Whether the IFFT points in the example HDL OFDM Transmitter can be adjusted

I want to get a higher data rate, so I need to adjust the number of subcarriers to 1000, I need 2046 points ifft, but I am not sure if I can adjust this parameter, or can I adjust other parameters to get a higher data rate?

Answer 1

[Parag]

Hi @yafei,

To achieve a higher data rate in the OFDM system, increasing the number of active subcarriers from 72 to 1000 is a valid approach. However, this requires adjustments to several other parameters to ensure proper system performance.

Key Changes Required:

1. FFT Length: To support 1000 subcarriers, the IFFT/FFT size must be increased accordingly. A size of 2048 points is recommended to accommodate 1000 active subcarriers and allow for guard bands.
2. Sample Rate: With a subcarrier spacing of 15 kHz, the new sample rate should be: 2048 × 15 kHz = 30.72 Msps This ensures that the subcarrier spacing and total bandwidth remain consistent.
3. Cyclic Prefix Length: The cyclic prefix (CP) should be scaled proportionally to maintain the same CP ratio. For example, with FFT length increasing from 128 to 2048 (a factor of 16), the CP should increase from 32 to around 512 samples.
4. Bandwidth: The new OFDM signal bandwidth will be approximately: 1000 × 15 kHz = 15 MHz Ensure that your system and regulatory constraints support this bandwidth.

Please refer to MATLAB documentation of OFDM Modulator for more details:

https://www.mathworks.com/help/comm/gs/ofdm-modulation-using-matlab.html

Hope this resolves the query!