In data communication, a digital data signal representing a binary sequence of bits in a computer is a typical rectangular pulse signal; The inherent frequency band of a rectangular pulse signal is called the fundamental frequency band, abbreviated as the baseband, and the rectangular pulse signal is called the baseband signal; The method of directly transmitting baseband signals on digital communication channels is called baseband transmission; At the transmitting end, the baseband transmission data is transformed into a direct transmission baseband signal by the encoder, such as Manchester code or differential Manchester code signal; At the receiving end, the decoder restores the same rectangular pulse signal as the transmitting end; Baseband transmission is the most basic method of data transmission. Broadband transmission: Dividing a channel into multiple subchannels to transmit audio, video, and digital signals is called broadband transmission. Broadband is a wider frequency band than audio bandwidth, which includes most of the electromagnetic wave spectrum. A system using this broadband transmission is called a broadband transmission system. By utilizing frequency band transmission, the link capacity can be decomposed into two or more channels, each of which can carry different signals, which is called broadband transmission. All channels in broadband transmission can send signals simultaneously. Such as CATV, ISDN, etc. The transmission frequency band is very wide in>= 128kbps broadband is used to transmit analog signals, with data transmission rates ranging from 0 to 400Mb/s, while the commonly used transmission rates are 5Mb/s to 10 Mb/s. It can accommodate all broadcasts and can perform high-speed data transmission. Broadband transmission systems are mostly analog signal transmission systems. Generally speaking, broadband transmission has the following advantages compared to baseband transmission: it can transmit sound, image, and data information in one channel, making the system versatile; A broadband channel can be divided into multiple logical baseband channels to achieve multiplexing, thus greatly increasing the capacity of the channel; Broadband transmission has a longer distance than baseband because baseband transmission directly transmits digital signals, the higher the transmission rate, the shorter the distance that can be transmitted
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