Qpsk constellation diagram explanation

1. What is constellation in QPSK?
2. What does a constellation diagram show?
3. How does QPSK modulation work?
4. What is the signal space representation of QPSK signal?

What is constellation in QPSK?

QPSK uses four points on the constellation diagram, equispaced around a circle. With four phases, QPSK can encode two bits per symbol, shown in the diagram with Gray coding to minimize the bit error rate (BER) – sometimes misperceived as twice the BER of BPSK.

What does a constellation diagram show?

The constellation diagram shows all the possible symbols that can be transmitted by the system as a collection of points. In a frequency or phase modulated signal, the signal amplitude is constant, so the points lie on a circle around the origin.

How does QPSK modulation work?

Quadrature Phase Shift Keying (QPSK) is a form of Phase Shift Keying in which two bits are modulated at once, selecting one of four possible carrier phase shifts (0, 90, 180, or 270 degrees). QPSK allows the signal to carry twice as much information as ordinary PSK using the same bandwidth.

What is the signal space representation of QPSK signal?

The QPSK signal space is thus two-dimensional, and represents four signal points. Figure 7.15f shows the signal space and the corresponding optimum (minimum-distance) decision regions. The signal points lie on a circle of radius , and are spaced every π/2 radians.