Step 1: Click on the 'Generate Message' button after filling in the input fields such as the number of OFDM symbols, number of subcarriers, cyclic prefix length, and SNR. This generates the input bitstream for modulation.
Step 2: Click on the 'Generate Subcarrier' button to map the generated data bits into subcarriers using 16-QAM modulation.
Step 3: Click on the 'Time Domain OFDM Without CP' button to perform IFFT and obtain the time-domain OFDM signal without adding a cyclic prefix.
Step 4: Click on the 'Time Domain OFDM With CP' button to add the cyclic prefix to the time-domain OFDM signal, simulating a practical OFDM frame structure.
Step 5: Click on the 'Received Subcarrier' button to simulate reception and retrieve the subcarriers for a selected OFDM symbol (after CP removal and FFT).
16-QAM Modulation: Each group of 4 bits is mapped to one of 16 predefined complex constellation points using Gray coding. The constellation points are:
(-3, -3), (-3, -1), (-1, -3), (-1, -1),
(-3, 3), (-3, 1), (-1, 3), (-1, 1),
(3, -3), (3, -1), (1, -3), (1, -1),
(3, 3), (3, 1), (1, 3), (1, 1)
Each point corresponds to a unique 4-bit symbol. For example, the binary data 0000 maps to (-3, -3), 0001 to (-3, -1), and so on. Gray coding ensures that adjacent points differ by only one bit to reduce bit errors.
Subcarrier Output: The subcarrier output represents the absolute (magnitude) values of the QAM-modulated subcarriers before IFFT is applied.
SNR (in dB)
Symbol Error Rate (SER)
Instructions for Demodulation of OFDM using 16-QAM
Step 1: You can Demodulate the OFDM Signal clicking on the 'Demodulate OFDM' button
In the demodulation part, maximum likelihood detection is used to find the closest constellation point to each received symbol. After identifying the nearest point, the Gray code mapping is reversed to recover the
original transmitted data. This approach ensures accurate data recovery even in the presence of noise.