QPSK | Quadrature Phase Shift Keying | Software Exp_4B | Communication_Lab_18ECL67
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Hi all, this is Siddhanna Janai.
Watch my video lecture on QPSK using MATLAB SIMULINK and
if you have any doubts ask me in the comments section.
QPSK:
Quadrature phase shift keying (QPSK) is another modulation technique, and it’s a particularly interesting one because it actually transmits two bits per symbol. In other words, a QPSK symbol doesn’t represent 0 or 1—it represents 00, 01, 10, or 11.
This two-bits-per-symbol performance is possible because the carrier variations are not limited to two states. In ASK, for example, the carrier amplitude is either amplitude option A (representing a 1) or amplitude option B (representing a 0). In QPSK, the carrier varies in terms of phase, not frequency, and there are four possible phase shifts.
We can intuitively determine what these four possible phase shifts should be: First we recall that modulation is only the beginning of the communication process; the receiver needs to be able to extract the original information from the modulated signal. Next, it makes sense to seek maximum separation between the four phase options, so that the receiver has less difficulty distinguishing one state from another. We have 360° of phase to work with and four phase states, and thus the separation should be 360°/4 = 90°. So our four QPSK phase shifts are 45°, 135°, 225°, and 315°.
Go through the following link for further details about QPSK
https://www.tutorialspoint.com/digita...