Error Rate Calculation

Compute bit error rate or symbol error rate of input data

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Libraries:
Communications Toolbox / Comm Sinks
Communications Toolbox HDL Support / Comm Sinks

Description

The Error Rate Calculation block compares input data from a transmitter with input data from a receiver. The block calculates the error rate as a running statistic by dividing the total number of unequal pairs of data elements by the total number of input data elements from one source.

You can use this block to compute the symbol or bit error rate because it does not consider the magnitude of the difference between input data elements. If the inputs are bits, then the block computes the bit error rate. If the inputs are symbols, then the block computes the symbol error rate.

This figure shows the block with all ports enabled.

Examples

Demodulate Noisy 16-APSK Signal Using Simulink

Apply 16-APSK modulation to a signal of random data. Pass the modulated signal through an AWGN channel. Demodulate the noisy 16-APSK signal. The example reports bit error rate (BER) and symbol error rate (SER) at two SNR settings.

The slex_16apsk_mod model passes a 16-APSK modulated signal through an AWGN channel, demodulates the signal and then computes the error rate statistics. The upper workflow computes the BER and the lower workflow computes the SER. Some block parameters get set by using workspace variables initialized in the PreLoadFcn callback function loads simulation variables into the workspace. For more information, see Model Callbacks (Simulink).

Run the model with the AWGN channel blocks set to EbN0 = 6 dB and display the computed BER and SER. The AWGN Channel block in the lower workflow converts the EbN0 setting to an EsN0 setting. The results are saved to the workspace variables BERVec and SERVec in 1-by-3 row vectors. The first element contains the error rate.

With EbN0 set to  6.00 dB, BER: 0.070
With EsN0 set to 12.02 dB, SER: 0.160

Change the EbN0 of the AWGN channel block to 10 dB. Run the model, display the computed BER and SER, and observe the decrease in error rate.

With EbN0 set to 10.00 dB, BER: 0.016
With EsN0 set to 16.02 dB, SER: 0.051

Calculate Errors for Delayed Selected Samples

Use the Error Rate Calculation block to compute the errors for selected samples in a delayed received frame.

Explore the Model

The model includes two error calculation paths. In the top error calculation path, the Error Rate Calculation block computes errors on each full frame of data. In the bottom error calculation path, the Error Rate Calculation block computes errors on the first three samples in each frame of data and the Sel input port specifies samples from the frame to include in the error calculations. Any delay in the received samples must be accounted in the input to the Sel port.

• Each Tx frame contains the integer sequence [1 2 3 4 5 6 7 8 9 10].

• Each Rx frame contains the integer sequence [1 3 2 4 5 6 7 8 9 10].

The Rx frame introduces two samples errors by switching two of the samples. A Delay block adds a specified delay to the received data.

Running the Model

Run the model with the delay set to 0.

With delay = 0
            Sample error rate | # errors | # samples
Full frame:       0.200       |     20   |   100
 Sub frame:       0.667       |     20   |    30

Run the model with the delay set to 2. The delay in the received samples is included for the input to the Sel port. The full frame error calculation skips two samples due to the receive delay setting.

With delay = 2
            Sample error rate | # errors | # samples
Full frame:       0.204       |     20   |    98
 Sub frame:       0.667       |     20   |    30

Ports

Input

Tx — Transmitted data

scalar | column vector

Transmitted data, specified as a scalar or column vector. Input signals, Tx and Rx must have same data type.

• If you specify the Tx or Rx input as a scalar, the block compares this value with all elements of the other input.

• If you specify Tx and Rx inputs as vectors, they must have the same size.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean

Rx — Received data

scalar | column vector

Received data, specified as a scalar or column vector. Input signals, Rx and Tx must have same data type.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean

Sel — Sample indices

positive integer | column vector of positive integers

Indices of the samples to consider when comparing data, specified as a positive integer or column vector of positive integers.

Dependencies

To enable this input, set the Computation mode parameter to Select samples from input port.

Data Types: double

Rst — Reset error count

scalar

Reset error count, specified as a scalar.

Dependencies

To enable this input, set the Reset port parameter to on.

Data Types: double | Boolean

Output

Out — Difference between transmitted and received data

column vector

Difference between transmitted and received data, returned as a column vector of the form [R; N; S], where:

• R is the error rate.

• N is the number of errors.

• S is the number of samples compared.

Dependencies

To enable this port, set the Output data parameter to Port.

Data Types: double

Parameters

To edit block parameters interactively, use the Property Inspector. From the Simulink^® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Receive delay — Received signal delay

0 (default) | nonnegative integer

Number of samples by which the received data lags behind the transmitted data, specified as a nonnegative integer. Use this parameter to align the samples for comparison in the transmitted and received input data vectors.

Computation delay — Computation delay

0 (default) | nonnegative scalar

Number of data samples that the object ignores at the beginning of the comparison, specified as a nonnegative integer. Use this parameter to ignore the transient behavior of both input signals.

Computation mode — Samples to consider

Entire frame (default) | Select samples from mask | Select samples from port

Samples to consider, specified as one of these values.

• Entire frame — Compare all the samples of the received data to those of the transmitted frame.

• Select samples from mask — Set the indices of the samples to consider when making comparisons in the Selected samples from frame parameter.

• Select samples from port — Set the indices of the samples to consider when making comparisons in the Sel input port.

Selected samples from frame — Sample indices

[] (default) | positive integer | column vector of positive integers

Indices of the samples to consider when comparing data, specified as a positive integer or column vector of positive integers. The default value, an empty vector, specifies that the block uses all samples from the received frame.

Dependencies

To enable this parameter, set the Computation mode parameter to Select samples from mask.

Output data — Output data location

Workspace (default) | Port

Output data location, specified as one of these options.

• Workspace — Send the output data to the workspace variable defined by the Variable name parameter.

• Port — Add an output data port to the block and send the output data to that port.

Variable name — Output data variable name

ErrorVec (default) | character vector | string scalar

Output data variable name in the MATLAB^® workspace.

Dependencies

To enable this parameter, set the Output data variable to Workspace.

Reset port — Option to add Rst input port

off (default) | on

Enable the Rst input port.

Stop simulation — Option to stop simulation after specified number of errors or comparisons

off (default) | on

Option to stop the simulation after the block detects the number of errors specified in the Target number of errors parameter or performs the number of comparisons specified in the Maximum number of symbols parameter.

Target number of errors — Option to stop simulation after specified number of errors

100 (default) | positive integer

Option to stop the simulation after detecting this number of errors, specified as a positive integer.

Dependencies

To enable this parameter, set the Stop simulation parameter to on.

Maximum number of symbols — Option to stop simulation after comparing specified number of symbols

1e6 (default) | positive integer

Option to stop the simulation after comparing this number of symbols, specified as a positive integer.

Note

If you use the Simulink Coder™ rapid simulation (RSim) target to build an RSim executable, then you can tune the Target number of errors and Maximum number of symbols parameters without recompiling the model. This is useful for Monte Carlo simulations in which you run the simulation multiple times (perhaps on multiple computers) with different amounts of noise.

Dependencies

To enable this parameter, set the Stop simulation parameter to on.

Block Characteristics

Data Types	Boolean | double | fixed point | integer | single
Multidimensional Signals	no
Variable-Size Signals	yes

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

When you set the Output data parameter to Workspace, the block generates no code. Similarly, no data is saved to the workspace if you set the Simulation mode parameter to Accelerator or Rapid Accelerator. If you need error rate information in these cases, set the Output data parameter to Port.

HDL Code Generation

Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

This block can be used for simulation visibility in subsystems that generate HDL code, but is not included in the hardware implementation.

Version History

Introduced before R2006a