C3B

Communications

  • Computer communications is the process of transferring data, instructions, and information between two or more computers or devices.
  • A communications system consists of:
    • Sending device
    • Communications channel
    • Receiving device

Uses of Computer Communications

  • Blogs

  • Chat rooms

  • E-mail

  • Fax

  • FTP

  • Instant messaging

  • Internet

  • Newsgroups

  • RSS

  • Video conferencing

  • VoIP

  • Web

  • Web 2.0

  • Web folders

  • Wikis

  • Users can send and receive wireless messages using wireless messaging services.

  • Text messaging (SMS) allows users to send and receive short text messages on a phone, 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.

  • Wireless Internet access points allow people to connect wirelessly to the Internet from various locations.

  • A cybercafé is a public location offering personal computers with Internet access for customers.

  • A global positioning system (GPS) is a navigation system using satellites to determine a GPS receiver’s geographic location.

  • GPS receivers are:

    • Built into many mobile devices
    • Available as a handheld device
    • Available with new vehicles

  • GPS Operation:

    • Step 1: GPS satellites orbit Earth, sending signals with their current position every thousandth of a second.
    • Step 2: A GPS receiver analyzes signals from at least 3 separate satellites to determine its location.

  • Groupware helps groups work together on projects and share information over a network and is a component of workgroup computing.

  • Major feature is group scheduling

  • Voice mail allows someone to leave a voice message for one or more people.

  • The computer in the 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.

  • Collaboration software includes tools that enable users to share documents via online meetings and communicate with other connected users.

  • 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.

Networks

  • A network is a collection of computers and devices connected via communications devices and transmission media.

  • Advantages of a network include:

    • Facilitating communications
    • Sharing hardware
    • Sharing data and information
    • Sharing software
    • Transferring funds

  • A local area network (LAN) connects computers and devices in a limited geographical area.

  • A wireless LAN (WLAN) is a LAN that uses no physical wires.

  • 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.

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

    • Client/server network
    • Peer-to-peer network

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

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

    • Star network
    • Bus network
    • Ring network

  • An intranet is an internal network that uses Internet technologies.

  • An extranet allows customers or suppliers to access part of its intranet.

Network Communications Standards

  • Ethernet

  • Token ring

  • TCP/IP

  • Wi-Fi

  • Bluetooth

  • UWB

  • IrDA

  • RFID

  • WiMAX

  • WAP

  • 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.

  • Wi-Fi identifies any network based on the 802.11 standard that facilitates wireless communication.

  • Sometimes referred to as wireless Ethernet.

  • 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.

  • 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

Communications Software

  • Communications software consists of programs that:
    • 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

Communications Over the Telephone Network

  • The public switched telephone network (PSTN) is the worldwide telephone system.
  • Dial-up lines
  • Dedicated lines
  • ISDN lines
  • DSL
  • FTTP
  • T-carrier lines
  • ATM
  • ADSL connections transmit data downstream at a much faster rate than upstream.

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.
  • A digital modem sends and receives data and information to and from a digital line.
    • DSL modem
    • Cable modem
  • 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.
  • A network card enables a computer or device to access a network and is available in a variety of styles; wireless network cards often have an antenna.
  • A wireless access point is a central communications device that allows computers and devices to transfer data wirelessly among themselves or to a wired network.
  • A router connects multiple computers or other routers together and transmits data to its correct destination on a network and many are protected by a hardware firewall.
  • A hub or switch connects several devices in a network together.

Home Networks

  • Home networks provide computers with the following capabilities:
    • 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
  • Types of wired home networks:
    • Ethernet
    • Powerline cable
    • Phoneline

Communications Channel

  • The amount of data that can travel over a communications channel is 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.

Physical Transmission Media

  • Twisted-pair cable
  • Coaxial cable
  • Fiber-optic cable

Wireless Transmission Media

  • Cellular radio is a form of broadcast radio that is used widely for mobile communications.
  • Microwaves are radio waves that provide a high-speed signal transmission.
  • 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.