XPost: comp.dsp, sci.crypt, sci.electronics.design
From: jya@ieee.org
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!
Predator, ijit!
Jerry
--
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