Note: Use the input fields to enter the number of OFDM symbols, number of subcarriers, cyclic prefix length, and SNR (in dB).
Step 1: Click on the 'Generate Message' button to generate the input bitstream for modulation.
Step 2: Click the 'Generate QAM Signal' button to generate the 16-QAM modulated signal from the input bitstream.
Step 3: Click on the 'Frequency domain ofdm' button to map the generated modulated symbols into ofdm symbols.
Step 4: Click on the 'Time Domain OFDM' button to perform IFFT and obtain the time-domain OFDM signal without adding a cyclic prefix.
Step 5: 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 6: Click on the 'Show Frequency Spectrums' button to view the frequency spectra of OFDM
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.
SNR (in dB)
Symbol Error Rate (SER)
Instructions for Demodulation of OFDM using 16-QAM
Step 1: Click on the 'Received Subcarrier' button to simulate reception and retrieve the subcarriers for a selected OFDM symbol (after CP removal and FFT).
Step 2: 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.
