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Main question: - what is the coding gain for a (7,4) Hamming Code? Additional questions: - is there a web resource where tables (or some other format) can be found containing coding gain info for Hamming and or other error correction codes? - are there texts that contain comprehensive tables of good codes and their coding gains? I'm not so interested in exotic codes that are mainly in academia or used for space comms. Regards, Phil

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D. R. E. Blahut, "Error-Correcting Codes for Digital Signal Processing". Is really good as far as I remember - got to be worth a try. Best of Luck - Mike "Phil" <p...@sympatico.ca> wrote in message news:1...@posting.google.com... > Main question: > - what is the coding gain for a (7,4) Hamming Code? > > Additional questions: > - is there a web resource where tables (or some other format) can be > found containing coding gain info for Hamming and or other error > correction codes? > - are there texts that contain comprehensive tables of good codes and > their coding gains? > > I'm not so interested in exotic codes that are mainly in academia or > used for space comms. > > Regards, > Phil

On an AWGN channel, at 10^-9 BER, about 0.5 dB coding gain. It's not a good code for this application. -- Tom "Phil" <p...@sympatico.ca> wrote in message news:1...@posting.google.com... > Main question: > - what is the coding gain for a (7,4) Hamming Code? > > Additional questions: > - is there a web resource where tables (or some other format) can be > found containing coding gain info for Hamming and or other error > correction codes? > - are there texts that contain comprehensive tables of good codes and > their coding gains? > > I'm not so interested in exotic codes that are mainly in academia or > used for space comms. > > Regards, > Phil

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On 22 Sep 2004 17:44:19 -0700, p...@sympatico.ca (Phil) wrote: >Main question: >- what is the coding gain for a (7,4) Hamming Code? As TOM mentioned, in AWGN it's not great. That's such a short code that one shouldn't expect much out of it, but you haven't mentioned an application or an expected channel. We're assuming AWGN. >Additional questions: >- is there a web resource where tables (or some other format) can be >found containing coding gain info for Hamming and or other error >correction codes? >- are there texts that contain comprehensive tables of good codes and >their coding gains? > >I'm not so interested in exotic codes that are mainly in academia or >used for space comms. > >Regards, >Phil Another good reference is Telecommunication Systems Engineering by Lindsey and Simon. It's a hard read, but has a lot of good reference stuff like code tables. I'm not sure whether this code is in there or not. Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org

Good point. I wasn't thinking very clearly when I made my original post. The scenario under consideration is AWGN at a BER = 10^-3 for a coherent BPSK system. I'm going to see if I can get my hands on any of the references over the weekend. Regards, Phil "Eric Jacobsen" <e...@ieee.org> wrote in message news:4...@news.west.cox.net... > On 22 Sep 2004 17:44:19 -0700, p...@sympatico.ca (Phil) > wrote: > > >Main question: > >- what is the coding gain for a (7,4) Hamming Code? > > As TOM mentioned, in AWGN it's not great. That's such a short code > that one shouldn't expect much out of it, but you haven't mentioned an > application or an expected channel. We're assuming AWGN. > > >Additional questions: > >- is there a web resource where tables (or some other format) can be > >found containing coding gain info for Hamming and or other error > >correction codes? > >- are there texts that contain comprehensive tables of good codes and > >their coding gains? > > > >I'm not so interested in exotic codes that are mainly in academia or > >used for space comms. > > > >Regards, > >Phil > > Another good reference is Telecommunication Systems Engineering by > Lindsey and Simon. It's a hard read, but has a lot of good reference > stuff like code tables. I'm not sure whether this code is in there or > not. > > Eric Jacobsen > Minister of Algorithms, Intel Corp. > My opinions may not be Intel's opinions. > http://www.ericjacobsen.org

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"TOM" <n...@noprovider.nodomain> wrote in message news:QAA4d.11969$464.9955@trnddc01... > On an AWGN channel, at 10^-9 BER, about 0.5 dB coding gain. It's not a > good code for this application. > > -- Tom The asymptotic coding gain for a rate R code that corrects t errors is R(t+1) for hard-decision decoding which works out to 8/7 or nearly 0.58 dB for the (7,4) Hamming code.

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On Fri, 24 Sep 2004 10:52:22 -0500, "Dilip V. Sarwate" <s...@YouEyeYouSee.edu> wrote: > >"TOM" <n...@noprovider.nodomain> wrote in message >news:QAA4d.11969$464.9955@trnddc01... >> On an AWGN channel, at 10^-9 BER, about 0.5 dB coding gain. It's not a >> good code for this application. >> >> -- Tom > > >The asymptotic coding gain for a rate R code that corrects t errors >is R(t+1) for hard-decision decoding which works out to 8/7 or >nearly 0.58 dB for the (7,4) Hamming code. Dilip, what do use to do this sort of analysis? I'm always trying to figure out reasonable ways to estimate either capacity or gain as a function of rate and block length. Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org

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"Eric Jacobsen" <e...@ieee.org> wrote in message news:4...@news.west.cox.net... > On Fri, 24 Sep 2004 10:52:22 -0500, "Dilip V. Sarwate" > <s...@YouEyeYouSee.edu> wrote: >>The asymptotic coding gain for a rate R code that corrects t errors >>is R(t+1) for hard-decision decoding which works out to 8/7 or >>nearly 0.58 dB for the (7,4) Hamming code. > > Dilip, what do use to do this sort of analysis? I'm always trying to > figure out reasonable ways to estimate either capacity or gain as a > function of rate and block length. Drawing from R. E. Blahut's Algebraic Codes for Data Transmission book (Cambridge Univ. Press), Chapter 12, the argument is essentially as follows. For DPSK, the BER is exponentially decreasing (of the form exp(-E/No)). However, for coded DPSK, this formula gives the raw error rate on the channel, and the E to be used is actually R.Eb where R is the code rate. If the code corrects t errors, (t << n), then the word error rate (probability decoder output dataword is incorrect) is dominated by the probability that there are t+1 channel errors, which has probability (n choose t+1) p^{t+1} (1-p)^{n-t-1} which is for all practical purposes of the form p^{t+1} = [exp(-R.Eb/No)]^{t+1} = exp(-R(t+1).Eb/No). The BER is bounded above by the word error rate, and so for a given BER specification, the coded system requires an SNR (Eb/No) smaller by a factor R(t+1) which is the coding gain. Hope this helps. (If not, wave hands vigorously while re-reading the argument... :-) )

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Dilip, Thanks for the explanation. I have seen a similar relationship (Gc Rc*dmin) in "Communication Systems Engineering" by Proakis and Salehi, but the 'why' was not clear. I'll be waving my hands this evening when I re-read your post. Phil "Dilip V. Sarwate" <s...@YouEyeYouSee.edu> wrote in message news:cj1pgd$9km$1...@news.ks.uiuc.edu... > > "Eric Jacobsen" <e...@ieee.org> wrote in message > news:4...@news.west.cox.net... > > On Fri, 24 Sep 2004 10:52:22 -0500, "Dilip V. Sarwate" > > <s...@YouEyeYouSee.edu> wrote: > > >>The asymptotic coding gain for a rate R code that corrects t errors > >>is R(t+1) for hard-decision decoding which works out to 8/7 or > >>nearly 0.58 dB for the (7,4) Hamming code. > > > > Dilip, what do use to do this sort of analysis? I'm always trying to > > figure out reasonable ways to estimate either capacity or gain as a > > function of rate and block length. > > Drawing from R. E. Blahut's Algebraic Codes for Data Transmission > book (Cambridge Univ. Press), Chapter 12, the argument is essentially > as follows. For DPSK, the BER is exponentially decreasing (of the form > exp(-E/No)). However, for coded DPSK, this formula gives the raw > error rate on the channel, and the E to be used is actually R.Eb where > R is the code rate. If the code corrects t errors, (t << n), then the word > error rate (probability decoder output dataword is incorrect) is dominated > by the probability that there are t+1 channel errors, which has probability > (n choose t+1) p^{t+1} (1-p)^{n-t-1} which is for all practical purposes > of the form p^{t+1} = [exp(-R.Eb/No)]^{t+1} = exp(-R(t+1).Eb/No). > The BER is bounded above by the word error rate, and so for a given > BER specification, the coded system requires an SNR (Eb/No) > smaller by a factor R(t+1) which is the coding gain. > > Hope this helps. (If not, wave hands vigorously while re-reading the > argument... :-) ) > >

Dilip, Thanks for that. I don't work with (n,k,t) type codes with a fixed correcting capability enough to have thought of this, but it makes sense. For more general codes, like CC or LDPC or whatever, it's still a problem to try to sort this stuff out. Cheers, Eric On Fri, 24 Sep 2004 13:37:01 -0500, "Dilip V. Sarwate" <s...@YouEyeYouSee.edu> wrote: > >"Eric Jacobsen" <e...@ieee.org> wrote in message >news:4...@news.west.cox.net... >> On Fri, 24 Sep 2004 10:52:22 -0500, "Dilip V. Sarwate" >> <s...@YouEyeYouSee.edu> wrote: > >>>The asymptotic coding gain for a rate R code that corrects t errors >>>is R(t+1) for hard-decision decoding which works out to 8/7 or >>>nearly 0.58 dB for the (7,4) Hamming code. >> >> Dilip, what do use to do this sort of analysis? I'm always trying to >> figure out reasonable ways to estimate either capacity or gain as a >> function of rate and block length. > >Drawing from R. E. Blahut's Algebraic Codes for Data Transmission >book (Cambridge Univ. Press), Chapter 12, the argument is essentially >as follows. For DPSK, the BER is exponentially decreasing (of the form >exp(-E/No)). However, for coded DPSK, this formula gives the raw >error rate on the channel, and the E to be used is actually R.Eb where >R is the code rate. If the code corrects t errors, (t << n), then the word >error rate (probability decoder output dataword is incorrect) is dominated >by the probability that there are t+1 channel errors, which has probability >(n choose t+1) p^{t+1} (1-p)^{n-t-1} which is for all practical purposes >of the form p^{t+1} = [exp(-R.Eb/No)]^{t+1} = exp(-R(t+1).Eb/No). >The BER is bounded above by the word error rate, and so for a given >BER specification, the coded system requires an SNR (Eb/No) >smaller by a factor R(t+1) which is the coding gain. > >Hope this helps. (If not, wave hands vigorously while re-reading the >argument... :-) ) > > Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org

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