Digital Communication | Advantages and Disadvantages

Digital Transmission of Data ( Digital Communication )The term data refers to information to be communicated. Data is in digital form if it comes from a computer. If the information is in the form of voice, video, or some other analog signal, it can be converted to digital form before it is transmitted. Digital communication … Read more

Transmission | A/D Conversion | A/D Conversion

What is Parallel and Serial Transmission? Transmission:- There are two ways to move binary bits from one place to another: transmit all bits of a word simultaneously or send only 1 bit at a time. These methods are referred to, respectively, as parallel transfer and serial transfer. Parallel Transfer In parallel data transfers, all the … Read more

Digital to Analog Converters | Analog to Digital Converters

Converters: There are many ways to convert digital codes to proportional analog voltages. However, the most popular methods are the R-2R, string, and weighted current source converters. These are available in integrated-circuit form and are also integrated into other larger systems on a chip (SoC). R-2R Converter The R-2R converter consists of four major sections, … Read more

PCM ( Pulse Code Modulation ) | T-Carrier Systems| Duplexing

Pulse-Code Modulation (PCM) PCM : The most popular form of TDM uses pulse-code modulation (PCM) (see Sec. 7-4), in which multiple channels of digital data are transmitted in serial form. Each channel is assigned a time slot in which to transmit one binary word of data. The data streams from the various channels are interleaved … Read more

FSK | PSK | DPSK | QPSK | QAM | Spectral Efficiency | Modem Concepts

Modem Concepts and Methods FSK | PSK | DPSK : Binary signals are switched dc pulses, so how do such signals get transmitted over telephone lines, cable TV, coaxial cables, twisted-pair cables, or wireless links? Binary pulses can be transported over short cables even at very high data rates. The transformers, capacitors, and other ac … Read more

Digital Codes | Hartley’s Law | ASCII | Asynchronous | Encoding Methods

Digital Codes Digital Codes: Data processed and stored by computers can be numerical (e.g., accounting records, spreadsheets, and stock quotations) or text (e.g., letters, memos, reports, and books). As previously discussed, the signals used to represent computerized data are digital, rather than analog. Even before the advent of computers, digital codes were used to represent … Read more

Multiplexer | Demultiplexer | FDM | TDM | PAM | Applications

Multiplexing Principles Multiplexer: Multiplexing is the process of simultaneously transmitting two or more individual signals over a single communication channel, cable, or wireless. In effect, it increases the number of communication channels so that more information can be transmitted. Often in communication, it is necessary or desirable to transmit more than one voice or data … Read more

Spread Spectrum | Wideband Modulation | Broadband Modem

Wideband Modulation Most modulation methods are designed to be spectrally efficient, i.e., to transmit as many bits per hertz as possible. The goal is to minimize the use of spectrum space and to transmit the highest speed possible in the given bandwidth. However, there is another class of modulation methods that do just the opposite. … Read more

Protocols | OSI Model | Error Detection | Redundancy | Convolutional

Protocols Protocols are rules and procedures used to ensure compatibility between the sender and receiver of serial digital data regardless of the hardware and software being used. They are used to identify the start and end of a message, identify the sender and the receiver, state the number of bytes to be transmitted, state a … Read more

Ethernet LANs| Coaxial Cable | Twisted-Pair Cable | Advance Ethernet

Ethernet LANs One of the oldest and by far the most widely used of all LANs is Ethernet. Ethernet, which was developed by Xerox Corporation at Palo Alto Research Center in the 1970s, was based on the Aloha wide-area satellite network implemented at the University of Hawaii in the late 1960s. In 1980, Xerox joined … Read more