Modeling of Digital Communication Systems Using SIMULINK

Chapter 3Digital Communications BER Performance in AWGN (BPSK and QPSK)

3.1 BPSK and QPSK Error Rate Performance in AWGN

This chapter introduces several topics in Simulink utilizing binary Phase-Shift Keying (BPSK) and quaternary Phase-Shift Keying (QPSK) modulations. Specifically these topics include:

• Construction of a Simulink model in simple steps
• Available menu choices
• Description of inputs and outputs in simulations
• Sample and frame-based computations
• Complex signal representations
• BPSK bit error rate (BER) simulated and theoretical results
• Comparison of additive white Gaussian noise (AWGN) and Gauss Simulink library blocks
• QPSK symbol error rate performance
• Fixed point error rate performance

3.2 Construction of a Simulink Model in Simple Steps

The BPSK simulation for computing the bit error rate (BER) will be developed in a sequence of steps as follows:

• Begin with the simplest Simulink BPSK model in a back to back configuration with no additive noise and verify proper operation (step 1)
• Add an AWGN block with very high E_b/N_o so that additive noise does not introduce errors and verify proper operation (step 2)
• Add scopes at the output of the BPSK modulator and input to the BPSK demodulator and observe multiple errors when E_b/N_o = −10 dB (step 3)
• Add an error rate calculation block and an associated display to produce an estimate of the BER at a specified E_b/N_o value (step 4)
• Add an information block and display the signal and port data types (step 5)

Figure 3.1