THE BIRTH OF INTERNET Seeds of internet were planted way back in 1979 ,when U.S military forces used it to communicate in better, organized and safer way at ARPA (Advanced research project agency). President of U.S was the first citizen to share this sophiciticated network to manage and share all important information. Gates of internet were open to general public by early 90’s.
INTRODUCTION With the introduction of internet, world changed quickly. We can experience world coming closer day by day by use of internet. ISP (internet service provider ) provides us with this internet facility. MODEM is a most important hardware that connects us and ISP and helps us to access this valuable gift ‘INTERNET’.
WHAT IS MODEM ??? A Modem (made of Modulator & Demodulator) is a device that converts data from digital computer signals to analogue signals that are generally ,sent over a phone line.
CONNECTING WORLD The sending modem modulates the data into a signal that is compatible with the phone line, and the receiving modem demodulates the signal back into digital data. Wireless modems convert digital data into radio signals and back.
WORKING OF MODEM•Modem is a full duplex device havingmodulator and demodulator.•Modulator converts digital to analogue signalsand sends info via LAN whereas demodulatorreceives info and converts analogue signals todigital signals.
TYPES OF MODEMS MODEMCABLE MODEM WIRELESS MODEM
1. Cable Modem A cable modem is basically used for the one-one basis or to connect multiple computers inside a building as the signals degrade as more users come online. Cable modem uses broadband Internet connection that is designed to operate over cable TV lines
STREAM Downstream data -- data sent from the Internet to an individual computer -- into a 6-MHz channel. Upstream data -- information sent from an individual back to the Internet
WIRELESS MODEMS Wireless modem is a modem which connects to a wireless network instead of to the telephone system. Wireless modems operate at speeds comparable to dialup modems, not anywhere near the speed of broadband Internet connections. Some wireless modems attach directly to your notebook computer or PDA.
Types of connections DSL connection Dialup connection Broadband connection
DIAL-UP Data is transmitted through an analog phone connection. An analog connection is the slowest type of connection available, and will not permit you to use your telephone for a voice connection at the same time that you are connected to the Internet. Dial-up connections allow only one computer at a time, per line, to be connected.
FEATURES Slow and Economical Connection to network is established by dialing a number provided by ISP Quality not so good because of telephone lines Phone modems only travel at speeds of 28.8k and 56k and less.
DSL DSL means Digital Subscribers Line This is a method of transmitting data over telephone lines prevalent in many countries. DSL connection uses existing 2-wire copper telephone line connected to the premise and will not tie up your phone as a dial-up connection does. DSL uses a sophisticated modulation scheme to pack data onto copper wires.
TYPES OF DSL All types of DSL technologies are collectively referred to as xDSL. xDSL connection speeds range from 128 Kbps to 8 Mbps. Two other types of DSL technologies are High- data-rate DSL (HDSL),Very high DSL (VDSL),Asymmetric Digital Subscriber Line(ADSL) and Symmetric Digital Subscriber Line (SDSL)
Advantages of DSL The speed is much higher than a regular modem (1.5 Mps vs. 56 kps) DSL doesnt necessarily require new wiring; it can use the phone line you already have. Modem generally comes with company.
Disadvantages of DSL : Service is better ,when you are near service provider. Sending data slower compared to receiving. The service is not available everywhere.
BROADBAND Cable Internet works by using TV channel space for data transmission, with certain channels used for downstream transmission, and other channels for upstream transmission. Coaxial cables are used by Broadband connection provides much greater bandwidth than telephone lines Broadband connection can be used to achieve extremely fast access. Its speed ranges from 512 Kbps to 20 Mbps.
FEATURES Broadband connection use complex waveforms to carry digital data. They are more advanced devices than traditional dial-up modems as they are capable of modulating/demodulating hundreds of channels simultaneously. New types of broadband modems are beginning to appear, such as doubleway satellite and powerline modems.
Transfer rates are affected by the number of subscribers online simultaneously.Broadband connections can be used by individual subscribers to connect one computer to one line, or can be used to connect multiple computers in a building to the Internet.
DSL vs CABLE Cable modem speeds are upto two times faster compared to DSL modem. Speeds in cable modem fluctuates depending on the number of subscribers on the network.but this is not the case in DSL. DSL boasts a bit better security compared to cable modem.