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16QAM and 16PSK

Started by Deamon January 7, 2011
Please  can anyone give me a pointer to a material that does an in
depth comparison of the 16QAM and 16PSK modulation in terms of
different properties and their SNR vs BER comparison. Any comment
about this modulation comparison would be helpful couldn't turn up
anything using google and even IEEE.

Thanks
On 01/07/2011 04:37 PM, Deamon wrote:
> Please can anyone give me a pointer to a material that does an in > depth comparison of the 16QAM and 16PSK modulation in terms of > different properties and their SNR vs BER comparison. Any comment > about this modulation comparison would be helpful couldn't turn up > anything using google and even IEEE.
Not in depth, but: (anything)PSK gives you a constant envelope to transmit with, which reduces the complexity of your transmitter's circuitry. Now, plot out a circle on a piece of paper, and draw 16 evenly spaced dots on that circle -- that's the constellation for 16PSK. Then inscribe a square within that circle, and populate the square with 16 evenly spaced dots. That's the constellation for 16QAM with the same maximum transmit power as your 16PSK. Which dots have more distance between them? If you think that the same maximum transmit power is to stringent a comparison, then figure out how to scale the square for the same _average_ power -- now compare the distance between the dots. 16QAM -- better noise performance (at least if it's additive Gaussian). 16PSK -- easier transmitter design. I've only personally encountered PSK up to 8, but I don't do slews of comms design. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
On Jan 7, 6:37&#2013266080;pm, Deamon <persistence...@gmail.com> wrote:
> Please &#2013266080;can anyone give me a pointer to a material that does an in > depth comparison of the 16QAM and 16PSK modulation in terms of > different properties and their SNR vs BER comparison. Any comment > about this modulation comparison would be helpful couldn't turn up > anything using google and even IEEE. > > Thanks
In addition to following Tim Wescott's excellent suggestions which will *really* help you a lot, you might want to look at a document titled Signal Space Concepts that is available at <http://courses.engr.illinois.edu/ece361/spring11/OldLectures.html> --Dilip Sarwate

Tim Wescott wrote:


> (anything)PSK gives you a constant envelope to transmit with, which > reduces the complexity of your transmitter's circuitry.
Except for bandlimited PSK does not have a constant envelope; in the other words, no advantage.
> I've only personally encountered PSK up to 8,
QAM clearly outperforms PSK at n >= 8. Consequently, there is no point in using more then 8-PSK. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
> > >Tim Wescott wrote: > > >> (anything)PSK gives you a constant envelope to transmit with, which >> reduces the complexity of your transmitter's circuitry. > >Except for bandlimited PSK does not have a constant envelope; in the >other words, no advantage. > >> I've only personally encountered PSK up to 8, > >QAM clearly outperforms PSK at n >= 8. Consequently, there is no point >in using more then 8-PSK.
You are just looking at this from a signal processing point of view. As Tim said, bring the transmitter into the analysis and things may look different. A constant power modulation allows options in transmitter design that can offer reduced cost (which Tim said) and higher efficiency (which he should have). Its not a clear choice until the constellation gets bigger, and PSK starts to look really bad. Steve

steveu wrote:

>> >>Tim Wescott wrote: >> >> >> >>>(anything)PSK gives you a constant envelope to transmit with, which >>>reduces the complexity of your transmitter's circuitry. >> >>Except for bandlimited PSK does not have a constant envelope; in the >>other words, no advantage. >> >> >>>I've only personally encountered PSK up to 8, >> >>QAM clearly outperforms PSK at n >= 8. Consequently, there is no point >>in using more then 8-PSK. > > > You are just looking at this from a signal processing point of view. As Tim > said, bring the transmitter into the analysis and things may look > different.
Like what?
> A constant power modulation allows options in transmitter design
However, bandlimited PSK is not a constant power modulation.
> that can offer reduced cost (which Tim said) and higher efficiency (which > he should have).
How?
> Its not a clear choice until the constellation gets > bigger, and PSK starts to look really bad.
Example? VLV
On Jan 8, 2:37&#2013266080;am, Deamon <persistence...@gmail.com> wrote:
> Please &#2013266080;can anyone give me a pointer to a material that does an in > depth comparison of the 16QAM and 16PSK modulation in terms of > different properties and their SNR vs BER comparison. Any comment > about this modulation comparison would be helpful couldn't turn up > anything using google and even IEEE. > > Thanks
I found the following book a good source for comparison of different modulation schemes: "Digital Modulation Techniques" by Fuqin XIONG The author compares QAM and PSK to show that QAM is superior to MPSK. Specifically for M=16 the difference is about 4.2dB (quoted from the book - "all rights reserved"). A simple explanation to this difference in favor of QAM modulation is that QAm uses both dimensions while PSK only uses the phase. Although MPSK only uses the phase to place the constellation it is not a constant envelope modulation. The signal still "needs" to move from one point to the other. Some methods are known to generate QPSK or rather OQPSK to constant or quasi-constant envelope but in the cost of increasing the spectral mask. Moti
On 01/07/2011 07:37 PM, Deamon wrote:
> Please can anyone give me a pointer to a material that does an in > depth comparison of the 16QAM and 16PSK modulation in terms of > different properties and their SNR vs BER comparison. Any comment > about this modulation comparison would be helpful couldn't turn up > anything using google and even IEEE. > > Thanks
One must ask themselves, "On what basis am I comparing?" In other words, what is important to me? Two common bases are: bandwidth efficiency and power efficiency. This handout from Brian Hughes (part of my information theory class at NCSU) explores this. Especially, see Figure 2.2. http://www.digitalsignallabs.com/modulation.pdf --Randy -- Randy Yates % "My Shangri-la has gone away, fading like Digital Signal Labs % the Beatles on 'Hey Jude'" yates@digitalsignallabs.com % http://www.digitalsignallabs.com % 'Shangri-La', *A New World Record*, ELO