Data Communication PDF

Data Communicati on Data communication on Telephone lines (usage of modems) Using digital data communications Wireless networks Data Communication It is an application of telecommunications technology for the purpose of transmitting data. It transmits data especially to, from, or between co...

Data Communicati on Data communication on Telephone lines (usage of modems) Using digital data communications Wireless networks Data Communication It is an application of telecommunications technology for the purpose of transmitting data. It transmits data especially to, from, or between computers It refers to the moving or transferring of data between two electronic devices. Requirements of Data Communications At least two devices ready to communicate A transmission medium A set of rules and procedures for proper communication (protocol) Standard data presentation Transmission of bits either serial or parallel Bit synchronization using start/stop bits in case of asynchronous transmission In synchronous transmission the agreed pattern of flag Signal encoding rules viz NRZ or RZ Other higher later protocol Communications Channels A communications channel is a pathway over which information can be conveyed. It may be defined by a physical wire connecting communicating devices or by a radio, laser, or other radiated energy source with no obvious physical presence.  Microwave Communication – line-of- Types of sight devices must be placed in Communicati relatively high locations. Information is converted to a microwave signal, sent on through the air to a received, and recovered. Types of Communicati on Satellite Communication – Communications satellites are relay stations that receive signals from one earth station and rebroadcast them to another. Data communications over Standard Telephone Lines The telephone circuits are often used to transfer data. Telephone networks use circuit switching. The telephone network had its beginnings in the late 1800s. The entire network, referred to as the plain old telephone system (POTS), was originally an analog system using analog signals to transmit voice. Networks commonly use dedicated media to transmit data. However, the public telephone system can also be used for data communications. Standard phone lines transmit data much more slowly than network media.  Analog Signal – a continuous Types of electrical signal that can vary in frequency and strength over time. It signals represent physical measurements and can take on any value within a given range.  Digital Signal – is an abstraction that Types of is discrete in time and amplitude. The signal’s value only exists at regular time intervals, since only the values of signals the corresponding physical signal at those sampled moments are significant for further digital processing.