A carrier wave is a waveform (usually sinusoidal) that is modulated (modified) to represent the information to be transmitted. This carrier wave is usually of much higher frequency than the modulating signal (the signal which contains the information).

The reason for this is that it is much easier to transmit a signal of higher frequency, and the signal will travel further.

Carrier waves are used when transmitting radio signals to a radio receiver. Frequency modulation (FM) and amplitude modulation (AM) signals are both transmitted with the help of carrier frequencies. The frequency for a given radio station is actually the carrier wave's center frequency.

In telecommunication, the term carrier (cxr) or carrier wave has the following meanings:

1. A waveform suitable for modulation by an information-bearing signal.

2. An unmodulated emission. Note: The carrier is usually a sinusoidal wave or a uniform or predictable series of pulses. Synonym: carrier wave. <p>
3. Sometimes employed as a synonym for a carrier system, or a synonym for a telecommunications provider company (operator), such as a common carrier.

Source: mostly from Federal Standard 1037C and from MIL-STD-188

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