Modeling of Digital Communication Systems Using SIMULINK

Chapter 11Digital Communications BER Performance in AWGN and Fading (Convolutional Coding)

11.1 Digital Communications with Convolutional Coding in AWGN and Fading

This chapter presents topics in Simulink incorporating convolutional error control coding in an AWGN and fading channel. Specific topics include:

• BER performance of convolutional coding and BPSK in AWGN
  • Hard-decision decoding
  • Soft-decision decoding
• BER performance of convolutional coding and BPSK in AWGN and Rayleigh fading with interleaving
  • Hard-decision decoding
  • Soft-decision decoding
• BER performance of convolutional coding, BPSK and Alamouti STBC in Rayleigh fading with interleaving

11.2 BER Performance of Convolutional Coding and BPSK in AWGN

11.2.1 Hard-Decision Decoding

In this section, Simulink models for convolutional codes with BPSK modulation in AWGN are presented. The BPSK demodulator is followed by a maximum likelihood decoder using the Viterbi algorithm (VA) where hard-decision decoding is selected. Simulink implements the convolutional encoder and decoder by means of a trellis structure for the generator polynomial with a specified constraint length and feedback taps given in octal. As an example, the poly2trellis(7, [171 133]) notation represents a trellis structure for a binary convolutional code with constraint length 7 and feedback taps located at the octal numbers 171 (binary 1111001) and 133(binary 1011011). Figure 11.1 shows the rate ½ convolutional encoder for the poly2trellis(7, [171 ...