A broadband medium is one that permits high-capacity communication links across it. This is the opposite of narrowband; both terms refer to the width of the band of frequency spectrum available for communication use. Broadband is also used to refer to broadband Internet access, where the connection used for access is e.g. a 512 kbit/s or better cable modem, rather than a telephone modem at less than 56 kbit/s.
Communications may utilise a number of distinct physical channels simultaneously; this is multiplexing for multiple access. Such channels may be distinguished by being separated from each other in time (time division multiplexing or TDMA), in carrier frequency (frequency division multiplexing, FDMA, or wavelength division multiplexing, WDM) or in access method (code division multiplexing or CDMA).
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