Supossing I'm able to get the same modulation level for all the SMs, por example 64QAM on UL/DL in the cell (SMs near may be integrated and SM farther may be with reflector or dish)
Is there any performance penalty on the distance (like in ubiquity => more distance, lower throughtput independently of modulation levels, this due to data packet/ack packet travel times) or the TDD protocol is like in Wimax, it has a gap on tx/rx transition and all the SMs transmit at the "distance corrected" time (farther SM transmit early) in order to compensate distance time propagation and not to have gaps in the UL subframe?
Setting PMP450 and ePMP to very far distances has negligable impact on throughput. I'm sure that CambiumMatt or Cambium_Sri could chime in with the technical details.
On both the 450 and ePMP platforms, the tx/rx gap is determined based on the Max Range setting on the AP. Typically you want to set the Max Range to account for the farthest SM under the AP. This allows the AP to properly adjust its timing advance mechanism for proper TDD operation. The larger the Max Range setting, the larger the tx/rx gap. That said and as Eric indicated, the throughput impact is negligible. In the real world, as the range increases, your throughput is heavily impacted by the link budget and RF environment than range which will be negligible.