OFDM using DSP Builder

You simply need to go back to:

Channel 1: 11

Channel 2: 00

Channel 3: 10

Channel 4: 11

Instead of the +0.7071 and -0.7071 values, you may transmit the 1 and 0 values to the FFT engine.

If you don't have pilot tones and you need only to transmit your payload data, that is simply what you need to do.

Of course the output scaling can be done by choosing the appropriate output dynamic range and pushing the maximum and minimum binary values into the FFT engine instead of 1 and 0.