Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
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.
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
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
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.
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
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
