Contents
What is OFDM and how it works?
OFDM: Orthogonal Frequency Division Multiplexing, is a form of signal modulation that divides a high data rate modulating stream placing them onto many slowly modulated narrowband close-spaced subcarriers, and in this way is less sensitive to frequency selective fading.
How is OFDM implemented?
OFDM modulation in a transmitter includes inverse fast Fourier transform (IFFT) operation and cyclic prefix insertion. In an OFDM receiver, the cyclic prefix is removed before the packet data is sent to FFT for demodulation.
What is OFDM technique?
In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. In OFDM, multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted to carry data in parallel.
What are the main basis of OFDM system?
OFDM is based on the well-known technique of Frequency Division Multiplexing (FDM). In FDM different streams of information are mapped onto separate parallel frequency channels. Each FDM channel is separated from the others by a frequency guard band to reduce interference between adjacent channels.
What is OFDM symbol length?
802.11ax introduces a longer OFDM symbol time of 12.8 μs, which is four times longer than the legacy symbol time of 3.2 μs. Subcarrier spacing is equal to the reciprocal of the symbol time. As a result of the longer symbol time, the subcarrier size and spacing decreases from 312.5 KHz to 78.125 KHz.
Why this cyclic prefix is important in OFDM?
The purpose of the cyclic prefix is to combat ISI and intra-symbol interference. The cyclic prefix is a guard time made up of a replica of the time-domain OFDM waveform. In addition to protecting the modulated symbol from ISI, a cyclic prefix gives the receiver added robustness against timing error.
Can a MATLAB program simulate an OFDM system?
OFDM system, and investigate how its performance is changed by varying some of its major parameters. This objective is met by developing a MATLAB program to simulate a basic OFDM system. From the process of this development, the mechanism of an OFDM system can be studied; and with a completed MATLAB
What kind of modulation is used in OFDM?
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. OFDM builds upon single carrier modulation such as QAM and can transmit at similar data rates.
What are the benefits of the OFDM scheme?
OFDM is a widely adopted scheme used within many wireless communications standards. Some benefits of OFDM include: Overcoming frequency selective fading and multipath distortions found in wideband channels Allowing channel estimation and equalization to occur independently at each subcarrier
How is the OFDM transmission scheme broken down?
The OFDM transmission scheme can be broken down into several components. The data is first coded and modulated, usually into QAM symbols. These symbols are loaded into equally spaced frequency bins and an inverse fast Fourier transform (IFFT) is applied to transform the signal into orthogonal overlapping sinusoids in the time domain.