Chapter 9 : Networks and Communications

Communications

-Communications describes a process in which two or more computers or devices transfer data, instructions, and information. Sending device, Communications channel, Receiving device.

Uses of Computer Communications

-Users can send and receive wireless messages using wireless messaging services. Text messaging allows users to send message thru phone or other mobile devices. Picture messaging allows users to send pictures and sound files. Video messaging allows users to send short video clips.

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

-A cyber cafe is a coffeehouse, restaurant, or other location that provides personal computers with Internet access to its customers.

-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.

-Groupware : helps groups of people work together on projects and share information over a network. Major feature is group scheduling.

-Voice mail : allows someone  to leave a voice message for one or more people. A voice mailbox is a storage location on a hard disk in the voice mail system.

Networks

-A network is a collection of computers and devices connected together via communications devices and transmission media. Advantages of a network include :Sharing hardware and software, Transferring funds, and Sharing data and information.

-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.

-A wide are network (WAN) is a network that covers a large geographical area.

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

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

-An extranet allows customer or suppliers to access part of its intranet.

Network Communications Standards

-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). TCIP/IP is a network standard that defines how messages are routed from one end of a network to another.

-Bluetooth defines how two Bluetooth devices use short-range radio waves to transmit data.

-WiMAX (802.16) : Developed by IEEE. Towers can cover a 30-mile radius. Provides wireless broadband Internet access.

-Wireless Application Protocol (WAP) : Specifies how some mobile devices can display the content of Internet services. Uses a client/server network.

Communications Software

Communications software consists programs that : 

1. Help users establish a connection to another computer or network. 

2 .Manage the transmission of data, instructions, and information. 

3. 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.

-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 deice and a receiving device.

-A digital modem sends and receives data and information to and from a digital line such as DSL modem and 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.

Home Networks

Home networks provide computers with the following capabilities : 

-Connect to the Internet at the same time

-Play multiplayer games

-Connect game consoles to the Internet.

Types of wired home networks : 

-Ethernet

-Powerline cable 

-Phoneline.

Wireless Transmission Media

Cellular radio is a form of broadcast radio that its 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 microwaves signals from an earth-based station, amplifies it, and broadcasts the signal over a wide area.