Which modulation is used in OFDM?

Which modulation is used in OFDM?

An OFDM carrier signal is the sum of a number of orthogonal subcarriers, with baseband data on each subcarrier being independently modulated commonly using some type of quadrature amplitude modulation (QAM) or phase-shift keying (PSK). This composite baseband signal is typically used to modulate a main RF carrier.

How does demodulation of OFDM work?

To see how OFDM works, it is necessary to look at the receiver. This acts as a bank of demodulators, translating each carrier down to DC. The resulting signal is integrated over the symbol period to regenerate the data from that carrier. The same demodulator also demodulates the other carriers.

What is the OFDM system explain with the help of a block diagram?

1. An OFDM is an Multicarrier Modulation Technique that use a overlap signals to divide the frequency selective channel into a number of narrow band flat fading channel. The block diagram of OFDM is shown in above figure. In this system input data are FEC coded with technique such as convolution code.

What is OFDM system?

OFDM is a subset of frequency division multiplexing in which a single channel utilizes multiple sub-carriers on adjacent frequencies. In addition the sub-carriers in an OFDM system are overlapping to maximize spectral efficiency. Ordinarily, overlapping adjacent channels can interfere with one another.

How does QAM modulation work?

QAM is a modulation scheme that transmits data by changing the amplitude, or power level, of two signals: first in-phase with the incoming data and the second 90 degrees out of phase. QAM relates to the number of bits of information encoded in each time period.

What should be the value of modulation index for under modulation?

For a perfect modulation, the value of modulation index should be 1, which means the modulation depth should be 100%. It is called as Under-modulation. Such a wave is called as an under-modulated wave. If the value of the modulation index is greater than 1, i.e., 1.5 or so, then the wave will be an over-modulated wave.

What are the principles of OFDM?

The OFDM concept is based on spreading the high speed data to be transmitted over a large number of low rate carriers. The carriers are orthogonal to each other and frequency spacing between them are created by using the fast Fourier transform (FFT).

What is OFDM receiver?

Orthogonal frequency-division multiplexing (OFDM) is a multi-carrier modulation system where data is transmitted as a combination of orthogonal narrowband signals known as subcarriers. However, OFDM is more robust to frequency selective fading and simplifies equalization at the receiver.

Is OFDM a modulation?

Orthogonal frequency division multiplexing (OFDM) is a modulation technique that is used in several applications ranging from cellular systems (3GLTE, WiMAX), wireless local area networks (LANs), digital audio radio, underwater communications, and even optical light modulation.

What are the main features of OFDM?

Key features of OFDM

• Multiple carriers (called subcarriers) carry the information stream.
• The subcarriers are orthogonal to each other.
• A guard interval is added to each symbol to minimize the channel delay spread and intersymbol interference.

What is the difference between OFDM and CDMA?

CDMA OFDM performs better compare to CDMA and provides better tolerance with respect to multiple delay spread. Peak power clipping performance of OFDM is better compare to CDMA. Gaussian Noise tolerance of OFDM is better compare to CDMA. OFDM based system in single cell environment can allocate about 2 to 10 times more subscribers compare to CDMA.

What are the types of modulation?

Types of modulation. Polarization modulation, in which the angle of rotation of an optical carrier signal is varied to reflect transmitted data. Pulse-code modulation, in which an analog signal is sampled to derive a data stream that is used to modulate a digital carrier signal. Quadrature amplitude modulation ( QAM ),…

What is digital amplitude modulation?

Pulse Amplitude Modulation is one of the kinds of modulation techniques used in signal transmission. Pulse amplitude modulation is the simplest form of modulation. It is Analog to digital conversion method where the message information is encoded in the amplitude of the series of signal pulses.

How is amplitude modulation achieved?

Amplitude modulation is achieved by superposing a message signal on a carrier wave in a way that causes the amplitude of the carrier wave to change in accordance with the message.