New answers tagged demodulation
1
The important part is that the symbol constellation is agreed upon between transmitter and receiver. The received amplitude will most likely randomly fluctuate over time, but eventually the receiver processing gets to a point where it needs to generate symbol estimates. For example, look at the transmission of a single symbol of 16 QAM. Lets say that the red ...
-1
Digital communications are defined by standard. Here some of them:
3GPP for mobile phones
ETSI with DVB for satellite broadcasting and terrestrial TV
IEEE 802.11 for Wifi
Inside each of those standards, there is a part which describes modulation schemes and constellation diagrams.
All wireless vendors implement them as it is written so they are compatible ...
2
n real life how does communicating wireless devices know which amplitude levels to agree on for digitally modulating-demodulating bitstreams?
You can't "agree" on levels, since the received amplitude depends on the attenuation on the channel, and that depends on distance and a lot of other factors.
So, your receiver depends on detecting something ...
3
To demodulate BPSK and QPSK as described by the OP is to simply take the sign of the waveform (decision), which has trivial computational complexity. The real complexity lies in everything that occurs prior to decision in a practical receiver: There is typically an equalizer to remove multi-path distortion, a matched filter to optimize the signal to noise ...
1
The question should be what is the complexity of taking the RF signal and producing a bit estimate for BPSK and QPSK. Read Dan's answer for more information.
For each received symbol, there is only one operation that you need to do and it is a comparison. You need to figure out which region the received symbol lies in, and that will give you a bit estimate. ...
0
In any PSK modulation, the information is only in the phase.
An unknown $h$ randomly rotates your phase. You know nothing about the phase that $x$ had when you observe $y$. Hence, you have zero mutual information.
One could write that down as a very short formal proof based on conditional entropies, but I don't think that'll help you; the more intuitive ...
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