![]() ![]() ![]() #OPTISYSTEM IMAGE MATALAB DATA TRANSFER CODE#S=ref(d) %map information symbols to modulated symbolsįull Matlab code available in the book Digital Modulations using Python class QAMModem(Modem): Ref=constructQAM(M) %construct reference constellation If(((M˜=1) & ˜mod(floor(log2(M)),2))=0), %M not a even power of 2Įrror('Only Square MQAM supported. % output and ref represents reference constellation that can be used in demod % vector d contains symbols whose values range 1:M. % using MQAM modulation, where M specifies order of M-QAM modulation and %=mqam_modulator(M,d) modulates the symbols defined by the vector d %Function to MQAM modulate the vector of data symbols - d Matlab codeįull Matlab code available in the book Digital Modulations using Matlab – build simulation models from scratch function =mqam_modulator(M,d) The resulting ideal constellations for Gray coded 16-QAM and 64-QAM are shown in Figure 1. Matlab code for dynamically generating M-QAM constellation points based on Karnaugh map Gray code walk is given below. Thus for constructing a M-QAM constellation, the PAM dimension is set as. For example, 16-QAM constellation points can be generated from two 4-PAM signals, similarly the 64-QAM constellation points can be generated from two 8-PAM signals.įor generating 16-QAM, the dimension D of PAM is set to. In one of the earlier articles, I have discussed the method of constructing constellation for rectangular QAM modulation using Karnaugh-map walks, where the inherent property of Karnaugh-maps is exploited to construct Gray coded QAM symbols.Īny rectangular QAM constellation is equivalent to superimposing two Amplitude Shift Keying (ASK)signals (also called Pulse Amplitude Modulation – PAM) on quadrature carriers. Rectangular (symmetric or square) constellations are the preferred choice of implementation due to its simplicity in implementing modulation and demodulation. There exist other constellation shapes (like circular, triangular constellations) that are more efficient (in terms of energy required to achieve same the error probability) than the standard rectangular constellation. The given simulation code is very generic, and it plots both simulated and theoretical symbol error rates for all M-QAM modulation techniques. A generic complex baseband simulation technique, to simulate all M-ary QAM modulation techniques is given here. ![]()
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