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利用matlab和SDR实现LTE信号的采集以及帧同步，MIB解码

利⽤matlab和SDR实现LTE信号的采集以及帧同步，MIB解码到这篇⽂章的同志们，⼀定正在LTE⽣死线上苦苦挣扎，⼤家都知道对LTE信号进⾏采集的时候，是采⽤30.72M（15K✖2048）的时钟频率，然后呢，LTE频带的带宽是18M（15K✖1200）为了避免⼤家少⾛弯路，我将代码附在⽂章末尾。我们可以采集到的信号如下图所⽰。

⼤家可以看到这与事实是相符合的，在中⼼频率的左右各是±9MHz，因此我们可以通过查移动，联通，电信对应的下⾏频段信息，然后就可以采集到信息了。

帧同步如下所⽰。

频偏估计以及MIB就不⼀⼀展⽰了，⼤家可以运⾏程序调参。

%% Connect to Radio

radioFound = false;

radiolist = findsdru;

for i = 1:length(radiolist)

if strcmp(radiolist(i).Status, 'Success')

if strcmp(radiolist(i).Platform, 'B210')

radio = comm.SDRuReceiver('Platform','B210', ...

'SerialNum', radiolist(i).SerialNum);

radio.MasterClockRate = 1.92e6 * 4; % Need to exceed 5 MHz minimum

radio.DecimationFactor = 4; % Sampling rate is 1.92e6

radioFound = true;

break;

end

if (strcmp(radiolist(i).Platform, 'X300') || ...

strcmp(radiolist(i).Platform, 'X310'))

radio = comm.SDRuReceiver('Platform',radiolist(i).Platform, ...

'IPAddress', radiolist(i).IPAddress);

radio.MasterClockRate = 184.32e6;

radio.DecimationFactor = 96; % Sampling rate is 1.92e6

radioFound = true;

end

市区工况油耗if (strcmp(radiolist(i).Platform, 'N300') || ...

strcmp(radiolist(i).Platform, 'N310'))

radio = comm.SDRuReceiver('Platform',radiolist(i).Platform, ...

'IPAddress', radiolist(i).IPAddress);

radio.MasterClockRate = 122.88e6;

radio.DecimationFactor = 64; % Sampling rate is 1.92e6

radioFound = true;

end

if (strcmp(radiolist(i).Platform, 'N320/N321'))

radio = comm.SDRuReceiver('Platform',radiolist(i).Platform, ...

'IPAddress', radiolist(i).IPAddress);

radio.MasterClockRate = 245.76e6;

radio.DecimationFactor = 128; % Sampling rate is 1.92e6

radioFound = true;

end

if ~radioFound

error(message('sdru:examples:NeedMIMORadio'));

end

radio.ChannelMapping = [1 2]; % Receive signals from both channels

radio.CenterFrequency = 900e6;

radio.Gain = 30;

radio.SamplesPerFrame = 19200; % Sampling rate is 1.92 MHz. LTE frames are 10 ms long radio.OutputDataType = 'double';

radio.EnableBurstMode = true;

radio.NumFramesInBurst = 4;

radio.OverrunOutputPort = true;

radio

%% Capture Signal

burstCaptures = zeros(19200,4,2);

len = 0;

地中海果蝇for frame = 1:4

while len == 0

[data,len,lostSamples] = step(radio);

burstCaptures(:,frame,:) = data;

end

len = 0;

end

release(radio);

eNodeBOutput = reshape(burstCaptures,[],2);

sr = 1.92e6 ; % LTE sampling rate

% Check for presence of LTE Toolbox

if isempty(ver('lte'))

error(message('sdru:examples:NeedLST'));

end

separator = repmat('-',1,50);

% plots

if (~exist('channelFigure','var') || ~isvalid(channelFigure))

channelFigure = figure('Visible','off');

end

[spectrumAnalyzer,synchCorrPlot,pdcchConstDiagram] = ...

hSIB1RecoveryExamplePlots(channelFigure,sr);

% PDSCH EVM

pdschEVM = comm.EVM();

pdschEVM.MaximumEVMOutputPort = true;

% Set eNodeB basic parameters

enb = struct; % eNodeB config structure

enb.DuplexMode = 'FDD'; % assume FDD duxplexing mode

enb.CyclicPrefix = 'Normal'; % assume normal cyclic prefix

enb.NDLRB = 6; % Number of resource blocks

ofdmInfo = lteOFDMInfo(enb); % Needed to get the sampling rate

if (isempty(eNodeBOutput))

fprintf('\nReceived signal must not be empty.\n');

return;

end

% Display received signal spectrum

fprintf('\nPlotting received \n');

step(spectrumAnalyzer, awgn(eNodeBOutput, 100.0));

if (sr~=ofdmInfo.SamplingRate)

fprintf('\nResampling from %0.3fMs/s to %0.3fMs/s for cell search / \n',sr/1e6,ofdmInfo.SamplingRate/1e6);

else

fprintf('\nResampling not required; received signal is at desired sampling rate for cell search / MIB decoding (%0.3fMs/s).\n',sr/1e6); end

% Downsample received signal

nSamples = ceil(ofdmInfo.SamplingRate/round(sr)*size(eNodeBOutput,1));

nRxAnts = size(eNodeBOutput, 2);

downsampled = zeros(nSamples, nRxAnts);

for i=1:nRxAnts

downsampled(:,i) = resample(eNodeBOutput(:,i), ofdmInfo.SamplingRate, round(sr));

end

%% Frequency offset estimation and correction

fprintf('\nPerforming frequency \n');

delta_f = lteFrequencyOffset(setfield(enb,'DuplexMode','FDD'), downsampled); %#ok<SFLD>

fprintf('Frequency offset: %0.3fHz\n',delta_f);

downsampled = lteFrequencyCorrect(enb, downsampled, delta_f);

%% Cell Search and Synchronization

% Cell search to find cell identity and timing offset

fprintf('\nPerforming \n');

[cellID, offset] = lteCellSearch(enb, downsampled);

corr = cell(1,3);

for i = 0:2

enb.NCellID = mod(cellID + i,504);

[~,corr{i+1}] = lteDLFrameOffset(enb, downsampled);

corr{i+1} = sum(corr{i+1},2);

end

threshold = 1.3 * max([corr{2}; corr{3}]); % multiplier of 1.3 empirically obtained

if (max(corr{1})<threshold)

warning('sdru:examples:WeakSignal','Synchronization signal correlation was weak; detected cell identity may be incorrect.'); end

enb.NCellID = cellID;

% plot PSS/SSS

synchCorrPlot.YLimits = [0 max([corr{1}; threshold])*1.1];

step(synchCorrPlot, [corr{1} threshold*ones(size(corr{1}))]);

% perform timing synchronisation

fprintf('Timing offset to frame start: %d samples\n',offset);

downsampled = downsampled(1+offset:end,:);

enb.NSubframe = 0;

% show cell-wide settings

fprintf('Cell-wide settings after cell search:\n');

disp(enb);

%% OFDM Demodulation and Channel Estimation

% Channel estimator configuration

cec.PilotAverage = 'UserDefined'; % Type of pilot averaging

cec.FreqWindow = 9; % Frequency window size

cec.TimeWindow = 9; % Time window size

cec.InterpType = 'cubic'; % 2D interpolation type

cec.InterpWindow = 'Centered'; % Interpolation window type

cec.InterpWinSize = 1; % Interpolation window size

% Assume 4 cell-specific reference signals for initial decoding attempt;

% ensures channel estimates are available for all cell-specific reference

% signals

enb.CellRefP = 4;

fprintf('Performing \n\n');

griddims = lteResourceGridSize(enb); % Resource grid dimensions

L = griddims(2); % Number of OFDM symbols in a subframe

% OFDM demodulate signal

rxgrid = lteOFDMDemodulate(enb, downsampled);

if (isempty(rxgrid))反猫眼窥镜

fprintf('After timing synchronization, signal is shorter than one subframe so no further demodulation will be performed.\n'); return;

end

% Perform channel estimation

if (strcmpi(enb.DuplexMode,'TDD'))

enb.TDDConfig = 0;

enb.SSC = 0;

end

[hest, nest] = lteDLChannelEstimate(enb, cec, rxgrid(:,1:L,:));

%% PBCH Demodulation, BCH Decoding, MIB parsing

fprintf('Performing \n');

pbchIndices = ltePBCHIndices(enb);

[pbchRx, pbchHest] = lteExtractResources( ...

pbchIndices, rxgrid(:,1:L,:), hest(:,1:L,:,:));

% Decode PBCH

[bchBits, pbchSymbols, nfmod4, mib, enb.CellRefP] = ltePBCHDecode( ...

enb, pbchRx, pbchHest, nest);负压脉动式清肺仪

% Parse MIB bits

enb = lteMIB(mib, enb);展示架制作

enb.NFrame = enb.NFrame+nfmod4;

% Display cell wide settings after MIB decoding

fprintf('Cell-wide settings after MIB decoding:\n');

disp(enb);

if (enb.CellRefP==0)

fprintf('MIB decoding failed (enb.CellRefP=0).\n\n');

return;

end

if (enb.NDLRB==0)

fprintf('MIB decoding failed (enb.NDLRB=0).\n\n');

return;

end

%% OFDM Demodulation on Full Bandwidth

fprintf('Restarting reception now that bandwidth (NDLRB=%d) \n',enb.NDLRB);

% Resample now we know the true bandwidth

ofdmInfo = lteOFDMInfo(enb);

if (sr~=ofdmInfo.SamplingRate)

fprintf('\nResampling from %0.3fMs/s to %0.\n',sr/1e6,ofdmInfo.SamplingRate/1e6);

else

fprintf('\nResampling not required; received signal is at desired sampling rate for NDLRB=%d (%0.3fMs/s).\n',enb.NDLRB,sr/1e6); end

nSamples = ceil(ofdmInfo.SamplingRate/round(sr)*size(eNodeBOutput,1));

resampled = zeros(nSamples, nRxAnts);

for i = 1:nRxAnts

resampled(:,i) = resample(eNodeBOutput(:,i), ofdmInfo.SamplingRate, round(sr));

end

% Perform frequency offset estimation and correction

fprintf('\nPerforming frequency \n');

delta_f = lteFrequencyOffset(setfield(enb,'DuplexMode','FDD'), resampled); %#ok<SFLD>

fprintf('Frequency offset: %0.3fHz\n',delta_f);

resampled = lteFrequencyCorrect(enb, resampled, delta_f);

% Find beginning of frame

fprintf('\nPerforming timing \n');

offset = lteDLFrameOffset(enb, resampled);

fprintf('Timing offset to frame start: %d samples\n',offset);

resampled = resampled(1+offset:end,:);

% OFDM demodulation

fprintf('\nPerforming \n\n');

rxgrid = lteOFDMDemodulate(enb, resampled);

%% SIB1 Decoding

% Check this frame contains SIB1, if not advance by 1 frame provided we

正弦波信号发生器

% have enough data, terminate otherwise.

if (mod(enb.NFrame,2)~=0)

if (size(rxgrid,2)>=(L*10))

rxgrid(:,1:(L*10),:) = [];

fprintf('Skipping frame %d (odd frame number does not contain SIB1).\n\n',enb.NFrame);

else

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