We an Orthogonal frequency-division multiplexing (OFDM) transmitter composed of a total N = 256 sub-carriers and a prefix cyclic of L = 32 samples. Among these N sub-carriers, the 16 first ones are allocated to transmit 64-QAM symbols. The transmitted power can be normalized to 1W (but it doesn’t matter much for this exercise). The AWGN channel model is considered.

Using MATLAB simulations, display the Bit Error Rate (BER) curve as function of Eb/No of the above OFDM system. Compare the obtained BER performance with the ones obtained when considering a 64-QAM single-carrier modulation (we wan to use the MATLAB function “berawgn” can be used to save time).

Yes… correct. Use of carrier in simulations consume more memory. Higher the carrier frequency, higher is the memory requirement to store all the sampled points.

Thank you Mr Mathuranathan for your clear and quick reply. My misunderstood rose from the fact that in my simulations the difference between passband simulations and complex simulations is only the use or not of a carrier, which means that I always have some oversampling factor (much smaller in complex envelope).

So, can we say that there exist three level of simulations?:

Passband Simulations (OF = N)
Complex Envelope (OF = M <<<< N)
Symbol Level (OF = 1)

Thank you very much

In waveform level simulations, depending on the sampling frequency, each transmitted symbol is composed of #L number of sampled bits. Thus the oversampling factor for such simulation models is set to L.

On the other hand, in the complex baseband model, we are not simulating bit-to-bit variations in the transmitted signal. Rather, we are interested in symbol-level simulation. Here, there is no sampling involved. Hence each transmitted symbol is equivalent to only one bit (at symbol sampling instant). Therefore, the oversampling factor L is set to 1.

I bought all your books, and I already understand passband and complex baseband simulation models, What I cannot get to know is why in your calculus of the Symbol Energy you assert that the oversampling factor is relevant only when the simulation is at waveform level but it musn’t be included when the simulation is complex baseband.

Thank you very much.
Regards

Hi Pedro,
Passband and complex baseband simulations are described in these URLs

1) Introduction – Digital Modulators and Demodulators – Passband Simulation Models:
https://www.gaussianwaves.com/2017/07/introduction-digital-modulators-and-demodulators-passband-simulation-models-chapter-2/

2) Complex Baseband Equivalent Models
https://www.gaussianwaves.com/2017/10/complex-baseband-equivalent-models/

Regards

Could you explain a bit deeper the difference between using complex baseband or passband simulations ir order to include or not the Oversampling Factor?.

Thank you very much