Plotting PSD of several multicarrier waveforms
The purpose is to compre the Power spectral density of several multicarrier waveform. The following module can be used:
module example_PSD_waveform
# ----------------------------------------------------
# --- Modules
# ----------------------------------------------------
using DigitalComm
# --- External Modules
using Plots
gr();
using Printf
using FFTW
# ----------------------------------------------------
# --- Core functions
# ----------------------------------------------------
""" psdWaveform.m
---
Compute the power spectral density (i.e the spectrum here) of the signal parametrized by the waveform structure waveform, for a number of symbol nbSymb.
The frequency allocation is the one inherited from the waveform structure (i.e waveform.allocatedSubcarriers).
# --- Syntax
( freq,psd ) = psdWaveform(waveform,nbSymb,allocatedSubcarriers);
# --- Input parameters
- waveform : Structure associated to transmitted waveform
- nbSymb : Number of symbol to be transmitted [Int]
- nbIt : Monte carlo parameter for PSD evaluation (should be > 1)
# --- Output parameters
- freq : Vector of frequency evaluation (between -0.5 and 0.5). [Array{Float64,L}]
- psd : Spectrum evaluated on freq [Array{Complex{Float64}},L]
# --- Input parameters
-
# --- Output parameters
-
# ---
# v 1.0 - Robin Gerzaguet.
"""
function psdWaveform(waveform,nbSymb,nbIt)
# ----------------------------------------------------
# --- PSD calculation
# ----------------------------------------------------
# --- Getting frequency allocation
allocatedSubcarriers = waveform.allocatedSubcarriers;
# --- Getting number of bits
# First, frequency size
nbSubcarriers = length(allocatedSubcarriers);
# Force a fiven mcs
mcs = 4; # QPSK.
# Deduce number of required bits
nbBits = nbSymb * nbSubcarriers * Int(log2(mcs));
# --- Init psd evaluator
psd = 0;
# --- Iterative PSD calculation
for iN = 1 : 1 : nbIt
# --- Binary sequence
bitSeq = genBitSequence(nbBits);
# Mapping
qamSeq = bitMappingQAM(mcs,bitSeq);
# --- T/F matrix
qamMat = reshape(qamSeq,nbSubcarriers,nbSymb);
# --- Signal
sigPSD = genSig(qamMat,waveform);
# --- Mean PSD:
psd = psd .+ 1/nbIt*1/length(sigPSD)*abs.(fftshift(fft(sigPSD))).^2;
end
# --- Calculating sampling frequency
# Returns Nyquist frequency
fe = 1;
Basefe = (0:(length(psd) .-1))./length(psd)*fe .-fe/2;
return (Basefe,psd);
end
# ----------------------------------------------------
# --- Main routine
# ----------------------------------------------------
function main()
# ----------------------------------------------------
# --- Overall parameters
# ----------------------------------------------------
# --- Overall PHY parameters
nbIt = 50; # --- Iteration number
nbSymb = 14; # --- Number of symbols (one frame)
nFFT = 1024; # --- Base FFT size
samplingFreq = 15.36; # --- Frequency value (MHz)
# --- Frequency allocation
#allocatedSubcarriers= getLTEAlloc(nFFT);
#allocatedSubcarriers = (1:12*4);
# 4 RB alloc. 1 RB space. 4 RB allocated
allocatedSubcarriers = [1:12*4; 12*5 .+ (1:12*4)];
# ----------------------------------------------------
# --- Waveform contender
# ----------------------------------------------------
# --- Init OFDM structure
ofdm = initOFDM(
nFFT, # --- nFFT : FFT size
72, # --- nCP : CP size
allocatedSubcarriers # --- allocatedSubcarriers : Subcarrier allocation
);
# --- Init SCFDMA structure
scfdma = initSCFDMA(
nFFT, # --- nFFT : FFT size
72, # --- nCP : CP size
allocatedSubcarriers, # --- allocatedSubcarriers : Subcarrier allocation
12; # --- sizeDFT : DFT preprocessing size
);
# --- Init UF-OFDM structure
ufofdm = initUFOFDM(
nFFT, # --- nFFT : FFT size
73, # --- L : Filter length (same size +1 due to conv)
allocatedSubcarriers, # --- allocatedSubcarriers : Subcarrier allocation
applyPD=1, # --- applyPD : Do predistortion at Tx stage
attenuation=40, # --- attenuation : Filter attenuation in dB
);
# --- Init BF-OFDM structure
bfofdm = initBFOFDM(
32, # --- nFBMC : PPN size (max number of carriers)
64, # --- nOFDM : Precoder size (OFDM sizer)
3, # --- K : Overlapping factor
9, # --- GI : CP size of precoder
0.5, # --- δ : compression factor
allocatedSubcarriers, # --- allocatedSubcarriers : Subcarrier allocation
"gaussian", # --- filterName : Pulse shape name
BT=0.36, # --- BT : Potential BT value for Gaussian
filterStopBand = 110, # --- filterStopBand : DC stopband value
fS=[], # --- fS : Potential frequency coefficient for FS filter
nFFT= 1024, # --- nFFT : associated FFT value in Rx
nCP= 72, # --- nCP : extended CP size
);
# --- Init WOLA-OFDM structure
wola = initWOLA(
nFFT, # --- nFFT : FFT size
72, # --- nCP : CP size
allocatedSubcarriers, # --- allocatedSubcarriers : Subcarrier allocation
"triangle", # --- Window type @Tx side
20, # --- Window size @Tx side
"triangle", # --- Window type @Rx side
20, # --- Window size @Rx side
);
fbmc = initFBMC(
nFFT, # --- nFFT : FFT size
4, # --- K : Overlapping factor
allocatedSubcarriers # --- allocatedSubcarriers : Subcarrier allocation
);
# ----------------------------------------------------
# --- Merging structures
# ----------------------------------------------------
# Create a dictionnary to rule them all
waveforms = initWaveforms(ofdm,
scfdma,
ufofdm,
bfofdm,
wola,
fbmc,
);
# ----------------------------------------------------
# --- PSD main calculation
# ----------------------------------------------------
# --- Init plot container
plt = plot(reuse=false);
decim = 1; # decimation for light plots
# --- Iterative PSD generation
for (name,struc) in waveforms
# --- Calculate PSD for the configuration
(fe,psd) = psdWaveform(struc,nbSymb,nbIt);
# Plot the result
plot!(plt,fe[1:decim:end].*samplingFreq,10 .* log10.(psd[1:decim:end]/maximum(psd)),label=name,legend=:topleft);
end
# --- Update plot and adding labels
# Purpose is to zoom out on allocated region.
scsN = (1/1024)*samplingFreq; # Subscarrier spacing (normalized)
rbV = (12*12); # See several RB for psd fall-off
ylims!(-120,5);
xlims!(-rbV*scsN,maximum(allocatedSubcarriers)*scsN+2*12*scsN);
xlabel!("Frequency [MHz]");
ylabel!("Spectrum");
display(plt)
end
endBy running example_PSD_waveform.main(); a comparison plot between the different PSD can be obtained
