Generation of Random Quaternary Signal with QAM Modulation and AWGN Channel Simulation

First, we will generate a random quaternary signal using a random number generator that produces symbols from the set {0,1,2,3}. This can be implemented in code using functions like randi() or random.randint() to create a sequence of base-4 symbols. Next, we will perform QAM modulation on this signal. For quaternary QAM, this typically involves mapping each symbol to a complex constellation point (e.g., 4-QAM with points at ±1±j). The implementation would use a lookup table or mathematical mapping function to convert symbols to complex-valued modulation symbols. The modulated signal will then be transmitted through an additive white Gaussian noise (AWGN) channel. To simulate this channel effect, we will add white Gaussian noise to the modulated signal using simple addition operations. This can be coded using noise generation functions like randn() to create complex Gaussian noise with specified variance proportional to the desired noise power. At the receiver end, we will perform demodulation by determining the closest constellation point to each received symbol (minimum Euclidean distance detection) and mapping back to the original symbols. The demodulation algorithm will involve calculating distances to all possible constellation points and selecting the nearest one. We will then compare the demodulated symbols with the original transmitted symbols to calculate the bit error rate (BER) by counting the number of incorrect symbol decisions divided by the total number of symbols transmitted. By systematically varying the noise power (which controls the signal-to-noise ratio), we will generate multiple BER measurements at different SNR levels. This data will be used to plot the SNR versus BER curve, typically using logarithmic scales for both axes. Finally, we will compare our performance curve with those of other classmates to evaluate the relative performance advantages and disadvantages of different modulation schemes under AWGN channel conditions.