Upload
axel-sherod
View
221
Download
1
Tags:
Embed Size (px)
Citation preview
Wireline and Wireless Technologies
Telecommunications andMobile Commerce
Learning ObjectivesUnderstand the basic telecommunications systemRecognize the differences between analog and digital
signalsDescribe the processes used by modems to send and
receive informationDescribe the major types of transmission technologiesDescribe the major types of networksDiscuss today’s wireless devices and wireless
transmission mediaDescribe wireless networks according to their effective
distanceDefine mobile computing and mobile commerceDiscuss the major m-commerce applications
The Telecommunications SystemA telecommunication system consists of
hardware and software that transmit information from one location to another
These systems can transmit text, data, graphics, voice, documents, or full-motion video information
They transmit this information with two basic types of signals, analog and digital
Analog vs. Digital SignalsAnalog signals are continuous waves that
transmit information by altering the characteristics of the waves
The characteristics include the wave’s amplitude and frequency
The human voice is an example of an analog signal
Digital signals are discrete pulses that are either on or off, representing a series of bits (0s and 1s)
This quality allows them to convey information in a binary form that can be clearly interpreted by computers
Analog and Digital Signals
Communications Processors
Communications processors are hardware devices that support data transmission and reception across a telecommunications system
One of these devices is a modem whose function is to convert digital signals to analog signals (modulation) and convert analog signals to digital signals (demodulation)
Examples are dial-up, DSL, and cable modems
Modem TypesThe U.S. public telephone system was originally designed
as an analog network to carry voice signals or soundsIn order for this type of circuit to carry digital information,
that information must be converted into an analog wave pattern by a relatively slow dial-up modem
Cable modems operate over coaxial cable (for example, cable TV) and they offer higher speeds than dial-up
A disadvantage is that they use a shared line which may slow transmission speed when large numbers of users access the same modem
DSL modems operate on the same lines as voice telephones and dial-up modems, but DSL signals do not interfere with voice service and they always maintain a connection
Communications Media and ChannelsFor data to be communicated from one
location to another, some form of pathway or medium must be used
These pathways are called communications channels
Examples of wireline media include:Twisted-pair wireCoaxial cableFiber-optic cable
Each type of wireline media has relative advantages and disadvantages
Twisted-Pair Wire
Coaxial Cable
Fiber-Optic Cable
Advantages and Disadvantages of Wireline Communications Channels
Channel Advantages Disadvantages
Twisted-pair wire InexpensiveWidely availableEasy to work with
Slow (low bandwidth)Subject to interferenceEasily tapped (low security)
Coaxial cable Higher bandwidth than twisted-pairLess susceptible to electromagnetic interference
Relatively expensive and inflexibleEasily tapped (low-to-medium security)Somewhat difficult to work with
Fiber-optic cable Very high bandwidthRelatively inexpensiveDifficult to tap (good security)
Difficult to work with (difficult to splice)
Transmission SpeedBandwidth is a measure of channel capacity (and
potential speed of transmission)Why is this an important issue?Analog signal speed is measured in hertz (Hz)Digital signal speed is measured in bits per second
(bps)The speed of particular communication channels
are as follows:Twisted-pair wire: up to 1 Gbps (billion bits per
second)Coaxial cable: up to 1 GbpsFiber-optic cable: more than 40 Tbps in a laboratory
(trillion bits per second)
Types of NetworksA computer network is a system that connects
computers via communications media so that data can be transmitted among them
Computer networks are essential to modern organizations for many reasonsEnable organizations to be more flexible to adapt to
changing business conditionsEnable companies to share hardware, software, and data
across the organization and among different organizationsMake it possible for geographically dispersed employees
and work groups to share documents and ideasAnd they are a critical link between businesses and
customers
Types of NetworksThere are various types of computer
networks, ranging from small to worldwideTypes of networks include:
Local area networks (LANs) – connect two or more devices in a limited geographic region, usually within the same building
Wide area networks (WANs) – networks that cover large geographic areas and are often provided by common carriers such as telephone companies and the international networks of global communications service providers
The Internet
Wireless DevicesIndividuals are finding it convenient and productive
to use wireless devices for several reasons:Can make productive use of time that was formerly
wastedTheir work locations are becoming much more flexibleEnables them to allocate their working time around
personal and professional obligationsThe Wireless Application Protocol (WAP) is the
standard that enables wireless devices to access Web-based information and services
Microbrowsers can work with smaller screen sizes and lower bandwidth
Wireless Transmission MediaWireless media, or broadcast media,
transmit signals without wires over the air or in space
The major types of wireless media are:MicrowaveSatelliteRadioInfrared
Each of these media has relative advantages and disadvantages
Advantages and Disadvantages of Wireless Media
Channel Advantages Disadvantages
Microwave High bandwidthRelatively inexpensive
Must have unobstructed line of sightSusceptible to environmental interference
Satellite High bandwidthLarge coverage area
ExpensiveMust have unobstructed line of sightSignals experience propagation delayMust use encryption for security
Radio High bandwidthSignals pass through wallsInexpensive and easy to install
Creates electrical interference problemsSusceptible to snooping unless encrypted
Infrared Low to medium bandwidthUsed only for shot distances
Must have unobstructed line of sight
SatelliteSatellite transmission systems make use of
communication satellitesThree types of satellites around the earth include:
Geostationary (GEO) – TV signalsMedium earth orbit (MEO) – GPSLow earth orbit (LEO) – Telephone
The characteristics of these systems are described in Table 7.3
A major limitation of GEO satellites is that their transmissions take a quarter of a second to send and return
Under what circumstances would this propagation delay matter?
Global Positioning System (GPS)
The GPS is a wireless system that uses satellites to enable users to determine their position anywhere on earth
GPS is supported by 24 MEO shared satellites
Internet over SatelliteIn many regions of the world, Internet over
Satellite (IoS), is the only option available for Internet connections
Installing cables is either too expensive or physically impossible
IoS enables users to access the Internet via GEO satellites from a dish mounted on the side of their homes
Drawbacks are that there is propagation delay and signals can be disrupted by environmental influences such as thunderstorms
Mobile CommerceMobile commerce (m-commerce) refers to
e-commerce transactions that are conducted in a wireless environment
The development of m-commerce is driven by the following factors:Widespread availability of wireless devicesNo need for a PCThe “cell phone culture”Declining pricesBandwidth improvement
M-Commerce ApplicationsFinancial services
Banking and paymentIntrabusiness applications
Content, services, and voice communication portals
Location-based applicationsShopping, location-based services and
advertisingTelemedicineWhat are some other potential m-
commerce applications?How is m-commerce different from
traditional PC-based e-commerce channels?