Modulate using orthogonal frequency division modulation
OFDM, in Digital Baseband sublibrary of Modulation
The OFDM Modulator Baseband block applies OFDM modulation to an incoming data signal. The block accepts one or two inputs depending on the state of the Pilot input port.
|Pilot Input Port||Signal Input||Pilot Input||Signal Output|
Ndata represents the number
of data subcarriers. For further information on how Ndata is
determined, see the
comm.OFDMModulator.info reference page.
Nsym represents the number of symbols determined by Number of OFDM symbols.
Nt represents the number of transmit antennas determined by Number of transmit antennas.
Npilot represents the number of pilot symbols determined by the first dimension size in the Pilot subcarrier indices array.
NCP represents the cyclic prefix length as determined by Cyclic prefix length.
NCPTotal represents the cyclic prefix length over all the symbols. When NCP is a scalar, NCPTotal = NCP × Nsym. When NCP is a row vector, NCPTotal = ∑ NCP.
NFFT represents the number of subcarriers as determined by FFT length.
Specify the FFT length, which is equivalent to the number of subcarriers. The length of the FFT, NFFT, must be greater than or equal to 8.
Assign the number of subcarriers to the left and right guard bands. The input is a 2-by-1 vector. The number of subcarriers must fall within [0, NFFT/2 − 1].
Select to insert a null on the DC subcarrier.
Select to allow the specifying of pilot subcarrier indices.
Specify the pilot subcarrier indices. This field is available only when the Pilot input port check box is selected. You can assign the indices to the same or different subcarriers for each symbol. Similarly, the pilot carrier indices can differ across multiple transmit antennas. Depending on the desired level of control for index assignments, the dimensions of the indices array vary. Valid pilot indices fall in the range
where the index value
cannot exceed the number of subcarriers. When the pilot indices are
the same for every symbol and transmit antenna, the property has dimensions
Npilot-by-1. When the pilot indices vary across
symbols, the property has dimensions of Npilot-by-Nsym.
If there is only one symbol but multiple transmit antennas, the property
has dimensions of Npilot-by-1-by-Nt.
If the indices vary across the number of symbols and transmit antennas,
the property will have dimensions of Npilot-by-Nsym-by-Nt.
If the number of transmit antennas is greater than one, ensure that
the indices per symbol are mutually distinct across antennas to minimize
interference. The default value is
[12; 26; 40; 54].
Specify the length of the cyclic prefix. If you specify a scalar, the prefix length is the same for all symbols through all antennas. If you specify a row vector of length Nsym, the prefix length can vary across symbols but remains the same through all antennas.
Select to apply raised cosine windowing. Windowing is the process in which the OFDM symbol is multiplied by a raised cosine window before transmission to reduce the power of out-of-band subcarriers, which serves to reduce spectral regrowth.
Set the length of the raised cosine window. The field is available
only when Apply raised cosine windowing between OFDM symbols is
selected. Use positive integers having a maximum value no greater
than the minimum cyclic prefix length. For example, in a configuration
in which there are four symbols with cyclic prefix lengths of
16 14 18], the window length cannot exceed 12.
Specify the number of OFDM symbols in the time-frequency grid.
Specify the number of transmit antennas, Nt, as a positive integer such that Nt ≤ 64.
Select the simulation type from these choices:
This block implements the algorithm, inputs, and outputs described
Modulator System object reference page. The object properties
correspond to the block parameters.
|Port||Supported Data Types|
 Dahlman, E., S. Parkvall, and J. Skold. 4G LTE/LTE-Advanced for Mobile Broadband.London: Elsevier Ltd., 2011.
 Andrews, J. G., A. Ghosh, and R. Muhamed. Fundamentals of WiMAX.Upper Saddle River, NJ: Prentice Hall, 2007.