PSK, or Phase Shift Keying, refers to a specific form of phase modulation. Phase shift keying is done through the use of a distinct number of states. On the other hand, phase modulation is a form of frequency modulation where the phase of the carrier wave is modulated to accept and encode digital information. Modulation takes place during each phase change.

QPSK, which stands for Quadrature Phase Shift Keying, refers to a type of phase modulation algorithm where there are four states involved. These four states also refer to four phases wherein a particular carrier is sent to QPSK. These states consist of 45, 135, 225, and 315 degrees.

QPSK is an algorithm providing procedures used in calculating and finding a specific value. With regards to its encoding, QPSK is capable of processing two bits for each symbol. This is due to the fact that QPSK has four possible states.

Compared to other phase modulation algorithms, QPSK has a higher tolerance level for link degradation. QPSK generally has a lower tendency of causing system failure. However, QPSK normally provides less data capacity than other types of algorithms.

QPSK is applied extensively on certain systems. It can be used to maintain the data rate while ensuring that the bandwidth of the signal is stable. This enables the system to efficiently utilize its bandwidth resources.

In addition, QPSK is implemented in transmitters and receivers used by particular communication systems. Wireless LAN standards also make use of QPSK in setting their structures. Likewise, certain Bluetooth technologies also apply QPSK in sending and receiving data.