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Mobile Communication and Mobile Computing Prof. Dr. Alexander Schill Department of Computer Science Institute for System.

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Presentation on theme: "Mobile Communication and Mobile Computing Prof. Dr. Alexander Schill Department of Computer Science Institute for System."— Presentation transcript:

1 Mobile Communication and Mobile Computing Prof. Dr. Alexander Schill Department of Computer Science Institute for System Architecture, Chair for Computer Networks

2 Structure of the Lecture Part I: Mobile Communication -Introduction and Principles -GSM, UMTS and LTE (2G-3G-4G Mobile Networks) -WiFi and Bluetooth -Satellite Systems and GPS Part II: Mobile Computing -Mobile Web -Location Based Services -Mobile Platforms and Applications 2

3 Introduction and Principles Applications like Civil Engineering 3 Building site Architect Enterprise A (main office) Enterprise B Construction supervisor Gigabit Ethernet UMTS, LTE GSM, UMTS Selected drafts, Videoconferences Material data, status data, dates Large archives, Videoconferences Drafts, urgent modification Enterprise A (branch office) Gigabit Ethernet Fast Ethernet

4 Example: Consumer Application 4 8:56 PM URL LOGIN Service Login Rent-A-Bike Alexander Schill Login: ********** Password:

5 Mobile Communication: Development Mobile Phone Networks Packet Networks Circuit Switched Networks Satellite Networks Local Networks 2005 D (GSM900) C Modacom Mobitex Tetra Inmarsat IR-LAN IMT/ UMTS IEEE Bluetooth Radio-LAN Iridium/ Globalstar E (GSM1800) HSCSD GPRS Cordless Telephony CTDECT G (LTE - advanced, WiMAX) EDGE LTE 2015

6 Used Acronyms 6 C: Analog “C” Network (1st Generation) CT: Cordless Telephone DECT: Digital Enhanced Cordless Telecommunications GSM: Global System for Mobile Communications (2nd Generation) GPRS: General Packet Radio Service HSCSD:High Speed Downlink Packet Access (advanced) High Speed Uplink Packet Access (advanced) High Speed Circuit Switched Data EDGE: Enhanced Data Rates for GSM Evolution IMT: International Mobile Telecommunications LTE:Long Term Evolution TETRA: Terrestrial Trunked Radio (Multicast Communication System) UMTS: Universal Mobile Telecommunications System (3rd Generation) 4G: 4th Generation Networks WiMAXWorldwide Interoperability for Microwave Access C: CT: DECT: GSM: GPRS: HSDPA+: HSUPA+: HSCSD: EDGE: IMT: LTE: TETRA: UMTS: 4G: WiMAX:

7 Correspondent data rates Mbit/s UMTS (pico cell) 10kbit/s GSM HSCSD/ GPRS EDGE 100kbit/s 1Mbit/s UMTS (macro cell) Satellites DECT 100Mbit/s 300Mbit/s 2015 LTE (uplink) / HSDPA+ LTE (downlink) WLAN 50Mbit/s 200Mbit/s HSUPA+

8 Cellular networks well known from mobile networks (GSM, UMTS) base station (BS) covers at least one cell; a combination of multiple cells is also called a cellular structure provides different kinds of handovers between the cells higher capacity and better coverage than non-cellular networks bidirectional* antennas instead of omni-directional** can better serve the selected sectors 8 along highways or train lines for covering of larger areas * **

9 Structure of a cellular network Major problems:  limited frequency resources  interference reuse of frequency channels in remote cells cluster of N cell types reuse distance where R – cell radius

10 FDMA (Frequency Division Multiple Access) frequencies are permanently assigned to transmission channels (known from broadcast radio) 10 k1k2k3k4k5k6 f1 f2 f3 f4 f5 f6 s – secure distance s FDMA selects frequency t f k1 k2 k3 k4 k5 k6

11 TDMA (Time Division Multiple Access) transmission medium is slot-assigned to channels for certain time, is often used in LANs Synchronization (timing, static or dynamic) between transmitting and receiving stations is required 11 k1k2k3k4k5k6 f1 t f k1k2k3k4k5k6k1 TDMA selects slot

12 Combination: FDMA and TDMA, (e.g. in GSM) GSM uses combination of FDMA and TDMA for better use of narrow resources the used bandwidth for each carrier is 200 kHz => approx. 124 * 8 = 992 channels 12 t f in MHz TS0TS1TS2TS3TS4TS5TS6TS7TS0 TS1TS2TS3TS4TS5TS6TS7TS0 TS1TS2TS3TS4TS5TS6TS7TS0 TS1TS2TS3TS4TS5TS6TS7TS0 TS1TS2TS3TS4TS5TS6TS7TS0 TS1TS2TS3TS4TS5TS6TS7TS0 890, kHz 935, MHz 45 MHz 25 MHz uplink downlink

13 CDMA (Code Division Multiple Access) 13 k1k2k3k4k5k6 f1 CDMA decoded definite Codes are assigned to transmission channels, these can be on the same Frequency for the same Time uses cost-efficient VLSI components high security level using spread spectrum techniques 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

14 GSM (Global System for Mobile Communication): Structure 14 AuCAuthentication Center BSS Base Station Subsystem BSCBase Station Controller BTSBase Transceiver Station EIREquipment Identity Register HLRHome Location Register Fixed network Switching Subsystems VLR Radio Subsystems HLRAuCEIR (G)MSC OMC BTS BSC BSS MS Network Management Call Management Data networks PSTN MS MSMobile Station (G)SMC(Gateway) Mobile Switching Center OMCOperation and Maintenance Center PSTNPublic Switched Telephone Network VLRVisitor Location Register

15 GSM: Protocols, incoming call 15 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 (3) HLR checks whether participant is authorized for corresponding service and asks for MSRN at the responsible VLR (4) MSRN will be returned to GMSC, can now contact responsible MSC

16 GSM: Protocols, incoming call 16 VLR BSS MSCGMSC HLRBSS (4) (2) (4) (5) (3) (10) (6) (11) (7) (8) (12) (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 ( ) Security check and connection setup (8) (9) (8)

17 Radio structure 17 1 TDMA-Slot, 144 Bit in 4,615 ms 8 TDMA-channels, together 271 kBit/s including error protection information 124 radio frequency channels (carrier), each 200 kHz 2 frequency bands, each 25 MHz, divided into radio cells MHz 960 MHz downlink uplink One or several carrier frequencies per BSC Physical channels defined by number and position of time slots

18 UMTS (Universal Mobile Telecomm. System): Characteristics UMTS is an implementation of IMT (International Mobile Telecommunications) by ETSI (European Telecommunication Standards Institute) relatively high data rates: 144 kbit/s mobile, up to 2 Mbit/s in local area (and even higher with advanced extension protocols) integration of different mobile radio communications-, wireless- and pager-systems into one common system speech-, data-, and multimedia- information services independent of network access support of different carrier services:  real-time capable / not real-time capable  circuit switched / packet switched Roaming also between UMTS, GSM/GPRS and satellite networks Asymmetrical data rates on up-/downlink, use of CDMA 18

19 UMTS: Hierarchical Cell Structure 19 expansionData rate (kbit/s) Max. velocity (km/h) Special features World Cellglobal-special satellite technology Macro Cellseveral km144>300complete national wide-area UMTS support Micro Cellseveral 100m384~100Greater cities, commonly used Pico Cellca. 100 m2000~10„Hotspots“ – e.g. airport, station Global Local Regional Home/ Office World Macro Micro Pico

20 UMTS Enhancement: HSPA(+) HSPA (High-speed Packet Access) = HSDPA+HSUPA HSDPA (High-speed Downlink Packet Access), extension of UMTS Data rates up to 14,4 Mbit/s (10,8 Mbit/s with error- correction encoding) on downlink channel (even higher rates proposed for the future and tested under lab conditions) Combination of channel bundling (TDMA), wideband code multiplex (W-CDMA) and improved coding (adaptive modulation and coding with advanced scheduling) adaptive switching between 4 QAM (quadrature amplitude modulation) up to 64 QAM (depending on channel quality) HSUPA (High-speed Uplink Packet Access) for upload 20

21 HSPA+: Modulation basics of QAM QAM (Quadrature Amplitude Modulation) is a combination of Amplitude Shift Keying ASK and Phase Shift Keying PSK 21 ASK (A=1/2) t t ASK+PSK (A=1/2, P= 90° ) t PSK (P=90° =1/4) t PSK (P=180° =1/2) t PSK (P=270° =3/4)

22 Bit value Amplitude 11/ Phase Shift No 1/4 1/2 3/4 HSPA+: Modulation basics of QAM QAM 16 QAM QPSK* * Quadrature Phase Shift Keying = 4 QAM (no info from amplitude) source: Fujitsu 8 QAM example: (3bits) In case of 8 QAM the 8 conforms to the highest possible number of codable states (the sensitivity to interference increases with the number of states)

23 HSPA+: MIMO antenna technique MIMO = Multiple Input / Multiple Output multiple antennas on sender and receiver side increase in spectral efficiency (and resulting data rate) and quality of transmission 23 Tx Rx MIMO Receiver Input Output Rx1 Rx2 2x2 MIMO Single Input / Single Output

24 LTE: Long Term Evolution Further extension of HSDPA with even higher data rates and – nevertheless – compatibility with UMTS Use of OFDM (Orthogonal Frequency Division Multiplex) and MIMO (Multiple Input – Multiple Output Antennas) Flexible channel bandwidths ranging from 1.4 MHz to 20 MHz (UMTS: static bandwidth of 5 MHz per channel); therefore better adaptation to user requirements Data rates: up to 300 MBit/s downlink and 75 MBit/s uplink; very low latency under 5 ms Official standard with implementations by several providers worldwide 24

25 IEEE Network Topologies (1) infrastructure mode  like a star-network  Access-Point (AP) is a central point  AP coordinates the network nodes and communicates with other networks 25 AP Three infrastructure APs in one fixed network Network

26 802.11– Network Topologies (2) Ad-hoc Mode  Like Peer-to-Peer Network  no central Station or higher-level infrastructure available  All network nodes are equivalent Direct connection the nodes see each other and can communicate one with each other 26 Beaconing-Mechanism every node sends a “Beacon”- Signal in certain intervals. Via this signal every node knows its direct neighbors. ad-hoc-nets appear spontaneously and organize and administrate themselves Indirect connection no direct communication possible special routing methods for transmission of the data (e.g. OLSR Optimized Link State Routing)

27 WiFi standards StandardFrequency Bandwidth Max. data rate DRmax Normal Data rate DR ModulationRange R (indoor/ outdoor) Remarks ,4 GHz2 MBit/s1,2 MBit/s DSSS (FHSS, Infrared) 30/300outdated a5 GHz54 MBit/s32 MBit/sOFDM10/100high data rate, but incompatible to other standards, low range b2,4 GHz11 MBit/s7 MBit/sDSSS30/300higher range, but lower data rate g2,4 GHz54 MBit/s32 MBit/sOFDM30/300higher data rate and range, but sensitive to noise n2,4 GHz and 5 GHz Up to 300 MBit/s ~ 100 MBit/s OFDM10/100very high data rate, but also sensitive to noise 27 DSSS... Direct Sequence Spread Spectrum FHSS … Frequency Hopping Spread Spectrum OFDM... Orthogonal Frequency Division Multiplexing

28 Bluetooth Harald Bluetooth was the King of Denmark in the 10th century Initiated by Ericsson, Intel, IBM, Nokia, Toshiba; Open Standard: IEEE Generally for wireless Ad-hoc-piconets (range < 10m); single-chip solution Frequency band in 2,4 GHz area Integrated security (128 bit encryption) Data rates: 28 Basic setup 2,4-Ghz- HF Bluetooth- Baseband- Controller Host- System 433,9 kBit/s asynchronous-symmetrical 723,2 kBit/s / 57,6 kbit/s asynchronous-asymmetrical 64 kBit/s synchronous, voice service Extensions up to 20 Mbit/s (IEEE a UWB (Ultra Wide Band))

29 Bluetooth - Comparison 29 FUNCTIONBluetooth v1.1IrDA Data 1.1IEEE (WiFi) Range:10 meters max.1 meter max meters max. (indoor / outdoor) Angle:omni-directionalca 30°omni-directional Frequency Band: ISM Band, 2.4 GHz Infrared RadiationISM Band, 2.4 GHz Mobility:mobilestationarymobile Data rate:723 kBit/s – 20 Mbit/s Varying (kBit/s – MBit/s range) 300 MBit/s Security level:HighLowHigh

30 Satellite Systems 30 Inter-Satellite Link Gateway Link Mobile User Link Spot beams Footprint Gateway Ground Station User GSM,... Internet

31 Geostationary Satellite systems 31 Principle: Satellite Uplink Downlink constant position to the Earth, 3 satellites cover complete earth (without polar caps), satellites move synchronously to the earth simple solution, long life time of the satellites: ~ 15 years large distance (36000 km), therefore high signal propagation delay low data rates, large transmission power required problems: –on the other side of the 60th degree of latitude reception problems (elevation) –because of high transmission power unfavorable for mobile telephones –signal propagation delay too high (0.25 s)

32 LEO Systems non-stationary satellites (LEO - Low Earth Orbit) distance to the earth ~ km shorter signal delay times (5-10 ms), lower transmission power of the mobile stations sufficient however more satellites necessary (> 50), frequent handover between satellites, approximately every 10 min. shorter lifetime of the satellites because of atmospheric friction (5-8 years) examples: Iridium, Teledesic, Globalstar 32

33 Global Positioning System, GPS 24 satellites on the 6 orbits (20200 km, time of circulation = 12h) 5 earth stations (Hawaii, Ascension Island, Diego Garcia, Kwajalein, Colorado Springs) Accuracy: up to 1 m (normally approx. 10 m) Functionality principle: Triangulation GPS-receiver calculates distance to the satellite based on Time of Arrival of the received signals distances to at least three satellites enable the calculation of position, a fourth satellite can be used for determination of elevation over zero official initiation 1995, testing since

34 Principle: TOA (Time of Arrival) 34 Distance d, Signal Delay T Mobile Object synchronized clocks measurement of signal delay based on speed of light between satellite and receiver, for instance T = 70 ms hence calculation of distance: d = T c = 0, s m/s = 2, m = km calculation of spheres around each satellite the position is on the intersection point of three spheres

35 Indoor Positioning using WiFi: Magic Map 35

36 Wireless Indoor Positioning System (WIPS) stand-alone infrastructure based positioning system based on infrared (IR) beacons installed in the rooms sending unique ID users’ badges receiving signals of local beacons received beacon ID is sent to location server via WLAN server maps received beacon ID to semantic location which is sent back to the user +advantage: users knows his own position – disadvantage: integration of two wireless techniques 36

37 Mobile Computing: Device heterogeneity 37 Solution: Responsive Web Design  Web pages with single HTML source (no separate mobile version!)  Adaptation based on Cascading Style Sheets (CSS) using: Fluid grids Flexible images CSS Media Queries

38 Fluid Grids 38 Page layout based on grids:  Maximum width as starting point  Layout defined by columns of dedicated width and bordering area Translation of fixed values into proportional values  % oder em (relative size) for block elements and font sizes  Values relative to parent element: Element-width / Parent-width = Relative value

39 Scalable Images : img {max-width: 100%;}  Scales image according to parent element size  Proportions of web page are maintained Alternative image sources: //small layout // larger layout //fallback for older browsers

40 CSS Media Queries 40 Definition of alternative Layouts for HTML-Markup Displaying/Hiding/Moving/Scaling of Elements Media features width | min-width | max-width | height | min-height |... device-width | min-device-width | max-device-width | device-height |... aspect-ratio | min-aspect-ratio | max-aspect-ratio orientation |... Media Queries: screen and (min-device-width: 480px) and (orientation: landscape) screen and (max-width: 1200px) and (min-resolution: 260dpi) and (aspect-ratio: 1/1)

41 Integration: HTML 5  HTML5 und CSS3 include: Device access CSS3 Multimedia Offline and Storage,…  Main design principle: Responsive Web Design Scalable Layout and Images Alternative Layouts and Content using Media Queries

42 What is Android? Open source software stack for mobile devices an Operating System a Middleware a set of basic applications Android SDK Developer Tools Emulator Sample Code Android Library Developing Language Java (managed code) Virtual Machine Dalvik (GNU/Linux kernel) 42

43 Android Architecture Application Framework (allows reuse and exchange of components) Programming in Java, with special VM implementation (Dalvik VM) Complete development environment Media Libraries - based on PacketVideo's OpenCORE; playback and recording of many popular audio, video and image formats, (MPEG4, H.264, MP3, AAC, AMR, JPG, and PNG) SQLite - lightweight relational database engine Google Maps support Integrated Browser - based on WebKit (open source) Optimized graphics libraries - 2D library, 3D library based on OpenGL 43

44 Android Architecture 44

45 Android Architecture Linux Kernel: As an abstraction layer between hard- and software Core system services (threading, low-level memory management, hardware drivers, power management) Dalvik Virtual Machine: alternative Java implementation no Sun certification basically just the syntax of the progr. language is the same Dalvik byte code (must be compiled for Dalvik VM) no full Java ME, no full Java SE (four major libraries 'lang', 'util', 'io', 'net' fully available) Optimized for mobile computers memory management every application runs in its own process optimized for many parallel VMs 45

46 Anatomy of an Android application Four building blocks (Activity, Broadcast Intent Receiver, Services, Content Providers) used components have to be declared in the Android Manifest file 46 Process Activity AActivity B intend Dalvik VM broad- cast intend Local Service service Binder Dalvik VM Remote Service Inter-process Communication AIDL

47 Building Blocks - Activities Activity : a single screen of the application extends the Activity class consists of user interface elements (views) that respond to events may return a value to another activity When a new screen opens, the previous is put onto a history stack. Methods of activity reflect lifecycle 47

48 Android Development Environment – Eclipse Plugin 48


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