Simulink Tutorial on Digital Modulation Methods - Cengage Learning

13.9. 16-ARY QUADRATURE AMPLITUDE-SHIFT KEYING (16-QAM) 627
SOLUTION
The binary representation of the decimal numbers yields a Gray mapping. The most
likely error event for sufficiently high SNR is detecting a constellation point with minimum
Euclidean distance to the actually transmitted constellation point. With Gray
mapping this error event results in only one bit error. Assigning a single bit error to the
more likely error events and multiple bit errors to less likely error events minimizes the
average bit error probability. A Gray mapping can also be found for higher-order QAM.
Start the simulation. Since the signals in the quadrature component look like the
respective in-phase signals, only the in-phase signals are depicted in Figures 13.116
to 13.125 for noiseless transmission. For noisy transmission the receiver scatter plot
looks similar to Figure 13.121.
Figure 13.116: In-phase source signal a_c(t)
Figure 13.117: In-phase baseband signal s_c(t)
Figure 13.118: In-phase component u_c(t) of the transmitted signal
Figure 13.119: Transmitted signal u(t)
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