Contents
What is OFDM symbol time?
OFDM are sometimes also referred to as OFDM tones. Each OFDM subcarrier is 312.5 KHz. Figure 1: 802.11n/ac 20 MHz channel—OFDM subcarriers. 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.
Where is OFDM used?
9.1 Introduction. 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 the principle 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).
How does an OFDM demodulator demultiplexes a time domain signal?
An OFDM demodulator demultiplexes a multi-subcarrier time-domain signal using orthogonal frequency division modulation. The OFDM demodulation uses an FFT operation that results in N parallel data streams. An OFDM demodulator consists of a bank of N correlators]
How is the complex number xdetermined in OFDM?
The number xdetermines the signal constellation of the corresponding subcarrier, such as 16 QAM or 32QAM. The complex numbers are modulated in a baseband fashion by the inverse FFT (IFFT) and converted back to serial data for transmission.
How are the subcarriers of an OFDM signal orthogonal?
The subcarriers are orthogonal to each other, and 3. A guard interval is added to each symbol to minimize the channel delay spread and intersymbol interference. The following figure illustrates the main concepts of an OFDM signal and the inter-relationship between the frequency and time domains.
How to calculate the number of OFDM symbols per antenna?
NSym is the number of OFDM symbols per antenna. NR is the number of receive antennas. The function assumes that the pilot subcarrier locations are the same across each OFDM symbol and transmit antenna. Use the comm.OFDMDemodulator to vary pilot subcarrier locations across OFDM symbols or antennas.