Bandwidth

Bandwidth is a term used in information technology to describe the capacity of a channel or medium to carry information. In data communications, bandwidth is commonly defined as the maximum rate at which data can be transmitted over a link, typically measured in bits per second (bps) and often expressed in kilobits per second, megabits per second, or gigabits per second. In signal processing and physics, bandwidth also refers to the width of the frequency spectrum occupied by a signal, measured in hertz.

The two contexts are related but distinct: a higher spectral bandwidth enables higher potential data rates, but the actual rate depends on modulation, coding, overhead, and noise. The Shannon-Hartley theorem provides a theoretical upper limit for the data rate given bandwidth and signal-to-noise ratio. In practice, throughput—the amount of useful data delivered per unit time—can be lower than the nominal bandwidth due to protocol overhead, congestion, and inefficiencies.

Common terms include channel bandwidth, system bandwidth, and link bandwidth. Bandwidth is directional in networks, with downstream and upstream bandwidth describing capacity in each direction. The term has entered everyday language to mean the amount of data a connection can carry in a given period.

Factors affecting bandwidth include physical medium (fiber, copper, wireless), distance, interference, sharing among users, and network equipment. Fiber-optic networks routinely provide very high bandwidth, while wireless connections vary with technology, environment, and user density.