MPEG2-Container (Data Transfer Unit) like DAB, Container doesnt define the type of data Service Information about MPEG2-Container-content: –NIT (Network Information Table): Information from a provider about offered services and optional data for the receiver –SDT (Service Description Table): Description and parameters for each service in the MPEG2-stream –EIT (Event Information Table): Data about actual transmission status –TDT (Time and Date Table): e.g. updating of DVB-receiver

206 Mobile Communication and Mobile Computing206 MPEG2/DVB-Container HDTV EDTV SDTV Single channel (High Definition TV) Several channels (Enhanced DTV) Several channels (Standard TV) Multimedia (data broadcasting) Possible contents of DVB/MPEG2-Container

207 Mobile Communication and Mobile Computing207 DVB used as medium for asymmetric Internet-access Client sends data query to Provider, Provider transmits data to the satellite network, receiver obtains data via DVB-receiver Feedback channel can be phone network, for on-demand services Data rates: –6 up to 38 Mbit/s downlink, 33 kbit/s up to over 100 kbit/s (ADSL) uplink Advantages: –data can be transmitted in parallel with TV –no additional costs for satellite provider –low priced for low-density populated areas Disadvantages: –all users need satellite antennas –only a minor part of the total bandwidth is usable –not suitable for high-density populated areas

208 Mobile Communication and Mobile Computing208 Internet DVB– Card in the PC Satellite provider dedicated line (user-to-user) Service Provider Content Provider DVB as medium for the asymmetric Internet-access

209 Mobile Communication and Mobile Computing209 3. Mobile Computing

210 Mobile Communication and Mobile Computing210 Layer 3 Mobile IP v4 & v6 DHCP

211 Mobile Communication and Mobile Computing211 Mobile IP (Internet Protocol)

212 Mobile Communication and Mobile Computing212 Problem situation computer mobility in heterogenic networks relocation between different IP-subnets Goal: transparent migration and localization, compatibility to IP, no changes of existing routers Idea: introduction of temporary/ actual IP-addresses (also care-of-address, COA); mapping of permanent to temporary IP-addresses using localization technique

213 Mobile Communication and Mobile Computing213 Requirements to MobileIP according to IETF Transparency: –mobile computer is permanently reachable via its previous home-address –can change its network access point freely –can also communicate after coupling/uncoupling Compatibility: –supports each layer below IP (also 1 & 2) –mobile computer can also communicate with each non- mobileIP-computer –no changes to existing computer/routers Security: –all registering messages must be authenticated

214 Mobile Communication and Mobile Computing214 IETF Mobile IP Goals/Restrictions Minimization of overheads: –mobile connections are possibly wireless and have limited band width –mobile connections have possibly higher error rate Efficiency and scalability: –support of a large quantities of mobile computers –support of a theoretically Internet-wide mobility

215 Mobile Communication and Mobile Computing215 Global Internet Home Subnet Anywhere Foreign Subnet Home Agent (HA) Router Foreign Agent (FA) Correspondent Node (CN) Architecture model Mobile Node

216 Mobile Communication and Mobile Computing216 Terms Mobile Node (MN) with permanent IP-address from Home Subnet Home Address permanent address of a mobile computer Home Agent (HA) with knowledge of actual residence of all MNs from so called Home Subnet, like GSM-HLR Care of Address temporary address of a mobile computer from Foreign Subnet Foreign Agent (FA) for assignment of temporary IP- addresses (care of address) and packet forwarding to MNs currently residing in its subnet

217 Mobile Communication and Mobile Computing217 Log on via Foreign Agent Log on with a FA - Care-of Address (address of FA, is just an intermediate target for all MN- related packets, tunnel-end) or Application of a co-located Care-of Address (address from Foreign-Subnet, MN is tunnel-end itself), but reception of an Agent Advertisement Message with a set R-bit, i.e. the MN is forced to log on with FA itself, although it can operate autonomously MN HA Foreign Subnet Home Subnet 1.) Registration.request 2.) relaying request 4.) Registration reply FA 3.) relaying.reply {grant, deny}

218 Mobile Communication and Mobile Computing218 Log on by Home Agent directly HA Home Subnet 1.) Registration.request 2.) Registration.reply {grant, deny} MN MN uses co-located Care-of Address MN is returned to Home Network and would like to log on/off itself with the HA Authentication: each mobile entity (MN, HA, FA) must be able to support a mobility security association, which is indicated via IP- address and SPI (Security Parameter Index). Mobile IP provides three different Authentication Extensions: Mobile - Home Authentication Ext. Mobile - Foreign Authentication Ext. Foreign - Home Authentication Ext.

219 Mobile Communication and Mobile Computing219 Addressing Problem: For the receivers 2 addresses are necessary (permanent and temporary IP-address respectively home address and COA) Methods of resolution: Encapsulation –IP in IP, standard method in MobileIPv4 –minimal Encapsulation IP-Option (not supported by all implementations)

220 Mobile Communication and Mobile Computing220 IP in IP Encapsulation IP-source/target address of external/outer IP-Header defines the end- points of the tunnel IP-source/target address of internal IP-Header represents the actual packet sender respectively receiver Internal IP-Header isn't changed using Encapsulator (exception: TTL) IP HEADER IP PAYLOAD IP HEADER OUTER IP HEADER

221 Mobile Communication and Mobile Computing221 Routing (unicast) Mobile Node: –in Home Network it operates like each other Node –in Foreign Network it must search a Default Router using the following rules: FA COA: –ICMP Router Advertisement-Part ; –IP-source address of Agent Advertisements (lower Prior.) co-located COA: ICMP Router Advertisement for this address Foreign Agent: –FA must check by reception of tunneled packets whether internal target address corresponds with one of the IP-addresses of Visitor List –FA must route the received packets of registered MNs!

222 Mobile Communication and Mobile Computing222 Routing (unicast) II Home Agent: –HA must intercept each packet for absent MN –in addition IP-target address of each incoming packets is verified –if MN has no mobile coupling presently, the packets sent to it must not be intercepted, MN is situated in Home Subnet and accepts packets itself or is off-line

223 Mobile Communication and Mobile Computing223 Routing (necessities) ARP (Address Resolution Protocol): –oriented to resolution of IP-addresses in physical (Hardware, Link Layer) addresses (Ethernet: MAC-addresses of controllers) Proxy ARP: –Proxy ARP-reply is an ARP-reply, which can be sent instead of a host A by other host B (with its hardware address) –Hosts, receiving this reply, associate the hardware-address of node B with the IP-address of node A and send future packets for A to B Gratuitous ARP: –is an ARP-reply, which is sent from a host, to force other hosts to update the records in their ARP-Caches –this ARP-reply contains the IP-address, which should be changed in the ARP- Caches, as well as the hardware address which should be updated

224 Mobile Communication and Mobile Computing224 Routing - Scenario MN leaves Home Network MN decides to register FA Care-of Address Before Registration Request: MN re-sets a reaction on future ARP-requests Registration Request contains and accepts HA Request, implements Gratuitous ARP (IP-address MN ===> own hardware- address) and uses Proxy ARP to respond to ARP- requests corresponding to MN hardware address

225 Mobile Communication and Mobile Computing225 Triangle Routing HA FA MN CN Foreign Network Home Network although CN is in the same Subnet like MN, packets are routed respectively tunneled via FA and primarily HA (possibly over half of terrestrial globe)!!! CN ===> MN: MN ===> CN: Be routed conventionally via Default Router Special case: Routing (MN & CN are in the same Subnet) Relief (IPv4): Route Optimization

226 Mobile Communication and Mobile Computing226 Optimizations: Routing Terms: Binding Cache: table with Mobility Bindings of MNs (on CN, can tunnel itself now) Binding Update: message, contains up-to-date Mobility Binding of a MN, particularly the Care-of Address Procedure: Update of Binding Caches Control seamless Handoffs between FAs

227 Mobile Communication and Mobile Computing227 Updating of Binding Caches Binding Cache of a CN: Care-of Address of one/several MNs, with respective Lifetime No Entry: non-optimal Routing, BUT: HA doesnt only tunnel a datagram from CN, but also sends a Binding Update to it CN should generate/change Binding Cache-Entry only then, when trusted Mobility Binding received (Bind. Upd.) for corresponding MN (ergo: Secure CN HA) If FA receives tunneled Packet for a MN that is no longer in Visitor List, then it must care that corresponding CN receives a Binding Update (Binding Warning to HA)

228 Mobile Communication and Mobile Computing228 Smooth Handoff between FAs Problem of Basis-MobileIP: MN is with a new FA, but the packets tunneled to old FA will be lost FA Smooth Handoff: MNs are informed via new FA (packet can be forwarded) also Packets of hosts with non-up-to-date entries in Binding Cache can be forwarded now from old FA to the new FAs Previous Foreign Agent Notification Extension enables to prompt the new FA to inform the old FA (Binding Update Message)

229 Mobile Communication and Mobile Computing229 MobileIP v4 & v6 in comparison Mobile IPv4 Mobile IPv6 Optimal Routing, only if MN in the Home Network. (Otherwise non-efficient Triangle-Routing) Optimal Routing is generally possible, if CN knows the Care-of Address Routing HA is a possible bottleneck, because all traffic to the MN is processed over it HA is load essentially reduced, because CNs can just directly communicate with mit MNs Bottle neck Authentication is prescribed only by Registration and then also between HA and MN only Authentication and encryption are possible anywhere, because they are supported from IPv6 Security Used FAs / HAs must not be off-line Short-time failure/re-configuration of HA is mastered thanks to Automatic Home Agent Discovery. IPv6 is essentially simpler to upgrade, therewith also Mobile IPv6 Robustness No good performance due to IPv4-requirements and non-optimal Routing Essentially better due to requirements from IPv6 (uniform Headers, less Over- heads) and optimal Routing Performance

230 Mobile Communication and Mobile Computing230 Assessment Mobile IP enables the unlimited accessibility/roaming of mobile computers using perpetuation of their addresses and step-less transfer between subnets Particularly necessary for applications without pull- semantics (for instance, distributed applications with mobile users, videoconferences, VoIP) Keeping of permanent addresses are also important corresponding to Firewalls etc. in the case of call semantics Successive availability in the form of products

231 Mobile Communication and Mobile Computing231 Dynamic Host Configuration Protocol (DHCP) Properties: permits automatic configuration (IP- address, subnet-mask, router, DNS-Server,...) and therewith integration of (mobile) computers Client/Server-Model Lease Concept Relevant for management of Care- of-Addresses Server AServer BClient DHCPDISCOVER Determination of configuration DHCPOFFER Selection of a configuration DHCPREQUEST (reject) DHCPREQUEST (options) Confirmation of configuration DHCPACK Determination of configuration

232 Mobile Communication and Mobile Computing232 DHCP Assessment no secure mechanisms standardized no standardized communication (signalization, for instance information exchange about managed address areas) between DHCP- servers good base for allocation of co-located COAs in MobileIP

233 Mobile Communication and Mobile Computing233 IPsec: Network security

234 Mobile Communication and Mobile Computing234 IPsec: Security on the network layer (1) IPsec - IP Security Protocol – new developed protocol from TCP/IP-Stack, related to the IPng - Group IPsec uses: –encryption services -> DES, TripleDES and 40-bit-DES between hosts at a VPN (virtual private network) –specification for Internet Key Management Protocol (IKMP), based on ISAKMP/Oakley (1998, Internet Security Association and Key Management Protocol - ISAKMP) IPSec-tunnels – encapsulation of TCP/IP-data via the ESP/AH- headers: –Developed by S.Kent, R. Atkinson IP Encapsulating Security Payload" (RFC 2406, 1998) and "IP Authentication Header" (RFC 2402, 1998) –relevant for key assignment to IP-subnets

235 Mobile Communication and Mobile Computing235 IPsec: Security on the network layer (2) Secrecy on the network layer: a sending host encrypts/authenticates data encapsulated in the IP-datagrams –TCP/UDP-segments –ICMP/SNMP-messages Authentication on the network layer: –target host can authenticate source IP-addresses Basic protocols: –Authentication Header (AH) Protocol –Encapsulation Security Payload (ESP) Protocol AH and ESP both requires target and source Handshake-Routine: –establishment of a logical channel via network layer, called Service Agreement (SA) –each SA is unidirectional Distinctly determined via: –security protocol (AH / ESP) –source IP-address –Con-ID of 32 Bit

236 Mobile Communication and Mobile Computing236 Encapsulation Security Payload (ESP) Protocol offers secrecy, host authentication and data integrity data, ESP trailers encrypted next header field is a trailer in the ESP ESP- authentication field is similar to AH- authentication field; protocol field = 50 ESP-Auth Protocol = 50 ESP-Trailer TCP-/UDP-Segment authenticated encrypted ESP-Header IP-Header

237 Mobile Communication and Mobile Computing237 Authentication Header (AH) Protocol offers host authentication and data integrity, but no secrecy AH headers inserted between IP-Header and IP-data field; protocol field = 51 participated routers process datagrams as usually AH-Header consists of: Con-ID authentication data: signed message digest calculated via original IP-Datagram, offers authentication of source hosts and data integrity next header field is specific data type (TCP, UDP, ICMP etc.) TCP-/UDP-Segment AH-Header IP-Header Protocol = 51

238 Mobile Communication and Mobile Computing238 Layer 4

239 Mobile Communication and Mobile Computing239 Problems of conventional protocols Problem: Loss of packets on the radio channels with higher bit- error rate (BER) results in frequent retransmissions of packets and therewith in further efficiency loss TCP-Protocol uses so called Slow-Start-mechanisms: window size is reduced by significant packet losses; this is reasonable for fixed networks, to react on overload, but not for packet losses due to higher BER limited suitability of conventional transport protocols for mobile communication!

240 Mobile Communication and Mobile Computing240 Conventional protocols Congestion Control: packet loss as a rule, in fixed networks occurs only by overload of several components reducing of transmission rate Slow Start: sender calculates a traffic window size start with window size 1 exponential growth till to Congestion Threshold then linear growth Fast Retransmit / Fast Recovery: If 3 DUPACK (duplicate ACK) are received -> sender informs about packet losses and repeats missing packets

241 Mobile Communication and Mobile Computing241 Resulting problems in mobile environment packet losses due to transmission errors are wrongly interpreted as traffic jam (Congestion)! > Slow Start is also wrong > Ideally the packets lost due to transmission errors are simply repeated (no effects on Congestion Control) great variances of Round-Trip-Time

242 Mobile Communication and Mobile Computing242 Scenario Mobile Host Fixed Host Access Point 1 Access Point 2

243 Mobile Communication and Mobile Computing243 Solutions Sender- transparent: to hide the packet losses transparent to the sender transmission repeat via Access Point –on layer 2 –on TCP-layer Wireless-aware sender: sender understands the reason of packet loss explicit notification of senders sender tries to determine the reason of loss Where will be the modifications carried out?: only by the sender only by the receiver only on the transient node (Access Point) combinations

244 Mobile Communication and Mobile Computing244 –Separation between transport functionality in the fixed network respectively in the mobile network: –MobileTCP is specially optimized (up to 100% of efficiency improvement possible) –system-internal TCP-Handovers are necessary, however transparent for fixed computer (Workstation) Work- station MSR Mobile node Mobile Support Router TCP Fixed network Mobile TCP Mobile network TCP-Handover by relocation of mobile node Solution Split Connection

245 Mobile Communication and Mobile Computing245 Example of I-TCP (indirect TCP) separation of TCP-connection at the Access Point optimized TCP over the wireless Link (not absolutely necessary) no changes of TCP for the fixed network transparent for Fixed Host loss of End-to-End-semantics Mobile Host Fixed Host Access Point 1 wireless TCP standard TCP

246 Mobile Communication and Mobile Computing246 Example of I-TCP Mobility: status and buffer transfer Mobile Host Fixed Host Access Point 1 Access Point 2

247 Mobile Communication and Mobile Computing247 I-TCP Assessment +no changes in the fixed network +the errors in the wireless part arent propagated to the fixed network +both parts can be optimized independently +relatively simple: wireless TCP concerns one Hop only +the properties of wireless networks (bit-error rate, delay time) are known, therefore fast retransmissions are possible loss of End-to-End-semantics additional costs (computation time, storage place) concerning the Access Point high delay times with handover caused by buffering of data by Access Point IT-security mechanisms must be adapted

248 Mobile Communication and Mobile Computing248 Example of Snoop transparent extension of Access Point from senders viewpoint Access Point listens to the traffic (snoops) and filters the ACKs buffering of data, are sent to the mobile computer after losses of packets in the wireless network a direct retransmission takes place between Access Point and Mobile Host Access Points send NACK after packet losses of MH Mobile Host Fixed Host Access Point 1 TCP Bufferlocal retransmission

249 Mobile Communication and Mobile Computing249 Snoop Assessment +maintenance of End-to-End-semantics +modifications only at the TCP-Stack of Access Points +errors in the wireless part can be corrected locally +Soft State +no status transfer at new Access Point is necessary +change is possible, also if the new Access Point possesses no Snoop no complete transparency of wireless connection handling of NACK requires the modifications of MH IT-security: encryption can prevent an access to TCP-Header (most of the up-to-date approaches use End-to-End-encryption!)

250 Mobile Communication and Mobile Computing250 Higher Layers and Services

251 Mobile Communication and Mobile Computing251 Wireless Application Protocol - WAP Based partially on the materials of WAP-Forum

252 Mobile Communication and Mobile Computing252 WAP – Standard Overview Goal: Fusion of Internet-Technologies and mobile radio, creation of new innovative services standardized by WAP-Forum (, initiated by Ericsson, Nokia, Motorola specifies application environment and protocols for mobile end-devices such as radio phones, PDAs, pagers

253 Mobile Communication and Mobile Computing253 Why WAP? Mobile radio networks and mobile phones possess special properties and requirements –Display: sizes and presented colors, numerical keyboard, lower processor performance and storage capacity... –Networks: low data rates, high delays and costs WAP offers the use of several carriers –TCP/IP, UDP/IP, USSD, SMS,... USSD - unstructured supplementary service data (GSM) SMS - short message service (GSM)

254 Mobile Communication and Mobile Computing254 Why WAP ? WAP-architecture has a modular organization the modules build together a complete Internet-protocol-stack WML-contents can be queried by HTTP-request-messages WAP uses XML (eXtensible Markup Language)-Standard as well as optimized contents and protocols user interface of conventional end-devices is supported by WML-components –enhances acceptance by users WAP uses conventional HTTP-Servers –existing development strategies are applicable in the future (common gateway interface - CGI, active server pages - ASP, netscape server API - NSAPI...)

255 Mobile Communication and Mobile Computing255 Why HTTP/HTML doesnt suffice? Big pipe - small pipe syndrome NNN Interactive NNN Intera ctive Internet HTTP/HTML Converting to binary format Mobile radio networks Enter name: 010011 010011 110110 010011 011011 011101 010010 011010 WAP

256 Mobile Communication and Mobile Computing256 WAP-overview WAP-standard defines: Environment = Wireless Application Environment (WAE) –WML (Wireless Markup Language) micro-browser –WMLScript virtual machine –WMLScript standard library –Wireless Telephony Application (WTA) Interface –Contents = WAP Content Types Layer architecture –Wireless Session Protocol (WSP) –Wireless Transaction Protocol (WTP) –Wireless Datagram Protocol (WDP) –Interface definitions for mobile network

257 Mobile Communication and Mobile Computing257 Comparison: Internet/WWW and WAP HTML JavaScript HTTP TLS - SSL TCP/IP UDP/IP Wireless Application Environment (WAE) Session Layer (WSP) Security Layer (WTLS) Transport Layer (WDP) other services and applications Transaction Layer (WTP) Carrier: SMSUSSDCDMACDPDetc.. GPRS Internet Wireless Application Protocol SMS - Short Message Service (GSM), GPRS - General Packet Radio Service (GSM II+), CDMA - Code Division Multiple Access, CDPD - Cellular Digital Packet Data

258 Mobile Communication and Mobile Computing258 Wireless Application Environment - WAE environment for distributed applications with specific reference to low-performance end-devices with limited operation comfort and mobile radio networks Goals: –network-independent application environment –optimized for application in mobile radio systems –Internet, i.e. WWW–programming model –high interoperability level

259 Mobile Communication and Mobile Computing259 WAE – abstract network architecture GatewayClient Network Application WSP/HTTP Request {URL} WSP/HTTP Reply {Content}

260 Mobile Communication and Mobile Computing260 Constituents Architecture –Programming model –Browser, Gateway, Content Server WML –as page markup language WMLScript –as scripting language WTA –offers access to phone services Content formats –sets free-defined formats: bitmaps, phonebook records, dates...

261 Mobile Communication and Mobile Computing261 Options User Agent Profiling –to user, end-device,... adapted contents Push-model –network initiates delivery of contents Options for performance improvement –Caching,...

262 Mobile Communication and Mobile Computing262 Sample: WAP-Gateway Web Server Contents CGI Scripts etc. WML Decks, WML-Script WAP Gateway WML Encoder WMLScript Compiler Protocol adapter HTTPWSP/WTP Client WML WML- Script WTAI etc. WAE User Agent

263 Mobile Communication and Mobile Computing263 Sample: WAP - Application Server Contents Application logic WML Decks, WML-Script WAP Application Server WML Encoder WMLScript Compiler Protocol adapter WSP/WTP Client WML WML- Script WTAI etc. WAE User Agent

264 Mobile Communication and Mobile Computing264 Wireless Markup Language - WML(1) HDML - Handheld Device Markup Language, W3C - World Wide Web Consortium, XML - eXtensible Markup Language HTML-like page markup language –different font styles are available, tables and graphics too, but limited based on W3C-XML uses HTML and HDML-elements Deck/Card-metaphor –interactions-/selection possibilities are separated in Cards –navigation (anchor: #) takes place between Cards –Deck-stack corresponds to a WML-file

265 Mobile Communication and Mobile Computing265 Wireless Markup Language - WML(2) explicit navigation model between Decks –Hyperlinks –Events from user interface –History variables and status-management –variable status can tell about validity of a stack

266 Mobile Communication and Mobile Computing266 WML– text styles Deck Card italic, bold, big, small, underlined

267 Mobile Communication and Mobile Computing267 WML-example (1) Selected input Script call Variables Navigation Amount: From: Euro... US Dollar To: