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which is better: PSK or FSK

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gks83

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fsk constelation

which is better: PSK or FSK

Specifically, BPSK and BFK. what if we increase the constellation?
thx
 

bandwidth of bfsk

What do u mean by better?

Let me try to answer your question comprehensively.

First, for the same data rate BFSK requires twice the bandwidth of BPSK.
BFSK also requires 3 dB more to achieve the same data rate. So for AWGN channel BPSK is always better than BFSK.

I should also mention that BPSK achieves the AWGN channel capacity at low SNR. Therefore it is best you can ever do.


What if we increase the constellation size..
MFSK will require log2(M) BW more than MPSK. But it will require log2(M)/2 times less power than MPSK. Thus it depends on what type of systems you operate.
Bandlimited or Power limited:

MFSK is better for Power limited and the other way for MPSK.

You can refer Proakis for more discussion on this.

Can anyone verify my answer?
 

    gks83

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compare bpsk bfsk

if bfsk is alwas bad..then why do we have it
 

fsk requires more bandwidth

because there are issues like fading in wireless communications.
 

    gks83

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8 fsk constellation

the better one comes what the Constraint is
if you consider in terms of power fsk is better compared to psk
but when the bandwidth is the Constraint psk is better compared to fsk

if we increase the constellation the problem is with the detection
while detecting the energy between the signals would be very less when we increase the constellation here comes the need to increase the power for detecting correctly

so everything is interlinked and atlast you have to go for a compromise in increasing the constellation such as power capacity of the transmission system and the error that you would allow
 

    gks83

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fsk constellation

RAMSYAM, I think you are confusing a little bit:

For FSK, increasing the constellation size actually reduces the energy required for a target BER. Only for PSK or QAM we need to increase energy to meet the target error rate.

For AWGN, BPSK>BFSK : Always.

ramsyam said:
the better one comes what the Constraint is
if you consider in terms of power fsk is better compared to psk
but when the bandwidth is the Constraint psk is better compared to fsk

if we increase the constellation the problem is with the detection
while detecting the energy between the signals would be very less when we increase the constellation here comes the need to increase the power for detecting correctly

so everything is interlinked and atlast you have to go for a compromise in increasing the constellation such as power capacity of the transmission system and the error that you would allow
 

    gks83

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constellation power bandwidth psk

FSK is constant envelope ,PSK has high Peak to average power ratio.
FSK dont need a highly-linear outpu power amplifier as PSK. Just like in GSM.
 

    gks83

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mfsk modulation

is that the reason why ofdm and fsk are not used together...the advantages are lost
 

    gks83

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mfsk snr

yes
 

    gks83

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gsm psk fsk

frome the point of BER the PSK is better
 

    gks83

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bandwidth mfsk

Again, it depends on the datarate at which you operate.

For the same power, MFSK is better than MPSK in terms of BER, but it takes up more BW.
 

    gks83

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modulation power require ber mfsk

PSk is better than FSk when the case related to GSM commnication it is immune against fading channel
 

bpsk bfsk compared

It depends on what kind of application (or more specifically, you care more about power efficiency or bandwidth efficiency).

PSK packs more and more bits into the same bandwidth. Thus, you increase your bandwidth efficiency at the expense of power efficiency (you need to pay more power for higher order modulation to achieve the same BER).

FSK is an orthorgonal modulation, which needs mroe bandwidth when you attempt to increase modulation order. However, the benefit is that from the BER~EbN0 curve, you get rewards by increase modulation order.
 

bandwidth of bpsk,bfsk

BFSK is easy to implement but I don't recall any large communication system that uses it, although MFSK is somehow used if you cosidered a frequency hopping as an MFSK modulation scheme, yet still it consumes more power than any other scheme like OFDM or CDMA and also it consumes more bandwidth than narrowband OFDM, but merely it depends always on the channel what is the most effective modulation scheme ... the more it is complex usually you get a better effeciency .. don't forget the channel coding .. it is a very complex statement to say that some modulation is better than the other, except in some defined situation and sometimes it is even hard to say which is better in the same situation
 

bandwidth of bpsk,bfsk

may be in wireline communication systeems On/OFF signalling similar to FSK are preferred over PSKs and QAMS.
 

    gks83

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fsk psk efficiency

i think PSK as noise interference will be less
 

mpsk vs. mfsk

what do u mean by nise interference
 

    gks83

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ber bfsk bpsk

BFSK is better in S/N,by spending much more widebands.so only finding what you apply it to ,so you can tell which is better or worse!
 

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