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Communications

Communications. C omputer communications is a process in which two or more computers/devices transfer data, instructions, and information. Communications. What is needed for successful communications? Sending device – initiates the transfer of information.

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Communications

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  1. Communications • Computer communicationsis a process in which two or more computers/devices transfer data, instructions, and information.

  2. Communications • What is needed for successful communications? • Sending device – initiates the transfer of information. • Receiving device – accepts the transmission of information. • Communications channel – media on which data, instructions, and information travel.

  3. Uses of Computer Communications

  4. Uses of Computer Communications

  5. Uses of Computer Communications • What are wireless Internet access points? • Allow people to connect wirelessly to the Internet in many public locations. • Cybercaféis a coffee house that provides computers with Internet access.

  6. Uses of Computer Communications • A global positioning system(GPS) is a navigation system that uses satellites to pinpoint the location of objects on the earth. • Originally developed for national security and later extended for public use. • The U.S. Dept. of Defense built Navstar GPS in the late 1980s to early 1990s to help soldiers navigate in foreign terrain at night, plan attacks, and aid in airstrikes. • GPS receivers are:

  7. Uses of Computer Communications

  8. Networks • What is a network? • A collection of computers and devices connected together via communications devices and transmission media. • Advantages of a network include:

  9. Networks What is a local area network(LAN) • A network that connects computers and devices in a small geographical area such as a home or office building. • A wireless LAN(WLAN) is a LAN that uses no physical wires. • A metropolitan area network (MAN) connects LANs in metropolitan area like a city or town.

  10. Networks • What is a wide area network (WAN) • a network that covers a large geographical area using many types of media. • Internet is the world’s largest WAN.

  11. Network Architecture • A network architecture is the design or framework of computer network. • Most popular types include: Client/Server Network Peer-to-Peer Network

  12. Network Architecture • Client/Server Network • One or more computers on thenetwork act as a server that controlaccess to resources. • Other computers on the network, or clients, access resources from a server.

  13. Network Architecture • Peer-to-Peer Network (P2P) • An Internet network on which users access each other’s hard disks and exchange files directly over the Internet. • Each computer, or peer, hasequal capabilities. • Sometimes called a file sharing network.

  14. Network Topology • A network topologyrefers to the layout of the computers and devices in a communications network. Star network Bus network Ring network

  15. Network Topology • Star Network Topology • All devices connect to a central device (hub or switch). • All data transferred from one computer to another passes through the hub or switch. • Most commonly used networktopology.

  16. Network Topology • Ring Network Topology • All devices connect to each other to form a closed loop or ring. • All data travels from device to device around entire ring. • Bus Network Topology • All devices connect to a central cable or bus.

  17. Networks

  18. Network Communications Standards

  19. Network Communications Standards

  20. Network Communications Standards • TCP/IP (Transmission Control Protocol/Internet Protocol • A communication protocol used by the Internet. • Transmits data by breaking it up into small pieces, or packets, which are sent over the network. • The data packets are reassembled once all packets reach their destination.

  21. Network Communications Standards • Wireless Fidelity (WI-FI) • A family of communication standards used for wireless networks.

  22. Network Communications Standards • WiMAX(802.16) • World-Wide Interoperability for Microwave Access • Used for wireless networking much like WIFI. • Faster speeds and longer range than Wi-Fi. • WiMAX antenna has a 31-mile range. • Perfect for city-wide Internet access. • Seattle’s Space Needle has a WiMAXantenna.

  23. Network Communications Standards • Bluetooth • Enables digital devices to communicate directly with each other wirelessly over short distances. • Can connect devices to a computer network using access points like Wi-Fi. • Bluetooth is too slow for video and other large data transfers between devices.

  24. Network Communications Standards • IrDAtransmits data wirelessly via infrared (IR) light waves • RFIDuses radio signals to communicate with a tag placed in or attached to an object, animal, or person.

  25. Network Communications Standards

  26. Communications Software • Communications softwareconsists of programs that:

  27. Communications Over the Telephone Network

  28. Communications Devices • A communications deviceis 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

  29. Communications Over the Telephone Network • What is a dedicated line? • A type of “always on” connections that is established between two communications devices. • Examples of dedicated lines • T-Carrier, CATV, DSL, ATM, ISDN.

  30. Communications Over the Telephone Network • DSL Modems are used to connect to a DSL network using a telephone line. • DSL connections transmit data downstream at a much faster rate than upstream.

  31. Communications Over the CATV Network • CATV networks are high-speed broadband networks. • Cable Modems are used to connect to the same network that provides your cable television.

  32. Types of Internet Connections

  33. Communications Devices • A wireless modemuses the cell phone network to connect to the Internet wirelessly from a notebook computer, a smart phone, or other mobile device.

  34. Communications Devices • What is a network card? • Enables a computer or device to access a network. • Without a network card a device would not be able to connect to a network or communicate. • Wireless network cards allow a computer or device to connect to a wireless network.

  35. Communications Devices • What is a wireless access point? • A central communications device that allows computers and devices to transfer data wirelessly among themselves or to a wired network. • Used to form wireless networks.

  36. Communications Devices • What is a hub or switch? • A communications device that is used as a central point for connecting computers and devices to form a network.

  37. Communications Devices • What is the difference between a hub or switch? • A switch passes information to only the computers that are communicating with one another. • A switch is more secure than a hub.

  38. Communications Devices • What is a router? • A communications device that connects multiple computers or other routers together and transmits data to its correct destination on a network. • Forwards data on the Internet using the fastest available path. • Many are protected by a hardware firewall.

  39. Communications Devices • What is a bridge and repeater? • A bridge is a device that is used to connect multiple network segments together. • A repeater connects multiple network segments together and is capable of regenerating the signal to extend the distance it can travel. • Both are used to form larger networks that span greater distances.

  40. Communications Devices • What is a bridge and repeater? Bridge Network B Network A

  41. Home Networks • Home networks provide computers with the following capabilities:

  42. Communications Channel • What is a communications channel? • The transmission media on which data travels in a communications system. • Bandwidth is the amount of data that can travel over a communications channel. • Transmission media are materials capable of carrying one or more signals.

  43. Physical Transmission Media

  44. Wireless Transmission Media

  45. Physical Transmission Media Twisted-pair cable Fiber-optic cable Coaxial cable

  46. Wireless Transmission Media • Broadcast radiotransmits radio signals over long and short distances. • Cellular radiois a form of broadcast radio that is used widely for mobile communications.

  47. Wireless Transmission Media • What is a cellular network? • A geographic area that isdivided into cells with a transceiver antenna and station at the center of eachcell. • A cellular carrier is a companythat builds and maintainsthese networks and provides cell phone service.

  48. Wireless Transmission Media • What is a microwave station? • Earth-based reflective dish used for microwave communications. • Microwavesare radio waves that provide a high-speed signal transmission.

  49. Wireless Transmission Media • A communications satelliteis 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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