User:MrZap/Noncoherent transmission

Noncoherent transmission refers to the reception of data where the phase of the carrier is unknown. A simple example of noncoherent transmission is on/off keying, where the receiving party only needs to detect the energy present and compare it to a treshold. A more sophisticated noncoherent transmission scheme is DPSK, where a change in carrier phase conveys an information symbol. Noncoherent transmission is opposed to coherent transmission, where the receiver estimates the phase of the carrier (for example by means of a phase-locked loop). Noncoherent transmission schemes usually have worse BER performance than coherent schemes, but other considerations (like implementation simplicity) can justify a noncoherent transmission scheme.

Hybrid coherent/noncoherent schemes are also possible, for example, wideband radio receivers usually perform despreading noncoherently, and demodulation coherently