| 1 | clc; clear all; close all;
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| 2 |
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| 3 | %% System Parameters
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| 4 | fc = 1413.5e6; % Center frequency
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| 5 | numRBGs = 4; % Number of RBGs
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| 6 | rbgSize = 8; % RBs per RBG
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| 7 | modulation = 'QPSK'; % Modulation scheme
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| 8 | numSubframes = 1; % Number of subframes
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| 9 | filenamePrefix = 'mimo_baseband';
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| 10 | gain_dB_list = [-20, -10, 0, 10, 20]; % Gain levels in dB
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| 11 |
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| 12 | %% 5G NR Downlink Configuration
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| 13 | cfgDL = nrDLCarrierConfig;
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| 14 | cfgDL.ChannelBandwidth = 50; % MHz
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| 15 | cfgDL.FrequencyRange = 'FR1';
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| 16 | cfgDL.NumSubframes = numSubframes;
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| 17 | cfgDL.CarrierFrequency = fc;
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| 18 |
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| 19 | cfgDL.SCSCarriers{1}.SubcarrierSpacing = 15;
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| 20 | cfgDL.SCSCarriers{1}.NSizeGrid = 150;
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| 21 | cfgDL.BandwidthParts{1}.SubcarrierSpacing = 15;
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| 22 | cfgDL.BandwidthParts{1}.NSizeBWP = 150;
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| 23 |
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| 24 | % PRB allocation
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| 25 | rbIndices = 0:149;
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| 26 |
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| 27 | %% Loop over gains
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| 28 | nfft = 4096;
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| 29 | for g = 1:length(gain_dB_list)
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| 30 | gain_dB = gain_dB_list(g);
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| 31 | gain_linear = 10^(gain_dB/20);
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| 32 |
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| 33 | cfgDL.PDSCH = {};
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| 34 | pdsch = nrWavegenPDSCHConfig;
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| 35 | pdsch.Modulation = modulation;
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| 36 | pdsch.NumLayers = 1;
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| 37 | pdsch.PRBSet = rbIndices;
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| 38 | pdsch.SymbolAllocation = [0, 14];
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| 39 | cfgDL.PDSCH{1} = pdsch;
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| 40 |
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| 41 | % Generate waveform
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| 42 | [waveform, info] = nrWaveformGenerator(cfgDL);
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| 43 | waveform_scaled = gain_linear * waveform;
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| 44 | numSamples = size(waveform_scaled, 1);
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| 45 | fs = numSamples / (numSubframes * 1e-3);
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| 46 |
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| 47 | % Plot PSD
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| 48 | [psd, f] = pwelch(waveform_scaled, hamming(nfft), [], nfft, fs, 'centered');
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| 49 | f_abs = f + fc;
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| 50 |
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| 51 | figure;
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| 52 | plot(f_abs/1e6, 10*log10(psd));
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| 53 | xlabel('Frequency (MHz)');
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| 54 | ylabel('PSD (dB/Hz)');
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| 55 | title(sprintf('PSD | Gain = %d dB', gain_dB));
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| 56 | grid on;
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| 57 | xline(1403, '--b', 'L-band Start');
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| 58 | xline(1430, '--b', 'L-band End');
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| 59 |
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| 60 |
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| 61 | % Compute L-band Leakage
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| 62 | bandMask = (f_abs >= 1400e6) & (f_abs <= 1430e6);
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| 63 | f_band = f_abs(bandMask);
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| 64 | psd_band = psd(bandMask);
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| 65 | df = mean(diff(f_band));
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| 66 | P_watt = sum(psd_band) * df;
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| 67 | P_dBm = 10 * log10(P_watt / 1e-3);
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| 68 | wl = physconst('Lightspeed')/fc;
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| 69 |
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| 70 |
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| 71 | Pr_dbm = P_dBm + gain_dB + 5 + 20*log10(wl/(4*pi*500*1000));
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| 72 | Prfi = 10 ^ ((Pr_dbm - 30)/10);
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| 73 |
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| 74 | Tb = (Prfi * 250) / (physconst('Boltzmann') * 30 * 1e6);
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| 75 | fprintf('Gain = %3d dB | Leaked Power into 1400–1427 MHz Band: %.2f dBm\n', gain_dB, P_dBm);
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| 76 |
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| 77 | % Plot spectrogram
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| 78 | window = 512; noverlap = 256; nfft_spec = 1024;
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| 79 | [S,F,T,P] = spectrogram(waveform_scaled, window, noverlap, nfft_spec, fs, 'centered');
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| 80 |
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| 81 | figure;
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| 82 | imagesc(T*1e6, (F+fc)/1e6, 10*log10(abs(P)));
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| 83 | axis xy;
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| 84 | colormap jet;
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| 85 | colorbar;
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| 86 | clim([-170 -85]);
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| 87 | title(sprintf('Spectrogram | Gain = %d dB', gain_dB));
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| 88 | xlabel('Time (\mus)');
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| 89 | ylabel('Frequency (MHz)');
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| 90 | yline(1403, '--b', 'L-band Start');
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| 91 | yline(1430, '--b', 'L-band End');
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| 92 |
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| 93 | end
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