Why QPSK is called quadrature shift keying?
Why QPSK is called quadrature shift keying?
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 correct format of phases in QPSK?
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°.
Where is QPSK modulation used?
QPSK (Quadrature Phase Shift Keying) scheme is used in various applications in modern digital communication system; it provides high performance on bandwidth efficiency and bit error rate. The areas include wireless communication, mobile communication and Satellite Communication.
What are the basic features of QPSK modulation?
QPSK Signal and Feature Parameters A QPSK signal can be expressed as where is the signal amplitude; is the carrier frequency; , , are set as 0, , , and , respectively, and the selection of is determined by the value of the base-band code.
What is the advantages of QPSK?
Advantages of QPSK: QPSK provide very good noise immunity. It provides low error probability. Bandwidth is twice efficient is compared to BPSK modulation. For the same BER, the bandwidth required by QPSK is reduced to half as compared to BPSK.
What is the symbol duration of QPSK?
In QPSK, the phase-shift θ(t) assumes one of the four constant values for every two input bits (i.e., the entire duration of a symbol), depending on the two consecutive bits being transmitted.
What are the types of QPSK?
The table below summarizes QPSK, OQPSK and pi/4 QPSK modulation types….pi/4 QPSK.
| QPSK | OQPSK | pi/4 QPSK |
|---|---|---|
| phase changes of +/- 90 and +/-180 degrees | phase changes of +/- 90 exist | Maximum phase change of +/-45 and +/-135 |
What is the symbol rate of QPSK?
two bits
Each of the four possible phases of carriers represents two bits of data. Thus, there are two bits per symbol. Since the symbol rate for QPSK is half of the bit rate, twice the information can be carried in the same amount of channel bandwidth as compared to binary phase shift keying.
What are the advantages of QPSK?
How many bits is QPSK?
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 is the limitation of QPSK?
QPSK is not more power efficient modulation technique compare to other modulation types as more power is required to transmit two bits. QPSK is more complex compared to BPSK receiver due to four states needed to recover binary data information.
