Why do we need QPSK?

Why do we need QPSK?

Compared to modulation schemes that transmit one bit per symbol, QPSK is advantageous in terms of bandwidth efficiency. For example, imagine an analog baseband signal in a BPSK (binary phase shift keying) system. BPSK uses two possible phase shifts instead of four, and thus it can transmit only one bit per symbol.

Where is QPSK modulation used?

QPSK allows the signal to carry twice as much information as ordinary PSK using the same bandwidth. QPSK is used for satellite transmission of MPEG2 video, cable modems, videoconferencing, cellular phone systems, and other forms of digital communication over an RF carrier.

What are the advantages of QPSK over PSK?

Very good noise immunity. For the same bit error rate, the bandwidth required by QPSK is reduced to half as compared to BPSK. Because of reduced bandwidth, the information transmission rate of QPSK is higher.

What is the purpose of digital modulation?

Digital modulation is used to transfer a digital bit stream over an analog channel at a high frequency. This enables us to transmit signals generated in a digital circuit across a physical medium. This is because digital signals can be handled with higher security and digital systems are readily and widely available.

What is QPSK modulation and demodulation?

November 7, 2020 October 19, 2010 by Mathuranathan. Quadrature Phase Shift Keying (QPSK) is a form of phase modulation technique, in which two information bits (combined as one symbol) are modulated at once, selecting one of the four possible carrier phase shift states.

How QPSK is implemented?

QPSK is one of the forms of Phase Shift Keying modulation scheme. This technique is widely preferred because of its advantages increased data rate and ease of implementation. AWGN noise is added to the QPSK output and the input signal is retrieved at the output after removing the noise.

What is the major advantage of using offset QPSK over standard QPSK?

From the obtained results it can be concluded that OQPSK performs better than QPSK modulation in terms of BER, which indicates that OQPSK has a better bandwidth efficiency and hence it can be used for systems with less power since it has a better channel frequency error.

Why is modulation necessary?

The signals within 20 Hz to 20 kHz frequency range can travel only a few distances. To send the message signal, the length of the antenna should be a quarter wavelength of the used frequency. Thus, modulation is required to increase the frequency of the message signal and to enhance its strength to reach the receiver.

How does QPSK transmitter work?

Differential Quadrature Phase Shift Keying (DQPSK) is a four-level modulation format. Two orthogonal phases of the same optical carrier are used to double the spectral efficiency by transmitting two bits at a time. This is done by converting two incoming electrical data streams into a four phase optical data signal.

How many basis functions are required in QPSK?

QPSK will show the constellation points lying on both x and y axes. This means that the QPSK modulated signal will have an in-phase component (I) and also a quadrature component (Q). This is because it has only two basis functions. A QPSK modulator can be implemented as follows.

What is the bandwidth requirement of QPSK?

QPSK is a modulation scheme that allows one symbol to transfer two bits of data. There are four possible two-bit numbers (00, 01, 10, 11). The bandwidth required for QPSK modulated channel is half of the bandwidth of BPSK.