about randomizer/scambler in Layer1

Dear experts,

I am quite new to the Layer 1 phy interface. I read about the WiMAX standard and it is stated that there is a Randomizer before the FEC added to the data. Since the objective of a Randomizer, to my understanding, is to eliminates the dependence of a signal's power spectrum upon the actual transmitted data. (e.g. eliminating long sequence of 1's)

But it does not make sense to me to have the Randomizer so high up in this model.

I mean after processes like modulation or interferencing etc, there is a possibility (I guess) that the scrambled bits happened to be 're-assembled' again. Why don't we put the Randomizer before transmitting, maybe before the 'preamble' is inserted, 'cause I think it can best fulfill its objective there.

Reply to
Leo.Hou
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