Binary Symmetric Channel
R2026bIntroduce binary errors
Binary Symmetric Channel block
To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.
Libraries:
Communications Toolbox /
Channels
Description
The Binary Symmetric Channel block introduces errors to the input signal transmitted through a binary symmetric channel. The errors are introduced based on the specified Error probability. For more information, see Tips.
Examples
The cm_ex_viterbi_decode_binary_seq model generates a binary sequence using the Random Integer Generator block. The sequence is encoded with the Convolutional Encoder block and then impaired with the Binary Symmetric Channel block. The Viterbi Decoder block decodes the data sequence and the bit error rate is computed.
The InitFcn callback is used to initialize workspace parameters for samples per frame, BSC error probability, and the Viterbi decoder traceback depth. The signal delay between the transmitted and received signal is equal to the traceback depth. The signal delay is needed for the error rate calculation.
To produce a binary bit stream, the Random Integer Generator block specifies a set size of 2, and output type of boolean.
The computed error rate approximates the Error probability specified in the Binary Symmetric Channel block.
Computed error rate = 0.095023
Pass a random signal through a binary symmetric channel (BSC), and then calculate the error rate to confirm the specified error probability matches the computed error rate.
The slex_bsc_channel model calculates the bit error rate (BER) of the BSC for the specified error propability and displays the results.
Run the model with the error probability of the BSC block set to 0.01. The results are saved to the base workspace variable ErrorVec in a 1-by-3 row vector. The first element contains the BER.
With error probability set to 0.01, BER: 0.009929
Change the error probability of the BSC block to 0.04. Run the model and observe the increase in BER.
With error probability set to 0.04, BER: 0.039889
Pass a random signal through a binary symmetric channel. For a specified error probability, compare the total number of errors indicated by the Err port to result reported by the Error Rate Calculation block.
The slex_bsc_channel_err model calculates the error rate of the BSC for the specified error propability and displays the results.
Run the model with the error probability of the BSC block set to 0.02. The results from the Error Rate Calculation block are saved to the base workspace variable ErrorVec in a 1-by-3 row vector. ErrorVec contains [ BER, TotalErrors, TotalSamplesProcessed ].
Total number of errors: 20296
The Err port for the Binary Symmetric Channel is a binary vector whose length matches the total number of samples processed. By summing the elements of the output Err vector you get the total number of errors introduced into the signal data. The sum of the elements of the Err vector is saved to the base workspace variable BscErrTotal.
BscErrTotal: 20296
The Error Rate Calculation blocks reports the same total number of errors indicated by BscErrTotal.
Pass a multi-channel random signal through a binary symmetric channel (BSC). For a specified error probability, compare the error rate comparing the Err port output for each channel.
The slex_multichannel_bcs_err model passes a multi-channel through a BSC block and cocmpares the error rate for each channel.
Set different BSC error probabilities for the individual channels of a multi-channel signal by defining the Error probability as a row vector set to [ 0.02 0.04 0.07 ].
The Err port for the Binary Symmetric Channel is a binary matrix whose dimensions match the input signal. Err contains the error results for each channel. Sum the elements of each column output in Err individually to get the total number of errors introduced per channel. Dividing each total by the total number of samples sent per channel yields the bit error rate for each channel.
BER for channel 1: 2.02960e-02 BER for channel 1: 3.97430e-02 BER for channel 1: 7.00090e-02
The computed BERs are approximately equal to the probabilities set in the Error probability parameter.
Ports
Input
Output
Parameters
Block Characteristics
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Programmatic Use: Add Block
To add the block programmatically, use the add_block function with one of these library block paths as the source.
"commchan3/Binary Symmetric Channel"
Example: add_block("commchan3/Binary Symmetric Channel","myModel/myBlock",MakeNameUnique="on")
Tips
When the input consists of not
Booleanvalues, Binary Symmetric Channel converts zero-valued elements to 0 and converts nonzero-valued elements to 1.The Binary Symmetric Channel block creates and uses an independent
RandStreamto provide a random number stream for probability determination.To generate repeatable results, use the same Initial seed value.
To generate independent probability statistics, set different Initial seed values for multichannel signals, multiple processing chains, or simulation runs.
