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What is Data Rate?

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Data rate is the rate at which data is transferred through some telecommunications or computing medium. It represents the number of binary digits (bits) that can be transferred or processed per unit of time.

The basic unit is the number of bits per second. The correct abbreviation is bit/s although it is often seens as b/s or bps. Another common unit is the number of bytes per second, where a capital B is used. Although a byte contains 8 bits, the number of B/s is not exactly 8 times the number of b/s, because bytes are usually transmitted with additional bits for redundancy checks and for timing.

The term baud (named after French telegraphy pioneer Emile Baudot) refers to the actual data transfer rate, which will be less than the underlying bit rate because not all of the bits carry useful data.

In the early days of data communication, binary data was transmitted by converting it to an analog signal and sending it over the existing analog communications infrastructure. This process is called modulation, and the reverse process at the receiving end is demodulation. The device to do this is the modulator/demodulator (usually abbreviated to modem).

Increasingly communications channels are implemented digitally, and it is analog voice signals that have to be digitized for transmission. This avoids the need for a modem for sending digital information, which as a consequence is now possible at much higher speeds than a decade ago.

In addition to transmission speeds, the data rate is also important in measuring the performance of data storage devices such as optical storage, hard disks and flash memory devices.

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