XPost: comp.dsp, sci.crypt, sci.electronics.design   
   From: spope33@speedymail.org   
      
   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   
      
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