Mobile Communications

Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Organization
Lecture Dates
• Monday, 16:30 – 18:00, AH5
• Wednesday, 13:30 - 15:00, 5052
Mobile Communications
Exercise Dates
• Wednesday, 13:30 - 15:00, 5052
Material (Slide Copies and Video Recordings)
http://www-i4.informatik.rwth-aachen.de/
content/teaching/lectures/sub/mobil/WS0708/index.html
Literature
Lehrstuhl für Informatik 4
RWTH Aachen
• J. Schiller: Mobile Communications. 2nd Edition, Addison Wesley, 2003
• V. Garg: Wireless Communications and Networking. Morgan Kaufmann, 2007
Contact
Dr. Dirk Thißen
Dirk Thißen
Lehrstuhl für Informatik 4, Room 4105B (Building E1)
Phone: 0241 / 80 - 21450
E-Mail: [email protected]
Prof. Dr. Otto Spaniol
Page 1
Chapter 1: Introduction
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Why Wireless Networks?
• 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
• 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!
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
Chapter 1: Introduction
Page 2
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
What is Mobile Communications?
• Wireless vs. Mobile
Chapter 1: Introduction
Page 3
• 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
Types of Wireless Networks
Possible Applications
Cellular 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
Chapter 1: Introduction
Page 5
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Chapter 1: Introduction
Page 6
Possible Applications
ad
ho
• Traveling salesmen
Direct access to customer files stored in a central location
Consistent databases for all agents
Mobile office
c
• Replacement of fixed networks
Remote sensors, e.g.,
weather, earth activities
Flexibility for trade shows
LANs in historic buildings
Personal Travel Assistant,
DAB, PDA, Laptop,
GSM/UMTS, WLAN,
Bluetooth, ...
Chapter 1: Introduction
• 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, ...
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
„Typical“ Application: Road Traffic
UMTS, WLAN,
DAB, GSM, ...
• 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
Page 7
• 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
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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 Wired Networks
Location Dependent Services
• Higher loss-rates due to interference
Emissions of e.g. engines, lightning
• Location aware services
What services, e.g., printer, fax, phone, server etc. exist in the local
environment
• Restrictive regulations of radio frequencies
Frequencies have to be coordinated, useful frequencies are almost all
occupied
• Follow-on services
Automatic call-forwarding, transmission of the actual workspace to the
current location
• Low transmission rates
Local some Mbit/s, regional currently up to 384 Kbit/s with GPRS/UMTS/…
• Information services
„Push“: e.g., current special offers in the supermarket
„Pull“: e.g., where is the Black Forrest Cherry Cake?
• Higher delays, higher jitter
Connection setup time with GSM in the second range, several hundred
milliseconds for other wireless systems
• Support services
Caches, intermediate results, state information etc. „follow“ the mobile
device through the fixed network
• Lower security, simpler active attacking
Radio interface accessible for everyone (shared medium), base station can
be simulated, thus attracting calls from mobile phones
• Privacy
Who should gain knowledge about the location?
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Chapter 1: Introduction
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Laptop
• fully functional
• standard applications
Sensors,
embedded
controllers
• 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): 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)
Palmtops
• tiny keyboard
• simple versions of
standard applications
Performance
Chapter 1: Introduction
Page 10
Early „Wireless Communication“
PDA
• simple graphical displays
• character recognition
• simplified WWW
Mobile phones
• voice, data
• simple graphical
displays
Chapter 1: Introduction
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Characteristics of Mobile Devices
Pager
• receive only
• tiny displays
• simple text messages
• Very different device capabilities
New concepts necessary in protocol design, e.g. energy efficiency
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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)
• 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
Chapter 1: Introduction
• 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)
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
• 1984 - CT-1 standard (Europe) for cordless telephones
Chapter 1: Introduction
Page 14
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
History of Wireless Communication
History of Wireless Communication
• 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, ...
Chapter 1: Introduction
• 1933 - Frequency modulation (E. H. Armstrong)
• 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
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Chapter 1: Introduction
Page 16
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Wireless Systems: Overview of the
Evolution
History of Wireless Communication
• 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
802.16 as WMAN, IEEE 802.20 (WWAN), IEEE 802.22 (WRAN)Page 17
Chapter1:IEEE
Introduction
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
• DECT - Digital Enhanced Cordless Telecommunications (Standard for wireless phones in a local
range)
wired devices
WMAN
WLAN
0.1
• GSM - Global System for Mobile Communication
(cellular phone system)
HIPERLAN
1.0
• UMTS - Universal Mobile Telecommunications
System (universal system, comprising several
different access systems)
UMTS
CORDLESS
(DECT)
0.01
• WLAN - Wireless Local Area Network (Standard
for wireless networking of (portable) computer)
CELLULAR
(GSM)
mobility
Office
Building stationary
Indoor
1982:
Inmarsat-A
1984:
CT1
1986:
NMT 900
•
1991:
CDMA
1991:
D-AMPS
1993:
PDC
1994:
DCS 1800
• 3rd generation (3G):
integration of
voice and data
• 4th generation (4G):
integration with Internet
(When 1:
and
how?)
Chapter
Introduction
1987:
CT1+
1988:
Inmarsat-C
generation: digital
1992:
GSM
wireless LAN
1980:
CT0
1981:
NMT 450
1983:
AMPS
2nd
cordless
phones
1989:
CT 2
1992:
Inmarsat-B
Inmarsat-M
1991:
DECT
1998:
Iridium
2000:
GPRS
analogue
199x:
proprietary
1997:
IEEE 802.11
1999:
802.11b, Bluetooth
2000:
IEEE 802.11a
2001:
IMT-2000/UMTS
since 2002:
IEEE 802.16/20/22
digital
200?:
Fourth Generation
(Internet based)
Page 18
Network Categories:
Personal Area Networks (PAN)
transmission
rate (MBit/s)
10.0
• 1st generation: analogue
satellites
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Wireless Systems
100.0
cellular phones
walk
Outdoor
drive
• HIPERLAN – alternative LAN to WLAN, „wireless
ATM enhancement“
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), ...
• 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
Chapter 1: Introduction
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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
Network Categories :
Wireless “Local” Area Networks
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)
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
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.
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Chapter 1: Introduction
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Page 22
Chapter 1: Introduction
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Overlay Networks
Mobility is not only Wireless Networks
• Invalid IP address in foreign network
• Routing problems
• TCP connections break down
→ TCP/IP modifications necessary!
integration of heterogeneous fixed and
mobile networks with varying
transmission characteristics
137.226.12.98
regional
Vertical
Handover
(IEEE 802.21)
metropolitan area
137.226.12/24
router
home network
campus
Internet
141.17.63/24
Horizontal
Handover
foreign network
router
Chapter 1: Introduction
indoor
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Chapter 1: Introduction
Page 24
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
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)
...
Page 25
Network
Network
Network
Data Link
Data Link
Data Link
Data Link
Physical
Physical
Physical
Physical
Medium
Chapter 1: Introduction
Page 26
Structure of the Lecture
• 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
Transport
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Tasks on Protocol Layers
Transport Layer
Transport
Radio
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Application Layer
Application
Network
• Portability
Power consumption
Limited computing power, sizes of display, ...
Usability
...
Chapter 1: Introduction
Application
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
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Chapter 1: Introduction
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