Here is a list of modulation schemes.
| Code | Description |
|---|---|
| Binary PSK (BPSK) code | Encodes one bit of information into a constellation of antipodal points \(\pm\alpha\) for complex \(\alpha\). These points are typically associated with two phases of an electromagnetic signal. |
| Frequency-shift keying (FSK) code | A \(q\)-ary frequency-shift keying (\(q\)-FSK) encodes one \(q\)-ary digit of information into signals with \(q\) different frequencies. In its standard orthogonal form, each symbol is carried by one of \(q\) approximately orthogonal tones over a fixed symbol interval. |
| Modulation scheme | A sphere packing mapped into a time-dependent electromagnetic signal [1,2]. There is a close relation between abstract real-space encodings and modulation schemes, and certain simple sphere packings are often synonymous with their corresponding modulation schemes. |
| Phase-shift keying (PSK) code | A \(q\)-ary phase-shift keying (\(q\)-PSK) encodes one \(q\)-ary digit of information into a constellation of \(q\) points distributed equidistantly on a circle in \(\mathbb{C}\) or, equivalently, \(\mathbb{R}^2\). |
| Pulse-amplitude modulation (PAM) code | Encodes a \(q\)-ary digit into a constellation of equally spaced points on the real line. A standard \(q\)-PAM constellation can be written as \(\{(2i-q-1)\alpha\}_{i=1}^{q}\) for some real scaling factor \(\alpha\); for \(q=8\), this yields \(\{ \pm \alpha,\pm 3\alpha,\pm 5\alpha, \pm 7\alpha \}\). The points in the constellation are typically associated with one quadrature of an electromagnetic signal. |
| Pulse-position modulation (PPM) code | A modulation code with \(q\) equal-energy signals in which each codeword has one pulse in one of \(q\) time slots and zeros elsewhere. |
| Quadrature PSK (QPSK) code | A quaternary encoding into a constellation of four points distributed equidistantly on a circle. For the case of \(\pi/4\)-QPSK, the constellation is \(\{e^{\pm i\frac{\pi}{4}},e^{\pm i\frac{3\pi}{4}}\}\). |
| Quadrature-amplitude modulation (QAM) code | Encodes into a finite set of points in \(\mathbb{R}^{2}\), often treated as \(\mathbb{C}\). Each point is associated with a complex amplitude of an electromagnetic signal, so information is encoded jointly in the in-phase and quadrature components [2; Ch. 16]. |
