OFDM Demodulator Baseband
Demodulate orthogonal frequency division modulated data
Library
OFDM, in Digital Baseband sublibrary of Modulation
Description
The Orthogonal Frequency Division Modulation (OFDM) Demodulator Baseband block demodulates an OFDM input signal. The block accepts a single input and has one or two output ports, depending on the status of Pilot output port.
Signal Dimensions
Pilot Output Port  Pilot Carrier Indices  Signal Input  Signal Output  Pilot Output 

false  N/A  N_{CPTotal}+N_{FFT}×N_{sym}byN_{r}  N_{data}byN_{sym}byN_{r}  N/A 
true  2D  N_{pilot}byN_{sym}byN_{r}  
3D  N_{pilot}byN_{sym}byN_{t}byN_{r} 
where
N_{CP} represents the cyclic prefix length as determined by Cyclic prefix length.
N_{CPTotal} represents the cyclic prefix length over all the symbols. When N_{CP} is a scalar, N_{CPTotal} = N_{CP} × N_{sym}. When N_{CP} is a row vector, N_{CPTotal} = ∑ N_{CP}.
N_{FFT} represents the number of subcarriers as determined by FFT length.
N_{sym} represents the number of symbols as determined by Number of OFDM symbols.
N_{r} represents the number of receive antennas as determined by Number of receive antennas.
N_{data} represents the number of data subcarriers. For further information on how N_{data} is determined, see the
info
reference page.N_{pilot} represents the number of pilot symbols determined by the second dimension in the Pilot subcarrier indices array.
N_{t} represents the number of transmit antennas. This parameter is derived from the third dimension of the Pilot subcarrier indices array.
Parameters
 FFT Length
Specify the FFT length, which is equivalent to the number of subcarriers. The length of the FFT, N_{FFT}, must be greater than or equal to 8.
 Number of guard bands
Assign the number of subcarriers to the left, N_{leftG}, and right, N_{rightG}, guard bands. The input is a 2by1 vector. The number of subcarriers must fall within [0,N_{FFT}/2 − 1].
 Remove DC carrier
Select to remove the DC subcarrier.
 Pilot output port
Select to separate the data from the pilot signal and output the demodulated pilot signal.
 Pilot subcarrier indices
Specify the pilot subcarrier indices. This field is available only when the Pilot output port check box is selected. You can assign the indices can be assigned 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 from 1 to 3. Valid pilot indices fall in the range
$$\left[{N}_{\text{leftG}}+1,\text{\hspace{0.17em}}{N}_{\text{FFT}}/2\right]\cup \left[{N}_{\text{FFT}}/2+2,\text{\hspace{0.17em}}{N}_{\text{FFT}}{N}_{\text{rightG}}\right],$$
where the index value cannot exceed the number of subcarriers. If the number of transmit antennas is greater than one, ensure that the indices per symbol are mutually distinct across antennas to minimize interference.
 Cyclic prefix length
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 N_{sym}, the prefix length can vary across symbols but remains the same length through all antennas.
 Number of OFDM symbols
Specify the number of OFDM symbols, N_{sym}, in the timefrequency grid.
 Number of receive antennas
Specify the number of receive antennas, N_{r}, as a positive integer such that N_{r} ≤ 64.
 Simulate using
Select the simulation type from these choices:
Code generation
Interpreted execution
Algorithms
This block implements the algorithm, inputs, and outputs described in the OFDM Demodulator
System object reference page. The object properties
correspond to the block parameters.
Supported Data Types
Port  Supported Data Types 

Input 

Pilot (optional) 

Output 

Pair Block
References
[1] Dahlman, E., S. Parkvall, and J. Skold. 4G LTE/LTEAdvanced for Mobile Broadband.London: Elsevier Ltd., 2011.
[2] Andrews, J. G., A. Ghosh, and R. Muhamed. Fundamentals of WiMAX.Upper Saddle River, NJ: Prentice Hall, 2007.