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Your Interactive Guide to the Digital World

Discovering � Computers 2012

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Communications

  • Computer communications describes a process in which two or more computers or devices transfer data, instructions, and information

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Sending device

Communications channel

Receiving device

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Communications

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Uses of Computer Communications

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Text messaging (SMS) allows users to send and receive short text messages on a phone or other mobile device or computer

Picture messaging allows users to send pictures and sound files

Video messaging allows users to send short video clips

Wireless instant messaging allows wireless users to exchange real-time messages with one or more other users

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Uses of Computer Communications

  • Wireless Internet access points allow people to connect wirelessly to the Internet from home, work, school, and in many public locations

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Uses of Computer Communications

  • A cybercafé is a coffeehouse, restaurant, or other location that provides personal computers with Internet access to its customers

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Uses of Computer Communications

  • A global positioning system (GPS) is a navigation system that consists of one or more earth-based receivers that accept and analyze signals sent by satellites in order to determine the GPS receiver’s geographic location
  • GPS receivers are:

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Built into many mobile devices

Available as a handheld device

Available with new vehicles

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Uses of Computer Communications

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Uses of Computer Communications

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Groupware

    • Helps groups of people work together on projects and share information over a network
    • Component of workgroup computing
    • Major feature is group scheduling

Voice mail

    • Allows someone to leave a voice message for one or more people
    • Computer in voice mail system converts an analog voice message into digital form
    • A voice mailbox is a storage location on a hard disk in the voice mail system

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Uses of Computer Communications

  • Many programs provide a means to collaborate, or work online, with other users connected to a server
  • Collaboration software includes tools that enable users to share documents via online meetings and communicate with other connected users

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Online meetings

Web conferences

Document management systems

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Uses of Computer Communications

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Uses of Computer Communications

  • Web services enable programmers to create applications that communicate with other remote computers over the Internet or on an internal business network
  • A mashup is a Web application that combines services from two or more sources

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Networks

  • A network is a collection of computers and devices connected together via communications devices and transmission media
  • Advantages of a network include:

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Facilitating communications

Sharing hardware

Sharing data and information

Sharing software

Transferring funds

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Networks

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Networks

  • A local area network (LAN) is a network that connects computers and devices in a limited geographical area
  • A wireless LAN (WLAN) is a LAN that uses no physical wires

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Networks

  • A metropolitan area network (MAN) connects LANs in a metropolitan area
  • A wide area network (WAN) �is a network that covers a �large geographical area

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Network architecture

  • The design of computers, devices, and media on a network is sometimes called the network architecture

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Client/server network

Peer-to-peer network

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Networks

  • Peer to Peer(P2P) describes an Internet network on which users access each other’s hard disks and exchange files directly over the Internet

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Networks

  • A Network topology refers to the layout of the computers and devices in a communications network

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Star network

Bus network

Ring network

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Network Communications Standards

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Ethernet

Token ring

TCP/IP

Wi-Fi

Bluetooth

UWB

IrDA

RFID

WiMAX

WAP

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Network Communications Standards

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Ethernet is a network standard that specifies no computer controls when data can be transmitted

The token ring standard specifies that computers and devices on the network share or pass a special signal (token)

TCP/IP is a network standard that defines how messages are routed from one end of a network to another

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Network Communications Standards

  • Wi-Fi identifies any network based on the 802.11 standard that facilitates wireless communication
  • Sometimes referred to as wireless Ethernet

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Network Communications Standards

  • Bluetooth defines how two Bluetooth devices use short-range radio waves to transmit data
  • UWB (ultra-wideband) specifies how two UWB devices use short-range radio waves to communicate at high speeds
  • IrDA transmits data wirelessly via infrared (IR) light waves
  • RFID uses radio signals to communicate with a tag placed in or attached to an object, animal, or person

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Network Communications Standards

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WiMAX (802.16)

    • Developed by IEEE
    • Towers can cover a 30-mile radius
    • Two types are fixed wireless and mobile wireless
    • Provides wireless broadband Internet access

Wireless Application Protocol (WAP)

    • Specifies how some mobile devices can display the content of Internet services
      • Web
      • E-mail
      • Chat rooms
    • Uses a client/server network

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Communications Software

  • Communications software consists of programs that:

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Help users establish a connection to another computer or network

Manage the transmission of data, instructions, and information

Provide an interface for users to communicate with one another

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Communications Over �the Telephone Network

  • The public switched telephone network (PSTN) is the worldwide telephone system

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Communications Over �the Telephone Network

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Dial-up lines

Dedicated line

ISDN line

DSL

FTTP

T-carrier line

ATM

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Communications Over �the Telephone Network

  • ADSL connections transmit data downstream at a much faster rate than upstream

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Communications Devices

  • A communications device is any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device
  • A dial-up modem converts signals between analog and digital

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Communications Devices

  • A digital modem sends and receives data and information to and from a digital line

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DSL modem

Cable modem

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Communications Devices

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Communications Devices

  • A wireless modem uses the cell phone network to connect to the Internet wirelessly from a notebook computer, a smart phone, or other mobile device

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Communications Devices

  • A network card enables a computer or device to access a network
  • Available in a variety of styles
  • Wireless network cards often have an antenna

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Communications Devices

  • A wireless access point(WAP) is a central communications device that allows computers and devices to transfer data wirelessly among themselves or to a wired network.

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Communications Devices

  • A router connects multiple computers or other routers together and transmits data to its correct destination on a network
  • Many are protected by a hardware firewall

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Communications Devices

  • A hub or switch connects several devices in a network together

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Home Networks

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  • Home networks provide computers with the following capabilities:

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Connect to the Internet at the same time

Share a single high-speed Internet connection

Access files and programs on other computers

Share peripherals

Play multiplayer games

Connect game consoles to the Internet

Subscribe to and use VoIP

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Home Networks

  • Types of wired home networks:

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Ethernet

Powerline cable

Phoneline

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Communications Channel

  • The amount of data that can travel over a communications channel sometimes is called the bandwidth
  • Latency is the time it takes a signal to travel from one location to another on a network
  • Transmission media carries one or more signals
  • Broadband media transmit multiple signals simultaneously

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Physical Transmission Media

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Physical Transmission Media

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Twisted-pair cable

Coaxial cable

Fiber-optic cable

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Wireless Transmission Media

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Wireless Transmission Media

  • Cellular communication uses multiple antennae (cell towers) to send and receive data within relatively small geographic regions (cells).
  • Most cell phones and mobile devices use cellular networks.

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Wireless Transmission Media

  • Microwaves are radio waves that provide a high-speed signal transmission

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Wireless Transmission Media

  • A communications satellite is a space station that receives microwave signals from an earth-based station, amplifies it, and broadcasts the signal over a wide area

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Summary

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Overview of communications terminology and applications

How to join computers into a network

Various communications devices, media, and procedures