On 8/5/13 2:59 PM, Vladimir Vassilevsky wrote:> On 8/5/2013 4:04 PM, Randy Yates wrote: >> Vladimir Vassilevsky <nospam@nowhere.com> writes: >> >>> On 8/5/2013 1:39 PM, Randy Yates wrote: >>>> Consider simple BPSK. Should the computation of Eb given the amplitude >>>> of an ideal bit include the effect of pulse-shaping? >>> >>> Of course it should. Eb is average squared distance between "0" and >>> "1". >> >> Vlad: "Yes." Eric: "No." Randy: <head-spin> >> > > Jacobsen thinks if he adds unmodulated component to signal, it somehow > changes Eb.well, Eric, at least i say "Eric". even when we have diametric conclusions. not being a communications guy (but there is a lot in common with general purpose DSP) i surely won't weigh in. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Eb (energy per bit)
Started by ●August 5, 2013
Reply by ●August 5, 20132013-08-05
Reply by ●August 5, 20132013-08-05
On Mon, 05 Aug 2013 19:05:33 -0400, Randy Yates <yates@digitalsignallabs.com> wrote:>Randy Yates <yates@digitalsignallabs.com> writes: > >> eric.jacobsen@ieee.org (Eric Jacobsen) writes: >> >>> On Mon, 05 Aug 2013 17:01:14 -0400, Randy Yates >>> <yates@digitalsignallabs.com> wrote: >>> >>>>eric.jacobsen@ieee.org (Eric Jacobsen) writes: >>>> >>>>> On Mon, 05 Aug 2013 14:39:44 -0400, Randy Yates >>>>> <yates@digitalsignallabs.com> wrote: >>>>> >>>>>>Consider simple BPSK. Should the computation of Eb given the amplitude >>>>>>of an ideal bit include the effect of pulse-shaping? >>>>> >>>>> It generally doesn't. Eb is just the total power divided by the bit >>>>> rate. >>>> >>>>Yeah, but "total power" (over a symbol period) depends on the pulse shape: >>>> >>>> Psym = (1 / Tsym) * \int_{0}^{Tsym} p^2(t) dt >>>> >>>>In fact, isn't Eb just Psym * Tsym (or Psym / R)? So Eb would be >>>> >>>> Eb = \int_{0}^{Tsym} p^2(t) dt >>>> >>>>? >>> >>> The power one cares about managing is the transmit power, which is >>> independent of pulse shape. >> >> Well I'm having a problem with this statement right out of the gate, >> Eric. We are talking about *average* transmit power, right? > >I see now we have failed to communicate. I think what you're trying to >say is that, no matter what the pulse shape is, the transmitter gain >will be bumped up so that maximum power is utilized. Correct?Many systems have adjustable Tx power, so it is whatever it is, and is generally measured as RMS power. Peak power is generally not useful for these metrics since the probability of the max peak may be data and/or modulation dependent, or not relevant to system performance. And, FWIW, since you're asking about pulse-shaped signals where Eb is a relevant metric, I am assuming the general case of a suppressed-carrier signal. If the system has pilot tones or subcarriers or other non-payload-related energy, then your question is not directly answerable because there is no consistent definition of Eb for those cases.>Randy Yates >Digital Signal Labs >http://www.digitalsignallabs.comEric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●August 5, 20132013-08-05
On Mon, 05 Aug 2013 18:56:37 +0000, Eric Jacobsen wrote:> On Mon, 05 Aug 2013 14:39:44 -0400, Randy Yates > <yates@digitalsignallabs.com> wrote: > >>Consider simple BPSK. Should the computation of Eb given the amplitude >>of an ideal bit include the effect of pulse-shaping? > > It generally doesn't. Eb is just the total power divided by the bit > rate. The pulse shape doesn't matter, since since things like Eb/No > are power efficiency metrics. If you make a crappy Rx filter that > causes a lot of ISI, you'll lose power efficiency.Actually, if Eb is the total power divided by the bit rate, then as long as each bit's pulse is orthogonal to all the other bit's pulses (or is so on average), then Eb _is_ taking the pulse shape into account. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●August 5, 20132013-08-05
>On Mon, 05 Aug 2013 19:05:33 -0400, Randy Yates ><yates@digitalsignallabs.com> wrote: > >>Randy Yates <yates@digitalsignallabs.com> writes: >> >>> eric.jacobsen@ieee.org (Eric Jacobsen) writes: >>> >>>> On Mon, 05 Aug 2013 17:01:14 -0400, Randy Yates >>>> <yates@digitalsignallabs.com> wrote: >>>> >>>>>eric.jacobsen@ieee.org (Eric Jacobsen) writes: >>>>> >>>>>> On Mon, 05 Aug 2013 14:39:44 -0400, Randy Yates >>>>>> <yates@digitalsignallabs.com> wrote: >>>>>> >>>>>>>Consider simple BPSK. Should the computation of Eb given theamplitude>>>>>>>of an ideal bit include the effect of pulse-shaping? >>>>>> >>>>>> It generally doesn't. Eb is just the total power divided by thebit>>>>>> rate. >>>>> >>>>>Yeah, but "total power" (over a symbol period) depends on the pulseshape:>>>>> >>>>> Psym = (1 / Tsym) * \int_{0}^{Tsym} p^2(t) dt >>>>> >>>>>In fact, isn't Eb just Psym * Tsym (or Psym / R)? So Eb would be >>>>> >>>>> Eb = \int_{0}^{Tsym} p^2(t) dt >>>>> >>>>>? >>>> >>>> The power one cares about managing is the transmit power, which is >>>> independent of pulse shape. >>> >>> Well I'm having a problem with this statement right out of the gate, >>> Eric. We are talking about *average* transmit power, right? >> >>I see now we have failed to communicate. I think what you're trying to >>say is that, no matter what the pulse shape is, the transmitter gain >>will be bumped up so that maximum power is utilized. Correct? > >Many systems have adjustable Tx power, so it is whatever it is, and is >generally measured as RMS power. Peak power is generally not useful >for these metrics since the probability of the max peak may be data >and/or modulation dependent, or not relevant to system performance. > >And, FWIW, since you're asking about pulse-shaped signals where Eb is >a relevant metric, I am assuming the general case of a >suppressed-carrier signal. If the system has pilot tones or >subcarriers or other non-payload-related energy, then your question is >not directly answerable because there is no consistent definition of >Eb for those cases.I'm still not sure what you are trying to say. Have you answered in this way because Randy specifically asked about PSK? Whatever you do with the pulse shaping for PSK you don't affect the power, as its a constant power modulation. So, the Eb is simply transmitter joules per second/bits per second. However, for modulations like QAM the pulse shaping affects the transmitted energy per bit. Regards, Steve _____________________________ Posted through www.DSPRelated.com
Reply by ●August 5, 20132013-08-05
On Mon, 05 Aug 2013 19:21:44 -0500, "steveu" <31473@dsprelated> wrote:>>On Mon, 05 Aug 2013 19:05:33 -0400, Randy Yates >><yates@digitalsignallabs.com> wrote: >> >>>Randy Yates <yates@digitalsignallabs.com> writes: >>> >>>> eric.jacobsen@ieee.org (Eric Jacobsen) writes: >>>> >>>>> On Mon, 05 Aug 2013 17:01:14 -0400, Randy Yates >>>>> <yates@digitalsignallabs.com> wrote: >>>>> >>>>>>eric.jacobsen@ieee.org (Eric Jacobsen) writes: >>>>>> >>>>>>> On Mon, 05 Aug 2013 14:39:44 -0400, Randy Yates >>>>>>> <yates@digitalsignallabs.com> wrote: >>>>>>> >>>>>>>>Consider simple BPSK. Should the computation of Eb given the >amplitude >>>>>>>>of an ideal bit include the effect of pulse-shaping? >>>>>>> >>>>>>> It generally doesn't. Eb is just the total power divided by the >bit >>>>>>> rate. >>>>>> >>>>>>Yeah, but "total power" (over a symbol period) depends on the pulse >shape: >>>>>> >>>>>> Psym = (1 / Tsym) * \int_{0}^{Tsym} p^2(t) dt >>>>>> >>>>>>In fact, isn't Eb just Psym * Tsym (or Psym / R)? So Eb would be >>>>>> >>>>>> Eb = \int_{0}^{Tsym} p^2(t) dt >>>>>> >>>>>>? >>>>> >>>>> The power one cares about managing is the transmit power, which is >>>>> independent of pulse shape. >>>> >>>> Well I'm having a problem with this statement right out of the gate, >>>> Eric. We are talking about *average* transmit power, right? >>> >>>I see now we have failed to communicate. I think what you're trying to >>>say is that, no matter what the pulse shape is, the transmitter gain >>>will be bumped up so that maximum power is utilized. Correct? >> >>Many systems have adjustable Tx power, so it is whatever it is, and is >>generally measured as RMS power. Peak power is generally not useful >>for these metrics since the probability of the max peak may be data >>and/or modulation dependent, or not relevant to system performance. >> >>And, FWIW, since you're asking about pulse-shaped signals where Eb is >>a relevant metric, I am assuming the general case of a >>suppressed-carrier signal. If the system has pilot tones or >>subcarriers or other non-payload-related energy, then your question is >>not directly answerable because there is no consistent definition of >>Eb for those cases. > >I'm still not sure what you are trying to say. Have you answered in this >way because Randy specifically asked about PSK? Whatever you do with the >pulse shaping for PSK you don't affect the power, as its a constant power >modulation. So, the Eb is simply transmitter joules per second/bits per >second. However, for modulations like QAM the pulse shaping affects the >transmitted energy per bit.Even for QAM Eb = total power/bit rate. Pulse shaping doesn't affect that. And by "bit rate" we mean the bit rate that matters to the measurement. e.g., If it's for payload, then it's information bit rate and even includes the effect of the FEC code rate. Otherwise it might be the uncoded bit rate that comes out of the slicer. Regardless, pulse shape doesn't matter in the measurement for PSK or QAM.>Regards, >Steve > >_____________________________ >Posted through www.DSPRelated.comEric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●August 5, 20132013-08-05
On Mon, 05 Aug 2013 19:14:00 -0500, Tim Wescott <tim@seemywebsite.really> wrote:>On Mon, 05 Aug 2013 18:56:37 +0000, Eric Jacobsen wrote: > >> On Mon, 05 Aug 2013 14:39:44 -0400, Randy Yates >> <yates@digitalsignallabs.com> wrote: >> >>>Consider simple BPSK. Should the computation of Eb given the amplitude >>>of an ideal bit include the effect of pulse-shaping? >> >> It generally doesn't. Eb is just the total power divided by the bit >> rate. The pulse shape doesn't matter, since since things like Eb/No >> are power efficiency metrics. If you make a crappy Rx filter that >> causes a lot of ISI, you'll lose power efficiency. > >Actually, if Eb is the total power divided by the bit rate, then as long >as each bit's pulse is orthogonal to all the other bit's pulses (or is so >on average), then Eb _is_ taking the pulse shape into account.In a sense, yes. But measuring Eb, which is what Randy asked about, can be and is usually done independent of the pulse shape and even ignorant of the pulse shape. To me that means it's not taken into account because it isn't part of the measurement.>-- > >Tim Wescott >Wescott Design Services >http://www.wescottdesign.com >Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●August 5, 20132013-08-05
eric.jacobsen@ieee.org (Eric Jacobsen) writes:> On Mon, 05 Aug 2013 19:14:00 -0500, Tim Wescott > <tim@seemywebsite.really> wrote: > >>On Mon, 05 Aug 2013 18:56:37 +0000, Eric Jacobsen wrote: >> >>> On Mon, 05 Aug 2013 14:39:44 -0400, Randy Yates >>> <yates@digitalsignallabs.com> wrote: >>> >>>>Consider simple BPSK. Should the computation of Eb given the amplitude >>>>of an ideal bit include the effect of pulse-shaping? >>> >>> It generally doesn't. Eb is just the total power divided by the bit >>> rate. The pulse shape doesn't matter, since since things like Eb/No >>> are power efficiency metrics. If you make a crappy Rx filter that >>> causes a lot of ISI, you'll lose power efficiency. >> >>Actually, if Eb is the total power divided by the bit rate, then as long >>as each bit's pulse is orthogonal to all the other bit's pulses (or is so >>on average), then Eb _is_ taking the pulse shape into account. > > In a sense, yes. > > But measuring Eb, which is what Randy asked about, ...Ah, but that is not what I asked about. I asked about *computing* Eb. Let me ask it another way. Let's say I want to generate an ideal, pulse-shaped BPSK signal with a specified Eb. How do I know how to relate the signal's peak value (we can call it A) to Eb? Does that relationship depend on the pulse shape? -- Randy Yates Digital Signal Labs http://www.digitalsignallabs.com
Reply by ●August 5, 20132013-08-05
Randy Yates <yates@digitalsignallabs.com> writes:> eric.jacobsen@ieee.org (Eric Jacobsen) writes: > >> On Mon, 05 Aug 2013 19:14:00 -0500, Tim Wescott >> <tim@seemywebsite.really> wrote: >> >>>On Mon, 05 Aug 2013 18:56:37 +0000, Eric Jacobsen wrote: >>> >>>> On Mon, 05 Aug 2013 14:39:44 -0400, Randy Yates >>>> <yates@digitalsignallabs.com> wrote: >>>> >>>>>Consider simple BPSK. Should the computation of Eb given the amplitude >>>>>of an ideal bit include the effect of pulse-shaping? >>>> >>>> It generally doesn't. Eb is just the total power divided by the bit >>>> rate. The pulse shape doesn't matter, since since things like Eb/No >>>> are power efficiency metrics. If you make a crappy Rx filter that >>>> causes a lot of ISI, you'll lose power efficiency. >>> >>>Actually, if Eb is the total power divided by the bit rate, then as long >>>as each bit's pulse is orthogonal to all the other bit's pulses (or is so >>>on average), then Eb _is_ taking the pulse shape into account. >> >> In a sense, yes. >> >> But measuring Eb, which is what Randy asked about, ... > > Ah, but that is not what I asked about. I asked about *computing* Eb. > > Let me ask it another way. Let's say I want to generate an ideal, > pulse-shaped BPSK signal with a specified Eb. How do I know how to > relate the signal's peak value (we can call it A) to Eb? Does that > relationship depend on the pulse shape?If you want to get picky about units, assume A is in volts and we are driving a resistance of 1 ohm. -- Randy Yates Digital Signal Labs http://www.digitalsignallabs.com
Reply by ●August 5, 20132013-08-05
Randy Yates <yates@digitalsignallabs.com> writes:> eric.jacobsen@ieee.org (Eric Jacobsen) writes: > >> On Mon, 05 Aug 2013 19:14:00 -0500, Tim Wescott >> <tim@seemywebsite.really> wrote: >> >>>On Mon, 05 Aug 2013 18:56:37 +0000, Eric Jacobsen wrote: >>> >>>> On Mon, 05 Aug 2013 14:39:44 -0400, Randy Yates >>>> <yates@digitalsignallabs.com> wrote: >>>> >>>>>Consider simple BPSK. Should the computation of Eb given the amplitude >>>>>of an ideal bit include the effect of pulse-shaping? >>>> >>>> It generally doesn't. Eb is just the total power divided by the bit >>>> rate. The pulse shape doesn't matter, since since things like Eb/No >>>> are power efficiency metrics. If you make a crappy Rx filter that >>>> causes a lot of ISI, you'll lose power efficiency. >>> >>>Actually, if Eb is the total power divided by the bit rate, then as long >>>as each bit's pulse is orthogonal to all the other bit's pulses (or is so >>>on average), then Eb _is_ taking the pulse shape into account. >> >> In a sense, yes. >> >> But measuring Eb, which is what Randy asked about, ... > > Ah, but that is not what I asked about. I asked about *computing* Eb. > > Let me ask it another way. Let's say I want to generate an ideal, > pulse-shaped BPSK signal with a specified Eb. How do I know how to > relate the signal's peak value (we can call it A) to Eb? Does that > relationship depend on the pulse shape?Or, given a pulse-shaped ideal BPSK signal with peak A, what is its Eb? -- Randy Yates Digital Signal Labs http://www.digitalsignallabs.com
Reply by ●August 5, 20132013-08-05
Randy Yates <yates@digitalsignallabs.com> writes:> Randy Yates <yates@digitalsignallabs.com> writes: > >> eric.jacobsen@ieee.org (Eric Jacobsen) writes: >> >>> On Mon, 05 Aug 2013 19:14:00 -0500, Tim Wescott >>> <tim@seemywebsite.really> wrote: >>> >>>>On Mon, 05 Aug 2013 18:56:37 +0000, Eric Jacobsen wrote: >>>> >>>>> On Mon, 05 Aug 2013 14:39:44 -0400, Randy Yates >>>>> <yates@digitalsignallabs.com> wrote: >>>>> >>>>>>Consider simple BPSK. Should the computation of Eb given the amplitude >>>>>>of an ideal bit include the effect of pulse-shaping? >>>>> >>>>> It generally doesn't. Eb is just the total power divided by the bit >>>>> rate. The pulse shape doesn't matter, since since things like Eb/No >>>>> are power efficiency metrics. If you make a crappy Rx filter that >>>>> causes a lot of ISI, you'll lose power efficiency. >>>> >>>>Actually, if Eb is the total power divided by the bit rate, then as long >>>>as each bit's pulse is orthogonal to all the other bit's pulses (or is so >>>>on average), then Eb _is_ taking the pulse shape into account. >>> >>> In a sense, yes. >>> >>> But measuring Eb, which is what Randy asked about, ... >> >> Ah, but that is not what I asked about. I asked about *computing* Eb. >> >> Let me ask it another way. Let's say I want to generate an ideal, >> pulse-shaped BPSK signal with a specified Eb. How do I know how to >> relate the signal's peak value (we can call it A) to Eb? Does that >> relationship depend on the pulse shape? > > Or, given a pulse-shaped ideal BPSK signal with peak A, what is its Eb?In these last two posts, instead of saying the _signal_, I should have stated the _pulse_. That is, A is the peak value of the pulse. -- Randy Yates Digital Signal Labs http://www.digitalsignallabs.com
