Department of Computer Science Institute for System Architecture, Chair for Computer Networks

Mobile Communication and Mobile Computing

Prof. Dr. Alexander Schill http://www.rn.inf.tu-dresden.de

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

Introduction and Principles

Applications like Civil Engineering

Large archives, Videoconferences

Enterprise A (main office)

Gigabit Ethernet

Drafts, urgent modification

Fast Ethernet

Enterprise A (branch office) Architect

Gigabit Ethernet

Selected drafts, Videoconferences

Enterprise B

UMTS, LTE

Construction supervisor

GSM, UMTS

Material data, status data, dates

Building site

3

Example: Consumer Application

8:56 PM http:// www.bike-rental ...

Rent-A-Bike Service Login

Login: Alexander Schill Password: ********** URL LOGIN 4

Mobile Communication: Development

Mobile Phone Networks Packet Networks Circuit Switched Networks Satellite Networks Cordless Telephony C CT D (GSM900) E (GSM1800) HSCSD GPRS Modacom Mobitex Tetra Inmarsat DECT Iridium/ Globalstar Radio-LAN Local Networks IR-LAN IEEE 802.11

Bluetooth EDGE IMT/ UMTS LTE 4G (LTE advanced, WiMAX) 1990 1995 2000 2005 2010 2015 5

Used Acronyms

C: C: Analog “C” Network (1st Generation) CT: CT: Cordless Telephone DECT: Digital Enhanced Cordless Telecommunications HSUPA+: HSCSD: High Speed Uplink Packet Access (advanced) High Speed Circuit Switched Data IMT:

LTE:

International Mobile Telecommunications Long Term Evolution 4th Generation Networks 6

Correspondent data rates

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

1995 2000 2005 2010 2015 7

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 along highways or train lines for covering of larger areas * ** 8

Structure of a cellular network

1 3 2 4 1 1 3 2 4 1

• Major problems:  limited frequency resources  interference • reuse of frequency channels in remote cells • cluster of N cell types • reuse distance

D

 3

N



R

• where R – cell radius 9

FDMA (Frequency Division Multiple Access)

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

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 k1 k2 k3 k4 k5 k6 TDMA selects slot f1 f k1 k2 k3 k4 k5 k6 k1 t 11

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 f in MHz 960 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 downlink 25 MHz 935,2 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 915 200 kHz TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 890,2 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 25 MHz 45 MHz t uplink 12

CDMA (Code Division Multiple Access)

k1 k2 k3 k4 k5 k6 CDMA decoded f1 • 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 13

GSM (Global System for Mobile

Communication): Structure

Fixed network Switching Subsystems Radio Subsystems OMC VLR HLR AuC EIR Data networks MS (G)MSC BSC BTS PSTN Call Management Network Management BSS BTS MS MS AuC Authentication Center BSS Base Station Subsystem BSC Base Station Controller BTS Base Transceiver Station EIR Equipment Identity Register HLR Home Location Register MS (G)SMC (Gateway) Mobile Switching Center OMC Mobile Station Operation and Maintenance Center PSTN VLR Public Switched Telephone Network Visitor Location Register 14

GSM: Protocols, incoming call

(8) (9) (12) BSS BSS VLR (8) (9) (8) (7) (11) MSC (6) (10) (12) (8) (4) (3) (5) BSS (4) HLR (2) GMSC (1) 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 15

GSM: Protocols, incoming call

(8) (9) (12) BSS BSS VLR (8) (9) (8) (7) (11) MSC (6) (10) (12) (8) (4) (3) (5) BSS (4) HLR (2) GMSC (1) 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 setup 16

Radio structure

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

890 935 downlink 915 MHz uplink 960 MHz

2 frequency bands, each 25 MHz, divided into radio cells • One or several carrier frequencies per BSC • Physical channels defined by number and position of time slots 17

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

UMTS: Hierarchical Cell Structure

Global Regional Local Home/ Office World Macro Micro Pico

expansion World Cell Macro Cell Micro Cell Pico Cell

global several km several 100m ca. 100 m

Data rate (kbit/s)

144 384 2000

Max. velocity (km/h)

>300 ~100 ~10

Special features

special satellite technology complete national wide-area UMTS support Greater cities, commonly used „Hotspots“ – e.g. airport, station 19

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

HSPA+: Modulation basics of QAM

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

HSPA+: Modulation basics of QAM

• 8 QAM example: (3bits)

Bit value

Amplitude Phase Shift • 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)

000 001 010 011 100 101 110 111

1 1/2 1 1/2 1 1/2 1 1/2 No No 1/4 1/4 1/2 1/2 3/4 3/4 * Quadrature Phase Shift Keying = 4 QAM (no info from amplitude) source: Fujitsu 22

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

Single Input / Single Output

Input Tx Rx Output

2x2 MIMO

Input Tx Rx1 Rx2 MIMO Receiver Output 23

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

IEEE 802.11 - 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 AP AP Three infrastructure APs in one fixed network AP Network 25

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 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) 26

802.11 - WiFi standards

Standard

802.11

802.11a

802.11b

Frequency Bandwidth

2,4 GHz 5 GHz

Max. data rate DRmax

2 MBit/s 54 MBit/s

Normal Data rate DR

1,2 MBit/s 32 MBit/s

Modulation

DSSS (FHSS, Infrared) OFDM

Range R (indoor/ outdoor)

30/300 10/100 2,4 GHz 11 MBit/s 7 MBit/s DSSS 30/300

Remarks

outdated high data rate, but incompatible to other standards, low range higher range, but lower data rate 802.11g

802.11n

2,4 GHz 2,4 GHz and 5 GHz 54 MBit/s 32 MBit/s Up to 300 MBit/s ~ 100 MBit/s OFDM OFDM 30/300 10/100 higher data rate and range, but sensitive to noise very high data rate, but also sensitive to noise DSSS ... Direct Sequence Spread Spectrum FHSS … Frequency Hopping Spread Spectrum OFDM ... Orthogonal Frequency Division Multiplexing 27

Bluetooth

• Harald Bluetooth was the King of Denmark in the 10th century • Initiated by Ericsson, Intel, IBM, Nokia, Toshiba; Open Standard: IEEE 802.15.1

• 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:      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 802.15.3a

UWB (Ultra Wide Band)) Basic setup 2,4-Ghz HF Bluetooth Baseband Controller Host System 28

Bluetooth - Comparison

FUNCTION

Range:

Bluetooth v1.1

10 meters max.

IrDA Data 1.1

1 meter max.

IEEE 802.11 (WiFi)

30-300 meters max. (indoor / outdoor) omni-directional Angle: omni-directional Frequency Band: Mobility: ISM Band, 2.4 GHz mobile Data rate: Security level: 723 kBit/s – 20 Mbit/s High ca 30 ° Infrared Radiation stationary Varying (kBit/s – MBit/s range) Low ISM Band, 2.4 GHz mobile 300 MBit/s High 29

Satellite Systems

Inter-Satellite Link Gateway Ground Station Gateway Link Spot beams Footprint GSM, ...

Internet Mobile User Link User 30

Geostationary Satellite systems

Principle: Uplink Satellite 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) 31

LEO Systems

• non-stationary satellites (LEO - Low Earth Orbit) • distance to the earth ~ 500 - 2000 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

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 1978 33

Principle: TOA (Time of Arrival)

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 = 0,7 • 10 -1 s • 3 • 10 8 m/s = 2,1 • 10 7 • calculation of spheres around each satellite m = 21.000 km • the position is on the intersection point of three spheres 34

Indoor Positioning using WiFi: Magic Map

35

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 IR receiver infrared beacons infrared WLAN location system

Mobile Computing: Device heterogeneity

• 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

37

Fluid Grids

960px 12px 69px

#page {width: 90%;} (90% des Browserfensters ->entpricht 960px) Banner 900 ÷ 960 = 0.9375

.banner {width: 93.75%;} Article 566 ÷ 900 = 62.8888889% .article { width: 62.8888889%; float: left; } Sidebar 331 ÷ 900 = 36.7777778% .sidebar { width: 36.7777778%; float: right; }

566px 331px 900px

• 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

38

Scalable Images

: img {max-width: 100%;}   Scales image according to parent element size Proportions of web page are maintained

Alternative image sources:

media

="(min-width: 18em)"

srcset

="med.jpg 1x, med-highres.jpg 2x"> //small layout // larger layout //fallback for older browsers

CSS Media Queries

• 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:  

@media screen and (min-device-width: 480px) and (orientation: landscape) @media screen and (max-width: 1200px) and (min-resolution: 260dpi) and (aspect-ratio: 1/1)

40

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

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

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

Android Architecture

44

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

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

Activity A

intend

Activity B

broad cast intend

Local Service Dalvik VM

Process Inter-process Communication AIDL

Remote Service Dalvik VM

Process 46

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 onCreate initialized removed onDestroy onRestart inactive onStart onStop visible onResume onPause active 47

Android Development Environment – Eclipse Plugin

48