Chapter 9 Networks and Communications 
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.

 •(WAP)Wireless application protocol

   -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
    -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 
  

   •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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