01 - introduction...ad hoc networks without former planning no problems with wiring (e.g. historical...

Lehrstuhl für Informatik 4

Kommunikation und verteilte Systeme

Chapter 1: Introduction

Mobile Communications

Lehrstuhl für Informatik 4RWTH Aachen

Dr. Dirk Thißen

Prof. Dr. Otto Spaniol




Dirk ThißenLehrstuhl für Informatik 4, Room 4105B (Building E1)Phone: 0241 / 80 - 21450E-Mail: [email protected]

Contact

http://www-i4.informatik.rwth-aachen.de/content/teaching/lectures/sub/mobil/WS0708/index.html

Material (Slide Copies and Video Recordings)

Organization

Lecture Dates

• Monday, 16:30 – 18:00, AH5• Wednesday, 13:30 - 15:00, 5052

• J. Schiller: Mobile Communications. 2nd Edition, Addison Wesley, 2003• V. Garg: Wireless Communications and Networking. Morgan Kaufmann, 2007

Literature

Exercise Dates

• Wednesday, 13:30 - 15:00, 5052




What is Mobile Communications?

• Two aspects of mobility:

� User mobility: a user communicates „anytime, anywhere, using any access technology“

� Device portability: A device can connect to the network anytime and anywhere

• Wireless vs. Mobile Example� � stationary computer

� � notebook in a hotel� � Wireless LAN in buildings� � Cellular phone

• The demand for mobile communication creates the need for integration of wireless networks into existing fixed networks:� In the local range: standardization of IEEE 802.11 (Wireless LAN, WLAN)

considering existing wired standards like Ethernet� In wide area range: e.g. internetworking of GSM and ISDN� In the Internet protocols: Mobile IP as enhancement of „normal“ IP




Why Wireless Networks?

• Characteristics� Mostly radio transmission, new protocols for data transmission are needed

• Advantages� Spatial flexibility in radio reception range

� Ad hoc networks without former planning� No problems with wiring (e.g. historical buildings, fire protection, esthetics)

� Robust against disasters like earthquake, fire – and careless users which remove connectors!

• Disadvantages

� Generally very low transmission rates for higher numbers of users� Often proprietary, more powerful approaches, standards are often restricted

� Consideration of lots of national regulations, global regulations are evolving slowly

� Restricted frequency range, interferences of frequencies




Types of Wireless NetworksCellular Networks• Base stations distributed over the area to be covered

• Each base station covers a cell• Need of an infrastructure network connecting all base stations

• Used for mobile phone networks and data networks like Wireless LAN

Mobile Ad-Hoc Networks (MANETs)

• Self-configuring network of mobile nodes• Each node serves as client and router

• No infrastructure (base stations) necessary, direct connections between any pair of nodes

• E.g. Bluetooth

Mesh Networks• Enhancement of above concepts: “Ad-hoc network with infrastructure”

• Allow a whole mesh of connections between wireless nodes• Increased fault tolerance• E.g. used in WiMAX




Possible Applications

• Vehicles

� Transmission of news, road condition, weather, music, e.g. via DAB (Digital Audio Broadcasting)

� Personal communication using the Global System for Mobile Communication (GSM)

� Location tracking via the Global Positioning System (GPS)� Local ad-hoc networks with vehicles close-by to prevent accidents,

guidance system, redundancy

� Vehicle data (e.g., from busses, high-speed trains) can be transmitted in advance for maintenance

• Emergencies

� Early transmission of patient data to the hospital, current status, first diagnosis

� Replacement of a fixed infrastructure in case of earthquakes, hurricanes, fire etc.

� Crisis, war, ...




„Typical“ Application: Road Traffic

ad hocUMTS, WLAN,

DAB, GSM, ...

Personal Travel Assistant,DAB, PDA, Laptop, GSM/UMTS, WLAN, Bluetooth, ...




Possible Applications

• Traveling salesmen� Direct access to customer files stored in a central location

� Consistent databases for all agents� Mobile office

• Replacement of fixed networks� Remote sensors, e.g.,

weather, earth activities� Flexibility for trade shows� LANs in historic buildings

• Entertainment, education, ...� Outdoor Internet access

� Intelligent travel guide with up-to-date location dependent information� Ad-hoc networks for multi user games




Location Dependent Services

• Location aware services� What services, e.g., printer, fax, phone, server etc. exist in the local

environment

• Follow-on services

� Automatic call-forwarding, transmission of the actual workspace to the current location

• Information services

� „Push“: e.g., current special offers in the supermarket� „Pull“: e.g., where is the Black Forrest Cherry Cake?

• Support services� Caches, intermediate results, state information etc. „follow“ the mobile

device through the fixed network

• Privacy� Who should gain knowledge about the location?




Wireless Networks in Comparison to Wired Networks

• Higher loss-rates due to interference� Emissions of e.g. engines, lightning

• Restrictive regulations of radio frequencies� Frequencies have to be coordinated, useful frequencies are almost all

occupied

• Low transmission rates� Local some Mbit/s, regional currently up to 384 Kbit/s with GPRS/UMTS/…

• Higher delays, higher jitter� Connection setup time with GSM in the second range, several hundred

milliseconds for other wireless systems

• Lower security, simpler active attacking

� Radio interface accessible for everyone (shared medium), base station can be simulated, thus attracting calls from mobile phones

• Very different device capabilities

� New concepts necessary in protocol design, e.g. energy efficiency




Characteristics of Mobile Devices

PerformancePerformance

Pager• receive only• tiny displays• simple text messages

Mobile phones• voice, data• simple graphical

displays

PDA• simple graphical displays• character recognition• simplified WWW

Palmtops• tiny keyboard• simple versions of

standard applications

Laptop• fully functional• standard applications

Sensors,embeddedcontrollers




Early „Wireless Communication“

• Many people in history used light for communication

� Heliographs, flags („semaphore“), ...� 150 BC smoke signals for communication

(Polybius, Greece)

� 1794: optical telegraph, Claude Chappe

• Here electromagnetic waves are of special importance:

� 1831 Faraday demonstrates electromagnetic induction� J. Maxwell (1831-79): theory of electromagnetic

fields, wave equations (1864)

� H. Hertz (1857-94): demonstrateswith an experiment the wave character of electrical transmission through space(1888, in Karlsruhe, Germany, at the location of today’s University of Karlsruhe)




History of Wireless Communication

• 1896 - Guglielmo Marconi

� First demonstration of wireless telegraphy (digital!)� Long wave transmission, high transmission power necessary (> 200kw)

• 1907 - Commercial transatlantic connections� Huge base stations (30 100m high antennas)

• 1915 - Wireless voice transmission New York - San Francisco

• 1920 - Discovery of short waves by Marconi

� Reflection at the ionosphere� Smaller sender and receiver, possible due to the invention of the vacuum

tube (1906, Lee DeForest and Robert von Lieben)

• 1926 - Train-phone on the line Hamburg - Berlin� Wires parallel to the railroad track





• 1928 - Many TV broadcast trials (across Atlantic, color TV, TV news)

• 1933 - Frequency modulation (E. H. Armstrong)

• 1958 - A-Netz in Germany� Analogue, 160MHz, connection setup only from the mobile station, no

handover, 80% coverage, 1971 11000 customers

• 1972 - B-Netz in Germany� Analogue, 160MHz, connection setup from the fixed network too (but

location of the mobile station has to be known)

� available also in Austria, Netherlands and Luxembourg, 1979 13000 customers in Germany

• 1979 - NMT at 450MHz (Scandinavian countries)

• 1982 - Start of GSM-specification

� Goal: pan-European digital mobile phone system with roaming

• 1983 - Start of the American AMPS (Advanced Mobile Phone System, analog)

• 1984 - CT-1 standard (Europe) for cordless telephones





• 1986 - C-Netz in Germany

� Analog voice transmission, 450MHz, hand-over possible, digital signaling, automatic location of mobile device

� Was in use until 2000, services: FAX, modem, X.25, e-mail, 98% coverage

• 1991 - Specification of DECT� Digital European Cordless Telephone (today: Digital Enhanced Cordless

Telecommunications)� 1880-1900MHz, ~100-500m range, 120 duplex channels, 1.2Mbit/s data

transmission, voice encryption, authentication, up to several 10000 user/km2, used in more than 50 countries

• 1992 - Start of GSM� In Germany as D1 and D2, fully digital, 900MHz, 124 channels

� Automatic location, hand-over, cellular� Roaming in Europe - now worldwide in more than 170 countries

� Services: data with 9.6kbit/s, FAX, voice, ...





• 1994 - E-Netz in Germany� GSM with 1800MHz, smaller cells� As E-plus in Germany (1997 98% coverage of the population)

• 1996 - HiperLAN (High Performance Radio Local Area Network)� ETSI, standardization of type 1: 5.15 - 5.30GHz, 23.5Mbit/s

� Recommendations for type 2 and 3 (both 5GHz) and 4 (17GHz) as wireless ATM-networks (up to 155Mbit/s)

• 1997 - Wireless LAN – IEEE 802.11� IEEE standard, 2.4GHz and infrared, 2Mbit/s

� Already many (proprietary) products available in the beginning

• 1998 - Specification of GSM successors

� UMTS (Universal Mobile Telecommunication System) as European proposals for IMT-2000

� Iridium: 66 satellites (+6 spare), 1.6GHz to the mobile phone





• 1999 - Standardization of additional wireless LANs

� IEEE standard 802.11b, 2.4-2.5GHz, 11Mbit/s� Bluetooth for piconets, 2.4Ghz, <1Mbit/s

Decision about IMT-2000

� Several “members” of a “family”: UMTS, cdma2000, DECT, …Start of WAP (Wireless Application Protocol) and i-mode

� Access to many (Internet) services via the mobile phone• 2000 - GSM with higher data rates

� HSCSD offers up to 57,6kbit/s� First GPRS trials with up to 50 kbit/s (packet oriented!)

UMTS auctions/beauty contests� Hype followed by disillusionment (approx. 50 B$ payed in Germany for 6

UMTS licenses!)

• 2001 - Start of 3G systems� Cdma2000 in Korea, UMTS in Europe, Foma (almost UMTS) in Japan

• since 2002 – Standardization of high-capacity wireless networks� IEEE 802.16 as WMAN, IEEE 802.20 (WWAN), IEEE 802.22 (WRAN)




Wireless Systems: Overview of the Evolution

cellular phones satellites wireless LANcordlessphones

1992:GSM

1994:DCS 1800

2001:IMT-2000/UMTS

1987:CT1+

1982:Inmarsat-A

1992:Inmarsat-BInmarsat-M

1998:Iridium

1989:CT 2

1991:DECT 199x:

proprietary

1997:IEEE 802.11

1999:802.11b, Bluetooth

1988:Inmarsat-C

analogue

digital

1991:D-AMPS

1991:CDMA

1981:NMT 450

1986:NMT 900

1980:CT0

1984:CT1

1983:AMPS

1993:PDC

2000:GPRS

200?:Fourth Generation(Internet based)

since 2002:IEEE 802.16/20/22

2000:IEEE 802.11a

• 1st generation: analogue

• 2nd generation: digital

• 3rd generation (3G): integration of voice and data

• 4th generation (4G): integration with Internet(When and how?)




Wireless Systems

100.0

10.0

1.0

0.1

0.01

Indoor Outdoor

Office Building stationary walk drive

wired devices

WLAN

HIPERLAN

UMTS

CORDLESS(DECT) CELLULAR

(GSM)

transmission rate (MBit/s)

mobility

• DECT - Digital Enhanced Cordless Telecommuni-cations (Standard for wireless phones in a local range)

• GSM - Global System for Mobile Communication (cellular phone system)

• UMTS - Universal Mobile Telecommunications System (universal system, comprising several different access systems)

• WLAN - Wireless Local Area Network (Standard for wireless networking of (portable) computer)

• HIPERLAN – alternative LAN to WLAN, „wireless ATM enhancement“

• WMAN – Wireless MAN (Bridging the last mile between a fixed network and the end user, wireless alternative to DSL)

• And furthermore: Satellite systems, Bluetooth in very short range

WMAN




Network Categories:Personal Area Networks (PAN)

Personal Area Networks (very small range)

• IEEE 802.15 (WPAN, Bluetooth):� Data rates up to 2 MBit/s� Range up to ca. 10/15 meters (with higher transmission power, also 100

meters are no problem), forming of small radio cells� Ad-hoc Networking: spontaneous (automatically) connection of several

devices (maximally 8) to an independent network

� Used with cellular phones, Personal Digital Assistants (PDAs), ...




Network Categories : Wireless “Local” Area Networks

Wireless LANs (small range)• IEEE 802.11 (Wireless LAN, WLAN)

� “The” standard for supporting mobile computers� High data rates: currently up to 54 MBit/s� Physical layer and MAC: often called “wireless variant of Ethernet”

� Base stations (Access Point, AP) connect WLAN with fixed Ethernet, additionally WLAN enables forming ad-hoc networks

� Transmission medium: radio and infrared

• IEEE 802.16 (WirelessMAN/WiMAX), 802.20 (WirelessWAN), 802.22 (Wireless Regional Area Network)

� 802.11 mainly supports mobility, 802.16 more focuses on connecting buildings� Higher data rates (32-134 Mb/s), larger range




Network Categories: Telecommunication Networks

Cordless Systems

• DECT (Digital Enhanced Cordless Telecommunications)� Standard for cordless telephony

� Transmission of voice and data in short range (at home)

Cellular Systems (medium range)

• GSM (Global System for Mobile Communications)� Mainly designed for voice transmission, also used for data transmission

(Wide Area Network)

� Low data rates (9,6 Kb/s)� Enhancements for data transmission (EDGE, GPRS, HSCSD)

• UMTS (Universal Mobile Telecommunications System)� Also: IMT-2000 (International Mobile Telecommunications)� Integration of “all” types of data, rates up to 2 Mb/s

… and for word-wide coverage: satellites.




Overlay Networks

regional

metropolitan area

campus

indoor

VerticalHandover(IEEE 802.21)

HorizontalHandover

integration of heterogeneous fixed andmobile networks with varyingtransmission characteristics




Mobility is not only Wireless Networks

router

router

home network

foreign network

Internet

137.226.12/24

141.17.63/24

137.226.12.98

• Invalid IP address in foreign network• Routing problems

• TCP connections break down→ TCP/IP modifications necessary!




Areas of Research in Mobile Communication

• Wireless communication

� Transmission quality (bandwidth, error rate, delay)� Modulation, coding, interference� Media access, regulations

� ...

• Mobility

� Location dependent services� Location transparency

� Quality of Service support (delay, jitter, security)� ...

• Portability� Power consumption

� Limited computing power, sizes of display, ...� Usability

� ...




Simple Reference Model used here

Application

Transport

Network

Data Link

Physical

Medium

Data Link

Physical

Application

Transport

Network

Data Link

Physical

Data Link

Physical

Network Network

Radio




Tasks on Protocol Layers

Physical Layer

Data Link Layer

Network Layer

Transport Layer

Application Layer

• Frequencies, modulation• Interferences, attenuation

• (Encryption)

• Medium access control• Multiplexing

• (Authentication)

• Addressing, routing• Device location• Handover

• Congestion and flow control• Quality of Service

• Service location

• Adaptive application• New applications




Structure of the Lecture

Chapter 2• Technical Basics: Layer 1• Methods for Medium Access: Layer 2

Chapter 3• Wireless Networks: Bluetooth, WLAN, WirelessMAN, and variants

• Mobile Networks: GSM, GPRS, UMTS• Satellites and Broadcast Networks

Chapter 4• Mobility on the network layer: Mobile IP, Routing, Ad-Hoc Networks

• Mobility on the transport layer: reliable transmission, flow control, QoS• Mobility support on the application layer

01 - introduction...ad hoc networks without former planning no problems with wiring (e.g. historical...

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