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The Edge of IT
ITEC-200 Fall 2006
Topic 4: Telecommunications &
Networks
Professor J. Alberto Espinosa
Agenda
• Learn the basics about
telecommunications
• Introduction to networking
concepts
Topic 4: Telecom p.2
Transaction
Processing
IT
Infrastructure
Business
Applications
Roadmap
Decision Support
Distributed Collaboration
Enterprise Collaboration
Financial Management
etc.
IT &
Business
Server
Appl
Client
Appl
DB
Database
IT Infrastrucure:
- HW & SW
- Database
- Telecom
Information
Business
Applications
DB
IT &
Business
Topic 4: Telecom p.3
Telecom Basics
Telecom
“Any sufficiently advanced technology is
indistinguishable from magic”
Arthur C. Clarke (a famous scientist)
2 worlds:
1
0
Digital signal (what computers understand: e.g., 00111001)
Analog signal (what humans sense)
Topic 4: Telecom p.5
Data and Transmission Signals
• Data is what you want to transmit
• Data is transmitted with signals through a communication medium
• Data can be analog (sine waves)
– i.e., what humans understand (e.g., voice, video)
• Or it can be digital (square signals representing 0’s and 1’s)
– i.e. what computers understand (e.g., bit and bytes)
• Analog and digital data can both be transmitted using either
analog or digital signals
Topic 4: Telecom p.6
Digital Data
Analog Data
Original Data Form
Examples of Data and Signals
• Internal computer bus
• Local area networks
• Computer data over
digital phone lines (DSL)
•
•
•
•
Video-conferencing
Digital cable TV
Music CD’s
MP3/media players
Digital Signal
• Computer data over
regular phone line
dial-up connection
(via modem)
• Regular telephone (voice
transmission)
• Regular TV
• Analog cable TV
• Radio transmission
Analog Signal
Transmission Mode
Topic 4: Telecom p.7
Example: How Modems Work
Computers send digital signals, but regular telephone lines only
transmit analog signals. A modem (modulator/demodulator)
converts the digital signals to analog (fast audible beeps) so that
the message can be transmitted through telephone lines
Digital Signal
Computer
Analog Signal
Modem
(Modulation)
Digital Signal
Modem
(Demodulation)
Computer
Topic 4: Telecom p.8
Transmission Medium
= physical medium through which data signals travel
• All signals travel as electromagnetic waves – i.e.,
pulses (of voltage, light, etc.) at a given frequency
(e.g., 1000 pulses per second or 1000 hertz, or 1
kilohertz)
– Examples of transmission media:
–
–
–
–
Twisted wire  inexpensive, available in most buildings
Coaxial cable  faster, thick, hard to wire
Fiber optic cable  expensive, faster, lighter, durable
Wireless  slower, flexible (microwave, radio, cellular, infrared)
Topic 4: Telecom p.9
Transmission Channels
• A channel is the link between a sending
and receiving point
• A medium is usually broken into several
channels, depending on the medium’s
capacity, so that data can be transmitted
simultaneously through various channels:
e.g., cable TV signal, cell phone signals
Topic 4: Telecom p.10
Characteristics of Channels
Transmission speed or capacity
• How much data you can send per second
• Kilo/Mega/Gigabits per second (Kbps/Mps/Gps)
• Affected by medium bandwidth, network traffic,
noise, transmission errors
Transmission Frequency
• Cycles per second of the electromagnetic signal
• Not necessarily related to transmission speed
• It is just the nature of how the signal travels through a
medium
• Measured in hertz (cycles per second), kilohertz, etc.
Bandwidth (see next slide)
Topic 4: Telecom p.11
Bandwidth
• Every data transmission medium (e.g., cables, airwaves,
etc.) and each of its channels, have a bandwidth that
affect the data transmission capacity of that medium or
channel:
More bandwidth  more channels 
more capacity to transmit data
Metaphor: wider highway  more lanes 
more traffic capacity
• Bandwidth (of a medium or channel) is defined as: the
difference between the highest and lowest
frequencies that can be transmitted (through that
medium or channel)
• e.g., if a channel or medium can transmit from 300Mz to
800Mz, the bandwidth is 800 - 300 = 500Mz
Topic 4: Telecom p.12
Splitting the Medium into Channels
• A useful physics principle about
electromagnetic waves: waves of
different frequencies don’t mix!! (sound check)
• Therefore, we can send more than one signal through a
medium, provided that each signal uses a different
frequency
– Ex. You 100+ TV channels through one channel
– Ex. Your cell phone signals don’t mix with those of your neighbor
– Ex. Signal from radio station doesn’t mix with another station
• But if the frequencies of two channels are too close to
one another, there may be some interference (noise,
etc.)
Topic 4: Telecom p.13
Bandwidth
Animation
Topic 4: Telecom p.14
Medium and Channel
Bandwidth Illustration
800 MHz
700 MHz
600 MHz
500 MHz
400 MHz
300 MHz
Channel Bandwidth = 400 MHz – 300 MHz = 100 MHz
Medium Bandwidth = 800 MHz – 300 MHz = 500 MHz
Number of Channels = 5 = 500 MHz / 100 MHz
Topic 4: Telecom p.15
Electromagnetic Wave Frequencies
Example: WiFi -- 2.4 GHz = 2.4x109 (unregulated frequency) (chart)
Kilohertz (KHz) = 103; Megahertz (MHz) = 106; Gigahertz (GHz) =109
Topic 4: Telecom p.16
Switching
• How does data travel over distance from point A to
point B?
• It travels from the source (the sending point), to the
destination (the receiving point)
• Going through switching points widely distributed
throughout the country (and the world)
• Every switching point has equipment (i.e., hardware and
software) called “switches” that take care of making the
necessary connections and finding the best routes
• There are two general types of switching methods:
“Circuit Switching” and “Packet Switching”
Topic 4: Telecom p.17
Circuit Switching
San Francisco
Washington, DC
Circuit Switches
• Dedicated path (“circuit”) between
communication points
• Connected through switching nodes
• Good for continuous transmissions
• e.g., voice and video (e.g., telephone networks)
• Inefficient otherwise (idle circuit connection ties
up the circuit)
Topic 4: Telecom p.18
Packet Switching
e.g. ATM, Frame Relay
• Data is broken into packets
• Each packet contains destination and
re-assembly info (packet #, msg #)
• Each packet is sent separately
• And reassembled at the receiving end
• Good for data transmissions
Miami
Packet Switches
Atlanta
Topic 4: Telecom p.19
Introduction to
Networking
A Network
• Is a number (2 or more) of interconnected
computer devices
• The connecting devices are called
“nodes”
Topic 4: Telecom p.21
Protocols
A Protocol =
“A set of rules and procedures that govern data
transmissions between components in a network”
For two entities (e.g., computers, persons, radios) to
communicate, there needs to be a protocol
• Implemented in software and/or hardware
• Examples of protocols: TCP, IP, FTP, HTTP
Topic 4: Telecom p.22
The Network Layer Architecture
• Networks are very complex
• Because there are too many HW and SW components
communicating with each other
• So, ensuring reliable/fast data communications requires
numerous networking steps and functions
• No single networking component can do this alone
• Thus, different networking functions are carried out by
different specialized components
• These components are arranged in layers.
• Each layer function is performed by specific HW and/or SW
• Each layer needs to follow the standard communication
protocols agreed upon for that layer
Topic 4: Telecom p.23
Physical Analogy: Postal Service
Actual
Communication
Application: write a letter
Application: read the letter
Mail Person
Mail Person
Local Post Office
(for zip code)
Local Post Office
(for zip code)
Mail Sorting Facility
Mail Sorting Facility
Trucks, Airplanes,
Trains, etc.
Data Flow
Trucks, Airplanes,
Trains, etc.
Physical Infrastructure:
Highways, Sky, Railways, etc.
Topic 4: Telecom p.24
Another Analogy: A Telephone Network
Application:
make a phone call
Actual
Communication
Telephone
Application:
receive a phone call
Telephone
End Office or PBX
End Office or PBX
Circuit Switch
Circuit Switch
Telephone Network
Telephone Network
Physical Media
Physical Media
Data Flow
Cables, Airwaves, etc.
Topic 4: Telecom p.25
A Generic 5-Layer Networking Model
(each layer has its own set of protocols)
Applications:
E-Mail, Web, Chat, etc.
Application Layer
Transport Layer
Data Communication
Each layer is HW
and/or SW performing
a distinct function
Applications:
E-Mail, Web, Chat, etc.
Application Layer
Transport Layer
Network Layer
Network Layer
Data Link Layer
Data Link Layer
Physical Layer
The data flows from
layer to layer and
through the network
Physical Layer
00100010010
Data Flow
Network
Topic 4: Telecom p.26
Network Layer Architecture: An Example
FYI Only – no need to study this
Application Layer
•
(SW) Communicates with the software applications (e.g., e-mail, web
pages) and break data into small packets and passes the packets to the
Transport Layer (and reassembles incoming packets into original data)
Transport Layer
•
(Usually SW) Communicates with the Application Layer, adds some digits
for error checking and flow control to each packet, and passes these larger
data packets to the Network Layer (and the other way around)
Network Layer
•
(HW and/or SW) Communicates with the Transport Layer, gets each
packet, adds network address information necessary to route the packets
through the network, and passes these packets to the Data Link Layer
(and picks up packets routed from other layers).
Data Link Layer
•
(Usually HW) Communicates with the Network Layer and manage the
traffic flow of data packets from the computer to Physical Layer (and
acknowledges receipt of incoming packets from other networks).
Physical Layer
•
(HW) Communicates with the Data Link Layer, gets the packets and
converts them into (analog or digital) signals that can be transmitted over
that particular network physical medium (cable, fiber optics, airwaves) (and
converts incoming signals into data packets)
Topic 4: Telecom p.27
Networking
Network =
• A facility that interconnects a number of devices
• To transmit data from one attached device to another
Networks are classified by their GEOGRAPHIC SCOPE:
1. Local Area Networks (LANs)
• typically within a single building (e.g. Kogod) or small
area (AU)
• Metropolitan Area Networks (MANs) are like LANs
but for multiple buildings throughout a city.
2. Wide Area Networks (WANs)
• over larger geographical areas (e.g., across states,
countries)
3. Inter-Networks = “internets” = networks of networks
• INTERconnected NETworks
Topic 4: Telecom p.28
1. Local Area Networks (LANs)
• Small scope network
• Typically within a single building (e.g. Kogod)
• Or within a small group of nearby buildings
(e.g., AU Campus)
• If the network spans several buildings
throughout a city it is often called a
Metropolitan Area Network (MAN)
• High data rates
Topic 4: Telecom p.29
Key Implementation
Decisions for LANs
Physical Layout
• Physical configuration of network cables (i.e., the medium)
in buildings
• Structured Cabling:
–
–
–
–
–
A standard for wiring commercial buildings
Horizontal wires connected vertically via “telecom closets”
Telecom closets connected vertically to closets in other floors
Via a “backbone” cable
Entry point into the building is through the “equipment room”
Transmission Medium (physical layer)
• Medium used to connect hardware nodes
• Twisted pair, co-axial, fiber optics, wireless, etc.
Network Topology
• Configuration of hardware nodes in the network
• Bus (i.e. linear) topology – most predominant today
Topic 4: Telecom p.30
Bus (linear) Topology w/Hubs
• Very popular  network is easily scalable via hubs:
– Passive Hubs  to connect nodes to the network
– Active Hubs  to connect other hubs (to amplify signal)
• Physically, it looks like star topology, but it is “bus topology”
• Every hub “extends” the bus
• Predominant with “Ethernet” networks (AU’s Novell LAN)
Wireless
Passive Hub
Active Hub
Terminator
Transceiver
Terminator
Passive
Hub
Topic 4: Telecom p.31
Wide Area Networks (WANs)
•
Cover large geographical areas (e.g., across
states, countries)
•
Wired, wireless or both
•
A company’s WAN is generally implemented by
interconnecting all the LANs in the company’s
multiple office locations
•
Each location’s LAN has a ROUTER that connects
the LAN to a WAN service provider’s access point
•
The connection from the router to the WAN service
access is called point-to-point connection
Topic 4: Telecom p.32
Point to Point Connections in WANs
Needed to connect your home or office to a
network service provider
• DSL: digital subscriber line, fast dedicated
(ADSL is asymmetric DSL  same as DSL but receive
speed is higher than send speed)
• ISDN: dial up digital telephone lines, fast
• T1, T3, etc.: fastest (1.5 Mbps +), dedicated digital
lines, which is always connected (no need to dialup)
• Note: two or more LAN’s in a city can also be
interconnected with point-to-point connections (forming
a MAN). For example, you can connect two office LANs
using a T1 line – the cost depends on the distance
between the two offices
Topic 4: Telecom p.33
Connection Through
Network Services in WANs
through “Packet Switching” Nodes
• There are many types of wide area network
services, which vary according to the type of
packet switching technology they use. The main
kinds of switching technologies are:
• Frame Relay:
– Variable transfer speed
– You pay more for faster speeds
– Speeds: 64 Kilobytes per second (Kbps) to 45 Mbps
• Asynchronous Transfer Mode (ATM)
–
–
–
–
NOT THE SAME AS A BANK’S ATM
Really fast networks
Very fast data packet switching at fixed speeds
Speed: up to 1 Gbps
Topic 4: Telecom p.34
Wide Area Networks
General Configuration
LAN 1
e.g. Dallas
Frame Relay
Network Service
T1, T3,
or ISDN
(point to
point)
Server
Frame Relay
Router
Client
WAN Service
access points
ATM
Network
Service
LAN 2
e.g.
New York
Server
ATM Router
T1, T3
or ISDN
Client
(point
to point)
Topic 4: Telecom p.35
Introduction to Inter-Networks:
The Internet,
Intranets and Extranets
3. Inter-Networking
An “internet” (in lower case) =
• a network of networks
(i.e., INTERconnected NETworks)
• Connected through routers and packet
switching nodes (Frame Relay, ATM, etc.)
“The Internet” (capitalized)
• the most popular public “internet”
• All nodes connected to “The Internet”
communicated using the same widely
adopted & supported protocol = “TCP/IP”
Topic 4: Telecom p.37
The TCP/IP Reference Model
(Internet = INTERconnected NETworks)
Ex: EMail, Browsers, etc.
Application 1
Application Layer
Examples
Ex: Mail Server, Web Server, etc.
•HTTP (Web)
•SHTTP (secure Web)
•SMTP, IMAP (e-mail)
Related Application
Application Layer
•FTP (file transfers)
TCP
IP
Network Access Layer
Physical Layer
•SNMP (network mgt)
“Transmission
Control Protocol”
Provides a reliable
connection between
the 2 applications
“Internet Protocol”
Routing functions
across multiple
networks using an
IP address
TCP
IP
Network Access Layer
Physical Layer
The Internet
Topic 4: Telecom p.38
Routers:
Application
Layer
“The Internet” is a network of
networks. A router connects two
networks (similar or dissimilar) –
e.g., your company’s LAN and its
Internet service provider’s network.
It routes IP packets from one
network to another through it’s IP
layer
Application
Layer
TCP
Router
TCP
IP
IP
IP
Network
Access Layer
(protocol 1)
Net 1 Access Net 1 Access
(protocol 1)
(protocol 2)
Network
Access Layer
(protocol 2)
Physical Layer 1
Physical Layer Physical Layer
Network 1
Network 2
Physical Layer 2
Network 1
Network 2
Topic 4: Telecom p.39
Intranets and Extranets
An “Intranet”
• A company’s internal network
• Spanning multiple geographic locations
• Interconnected via the Internet instead of a WAN
• Usually protected by “Firewalls”
• Usually secured with “Virtual Private Networks
(VPNs)”
An “Extranet”
• Similar to an intranet, but external with other
companies
Topic 4: Telecom p.40
Firewalls and VPNs
Firewalls
• Hardware and/or software that restrict access into and out
of a the company‘s internal networks or intranets
– They protect your internal network from outsiders
– They don’t protect your communications outside
“Virtual private networks (VPNs)”
• Provide secure internal networks or intranets
• Protect your internal communications on the outside
• Uses “Tunneling” (encrypt transmissions betw points)
Topic 4: Telecom p.41
Firewall
IP
Router
T1, T3,
or ISDN
(point to
point)
Internet Service
Access Points
IP
Router
VPN
(Tunnelling)
VPN
Internet
VPN
IP
Router
Firewall
T1, T3
or ISDN
(point
to point)
LAN Company B
LAN Company A
Intranets, Extranets,
Firewalls & VPNs (cont’d.)
Extranet
Intranet
Firewall
LAN Company A
Topic 4: Telecom p.42
T1, T3,
ISDN
(point to
point)
IP Router
w/Firewall
and VPN
Most commercial
routers have built
in firewall and
VPN functions
Intranet
Internet Service
Access Points
LAN Company B
LAN Company A
Network Configuration Example:
(1) thru the Internet (no WAN)
IP Router
w/Firewall
and VPN
Internet
IP Router
w/Firewall
and VPN
T1, T3
ISDN
(point
to point)
Extranet
LAN Company A
Topic 4: Telecom p.43
T1, T3,
or ISDN
ATM, Frame
Relay or
other Router
WAN
WAN Service
Access Points
WAN
IP Router
w/Firewall
and VPN
Internet Service
Access Points
Router w/IP,
ATM, Frame T1, T3
Relay, Firewall ISDN
and VPN
support
LAN Company B
LAN 1 Company A
Network Configuration Example:
(2) thru WAN + Internet
Internet
Extranet
LAN 2 Company A
Topic 4: Telecom p.44
Client-Server
Architecture
• A key technological development in the 90’s
• A form of “distributed computing”
• Most predominant computing architecture today
• Software application (i.e., processing) is split into tasks
• These tasks are distributed among computers
• Depending where it is more efficient to do the
processing
Topic 4: Telecom p.45
Clients and Servers
Clients
– Request specialized services from servers, and
– Perform other tasks for users (e.g., screen displays)
Servers
– Acknowledge service requests from clients, and
– Provide requested services (i.e., tasks, processes)
– Via responses to clients
• Servers and clients connect via networks
• Client and servers don’t work in isolation, but they are
designed to work together (i.e. there is no client without
a server, there is no server without a client)
Topic 4: Telecom p.46
Client-Server Computing
Client
(cont’d.)
Client
Network
Server
Service Request
Response
Server
Client
Server
Client
Topic 4: Telecom p.47
Examples of Servers
• A server can be hardware, software or both
• File Server  central file storage, process file requests
(ex. Novell’s NetWare, Windows NT)
• Database Server  back-end DBMS functions
(ex. MS SQL Server, Oracle Server, Lotus Notes Server)
• Web Server  store and fetch web files on request
(ex. Apache, Microsoft IIS)
• Print Server  print job queuing for central printers
• Mail Server  routes mail to users and other mail servers
Topic 4: Telecom p.48
Examples of Clients
• A client can be hardware, software or both
• Networked PCs  request files and other services
from file servers (Windows 2000, XP)
• Database Clients  request records from database
server, process data locally, screen formatting, etc.
(Lotus Notes client, MS Access)
• Web Browsers  request web files from web servers,
translate HTML code into formatted screen displays
(Internet Explorer, Netscape)
• Mail Client  Send/retrieve mail to/from mail servers,
organize and display user mail
(Outlook Express; Lotus Notes mail client)
Topic 4: Telecom p.49
Generic Client-Server Architecture
There are many variants of this architecture
as presented in the next few slides
Client
To format and display
information to end users
Server
Presentation Software
Request
Client Application
Software
Response
Server Application
Software
Client Communication
Software
Server Communication
Software
Client Operating System
Server Operating System
Client Hardware
Server Hardware
Network
Topic 4: Telecom p.50
Example: Client-Server
Database Management Systems (DBMS)
Client Workstation
Presentation Software
Database Application
Server
Request
Client Front-End
DBMS
Response
Server Back-End
DBMS
Client Communication
Software
Server Communication
Software
Client Operating System
Server Operating System
Hardware Platform
Databases
Hardware Platform
Network
Topic 4: Telecom p.51
Ex.: Web Client-Server
Client
Server
Browser
Web Server
HTTP
HTTP
TCP/IP
TCP/IP
Client Communication
Software
Server Communication
Software
Client Operating System
Server Operating System
Hardware Platform
Web pages
(HTML and
other files)
Hardware Platform
Network
Topic 4: Telecom p.52
Ex.: Web Client-Server +
HTML
Database Server
Response
Client
Server
HTML
Form
Web Server
SQL
Queries
DBMS Server
Browser
HTTP
Web pages
(HTML and
other files)
HTTP
Databases
TCP/IP
TCP/IP
Client Communication
Software
Server Communication
Software
Client Operating System
Server Operating System
Hardware Platform
Hardware Platform
Network
Topic 4: Telecom p.53
Ex.: “Thin Client” or “Fat Server” model
Most of the processing is done by the server
Thin Client
Presentation Software
Fat Server
Example:
•Web Server-Browser
Applications
•The trend these days
•Easy to support and
upgrade applications
for distributed use
Application Software
DBMS
Client Communication
Software
Server Communication
Software
Client Operating System
Server Operating System
Hardware Platform
Hardware Platform
Network
Topic 4: Telecom p.54
Ex.: “Fat Client” or “Thin Server” model
Most of the processing is done by the client
Thin Server
Fat Client
Example:
Presentation Software
•File Servers (Novell’s
NetWare—your G drive,
Windows NT)
Application Software
Client Communication
Software
Server Communication
Software
Client Operating System
Server Operating System
(incl. file management)
Hardware Platform
Hardware Platform
Network
Topic 4: Telecom p.55
Examples of “Very Thin” Servers:
Embeddable Web Servers
Topic 4: Telecom p.56
Introduction to
Wireless Communications
and Networks
Wireless Communications
•One of the fastest growing areas of IT
•There are many types of wireless technologies available
these days. The only similarity is that they don’t use wires.
Otherwise they are all very different.
•Some key concepts to help you distinguish these
technologies:
–Line-of-sight: when physical objects in between devices
block communications (e.g. your TV remote control)
–Frequencies:
•Lower frequencies = longer distance, less line-of-sight
required (e.g., radio waves, cell phone signals)
•Higher frequencies = shorter distances, line-of-sight
required (e.g., visible light, infrared)
Topic 4: Telecom p.58
Wireless Technologies
Examples:
•Wireless Telephony
•Wireless Ethernet and WiFi
•Microwave Antennas
•Bluetooth
•Infrared
•Radio Frequency Identifiers (RFID)
Topic 4: Telecom p.59
Wireless Telephony
•Mobile units communicate with ground
antennas
•Ground antennas are connected with each
other with ground wires
•And with the PSTN (public service telephone
network), also known as POTS (plain old
telephone systems)
•Your telephone signal travels from your
mobile cell phone, to a ground antenna, to
the regular telephone system
Topic 4: Telecom p.60
Evolution of Wireless Telephony
• 1st. Generation (1G) Wireless: analog service
• 2nd. Generation (2G) Wireless: digital service (PCS in
the US, GSM in Europe)  compression (more
channels), encryption and data transmission are
enabled with digital communication
• 2.5 G: provide packet switching services for more
efficient transmission of data (e-mail, minimal web
access, PDA’s, etc.)
• 3G: high speed multi-media transmission and better
Internet access
• (see http://www.devx.com/wireless/Door/11259 for terminology)
Topic 4: Telecom p.61
Wireless Telephony Networks (Cellular)
1st Generation: to analog
2nd Generation: to digital
3rd Generation: to IP net
Handover
MS
To Landline Telephone Networks
Radio Frequency
Channels
4,8,12
1,5,9
3,7,11
3,7,11
2,6,10
Radio
Frequency
Channel
Reuse
1,5,9
Land Links
Radio Links
4,8,12
BS = Base Station
MS = Mobile Station
MSC = Main Switching Center
Topic 4: Telecom p.62
Wireless Ethernet & WiFi
• Wireless Ethernet & Wireless Fidelity (WiFi) are standards for
wireless local area networks
• Standards: 802.11a, b, g, etc. – different speeds, frequencies,
capacities and ranges (see http://www.devx.com/wireless/Door/11259 for terminology)
• Short range (up to 250 ft) communication between devices (note:
this is changing with new technologies like WiMax)
• Large office LANs have wireless transceivers (i.e.,
transmitters/receivers) attached to the wired network, so that
wireless devices (e.g., network cards on your laptops) can connect
to the wired network over the airwaves
• Small LANs and home networks have a wireless router attached to
the wired Internet service access (e.g., DSL, cable modem) with
which all wireless devices communicate
• Wireless access points are called “hot spots”
• Great for mobility and when wiring buildings is difficult
Topic 4: Telecom p.63
Wireless LANs
Wireless
Transceiver
Wired Office LAN
Transceiver
Wired connection to DSL,
Cable Modem or other
Internet Access Service
Wireless Router
Home Wireless LAN
Topic 4: Telecom p.64
Other Wireless Technologies
Microwave Antennas
–Low frequency antennas to interconnect, for example,
two nearby buildings (with roof microwave antennas)
without wires
Bluetooth (named for a Danish King)
–Wireless technology developed by a group of
companies (IBM, Nokia, Intel, Lucent, etc.) to connect
small devices wirelessly from short distances (30-50 ft)
–Ideal for wireless speakers, keyboards, printers
–Less line-of-sight required than infrared
Infrared
–High frequency signals to send signals from one
device to another at very short distances and line-ofsight
–Ex. TV remote controls, printer infrared ports
Topic 4: Telecom p.65
Other Wireless Technologies (cont’d)
Radio Frequency Identifiers (RFID’s)
– Devices (small chips, tags, etc.) that contain small amounts of
data that can be transmitted to an RFID sensor wirelessly
– The tags can be passive (RFID tag has no power, the reader
reads the RFID) or active (the RFID tag has a power source and
can beam its own signals to the sensor)
– The RFID readers are connected to networks that transmit the
data (e.g., EZ Pass)
RFID Sensor
EZ Pass
Database
in remote
central
location
Beam signal
Bounce signal with
RFID tag code
RFID Tag
Topic 4: Telecom p.66