I have a basic question about maximum likelihood (ML) estimator and its implementation with power allocation.

Suppose we are using $MIMO$ system with $4$x$4$ transmit and receive antennas, so the received signal which includes the signal + noise + ISI can be written :

$y = HX + n$

$H,X, n $ are the channel, transmitted signal and noise, respectively. suppose that only first antennas is active and other antennas are not active, so the transmitted signal will be as below: enter image description here

My question is about the possibility to use power allocation to detect the active antenna, which means the estimated signal will be as:

enter image description here

I am asking if we can detect the active antenna in that way, is that possible ? Is there another method we can use instead of that ? Is there any document explain that ?

Thank you.

  • $\begingroup$ Have a look into spatial modulation. $\endgroup$
    – BlackMath
    Apr 12, 2019 at 11:50
  • $\begingroup$ @BlackMath Yes it's the same of Spatial modulation, but I think even if using this algorithm with SM, it can't be used. (as mentioned in below answer) $\endgroup$ Apr 12, 2019 at 12:00

1 Answer 1


What you mention could be right in low modulation order, such as QAM but in 16-QAM and 32-QAM, the amplitude is changed also, I mean you will have different amplitude levels, so you can't implement that detector.

  • $\begingroup$ Yes, I got it. thank you $\endgroup$ Apr 12, 2019 at 12:00

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