XPost: comp.dsp, sci.crypt, sci.electronics.design   
   From: spope33@speedymail.org   
      
   Eric Jacobsen   wrote:   
      
   >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.   
      
   You're right in that the rate 1/2 convolutional code (which is   
   very popular for SATCOM and is specified for such use in MIL-STD-188)   
   just misses working at the 10% raw BER channel condition point.   
   For noisier satellite channels it's more popular to lower the signalling   
   rate than it is to lower the code rate.   
      
   (We could also have a philosophical discussion as to whether adding   
   spreading constitutes lowering the code rate...)   
      
   Steve   
      
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