Mobile Computing
Lecture #02
By
Hannan Bin Liaqat
Department of CS& IT
University of Gujrat
Today’s Lecture Agenda
What is Wireless Networks?
Types of Wireless Networks
History of Wireless Networks
Advantages of Wireless Networks
Disadvantages of Wireless Networks
What is Networks?
Definition:
Two or more computer or computing devices connected
together through connecting devices
Purpose of networking:
1- Communication
2- Sharing
Types of Networks
There are mainly two types of networks
1- Wired networks
2- wireless networks
Wired Networks:
In which all computer or computing devices are connected
through guided medium (cables)
Types of Networks
Wireless Networks:
in which all computers and computing devices are connected
through unguided medium (radio waves)
Wireless Networks …
Wireless Networks operate in almost the same way
as wired Networks
Using the same networking protocols
Supporting almost the same applications
Types of Wireless Networks
There are mainly two types of wireless networks
1- Infrastructural wireless networks
2- Infrastructure less wireless networks
Infrastructural wireless networks:
Definition:
Infrastructure wireless networks are the wireless network that
contains wireless router/access point and enables other
computers connect to it wirelessly. This is the common
deployment to build a home wireless network.
Infrastructural wireless networks:
Diagram:
Basics Elements
1- wireless router/Access point
Responsible for sending packets between wired network
and wireless hosts in its “area”
2- computers (lap top)/other devices
3- applications running on the computers
Infrastructure less wireless networks
Ah Hoc Networks
Infrastructure less networks are also called Ah hoc networks
In this type of communication devices or computers
communicate directly with each other without the need for a
wireless router or access point
Basics Elements
1- computers (lap top)/other devices
Each computer is responsible for sending/forwarding packets
to other computers in its area (transmission range)
2- applications running on the computers
Infrastructure less wireless networks
Ah Hoc Networks
Early history of wireless
communication
Many people in history used light for communication
heliographs, flags
150 BC smoke signals are used for communication;
(Polybius, Greece)
1794, optical telegraph
Introduction of electromagnetic waves:
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
History of wireless communication
I
1895 Marconi
first demonstration of wireless telegraphy (digital!)
long wave transmission
1907 Commercial transatlantic connections
huge base stations
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
1926 Train-phone on the line Hamburg - Berlin
wires parallel to the railroad track
History of wireless communication
1928 many TV broadcast trials (across Atlantic, color TV, TV news)
1933 Frequency modulation
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)
1982 Start of GSM-specification
1983 Start of the American AMPS (Advanced Mobile Phone
System, analog)
1984 CT-1 standard (Europe) for cordless telephones
History of wireless communication
1986 C-Netz in Germany
analog voice transmission, 450MHz, hand-over possible, digital
signaling, automatic location of mobile device
1991 Specification of DECT
Digital European Cordless Telephone (today: Digital Enhanced
Cordless Telecommunications)
1992 Start of GSM
1994 E-Netz in Germany
GSM with 1800MHz, smaller cells, supported by 11 countries
1996 HiperLAN (High Performance Radio Local Area Network)
1997 Wireless LAN - IEEE802.11
1998 Specification of GSM successors
for UMTS (Universal Mobile Telecommunication System
1.13.1
Advantages of Wireless Networks
Minimum installation issues
Freedom to roam
Scalability
No cables
Disadvantages of Wireless Networks
Careful planning of network essential
Environment generally unfriendly
Security
Safety
Spectrum licenses
Poor data rates
