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Added Matlab model for PRACH detection probability test

This commit is contained in:
Ismael Gomez 2016-04-28 18:25:34 +02:00
parent d3ce6e83f0
commit 71d7151b1b
4 changed files with 154 additions and 7 deletions
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151
matlab/tests/prach_detect_test.m Normal file
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@ -0,0 +1,151 @@
%% PRACH Detection Conformance Test
clear
numSubframes = 50; % Number of subframes frames to simulate at each SNR
SNRdB = linspace(-12,-4,7); % SNR points to simulate
foffset = 270.0; % Frequency offset in Hertz
%% UE Configuration
% User Equipment (UE) settings are specified in the structure |ue|.
ue.NULRB = 6; % 6 Resource Blocks
ue.DuplexMode = 'FDD'; % Frequency Division Duplexing (FDD)
ue.CyclicPrefixUL = 'Normal'; % Normal cyclic prefix length
ue.NTxAnts = 1; % Number of transmission antennas
%% PRACH Configuration
prach.Format = 0; % PRACH format: TS36.104, Table 8.4.2.1-1
prach.SeqIdx = 22; % Logical sequence index: TS36.141, Table A.6-1
prach.CyclicShiftIdx = 1; % Cyclic shift index: TS36.141, Table A.6-1
prach.HighSpeed = 0; % Normal mode: TS36.104, Table 8.4.2.1-1
prach.FreqOffset = 0; % Default frequency location
prach.PreambleIdx = 32; % Preamble index: TS36.141, Table A.6-1
info = ltePRACHInfo(ue, prach); % PRACH information
%% Propagation Channel Configuration
% Configure the propagation channel model using a structure |chcfg| as per
% TS36.104, Table 8.4.2.1-1 [ <#9 1> ].
chcfg.NRxAnts = 1; % Number of receive antenna
chcfg.DelayProfile = 'EPA'; % Delay profile
chcfg.DopplerFreq = 70.0; % Doppler frequency
chcfg.MIMOCorrelation = 'Low'; % MIMO correlation
chcfg.Seed = 1; % Channel seed
chcfg.NTerms = 16; % Oscillators used in fading model
chcfg.ModelType = 'GMEDS'; % Rayleigh fading model type
chcfg.InitPhase = 'Random'; % Random initial phases
chcfg.NormalizePathGains = 'On'; % Normalize delay profile power
chcfg.NormalizeTxAnts = 'On'; % Normalize for transmit antennas
chcfg.SamplingRate = info.SamplingRate; % Sampling rate
%% Loop for SNR Values
% Initialize the random number generator stream
rng('default');
% Initialize variables storing probability of detection at each SNR
pDetection = zeros(2,length(SNRdB));
for nSNR = 1:length(SNRdB)
% Scale noise to ensure the desired SNR after SC-FDMA demodulation
ulinfo = lteSCFDMAInfo(ue);
SNR = 10^(SNRdB(nSNR)/20);
N = 1/(SNR*sqrt(double(ulinfo.Nfft)))/sqrt(2.0);
% Detected preamble count
detectedCount = 0;
detectedCount_srs = 0;
% Loop for each subframe
for nsf = 1:numSubframes
% PRACH transmission
ue.NSubframe = mod(nsf-1, 10);
ue.NFrame = fix((nsf-1)/10);
% Set PRACH timing offset in us as per TS36.141, Figure 8.4.1.4.2-2
prach.TimingOffset = info.BaseOffset + ue.NSubframe/10.0;
prach.TimingOffset = 0;
% Generate transmit wave
txwave = ltePRACH(ue, prach);
% Channel modeling
chcfg.InitTime = (nsf-1)/1000;
%[rxwave, fadinginfo] = lteFadingChannel(chcfg, ...
% [txwave; zeros(25, 1)]);
rxwave=txwave;
% Add noise
noise = N*complex(randn(size(rxwave)), randn(size(rxwave)));
rxwave = rxwave + noise;
% Remove the implementation delay of the channel modeling
%rxwave = rxwave((fadinginfo.ChannelFilterDelay + 1):1920, :);
% Apply frequency offset
%t = ((0:size(rxwave, 1)-1)/chcfg.SamplingRate).';
%rxwave = rxwave .* repmat(exp(1i*2*pi*foffset*t), ...
% 1, size(rxwave, 2));
% PRACH detection for all cell preamble indices
[detected, offsets] = ltePRACHDetect(ue, prach, rxwave, (0:63).');
txwave_srs = srslte_prach(ue, prach);
plot(abs(txwave-txwave_srs))
[detected_srs] = srslte_prach_detect(ue, prach, rxwave);
% Test for preamble detection
if (length(detected)==1)
% Test for correct preamble detection
if (detected==prach.PreambleIdx)
detectedCount = detectedCount + 1; % Detected preamble
% Calculate timing estimation error. The true offset is
% PRACH offset plus channel delay
% trueOffset = prach.TimingOffset/1e6 + 310e-9;
% measuredOffset = offsets(1)/chcfg.SamplingRate;
% timingerror = abs(measuredOffset-trueOffset);
%
% % Test for acceptable timing error
% if (timingerror<=2.08e-6)
% detectedCount = detectedCount + 1; % Detected preamble
% else
% disp('Timing error');
% end
else
disp('Detected incorrect preamble');
end
else
disp('Detected multiple or zero preambles');
end
if (length(detected_srs)==1 && detected_srs==prach.PreambleIdx)
detectedCount_srs = detectedCount_srs + 1;
end
end % of subframe loop
% Compute final detection probability for this SNR
pDetection(1,nSNR) = detectedCount/numSubframes;
pDetection(2,nSNR) = detectedCount_srs/numSubframes;
end % of SNR loop
%% Analysis
plot(SNRdB, pDetection)
legend('Matlab','srsLTE')
grid on
xlabel('SNR (dB)')
ylabel('Pdet')

2
srslte/lib/phch/prach.c
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@ -469,7 +469,7 @@ int srslte_prach_detect(srslte_prach_t *p,
sig_len > 0 &&
indices != NULL)
{
if(sig_len != p->N_ifft_prach){
if(sig_len < p->N_ifft_prach){
fprintf(stderr, "srslte_prach_detect: Signal is not of length %d", p->N_ifft_prach);
return SRSLTE_ERROR_INVALID_INPUTS;
}

6
srslte/lib/phch/test/prach_detect_test_mex.c
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@ -79,8 +79,6 @@ void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
mexutils_read_uint32_struct(PRACHCFG, "CyclicShiftIdx", &zero_corr_zone);
uint32_t high_speed_flag = 0;
mexutils_read_uint32_struct(PRACHCFG, "HighSpeed", &high_speed_flag);
uint32_t timing_offset = 0;
mexutils_read_uint32_struct(PRACHCFG, "TimingOffset", &timing_offset);
uint32_t frequency_offset = 0;
mexutils_read_uint32_struct(PRACHCFG, "FreqOffset", &frequency_offset);
@ -95,8 +93,8 @@ void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
uint32_t preambles[64];
uint32_t nof_detected = 0;
mexPrintf("nof_samples=%d\n", nof_samples);
if (srslte_prach_detect(&prach, frequency_offset, input_signal, nof_samples, preambles, &nof_detected)) {
if (srslte_prach_detect(&prach, frequency_offset, &input_signal[prach.N_cp], nof_samples, preambles, &nof_detected)) {
mexErrMsgTxt("Error detecting PRACH\n");
return;
}

2
srslte/lib/phch/test/prach_test_mex.c
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@ -78,8 +78,6 @@ void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
mexutils_read_uint32_struct(PRACHCFG, "CyclicShiftIdx", &zero_corr_zone);
uint32_t high_speed_flag = 0;
mexutils_read_uint32_struct(PRACHCFG, "HighSpeed", &high_speed_flag);
uint32_t timing_offset = 0;
mexutils_read_uint32_struct(PRACHCFG, "TimingOffset", &timing_offset);
uint32_t frequency_offset = 0;
mexutils_read_uint32_struct(PRACHCFG, "FreqOffset", &frequency_offset);