September 20,2016. Tuesday
All chapters are now completed
Comunications
•Digital communication is the process in which two or more
computers or devices transfer data, instructions and information.
•Computer 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
•Types of Uses of Computer Communications
-Blogs, Chat rooms, E-mail, Fax, FTP, Instant messaging, Internet
, Newsgroups, RSS, Video conferencing, VolP, Web, Web 2.0, Web folders and Wikis
•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.
•Wireless internet access point allow people to connect
wirelessly to the Internet from home, work, school and in many public
locations.
•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 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
•Wireless Internet access points allow people to connect wirelessly to the Internet from home, work, school, and in many public locations
•A cybercafé 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
•GPS receivers are:
-Built into many mobile devices
-Available as a handheld device
-Available with new vehicles
•How a GPS Works
•Groupware
-Helps groups of people work together on projects and share 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
•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
-Online meetings
-Web conferences
-Document management systems
•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 together 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) 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 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 sometimes called the network architecture
•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
•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
-Ethernet is a network standard that specifies no central
computer or device on the network should control when data can be transmitted.
•Token ring
-Token ring standard specifies that computers and devices on
the network share or pass a special signal, called a token, in an unidirectional manner and in a preset order.
•TCP/IP
-Transmission control protocol/Internet protocol (TCP/IP) is a network protocol that defines how messages are routed from one end of a network
to the other, ensuring the data arrives correctly.
•Wi-Fi
-Wireless fidelity (Wi-Fi) identifies any network based on the 802.11 standards.
-802.11 is a series of network standards that specifies how two wireless devices communicate over the air with each other.
•Bluetooth
-Bluetooth is a network protocol that defines how two Bluetooth devices use short-range radio waves to transmit data.
•UWB
-Ultra-wideband (UWB) is a network standard that specifies how two UWB devices use short-range radio waves to communicate at high speeds with
each other.
•IrDA
-Infrared data association (IrDA) is used to transmit data
wirelessly to each other via infrared (IR) light waves.
•RFID
-Radio frequency identification (RFID) is a protocol that
defines how a network uses radio signals to communicate with a tag placed in or
attached to an object, an animal or a person.
•WiMAX
-Developed by IEEE.
-Towers can cover a 30-mile radius.
-Two types are fixed wireless and mobile wireless.
-Provides wireless broadband Internet access.
-Specifies how some mobile devices can display the content of Internet services.
-Web
-E-mail
•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
•Example of How Communications Standards Work Together
•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
•How Electronic RFID Toll Collection Works
•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
-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
•Dedicated line
-Dedicated line is a type of always-on physical connection that is established between two communications devices.
•ISDN line
- Integrated services digital network (ISDN) is a set of
standards for digital transmission of data over standard copper phone lines.
•DSL
-Digital subscriber line (DSL) transmits on existing standard copper phone wiring.
•FTTP
- Fiber to the premises (FTTP) uses fiber-optic cable to provide extremely high-speed Internet access to a user's physical permanent location.
•T-carrier line
-T-carrier line is any of several types of long-distance
digital phone lines that carry multiple signals over a single communications
line.
•ATM
-Asynchronous transfer mode (ATM) is a service that carries voice, data, video and media at very high speeds.
•ADSL connections transmit data downstream at a much faster rate than upstream
-Asymmetric digital subscriber line (ADSL) is a type of DSL
that supports faster downstream rates than upstream rates.
•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
Communications Devices
•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
•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
•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 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
Physical Transmission Media
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
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