Mobile Communications

Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Organization
Lecture Dates
• Wednesday, 13:30 - 15:00, in 5052
Mobile Communications
Material (Slide Copies and Video Recordings)
http://www-i4.informatik.rwth-aachen.de/
content/teaching/lectures/sub/mobil/WS0506/index.html
Literature
Lehrstuhl für Informatik 4
RWTH Aachen
J. Schiller: Mobile Communications. 2nd Edition, Addison Wesley, 2003
Contact
Dirk Thißen
Lehrstuhl für Informatik 4, Room 4226 (Building E1)
Phone: 0241 / 80 - 21450
E-Mail: [email protected]
Dr. rer. nat. Dirk Thißen
Prof. Dr. Otto Spaniol
Seite 1
Chapter 1: Introduction
Chapter 1: Introduction
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
What is Mobile Communications?
Why Wireless Networks?
• Two aspects of mobility:
User mobility: a user communicates (wireless) „anytime, anywhere, with
anyone“
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
Personal Digital Assistants (PDA)
• 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, ETSI HIPERLAN
– In the Internet: Mobile IP as enhancement of „normal“ IP
– In wide area range: e.g. internetworking of GSM and ISDN
Chapter 1: Introduction
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•
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
Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Applications I
„Typical“ Application: Road Traffic
• Vehicles
Transmission of news, road condition, weather, music via DAB (Digital
Audio Broadcasting)
Personal communication using GSM
Location tracking via GPS
Local ad-hoc network 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
UMTS, WLAN,
DAB, GSM,
TETRA, ...
• 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, ...
Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
ho
c
Personal Travel Assistant,
DAB, PDA, Laptop,
GSM, UMTS, WLAN,
Bluetooth, ...
Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Applications II
Location Dependent Services
• Location aware services
What services, e.g., printer, fax, phone, server etc. exist in the local
environment
• Traveling salesmen
Direct access to customer files stored in a central location
Consistent databases for all agents
Mobile office
• Follow-on services
Automatic call-forwarding, transmission of the actual workspace to the
current location
• Replacement of fixed networks
Remote sensors, e.g., weather, earth activities
Flexibility for trade shows
LANs in historic buildings
• Information services
„Push“: e.g., current special offers in the supermarket
„Pull“: e.g., where is the Black Forrest Cherry Cake?
• Entertainment, education, ...
Outdoor Internet access
Intelligent travel guide with up-to-date location dependent information
Ad-hoc networks for multi user games
Chapter 1: Introduction
ad
• Support services
Caches, intermediate results, state information etc. „follow“ the mobile
device through the fixed network
• Privacy
Who should gain knowledge about the location?
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Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Wireless Networks in Comparison to Fixed
Networks
Mobile Devices
Pager
• receive only
• tiny displays
• simple text messages
PDA
• simple graphical displays
• character recognition
• simplified WWW
Laptop
• fully functional
• standard applications
• Higher loss-rates due to interference
Emissions of e.g. engines, lightning
• Restrictive regulations of 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/…
Sensors,
embedded
controllers
Mobile phones
• voice, data
• simple graphical
displays
• Higher delays, higher jitter
Connection setup time with GSM in the second range, several hundred
milliseconds for other wireless systems
Palmtops
• tiny keyboard
• simple versions of
standard applications
• Lower security, simpler active attacking
Radio interface accessible for everyone, base station can be simulated, thus
attracting calls from mobile phones
Performance
Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Early „Wireless Communication“
History of 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
• 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)
• 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): demonstrates
with an experiment the wave character
of electrical transmission through space
(1888, in Karlsruhe, Germany, at the
location of today’s University of Karlsruhe)
Chapter 1: Introduction
• Always shared medium
Secure access mechanisms important
• 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
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Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
History of Wireless Communication
History of Wireless Communication
• 1928 - Many TV broadcast trials (across Atlantic, color TV, TV news)
• 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
• 1933 - Frequency modulation (E. H. Armstrong)
• 1958 - A-Netz in Germany
Analog, 160MHz, connection setup only from the mobile station, no
handover, 80% coverage, 1971 11000 customers
• 1972 - B-Netz in Germany
Analog, 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
Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
• 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, ...
Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
History of Wireless Communication
History of Wireless Communication
• 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, 2.4 - 2.5GHz 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
Chapter 1: Introduction
• 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
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• 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 licences!)
• 2001 - Start of 3G systems
Cdma2000 in Korea, UMTS in Europe, Foma (almost UMTS) in Japan
• 2002 – Standardization of high-capacity wireless networks
802.16 als Wireless MAN
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Chapter1:IEEE
Introduction
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Wireless Systems: Overview of the
Evolution
Wireless Systems
• CT - Cordless Telephony (analogous predecessor
of DECT)
transmission
rate (MBit/s)
• DECT - Digital Enhanced Cordless Telecommunications (Standard for wireless phones in a local
range)
wired devices
100.0
10.0
WMAN
WLAN
HIPERLAN
1.0
0.1
• GSM - Global System for Mobile Communication
(cellular phone system)
(CT, DECT)
0.01
Office
Building stationary
Indoor
walk
Outdoor
mobility • HIPERLAN – alternative LAN to WLAN, „wireless
ATM enhancement“
drive
• WMAN – Wireless MAN (Bridging the last mile
between a fixed network and the end user,
wireless alternative to DSL)
• And furthermore: Satellite systems,
Bluetooth/IrDA in very short range
Chapter 1: Introduction
1991:
CDMA
1991:
D-AMPS
1993:
PDC
1994:
DCS 1800
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1987:
CT1+
1989:
CT 2
1992:
Inmarsat-B
Inmarsat-M
1991:
DECT
1998:
Iridium
2000:
GPRS
digital
199x:
proprietary
1997:
IEEE 802.11
1999:
802.11b, Bluetooth
2000:
IEEE 802.11a
2001:
IMT-2000/UMTS
4G – fourth generation: when and how?
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
2002:
IEEE 802.16
200?:
Fourth Generation
(Internet based)
Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Contents of this lecture:
Personal Area Networks
Contents of this lecture:
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
Personal Area Networks (very small range)
• IrDA (Infrared Data Association)
Standard for connecting devices using infrared light
Data rate up to 4 Mb/s gross, used only 115 Kb/s
Range of some meters, only line of sight
Susceptible to disturbances
• IEEE 802.15 (WPAN, Bluetooth):
Data rates up to 723 Kb/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), ...
Chapter 1: Introduction
1984:
CT1
1988:
Inmarsat-C
analogue
wireless LAN
1980:
CT0
1986:
NMT 900
1992:
GSM
cordless
phones
1982:
Inmarsat-A
1983:
AMPS
• WLAN - Wireless Local Area Network (Standard
for wireless networking of (portable) computer)
CELLULAR
(GSM)
satellites
1981:
NMT 450
• UMTS - Universal Mobile Telecommunications
System (universal system, comprising several
different access systems)
UMTS
CORDLESS
cellular phones
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• IEEE 802.16 (WirelessMAN)
802.11 mainly supports mobility, 802.16 more focuses on connecting buildings
Higher data rates (32-134 Mb/s), larger range
• HIPERLAN (High Performance Radio Local Area Network)
Several variants, from Type 1 with 23,5 Mb/s up to Type 4 with 155 Mb/s
Range varies between 50 meter up to 5 kilometer
No products
Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Contents of this lecture:
Telecommunication Networks
Overlay Networks
Cordless Systems
• DECT (Digital Enhanced Cordless Telecommunications)
Standard for cordless telephony
Transmission of voice and data in short range (at home)
integration of heterogeneous fixed and
mobile networks with varying
transmission characteristics
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)
regional
Vertical
Handover
metropolitan area
• UMTS (Universal Mobile Telecommunications System)
Also: IMT-2000 (International Mobile Telecommunications)
Integration of “all” types of data, rates up to 2 Mb/s
campus
Horizontal
Handover
… and for word-wide coverage: satellites.
Chapter 1: Introduction
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Chapter 1: Introduction
indoor
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Areas of Research in Mobile Communication
Simple Reference Model used here
• 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)
...
Application
Transport
Transport
Network
• Portability
Power consumption
Limited computing power, sizes of display, ...
Usability
...
Chapter 1: Introduction
Application
Network
Network
Data Link
Data Link
Data Link
Data Link
Physical
Physical
Physical
Physical
Radio
Seite 23
Network
Chapter 1: Introduction
Medium
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Relation to OSI Reference Model
Application Layer
Transport Layer
• Service location
• Adaptive application
• New applications
Chapter 2
• Technical Basics: Layer 1
• Methods for Medium Access: Layer 2
• Congestion and flow control
• Quality of Service
Network Layer
• Addressing, routing
• Device location
• Handover
Data Link Layer
• Medium access control
• Multiplexing
• Authentication
Physical Layer
• Frequencies, modulation
• Interferences, attenuation
• Encryption
Chapter 1: Introduction
Structure of the Lecture
Chapter 3
• Wireless Networks: Bluetooth, WLAN, WirelessMAN, WirelessWAN
• 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
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Chapter 1: Introduction
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