XPost: comp.dsp, sci.crypt, sci.electronics.design   
   From: krw@att.bizzzzzzzzzzz   
      
   On Mon, 21 Dec 2009 16:31:33 -0800, Son of a Sea Cook   
    wrote:   
      
   >On Mon, 21 Dec 2009 15:11:34 -0500, Jerry Avins  wrote:   
   >   
   >>Eric Jacobsen wrote:   
   >>> On 12/21/2009 12:42 PM, Steve Pope wrote:   
   >>>> Eric Jacobsen  wrote:   
   >>>>   
   >>>>> On 12/20/2009 3:42 PM, Steve Pope wrote:   
   >>>>   
   >>>>>> A rate 1/2 coded system operating at an Eb/No of +2 dB has the   
   >>>>>> same raw BER as an uncoded system operating at an Eb/No of -1 dB.   
   >>>>>>   
   >>>>>> A rate 1/3 coded system operating at an Eb/No of +3.77 dB has   
   >>>>>> the same raw BER as an uncoded system operating at -1 dB.   
   >>>>   
   >>>>>> (Unless I'm confused, which has happened before...)   
   >>>>   
   >>>>> Doh!  I think I went the wrong way with the 3db and 4.77dB differences.   
   >>>>> I get stuff like that backwards all the time.   
   >>>>   
   >>>> Okay, we're in sync, even if our hypothetical modem isn't.   
   >>>>   
   >>>>>> I'm not too skeptical.  I would posit that GSM phones in their   
   >>>>>> basic 2G mode operate under conditions this bad, and 802.11 systems   
   >>>>>> at 1 mbps might also.   
   >>>>   
   >>>>> I'm less skeptical now.  ;)   
   >>>>   
   >>>> Right.   
   >>>>   
   >>>> The AWGN channel exhibiting 10% raw BER is still 3 dB less noisy than   
   >>>> rate 1/3 BPSK capacity, and popular binary convolutional   
   >>>> codes generally start functioning when you're 2 dB to 3 dB from capacity.   
   >>>>   
   >>>> The near-channel-capacity codes are generally functional around 1 dB   
   >>>> from capacity, sometimes less.   
   >>>>   
   >>>> Steve   
   >>>   
   >>> Yeah, we're on the same page.  Since the context was a satellite link,   
   >>> I'd still be skeptical that anyone would bother to use an R = 1/3 code   
   >>> over a satellite, just because of the spectral efficiency (since   
   >>> transponder bandwidth is muy expensive).  For R = 1/2, which is more   
   >>> believable, my skepticism remains healthy.   
   >>   
   >>Remember: this is military money. Those birds are $30 million a pop.   
   >>   
   >>Jerry   
   >   
   >   
   >  Yer nuts.  Satellites are $400 million each, and that is a commercial   
   >bird!   
      
   AlwaysWrong gets it wrong once again.  The "bird" in question was the   
   Predator, not the Satellite, DimBulb.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)