What is basic principle of OFDM?

What is basic principle of OFDM?

The basic principle of OFDM is to split a high-rate datastream into a number of lower rate streams that are transmitted simultaneously over a number of subcarriers.

What is OFDM technique?

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 is QAM OFDM?

QAM, Quadrature Amplitude Modulation. OFDM, Orthogonal Frequency Domain multiplexing – is a complex form of modulation that combines QAM and frequency-division multiplexing (FDM). QAM sub-carriers are spaced closely to enable high data rate with long symbol duration.

How does OFDM transceiver work?

An OFDM transmitter modulates the data to be transmitted and data is then converted from serial to parallel N sub-carriers. Inverse Fast Fourier Transform (IFFT) is performed on each sub-carrier data to convert it to time domain and a cyclic prefix is added.

How orthogonality is achieved in OFDM?

In OFDM, multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted to carry data in parallel. In coded orthogonal frequency-division multiplexing (COFDM), forward error correction (convolutional coding) and time/frequency interleaving are applied to the signal being transmitted.

What are the problems in OFDM?

Typically linearity, image rejection, phase distortion and phase noise issues for OFDM are addressed through the addition of costly and power-hungry external components including surface acoustic wave (SAW) filters and crystal oscillators that contribute to a higher system bill of materials (BOM) and increased power …

What is the difference between OFDM and QAM?

Orthogonal Frequency Division Multiplexing (OFDM) is an efficient modulation format used in modern wireless communication systems including 5G. OFDM combines the benefits of Quadrature Amplitude Modulation (QAM) and Frequency Division Multiplexing (FDM) to produce a high-data-rate communication system.

What are pilot symbols in OFDM?

Training OFDM symbols or equivalently OFDM preambles are transmitted at the beginning of the transmission record, while pilot symbols (complex exponentials in time) are embedded in each OFDM symbol, and they are separated from information symbols in the frequency-domain [1–3].

How does orthogonality allow for increased capacity?

How does orthogonality allow for increased capacity? Spectral density -> 0, signals can overlap, allows signals to be packed together. Signal that is spread over a wider bandwidth. Benefits: Noise immunity, encryption, multiple users.

What is the main disadvantage of OFDM?

The main drawbacks of OFDM are its high peak to average power ratio and its sensitivity to phase noise and frequency offset.

What is OFDM and how does it work?

Instead of trying to mitigate frequency selective fading as a whole (which occurs when a huge bandwidth is allocated for the data transmission over a frequency selective fading channel), OFDM mitigates the problem by converting the entire frequency selective fading channel into small flat fading channels (as seen by the individual subcarriers).

What is the difference between OFDM and modulation?

Orthogonal Frequency Division Multiplexing (OFDM) Modulation – a mapping of the information on changes in the carrier phase, frequency or amplitude or combination. Multiplexing – method of sharing a bandwidth with other independent data channels. OFDM is a combination of modulation and multiplexing.

What are some examples of OFDM systems?

Some of the first systems to adopt OFDM were digital broadcasting – here OFDM was able to provide a highly reliable form of data transport over a variety of signal path conditions. Once example was DAB digital radio that was introduced in Europe and other countries.

What are the characteristics of OFDM signals?

High peak to average power ratio: An OFDM signal has a noise like amplitude variation and has a relatively high large dynamic range, or peak to average power ratio.