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I saw a paper,https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8283591 ,and it said

Each DA (distributed antenna) port in the DAS (distributed antenna system) is usually equipped with its own power amplifier at the analog front-end. Thus, individual power constraint at each antenna should be considered for the DAS unlike the conventional systems which normally impose sum power constraint

because the author said that the fig(a) unlike the conventional systems which normally impose sum power constraint,so i think there are some advantages,which are better than conventional systems ,in the fig(a) system,Does anyone know what are the advantage about the fig(a) system?
enter image description here

fig(a)

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  • $\begingroup$ I don't see any difference between the two schemes, aside from the color and position in which the "main processing unit" is drawn. $\endgroup$ – Marcus Müller Jun 26 '19 at 5:45
  • $\begingroup$ neither do i,i delete the fig(b) part,do you know what is the advantage of equipped with its own power amplifier for each DA? $\endgroup$ – XM551 Jun 26 '19 at 5:48
  • $\begingroup$ That you have more power amplifiers and thus potentially more power in the system? Honestly, that's the way cellular systems are set up, anyways, because you don't want to transport high-powered RF signals over large distances. You'd rather transport a low powered or even just a digital signal, and then power-amplify it close to the antenna. $\endgroup$ – Marcus Müller Jun 26 '19 at 5:53
  • $\begingroup$ Oh so it depends on where should i use system?if i want to transport signal over large distance,but i just have low power to transmit the signal,so i need the power amp to amplify my tiny signal so i can transport the signal over large distance? $\endgroup$ – XM551 Jun 26 '19 at 6:06
  • $\begingroup$ no, the opposite, as I said: You don't want to invest in cabling that is able to transport the amplified signal over a large distance. That's expensive. Instead, you get cheap cabling and an amplifier at each antenna mast. In fact, you often even don't get RF cabling, but transport the signal either mixed to optical frequencies, or as digital signal, to the radioheads at each antenna mast. I mean, why would you invest in a 100W amplifier at some central point when the 1000m cabling from there to your antenna system eat 80W of that in the end? That'd be a huge waste of power and money. $\endgroup$ – Marcus Müller Jun 26 '19 at 6:10

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