Modulation V.s PAR

I wonder if OFDM modulation rate, like 64QAM, 256QAM, would impact peak-average-ratio?

I just know the number of subcarriers is relevant to peak-average-ratio.

Hello,

If you take no measures, and you have N non-coherent sinusoidal signals with equal power, PAR = N.

Power is proportional to N, but peak voltage when all signals are in phase, is also proportional with N, so Peak power is proportional with N^2.

The probability of getting the PEP value is very low for large N, and this can be used to modify the signal (accept errors or avoiding certain bit patterns, etc).

I think looking for: peak average ratio reduction OFDM, will give you many useful info, as this is a hot topic.

Maybe I didn't state my question clearly, or didn't understand you correctly.

My question is, give an example, an OFDM signal with 1024 subcarriers and 64QAM has a PAR of 10dB. If its modulation changed to 256QAM, would it impact PAR?

Hello,

256 QAM has a little higher PAR then 64 QAM. When you put it in a 1024 subcarrier system you have a higher raw data rate. So you could exclude more constellation that may result in high peak power.

So my feeling says that the PAR for 256 QAM / 1024 could be less then that for 64 QAM / 1024 given the same effective input datastream.

To be more precise, 64QAM has 3.68dB and 256QAM has 4.23 dB Peak to Average.

Theoretically the PAR[dB] of a multicarrier signal is 10*LOG(Number_of_Carriers).

In reality the PAR is less than this from multiple reasons. Due to this reduction in PAR, the difference using 64QAM or 256QAM carriers is less important.

Thanks for replies.

Can you give details of PAR calculation for different modulations?