Hi all, does anyone know what BER should I expect after the Viterbi decoding if the channel BER is 7.0e-3? Constraint length 7, Generator (177, 133), punturing to code rate 5/6. Thanks! Cheers, Lanbaba
BER performance of Viterbi decoder
Started by ●January 10, 2006
Reply by ●January 10, 20062006-01-10
lanbaba wrote:> Hi all, > > does anyone know what BER should I expect after the Viterbi decoding if > the channel BER is 7.0e-3? Constraint length 7, Generator (177, 133), > punturing to code rate 5/6. Thanks! >Indeed the R = 5/6 K = 7 code looks inadequate for the input BER = 7e-3, and I doubt if there is going to be any BER improvement at all. I would use a code with R ~ 1/2...1/3 for this kind of BER, expecting the improvement about a factor of 10. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Reply by ●January 10, 20062006-01-10
On Tue, 10 Jan 2006 08:08:29 -0600, "lanbaba" <lanbaba@gmx.ch> wrote:>Hi all, > >does anyone know what BER should I expect after the Viterbi decoding if >the channel BER is 7.0e-3? Constraint length 7, Generator (177, 133), >punturing to code rate 5/6. Thanks! > >Cheers, LanbabaThere are a lot of curves available for the (177, 133) code, since it is nearly universally used. I'm assuming you mean for antipodal (BPSK) signalling in AWGN, and that curve shouldn't be too difficult to find. You might try some of the common FEC/ECC textbooks or Lindsay and Simon. Data sheets used to be a good source for this, and perhaps somebody like AHA has it on their website. If I had one handy I'd make it available, but I don't. Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●January 10, 20062006-01-10
>Indeed the R = 5/6 K = 7 code looks inadequate for the input BER = 7e-3, >and I doubt if there is going to be any BER improvement at all. I would >use a code with R ~ 1/2...1/3 for this kind of BER, expecting the >improvement about a factor of 10.Hi Vladimir, actually I share your view. But when I saw a performance curve of the Xilinx Viterbi decoder I was a bit surprised. In Figure 29 of their data sheet in www.xilinx.com/bvdocs/ipcenter/data_sheet/viterbi.pdf a large gain is achieved for channel BER 7e-3 even with code rate 7/8! Any advice? Cheers, Zhenlan
Reply by ●January 10, 20062006-01-10
>You might try some of the common FEC/ECC textbooks or Lindsay and >Simon. Data sheets used to be a good source for this, and perhaps >somebody like AHA has it on their website. >Eric, Who/what is AHA? Lanbaba
Reply by ●January 10, 20062006-01-10
lanbaba wrote:>>Indeed the R = 5/6 K = 7 code looks inadequate for the input BER = 7e-3, >>and I doubt if there is going to be any BER improvement at all. I would >>use a code with R ~ 1/2...1/3 for this kind of BER, expecting the >>improvement about a factor of 10. > > > Hi Vladimir, > > actually I share your view. But when I saw a performance curve of the > Xilinx Viterbi decoder I was a bit surprised. In Figure 29 of their data > sheet in www.xilinx.com/bvdocs/ipcenter/data_sheet/viterbi.pdf a large > gain is achieved for channel BER 7e-3 even with code rate 7/8! Any > advice?From fig.29 it is clear that the 7/8 code actually results in the loss in BER at the channel BER = 7e-3, and this is what is anticipated. VLV
Reply by ●January 11, 20062006-01-11
> From fig.29 it is clear that the 7/8 code actually results in the loss >in BER at the channel BER = 7e-3, and this is what is anticipated. > >VLV >Sorry, but why that? In Fig. 29 of the Xilinx data sheet, the coded BER is about 0.0008 with code rate 7/8 for uncoded BER = 0.007, 10 times lower, or do I see something fundamentally wrong? LBB
Reply by ●January 11, 20062006-01-11
I wrote a small matlab program and get coded BER = 0.0110 for uncoded BER =
0.0078 for the aformentioned code with hard decision Viterbi. This verifies
Vladimir's statement. Still wondering about Xilinx's data sheet.
LBB
Reply by ●January 11, 20062006-01-11
On Tue, 10 Jan 2006 16:12:16 -0600, "lanbaba" <lanbaba@gmx.ch> wrote:> >>You might try some of the common FEC/ECC textbooks or Lindsay and >>Simon. Data sheets used to be a good source for this, and perhaps >>somebody like AHA has it on their website. >> > >Eric, > >Who/what is AHA? > >Lanbabawww.aha.com Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●January 11, 20062006-01-11
lanbaba wrote:> > From fig.29 it is clear that the 7/8 code actually results in the loss > >in BER at the channel BER = 7e-3, and this is what is anticipated. > > > >VLV > > > > Sorry, but why that? In Fig. 29 of the Xilinx data sheet, the coded BER is > about 0.0008 with code rate 7/8 for uncoded BER = 0.007, 10 times lower, or > do I see something fundamentally wrong? > > LBBThats what I see also.... I see approx 2dB gain????? please explain.... Mark
