XPost: comp.dsp, sci.crypt, sci.electronics.design   
   From: eric.jacobsen@ieee.org   
      
   On 12/19/2009 7:40 PM, Andrew Swallow wrote:   
   > Eric Jacobsen wrote:   
   >> On 12/19/2009 12:24 PM, Archimedes' Lever wrote:   
   >>> On Fri, 18 Dec 2009 19:04:59 -0600, krw wrote:   
   > {snip}   
   >   
   >>>   
   >>> You're an idiot. Most digital links can handle up to 10 percent bit   
   >>> error rate before correction coding fails to fix it.   
   >>   
   >> Generally not. Raw BER for BPSK at 0dB is less than 10 percent, and   
   >> few codes can operate that far down. Even capacity-approaching codes   
   >> generally need input error rates higher than that.   
   >>   
   >> Can you name a code and what code rate would be required to operate   
   >> with an input BER of 10e-1? I wouldn't think anyone would use a   
   >> deep-space code on a satellite because of bandwidth efficiency issues.   
   >>   
   >   
   > Tactical military links to a mobile destination are being specified   
   > as static civilian links. An error rate of 1 in 10 on a battle   
   > field is far from impossible. The military will simply have to live   
   > with losing half their bandwidth to the FEC. The links also suffer   
   > badly from block errors - a mixture of motor bike engines and   
   > frequency hopping jammers. No need to be paranoid, the jammers have   
   > operators who are out to get you.   
   >   
   > Andrew swallow   
      
   The point was really that even from an advanced FEC standpoint an input   
   BER of 1 in 10 isn't practical to work with for the described   
   application.   Yielding half the bandwidth to FEC overhead is actually   
   practical, and using R = 1/2 coding over satellite channels is quite   
   common.   Using something like an R = 1/6 capacity-approaching code to   
   be able to handle such low input error rates is, I think, not practical.   
      
   So I think there's a lot of misinformation being thrown around this   
   thread, but that's probably not surprising anybody.   
   --   
   Eric Jacobsen   
   Minister of Algorithms   
   Abineau Communications   
   http://www.abineau.com   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)