According to the most common definition of digital signal, both baseband and passband signals representing bit-streams are considered as digital transmission, while an alternative definition only considers the baseband signal as digital, and passband transmission of digital data as a form of digital-to-analog conversion. The passband modulation and corresponding demodulation (also known as detection) is carried out by modem equipment.
#DATA COMMUNICATION AND COMPUTER NETWORKS PDF IN HINDI CODE#
The messages are either represented by a sequence of pulses by means of a line code (baseband transmission), or by a limited set of continuously varying wave forms (passband transmission), using a digital modulation method. While analog transmission is the transfer of a continuously varying analog signal over an analog channel, digital communications is the transfer of discrete messages over a digital or an analog channel. The data are represented as an electromagnetic signal, such as an electrical voltage, radiowave, microwave, or infrared signal. Examples of such channels are copper wires, optical fibers, wireless communication channels, storage media and computer buses. The data link layer protocols of the virtual network are said to be tunneled through the larger network when this is the case.ĭata transmission, digital transmission or digital communications is the physical transfer of data (a digital bit stream or a digitized analog signal1) over a point-to-point or point-to-multipoint communication channel. Virtual private network A (VPN) is an overlay network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires. Enterprise private network An is a network that a single organization builds to interconnect its office locations (e.g., production sites, head offices, remote offices, shops) so they can share computer resources. WAN technologies generally function at the lower three layers of the: the, the, and the. A WAN often makes use of transmission facilities provided by common carriers, such as telephone companies. A WAN uses a communications channel that combines many types of media such as telephone lines, cables, and air waves.
Wide area network A (WAN) is a computer network that covers a large geographic area such as a city, country, or spans even intercontinental distances.