How to Simulate BER in Simulink: Step-by-Step Guide

To simulate BER in Simulink, use the Random Integer Generator to create data, pass it through a channel model like AWGN Channel, then use the Error Rate Calculation block to measure bit errors by comparing transmitted and received signals. Run the simulation and observe the BER output from the error rate block.

Syntax

Simulating BER in Simulink involves connecting these main blocks:

• Random Integer Generator: Generates random bits or symbols.
• Modulator: Converts bits to modulated signals (e.g., QPSK).
• Channel Model: Simulates noise or fading (e.g., AWGN Channel).
• Demodulator: Converts received signals back to bits.
• Error Rate Calculation: Compares transmitted and received bits to compute BER.

Each block has parameters to set, like modulation order or noise level.

plaintext

Random Integer Generator -> Modulator -> AWGN Channel -> Demodulator -> Error Rate Calculation

Example

This example simulates a simple QPSK communication system with AWGN noise and calculates the BER.

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1. Add a <code>Random Integer Generator</code> block and set <code>M = 4</code> for QPSK symbols.<br>2. Connect it to a <code>QPSK Modulator Baseband</code> block.<br>3. Add an <code>AWGN Channel</code> block and set the desired <code>SNR</code> in dB.<br>4. Connect the channel output to a <code>QPSK Demodulator Baseband</code> block.<br>5. Use an <code>Error Rate Calculation</code> block to compare the original and demodulated signals.<br>6. Run the simulation and observe the BER output from the error rate block's output port.<br><br>Example parameter values:<br>- Random Integer Generator: M = 4, Sample time = 1e-6<br>- AWGN Channel: Eb/No = 10 dB, bits per symbol = 2<br>- Simulation stop time: 1e-3 seconds

Output

Error rate output example: [0.0012 1000 120000]
(0.0012 is the BER, 1000 is number of errors, 120000 is total bits processed)

Common Pitfalls

• Not matching modulation order between modulator and demodulator causes errors.
• Forgetting to set the bits per symbol parameter in the AWGN Channel leads to incorrect noise scaling.
• Not connecting the transmitted and received signals correctly to the Error Rate Calculation block results in zero or invalid BER.
• Running simulation for too short time may give unreliable BER estimates.

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Wrong way:
Random Integer Generator (M=4) -> QPSK Modulator
-> AWGN Channel (bits per symbol not set)
-> QPSK Demodulator
-> Error Rate Calculation

Right way:
Set AWGN Channel 'Bits per symbol' = 2 to match QPSK
Ensure Error Rate Calculation inputs are:
- Original bits from Random Integer Generator
- Demodulated bits from QPSK Demodulator

Quick Reference

Block	Purpose	Key Parameter
Random Integer Generator	Generate random bits/symbols	M (modulation order)
Modulator (e.g., QPSK Modulator Baseband)	Convert bits to modulated signals	Modulation type
AWGN Channel	Add noise to signal	Eb/No (dB), Bits per symbol
Demodulator (e.g., QPSK Demodulator Baseband)	Convert signals back to bits	Modulation type
Error Rate Calculation	Calculate BER by comparing bits	None (connect inputs properly)

Key Takeaways

Use matching modulation settings between modulator and demodulator for accurate BER.

Set the 'Bits per symbol' parameter in the AWGN Channel to scale noise correctly.

Connect original and received bits properly to the Error Rate Calculation block.

Run simulation long enough to get reliable BER estimates.

Use Simulink communication blocks to build a complete BER simulation chain.