16PSK

16PSK, or 16-point phase-shift keying, is a modulation scheme used in digital communications. It encodes 4 bits per symbol by selecting one of 16 equally spaced constellation points on the unit circle, corresponding to phases evenly distributed around the circle (0, 2π/16, ..., 15·2π/16).

In coherent detection, the receiver estimates the transmitted symbol by comparing the received phase to the nearest constellation phase. The 16PSK constellation has a constant envelope, so all symbols share the same amplitude. The energy per symbol Es relates to the bit energy Eb by Es = log2(16) · Eb = 4 · Eb.

The constellation’s minimum angular separation is 2π/16 = π/8, which corresponds to a chord distance of 2 sin(π/16) on a unit-radius circle. In additive white Gaussian noise (AWGN), the symbol error rate for M-PSK is often approximated by P_s ≈ 2 Q( sqrt(2 Eb/N0) sin(π/M) ), making 16PSK more susceptible to errors than schemes with larger minimum distances at equivalent energy per bit.

Compared with 16QAM, 16PSK provides the same 4 bits per symbol but typically exhibits different trade-offs. 16PSK has a constant envelope, which is advantageous for nonlinear power amplifiers and amplitude-distortion robustness, but it generally offers poorer symbol-error performance at a given SNR due to tighter phase spacing. It is more sensitive to phase noise and phase errors than amplitude-imperfect distortions.

Applications of 16PSK appear in systems where spectral efficiency matches 4 bits per symbol and hardware constraints favor constant envelope transmission, though many modern implementations favor QAM variants for higher noise robustness.