CHAPTER 7. WIRELESS, MOBILE COMPUTING, AND MOBILE COMMERCE.
Wireless: telecommunication in which electromagnetic waves in the form of wire or cable, carry
signal between communicating devices.
Without wires. Can be mobile or fixed. Changes location over time.
Traditional- fixed computer ineffective or inefficient.
Wireless technologies- mobile computing, mobile commerce, and pervasive computing.
Mobile computing: real time, wireless connection between a mobile device and other computing
environments such as intranet/extranet.
Mobile commerce/m-commerce: EC transactions conducted in a wireless environment, especially
Pervasive computing/ubiquitous computing: means that virtually every object has processing
power with wireless or wired connections to a global network.
Wireless devices: advantages:
Saves time that can be used effectively for some useful purpose
Mobile- makes it flexible for a person to go anywhere with the devices.
Allocate working time between personal and professional obligations.
WAP: wireless application protocol (WAP) is the standard that enables wireless devices to access
web-based information and services.
Micro browsers: internet browsers with a small file size that can work within the confines of
small screen sizes on wireless devices and relatively low bandwidths of wireless networks. Eg.
Apple iphone- safari browser.
Smart phones- cellular telephony, Bluetooth, Wi-Fi, a digital camera, global positioning
system(GPS), an organizer, a scheduler, an address book, calculator, access to e-mail, Short
message service(SMS), instant messaging, text messaging, mp3 music player, video player,
internet access with full function browser, QWERTY keyboard.
Lack of privacy- user can copy and pass confidential information.
Jamming devices- jam signals from phones when they enter specific locations.
Wireless transmission media: wireless media/broadcast media transmit signals
without wires over the air or space.
Channel Advantages disadvantages
Microwave High bandwidth Must have unobstructed line of
microwave transmission Relatively inexpensive sight systems high volume, long Susceptible to environmental
distance, line-of-sight interference, severe weather
Satellite High bandwidth Expensive
Satellite transmission systems Large coverage area Must have unobstructed line of
make use of communication sight signals experience
satellites. propagation delay
Must use encryption for
Radio High bandwidth Creates electrical interference
Signals pass through walls problems.
Inexpensive and easy to install Susceptible to snooping unless
Infrared Low to medium bandwidth Must have unobstructed line of
Used only for short distances sight
Microwave: towers cannot be spaced more than 50km apart.
Satellite: 3 basic types of satellites-
Type Characteristics Orbit Numb Use
Geostation Satellites remain stationary relative to point35900km 8 TV
ary on earth signal
Few satellites needed for global coverage*
Transmission delay (approx. 0.25sec-also
called propagation delay)
Most expensive to build and launch
Longest orbital life(many years)*
Medium Satellites move relative to the point on earth10354km 10-12 GPS
earth orbit Moderate no. Needed for global coverage
(MEO) Requires medium-powered transmitters
Negligible transmission delay*
Less expensive to build and launch*
Moderate orbital life ( 6-12years)
Low earth Satellites move rapidly relative to point on 640- Many telepho
orbit earth 1125km ne
(LEO) Large number needed for global coverage
Requires only low-power transmitters
Negligible transmission delay*
Least expensive to build and launch*
Shortest orbital life( as low as 5 years)
Geo satellite orbit has a fixed position right above the earths equator, thus its orbital period
matches 24hrs rotation of the earth.
Leo has the ability to pick up weak transmissions-satellite telephone to operate.
A single organization often produces multiple Leo satellites- known as LEO constellations.
Eg. Iridium has Leo constellations in orbit that consist of 66 satellites and 12 in-orbit square
Two major satellite applications-1) Global positioning system (GPS): wireless system that uses satellites to enable users to
determine their position anywhere on earth. Has 24MEO satellites shared worldwide.
Known speed of signals and distance between various signals- locates position and finds
user/ receiving station within 3 metres. Converts users latitude longitude to electronic
map for driving directions.
Russian GPS- GLONASS by 1995 but failed.
European Union GPS- Galileo by 2013
China GPS- Beidou by 2015
2) Internet transmission via satellites (IoS): installing necessary cables are expensive /
Enables users to have access to GEO satellite internet using a dish mounted on the side of
Disadvantage is disruption due to propagation delay and weather conditions.
Microwave transmission- within line of sight. But earth has a huge footprint: