flushFilter
Syntax
Description
passes zeros through the transmit filter in the input waveform generator to flush the
residual data samples that remain in the filter state. The function returns the residual
data samples.out
= flushFilter(obj
)
You must call the input waveform generator System object (not only create the object)
prior to using the flushFilter
object function. The number of zeros
passed through the transmit filter depends on the filter delay. This object function is
required for the receiver simulations to recover all of the bits in the last physical layer
frame.
Examples
Get DVB-S2 Waveform Generator Information and Check Transmit Filter Delay
Get information from a dvbs2WaveformGenerator
System object by using the info
function. Then retrieve the filter residual samples by using the flushFilter
object function.
This example uses MAT-files with LDPC parity matrices. If the MAT-files are not available on the path, download and unzip the MAT-files by entering this code at the MATLAB command prompt.
if ~exist('dvbs2xLDPCParityMatrices.mat','file') if ~exist('s2xLDPCParityMatrices.zip', 'file') url = 'https://ssd.mathworks.com/supportfiles/spc/satcom/DVB/s2xLDPCParityMatrices.zip'; websave('s2xLDPCParityMatrices.zip',url); unzip('s2xLDPCParityMatrices.zip'); end addpath('s2xLDPCParityMatrices'); end
Specify the number of physical layer (PL) frames per stream.
numFrames = 1;
Create a Digital Video Broadcasting standard (DVB-S2) System object, and then specify its properties.
s2WaveGen = dvbs2WaveformGenerator; s2WaveGen.NumInputStreams = 2; s2WaveGen.MODCOD = [21 16]; s2WaveGen.DFL = 47008; s2WaveGen.ISSYI = true; s2WaveGen.SamplesPerSymbol = 2; disp(s2WaveGen)
dvbs2WaveformGenerator with properties: StreamFormat: "TS" NumInputStreams: 2 FECFrame: "normal" MODCOD: [21 16] DFL: 47008 ScalingMethod: "outer radius as 1" HasPilots: 0 RolloffFactor: 0.3500 FilterSpanInSymbols: 10 SamplesPerSymbol: 2 ISSYI: true ISCRFormat: "short" Show all properties
Get the characteristic information about the DVB-S2 waveform generator.
info(s2WaveGen)
ans = struct with fields:
ModulationScheme: {'16APSK' '8PSK'}
LDPCCodeIdentifier: {'5/6' '8/9'}
Create the bit vector of input information bits, data
, of concatenated TS user packets.
syncBits = [0 1 0 0 0 1 1 1]'; % Sync byte for TS packet is 47 Hex pktLen = 1496; % UP length without sync bits is 1496 data = cell(1,s2WaveGen.NumInputStreams); for i = 1:s2WaveGen.NumInputStreams numPkts = s2WaveGen.MinNumPackets(i)*numFrames; txRawPkts = randi([0 1],pktLen,numPkts); ISSY = randi([0 1],16,numPkts); % ISCRFormat is 'short' by default % 'short' implies the default length of ISSY as 2 bytes txPkts = [repmat(syncBits,1,numPkts);txRawPkts;ISSY]; % ISSY is appended at the end of UP data{i} = txPkts(:); end
Generate a DVB-S2 time-domain waveform using the information bits.
txWaveform = [s2WaveGen(data)];
Check the filter residual data samples that remain in the filter delay.
flushFilter(s2WaveGen)
ans = 20×1 complex
0.0153 + 0.4565i
0.2483 + 0.5535i
0.3527 + 0.3972i
0.3541 - 0.0855i
0.3505 - 0.4071i
0.4182 - 0.1962i
0.5068 + 0.0636i
0.4856 - 0.1532i
0.3523 - 0.4153i
0.1597 - 0.2263i
⋮
Recover Data Bits from Transport Stream DVB-S2 Transmission
Recover user packets (UPs) for multiple physical layer (PL) frames in a single transport stream Digital Video Broadcasting Satellite Second Generation (DVB-S2) transmission.
This example uses MAT-files with LDPC parity matrices. If the MAT-files are not available on the path, download and unzip the MAT-files by entering this code at the MATLAB command prompt.
if ~exist('dvbs2xLDPCParityMatrices.mat','file') if ~exist('s2xLDPCParityMatrices.zip','file') url = 'https://ssd.mathworks.com/supportfiles/spc/satcom/DVB/s2xLDPCParityMatrices.zip'; websave('s2xLDPCParityMatrices.zip',url); unzip('s2xLDPCParityMatrices.zip'); end addpath('s2xLDPCParityMatrices'); end
Specify the number of PL frames per stream. Create a DVB-S2 System object.
nFrames = 2; s2WaveGen = dvbs2WaveformGenerator;
Create the bit vector of information bits, data
, of concatenated TS UPs.
syncBits = [0 1 0 0 0 1 1 1]'; % Sync byte for TS packet is 47 Hex pktLen = 1496; % UP length without sync bits is 1496 numPkts = s2WaveGen.MinNumPackets*nFrames; txRawPkts = randi([0 1],pktLen,numPkts); txPkts = [repmat(syncBits,1,numPkts); txRawPkts]; data = txPkts(:);
Generate the DVB-S2 time-domain waveform using the input information bits. Flush the transmit filter to handle the filter delay and recover the complete last frame.
txWaveform = [s2WaveGen(data); flushFilter(s2WaveGen)];
Add additive white Gaussian noise (AWGN) to the generated waveform.
sps = s2WaveGen.SamplesPerSymbol;
EsNodB = 1;
snrdB = EsNodB - 10*log10(sps);
rxIn = awgn(txWaveform,snrdB,'measured');
Create a raised cosine receiver filter.
rxFilter = comm.RaisedCosineReceiveFilter( ... 'RolloffFactor',s2WaveGen.RolloffFactor, ... 'InputSamplesPerSymbol',sps,... 'DecimationFactor',sps); s = coeffs(rxFilter); rxFilter.Gain = sum(s.Numerator);
Apply matched filtering and remove the filter delay.
filtOut = rxFilter(rxIn); rxFrame = filtOut(rxFilter.FilterSpanInSymbols+1:end);
Recover UPs. Display the number of frames lost and the UP cyclic redundancy check (CRC) status.
[bits,FramesLost,pktCRCStat] = dvbs2BitRecover(rxFrame,10^(-EsNodB/10)); disp(FramesLost)
0
disp(pktCRCStat)
{20×1 logical}
Get DVB-S2X Waveform Generator Information and Check Transmit Filter Delay
Get information from a dvbs2xWaveformGenerator
System object by using the info
function. Then retrieve the filter residual samples by using the flushFilter
object function.
This example uses MAT-files with LDPC parity matrices. If the MAT-files are not available on the path, download and unzip the MAT-files by entering this code at the MATLAB command prompt.
if ~exist('dvbs2xLDPCParityMatrices.mat','file') if ~exist('s2xLDPCParityMatrices.zip','file') url = 'https://ssd.mathworks.com/supportfiles/spc/satcom/DVB/s2xLDPCParityMatrices.zip'; websave('s2xLDPCParityMatrices.zip',url); unzip('s2xLDPCParityMatrices.zip'); end addpath('s2xLDPCParityMatrices'); end
Specify the number of physical layer (PL) frames per stream.
numFrames = 2;
Create a Digital Video Broadcasting Satellite Second Generation extended (DVB-S2X) System object and specify its properties. Use time slicing technique and variable coding and modulation configuration mode.
s2xWaveGen = dvbs2xWaveformGenerator();
s2xWaveGen.HasTimeSlicing = true;
s2xWaveGen.NumInputStreams = 2;
s2xWaveGen.PLSDecimalCode = [135 145]; % QPSK 9/20 and 8PSK 25/36
s2xWaveGen.DFL = [18048 44656];
s2xWaveGen.PLScramblingIndex = [0 1];
disp(s2xWaveGen)
dvbs2xWaveformGenerator with properties: StreamFormat: "TS" HasTimeSlicing: true NumInputStreams: 2 PLSDecimalCode: [135 145] DFL: [18048 44656] PLScramblingIndex: [0 1] RolloffFactor: 0.3500 FilterSpanInSymbols: 10 SamplesPerSymbol: 4 ISSYI: false Show all properties
Get the characteristic information about the DVB-S2X waveform generator.
info(s2xWaveGen)
ans = struct with fields:
FECFrame: {'normal' 'normal'}
ModulationScheme: {'QPSK' '8PSK'}
LDPCCodeIdentifier: {'9/20' '25/36'}
Create the bit vector of input information bits, data
, of concatenated TS user packets for each input stream.
syncBits = [0 1 0 0 0 1 1 1]'; % Sync byte for TS packet is 47 Hex pktLen = 1496; % UP length without sync bits is 1496 data = cell(1, s2xWaveGen.NumInputStreams); for i = 1:s2xWaveGen.NumInputStreams numPkts = s2xWaveGen.MinNumPackets(i)*numFrames; txRawPkts = randi([0 1], pktLen, numPkts); txPkts = [repmat(syncBits, 1, numPkts); txRawPkts]; data{i} = txPkts(:); end
Generate a DVB-S2X time-domain waveform using the information bits.
txWaveform = s2xWaveGen(data);
Check the filter residual data samples that remain in the filter delay.
flushFilter(s2xWaveGen)
ans = 40×1 complex
-0.2412 - 0.0143i
-0.2619 - 0.0861i
-0.2726 - 0.1337i
-0.2511 - 0.1597i
-0.1851 - 0.1680i
-0.0780 - 0.1602i
0.0448 - 0.1288i
0.1598 - 0.0751i
0.2482 - 0.0049i
0.3026 + 0.0702i
⋮
Get CCSDS TM Waveform Generator Information and Check Transmit Filter Delay
Get information from a ccsdsTMWaveformGenerator
System object by using the info
function. Then retrieve the filter residual samples by using the flushFilter
object function.
Create a Consultative Committee for Space Data Systems (CCSDS) Telemetry (TM) System object. Set the waveform type as synchronization and channel coding
with low-density parity-check (LDPC) channel coding. Display the properties.
tmWaveGen = ccsdsTMWaveformGenerator; tmWaveGen.WaveformSource = "synchronization and channel coding"; tmWaveGen.ChannelCoding = "LDPC"; tmWaveGen.NumBitsInInformationBlock = 1024; tmWaveGen.Modulation = "QPSK"; tmWaveGen.CodeRate = "1/2"; disp(tmWaveGen)
ccsdsTMWaveformGenerator with properties: WaveformSource: "synchronization and channel coding" HasRandomizer: true HasASM: true PCMFormat: "NRZ-L" Channel coding ChannelCoding: "LDPC" NumBitsInInformationBlock: 1024 CodeRate: "1/2" IsLDPCOnSMTF: false Digital modulation and filter Modulation: "QPSK" PulseShapingFilter: "root raised cosine" RolloffFactor: 0.3500 FilterSpanInSymbols: 10 SamplesPerSymbol: 10 Use get to show all properties
Specify the number of transfer frames.
numTF = 20;
Get the characteristic information about the CCSDS TM waveform generator.
info(tmWaveGen)
ans = struct with fields:
ActualCodeRate: 0.5000
NumBitsPerSymbol: 2
SubcarrierFrequency: []
Generate the input bits for the CCSDS TM waveform generator, and then generate the waveform.
bits = randi([0 1], tmWaveGen.NumInputBits*numTF,1); waveform = tmWaveGen(bits);
Check the filter residual data samples that remain in the filter delay.
flushFilter(tmWaveGen)
ans = 100×1 complex
-0.0772 - 0.0867i
-0.0751 - 0.0859i
-0.0673 - 0.0788i
-0.0549 - 0.0654i
-0.0388 - 0.0469i
-0.0200 - 0.0250i
0.0002 - 0.0012i
0.0208 + 0.0227i
0.0405 + 0.0453i
0.0587 + 0.0653i
⋮
Input Arguments
obj
— Waveform generator
dvbs2WaveformGenerator
| dvbs2xWaveformGenerator
| ccsdsTMWaveformGenerator
Waveform generator object, specified as a dvbs2WaveformGenerator
, dvbs2xWaveformGenerator
, or ccsdsTMWaveformGenerator
System object™.
To enable the flushFilter
object function when you specify
obj
as a ccsdsTMWaveformGenerator
System object, you must set these dependencies in the
ccsdsTMWaveformGenerator
object.
Set the
WaveformSource
property to"synchronization and channel coding"
.Set the
ChannelCoding
property to one of these values."none"
"RS"
"turbo"
"LDPC"
— In this case, you must also set theIsLDPCOnSMTF
property to0
(false
)"convolutional"
— In this case, you must also set theConvolutionalCodeRate
property to either"1/2"
or"2/3"
"concatenated"
— In this case, you must also set theConvolutionalCodeRate
property to either"1/2"
or"2/3"
Set the
Modulation
property to either"BPSK"
or"QPSK"
.
Output Arguments
out
— Residual data samples that remain in filter state
column vector
Residual data samples that remain in the filter state, returned as a column vector.
The length of the column vector is equal to the product of the
SamplesPerSymbol
and FilterSpanInSymbols
properties of the input object, obj
.
When you specify obj
as
dvbs2WaveformGenerator
or
dvbs2xWaveformGenerator
System object and the NumInputStream
property as a value greater
than 1, the data fields generated from different input streams are merged in a
round-robin technique into a single stream. The residual samples of the frame after the
merging process are flushed out.
Data Types: double
Complex Number Support: Yes
Version History
Introduced in R2021a
See Also
Functions
Objects
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