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Which modulation is used in OFDM?
Orthogonal Frequency Division Multiplexing
Orthogonal Frequency Division Multiplexing (OFDM) is a digital multi-carrier modulation scheme that extends the concept of single subcarrier modulation by using multiple subcarriers within the same single channel.
How many sub channels will be required for OFDM?
Each OFDM channel consists of 128 to 2048 sub-carriers and can occupy bandwidths from 1.25 MHz to 20 MHz. In addition, each of these sub-carriers is modulated using BPSK, QPSK, 16-QAM, or 64-QAM modulation, depending on the requirements of the physical channel.
What type of multiplexing does OFDM use?
Frequency Division Multiplexing
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 modulation 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.
How do you calculate subcarriers?
Choosing the first subcarrier to have a frequency such that it has an integer number of cycles in a symbol period, and setting the spacing between adjacent subcarriers (subcarrier bandwidth) to be BSC = B/L, where B is the nominal bandwidth (equal to data rate), and L is the number of subcarriers, ensures that all …
What is slot format in 5G?
Slot formats are a fundamentally new concept in 5G NR. They help to realize different downlink and uplink allocations, particularly in time division duplex (TDD) mode. Based on an example with 120 kHz subcarrier spacing, the video explains some unique characteristics compared to TD-LTE.
What are the different types of modulation in OFDM?
Within the OFDM signal it is possible to choose between three types of modulation for the LTE signal: QPSK (= 4QAM) 2 bits per symbol. 16QAM 4 bits per symbol. 64QAM 6 bits per symbol.
How is OFDM used in a multi channel communication system?
OFDM communications systems are able to more effectively utilize the frequency spectrum through overlapping sub-carriers. These sub-carriers are able to partially overlap without interfering with adjacent sub-carriers because the maximum power of each sub-carrier corresponds directly with the minimum power of each adjacent channel.
How big is the bandwidth of an OFDM channel?
In addition, it fully utilizes the OFDM approach to a communications channel. For this reason, it is more resilient to multi-path symbol interference and can be used to transmit data distances of up to 30 miles. Each OFDM channel consists of 128 to 2048 sub-carriers and can occupy bandwidths from 1.25 MHz to 20 MHz.
Why does OFDM require accurate frequency synchronization?
OFDM requires very accurate frequency synchronization between the receiver and the transmitter; with frequency deviation the subcarriers will no longer be orthogonal, causing inter-carrier interference (ICI) (i.e., cross-talk between the subcarriers).