Comp.dsp | Difference Between C/N And SNR And Understanding

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> Hi, > All Experts. I have confusion in understanding the relation between > C/N and SNR. I read through few articles and came up with following > explanations. please correct if i am wrong in my understanding. [Before > that i would like to thank all for posting answers or views on my > questions as it is helping me a lot to understanding your way of > thinking..expert way of thinking..really grateful to all of you]. > > first point > =========== > C/N is measure of UNMODULATED carrier power and noise ratio. SNR is > measure of MODULATED carrier (i.e. carrier with information on it) > power and noise ratio. > > second point > =========== > C/N is basically a RF domain measurement (pre-detected measurements) SNR > is a baseband domain measurement (post detected measurements on baseband > signals)

> > third point [i took it from this link > http://www.insidegnss.com/node/1637] ============ > C/N0 assumes that the noise has infinite bandwidth (and thus power) > and therefore characterizes it using a density, that is, as the amount > of noise power per unit of bandwidth (i.e., watts/Hz) Conversely, SNR > considers the total noise power in a certain bandwidth (i.e., watts). > C/N0 can be derived from SNR if the noise bandwidth of the SNR > measurement is known

> fourth point(this i took from wikipedia) ======== > Digitally modulated signals (e.g. QAM or PSK) are basically made of two > CW carriers (the I and Q components, which are out-of-phase carriers) . > In fact, the information (bits or symbols) is carried by given > combinations of phase and/or amplitude of the I and Q components. It is > for this reason that, in the context of digital modulations, digitally > modulated signals are usually referred to as carriers. Therefore, the > term carrier-to-noise-ratio (CNR), instead of signal-to-noise-ratio > (SNR) is preferred to express the signal quality when the signal has > been digitally modulated. > > ========== > few points finally > 1. so, i would demarcate the mixer as the partition for using the > terminology C/N and SNR. > from antenna to mixer stage, C/N terminology is used and after mixer to > baseband SNR terminology is used. 2. In fourth point, can i conclude SNR > = C/N [as C/N terminology is used in baseband domain]..the reason why i > am asking this is many of IEEE standards specify C/N for digital > modulations [for example 802.11 and 802.16 standard].

>�I hadn't heard the term "C/N ratio" before

>CNR = Carrier to Noise Ratio. For non-suppressed carrier modulation, >like AM, this is the ratio of the unmodulated carrier wave power to >noise. For a signal with no carrier wave (suppressed-carrier signals >like PSK), the carrier power is typically taken as the signal power, >hence CNR = SNR. For PSK there is a rational basis for this, since if >the modulation is removed from the PSK signal (i.e., you stop >modulating it so that it becomes a CW), the modulated spectrum >collapses to a line that has the same total power as the original >modulated signal.

>For AM or FM the signal component of the composite signal + carrier >may not be equal in power level to the carrier component of the >composite signal. In this case CNR != SNR.

> On Jan 11, 11:53&nbsp;am, Tim Wescott <[email protected]> wrote: > >>&nbsp;I hadn't heard the term "C/N ratio" before > > The term C/N ratio *has* been used in the past in this newsgroup, though > not very frequently. Here, for example, is what Eric Jacobsen said once > upon a time in a different avatar than his current one (though not as > ministerially as when he worked for another employer). > >>CNR = Carrier to Noise Ratio. For non-suppressed carrier modulation, >>like AM, this is the ratio of the unmodulated carrier wave power to >>noise. For a signal with no carrier wave (suppressed-carrier signals >>like PSK), the carrier power is typically taken as the signal power, >>hence CNR = SNR. For PSK there is a rational basis for this, since if >>the modulation is removed from the PSK signal (i.e., you stop modulating >>it so that it becomes a CW), the modulated spectrum collapses to a line >>that has the same total power as the original modulated signal. > >>For AM or FM the signal component of the composite signal + carrier may >>not be equal in power level to the carrier component of the composite >>signal. In this case CNR != SNR.

>On Jan 11, 11:53=A0am, Tim Wescott <[email protected]> wrote: > >>=A0I hadn't heard the term "C/N ratio" before > >The term C/N ratio *has* been used in the past in this >newsgroup, though not very frequently. Here, for example, >is what Eric Jacobsen said once upon a time in a different >avatar than his current one (though not as ministerially as >when he worked for another employer). > >>CNR =3D Carrier to Noise Ratio. For non-suppressed carrier modulation, >>like AM, this is the ratio of the unmodulated carrier wave power to >>noise. For a signal with no carrier wave (suppressed-carrier signals >>like PSK), the carrier power is typically taken as the signal power, >>hence CNR =3D SNR. For PSK there is a rational basis for this, since if >>the modulation is removed from the PSK signal (i.e., you stop >>modulating it so that it becomes a CW), the modulated spectrum >>collapses to a line that has the same total power as the original >>modulated signal. > >>For AM or FM the signal component of the composite signal + carrier >>may not be equal in power level to the carrier component of the >>composite signal. In this case CNR !=3D SNR.

> Hi, > &#4294967295; &#4294967295;All Experts. I have confusion in understanding the relation between > C/N and SNR. I read through few articles and came up with following > explanations. please correct if i am wrong in my understanding. > [Before that i would like to thank all for posting answers or views on > my questions as it is helping me a lot to understanding your way of > thinking..expert way of thinking..really grateful to all of you]. > > first point > =========== > C/N is measure of UNMODULATED carrier power and noise ratio. > SNR is measure of MODULATED carrier (i.e. carrier with information on > it) &#4294967295;power and noise ratio. > > second point > =========== > C/N is basically a RF domain measurement (pre-detected measurements) > SNR is a baseband domain measurement (post detected measurements on > baseband signals) > > third point [i took it from this linkhttp://www.insidegnss.com/node/1637] > ============ > &#4294967295;C/N0 assumes that the noise has infinite bandwidth (and thus power) > and therefore characterizes it using a density, that is, as the amount > of noise power per unit of bandwidth (i.e., watts/Hz) > Conversely, SNR considers the total noise power in a certain bandwidth > (i.e., watts). &#4294967295;C/N0 can be derived from SNR if the noise bandwidth of > the SNR measurement is known > > fourth point(this i took from wikipedia) > ======== > Digitally modulated signals (e.g. QAM or PSK) are basically made of > two CW carriers (the I and Q components, which are out-of-phase > carriers) . In fact, the information (bits or symbols) is carried by > given combinations of phase and/or amplitude of the I and Q > components. It is for this reason that, in the context of digital > modulations, digitally modulated signals are usually referred to as > carriers. Therefore, the term carrier-to-noise-ratio (CNR), instead of > signal-to-noise-ratio (SNR) is preferred to express the signal quality > when the signal has been digitally modulated. > > ========== > few points finally > 1. so, i would demarcate the mixer as the partition for using the > terminology C/N and SNR. > from antenna to mixer stage, C/N terminology is used and > after mixer to baseband SNR terminology is used. > 2. In fourth point, can i conclude SNR = C/N [as C/N terminology is > used in baseband domain]..the reason why i am asking this is many of > IEEE standards specify C/N for digital modulations [for example 802.11 > and 802.16 standard]. > > Thanks > aizza ahmed

>>The term C/N ratio *has* been used in the past in this >>newsgroup, though not very frequently. Here, for example, >>is what Eric Jacobsen said once upon a time in a different >>avatar than his current one (though not as ministerially as >>when he worked for another employer).

>>>For AM or FM the signal component of the composite signal + carrier >>>may not be equal in power level to the carrier component of the >>>composite signal. In this case CNR !=3D SNR.

> Thanks for that blast from the past.

> And that's still as good as I can figure out how people use the terms. > Like a lot of terms in technology, people just use these terms and > sometimes they're not universally defined.

> As mentioned (even by the > OP), when it comes to most digitally-modulated signals C/N and SNR are > pretty much interchangeable, and so is EVM. At least I've never been > able to detect any clear differences in the definitions to be able to > point to something and say "that's how it's different than the > others".

> I think most of what the OP posted makes some sense, but I wouldn't > count on the terms being consistently used the way he's described. I > haven't seen most of those definitions before and wouldn't be aware > that somebody thought those distinctions existed formally without them > being explicit about it.