gamabetaalpha
Newbie level 1
Why My OFDM Received Samples in Reversed Order from the Transimitted?
Hi everyone, new here and ask for help.
I am working on OFDM now. In my experiments I find a very weird problem. After transmitted and received at the Rx, the sample order of OFDM samples in a symbol is in a reversed order of the Tx ones. Also, the signs of I/Q are also weird.(It is QPSK OFDM).
Here is an example. In Tx, the freq. domain samples are [0,a,b,0,0,0,c,d]. Zeros are zero paddings.
a,b,c,d∈(-1-i,-1+i,1-i,1+i);
However the received samples after FFT are [0,signchange(d),signchange(c),0,0,0,signchange(b),signchange(a)],
in which the signchange is this manipulation: signchange(x+i*y)=-y-i*x; I have checked the function, it is this function: signchange(P)=-i*conj(P).
This problem happens occasionally, i.e., sometimes the Rx samples is in the right order,sometimes in this order.
How could that problem come from? I have been quite curious for a long time.
Thanks for your attention.
Hi everyone, new here and ask for help.
I am working on OFDM now. In my experiments I find a very weird problem. After transmitted and received at the Rx, the sample order of OFDM samples in a symbol is in a reversed order of the Tx ones. Also, the signs of I/Q are also weird.(It is QPSK OFDM).
Here is an example. In Tx, the freq. domain samples are [0,a,b,0,0,0,c,d]. Zeros are zero paddings.
a,b,c,d∈(-1-i,-1+i,1-i,1+i);
However the received samples after FFT are [0,signchange(d),signchange(c),0,0,0,signchange(b),signchange(a)],
in which the signchange is this manipulation: signchange(x+i*y)=-y-i*x; I have checked the function, it is this function: signchange(P)=-i*conj(P).
This problem happens occasionally, i.e., sometimes the Rx samples is in the right order,sometimes in this order.
How could that problem come from? I have been quite curious for a long time.
Thanks for your attention.
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