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Discussion Groups | Matlab DSP | channel coding in flat fading

Technical discussion about Matlab and issues related to Digital Signal Processing.

  

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channel coding in flat fading - sairamesh90 - Oct 15 2:33:00 2004





Hi,
I am implementing a channel coding scheme, and i got the standard
BER plots in AWGN chanels, now i am testing the coding scheme in
Rayleigh flat fading channels. But I did not got any performance
improvement compared to the uncoded system(BPSK) in flat fading channels.
Now I am wondering whether to I have to design an interleaver to get
good performance(Is it essential??).
Does any one simulated any coding scheme(BCH, Conv. code, etc) and
tested the performance with/without interleaver in flat fading
chanenls(Rayleigh)??
Help in this regard is highly appreciated!
Regards,
-SaiRamesh.






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Re: channel coding in flat fading - Tarang Dadia - Oct 15 16:45:00 2004


Sairamesh,

What channel coding schemes are you using?? wht is the code rate.??

I would recommend you to first check your channel coding scheme in
AWGN channel and compare with your BER perf obtained for uncoded case
in AWGN channel. Doing that u can atleast be sure that your channel
coding algorithm works well.

Hope this helps.
Tarang On Fri, 15 Oct 2004 02:33:27 -0000, sairamesh90 <> wrote: > Hi,
> I am implementing a channel coding scheme, and i got the standard
> BER plots in AWGN chanels, now i am testing the coding scheme in
> Rayleigh flat fading channels. But I did not got any performance
> improvement compared to the uncoded system(BPSK) in flat fading channels.
> Now I am wondering whether to I have to design an interleaver to get
> good performance(Is it essential??).
> Does any one simulated any coding scheme(BCH, Conv. code, etc) and
> tested the performance with/without interleaver in flat fading
> chanenls(Rayleigh)??
> Help in this regard is highly appreciated!
> Regards,
> -SaiRamesh. > _____________________________________
> /groups.php3 >
> Yahoo! Groups Sponsor
>
> ADVERTISEMENT > ________________________________
> Yahoo! Groups Links
>
> To






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Re: channel coding in flat fading - Tarang Dadia - Oct 16 16:29:00 2004


I know u mite b doing it properly...but just wanted to make sure that
u r comparing against proper result. so are you comparing with uncoded
case in rayleigh to coded case. or r u comparing ur coded case in
rayleigh to uncoded case in AWGN?
do let me know
Tarang On Fri, 15 Oct 2004 23:51:53 -0700 (PDT), nammi sairamesh
<> wrote:
> Tarang,
> I am using a family of product code with a
> code rate of .75. I got exact performance in AWGN
> chnanels. with a significant performance gain. But in
> Rayleigh fading I am not getting any gain without any
> Interleaver.
> Best Regards,
> -SaiRamesh. > --- Tarang Dadia <> wrote:
>
> > Sairamesh,
> >
> > What channel coding schemes are you using?? wht is
> > the code rate.??
> >
> > I would recommend you to first check your channel
> > coding scheme in
> > AWGN channel and compare with your BER perf obtained
> > for uncoded case
> > in AWGN channel. Doing that u can atleast be sure
> > that your channel
> > coding algorithm works well.
> >
> > Hope this helps.
> > Tarang
> >
> >
> > On Fri, 15 Oct 2004 02:33:27 -0000, sairamesh90
> > <> wrote:
> > >
> > >
> > > Hi,
> > > I am implementing a channel coding scheme,
> > and i got the standard
> > > BER plots in AWGN chanels, now i am testing the
> > coding scheme in
> > > Rayleigh flat fading channels. But I did not got
> > any performance
> > > improvement compared to the uncoded system(BPSK)
> > in flat fading channels.
> > > Now I am wondering whether to I have to design an
> > interleaver to get
> > > good performance(Is it essential??).
> > > Does any one simulated any coding scheme(BCH,
> > Conv. code, etc) and
> > > tested the performance with/without interleaver in
> > flat fading
> > > chanenls(Rayleigh)??
> > > Help in this regard is highly appreciated!
> > > Regards,
> > > -SaiRamesh.
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > _____________________________________
> > > /groups.php3
> > >
> > >
> > >
> > > Yahoo! Groups Sponsor
> > >
> > > ADVERTISEMENT
> > >
> > >
> > > ________________________________
> > > Yahoo! Groups Links
> > >
> > > To
> > _______________________________



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Re: channel coding in flat fading - raja venkat - Oct 24 13:36:00 2004


hi;
 
i dont think that an interleaver would perform in an dynamic enviroinment which i guess u r tryin to simulate. i would advice u to go for an LMS filter or something like that which would work just fine and the performance would increase drastically. u can also goahead and design some other kiind of simple adaptive filter to countaertact the effect of the noise .......
 
lemme know if any further quiries ..........
Tarang Dadia <t...@gmail.com> wrote:

Sairamesh,

What channel coding schemes are you using?? wht is the code rate.??

I would recommend you to first check your channel coding scheme in
AWGN channel and compare with your BER perf obtained for uncoded case
in  AWGN channel. Doing that u can atleast be sure that your channel
coding algorithm works well.

Hope this helps.
TarangOn Fri, 15 Oct 2004 02:33:27 -0000, sairamesh90 <s...@yahoo.com> wrote:> Hi,
>     I am implementing a  channel coding scheme, and i got the standard
> BER plots in AWGN chanels, now i am testing the coding scheme in
> Rayleigh flat fading channels.  But I did not got any performance
> improvement compared to  the uncoded system(BPSK) in flat fading channels.
> Now I  am wondering whether to I have to design an interleaver to get
> good performance(Is it essential??).
> Does any one simulated any coding scheme(BCH, Conv. code, etc) and
> tested the performance with/without interleaver in flat fading
> chanenls(Rayleigh)??
> Help in this regard is highly appreciated!
> Regards,
> -SaiRamesh.> _____________________________________
> /groups.php3>
> Yahoo! Groups Sponsor
>
> ADVERTISEMENT> ________________________________
> Yahoo! Groups Links
>
> To


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Re: channel coding in flat fading - Tarang Dadia - Oct 24 16:24:00 2004


Raja,

Interleavers are introduce in the system in order to increase the
performance in such dynamic environment.

Tarang On Sun, 24 Oct 2004 14:36:17 +0100 (BST), raja venkat
<> wrote: > hi;
>
> i dont think that an interleaver would perform in an dynamic enviroinment
> which i guess u r tryin to simulate. i would advice u to go for an LMS
> filter or something like that which would work just fine and the performance
> would increase drastically. u can also goahead and design some other kiind
> of simple adaptive filter to countaertact the effect of the noise .......
>
> lemme know if any further quiries ..........
> Tarang Dadia <> wrote:
>
> Sairamesh,
>
> What channel coding schemes are you using?? wht is the code rate.??
>
> I would recommend you to first check your channel coding scheme in
> AWGN channel and compare with your BER perf obtained for uncoded case
> in AWGN channel. Doing that u can atleast be sure that your channel
> coding algorithm works well.
>
> Hope this helps.
> Tarang > On Fri, 15 Oct 2004 02:33:27 -0000, sairamesh90 <>
> wrote:
> >
> >
> > Hi,
> > I am implementing a channel coding scheme, and i got the standard
> > BER plots in AWGN chanels, now i am testing the coding scheme in
> > Rayleigh flat fading channels. But I did not got any performance
> > improvement compared to the uncoded system(BPSK) in flat fading channels.
> > Now I am wondering whether to I have to design an interleaver to get
> > good performance(Is it essential??).
> > Does any one simulated any coding scheme(BCH, Conv. code, etc) and
> > tested the performance with/without interleaver in flat fading
> > chanenls(Rayleigh)??
> > Help in this regard is highly appreciated!
> > Regards,
> > -SaiRamesh.
> >
> >
> >
> >
> >
> >
> >
> >
> > _____________________________________
> > /groups.php3
> >
> >
> >
> > Yahoo! Groups Sponsor
> >
> > ADVERTISEMENT
> >
> >
> > ________________________________
> > Yahoo! Groups Links
> >
> > To > _____________________________________
> /groups.php3 >
> Yahoo! Groups Sponsor
>
> ADVERTISEMENT > ________________________________
> Yahoo! Groups Links
>
> To > Yahoo! India Matrimony: Find your life partner online.





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Re: channel coding in flat fading - nammi sairamesh - Oct 24 18:33:00 2004


Raja,
Thanks for your suggestion! This is a flat
fading channel! so the channel is just a single tap!
I found few claws in your ideas, as

1. Adaptive filter needs training?? who is going to
train symbols?
2. Implementation of adaptive filter is costly.
3. No book on digital comunication specifies that we
have to use adaptive filter to mitigate the effects of
fading!!!
But , i can understand we have to use one kind of
filtering (Equlaizer) to mitigate the effects of
frequency selective fading (number of taps in the
channel >1). That too the system is perfect only with
the full CSI(channel state information).
I don't think it is a good option than using an
interleaver!
Regards,
-SaiRamesh. --- raja venkat <> wrote: > hi;
>
> i dont think that an interleaver would perform in an
> dynamic enviroinment which i guess u r tryin to
> simulate. i would advice u to go for an LMS filter
> or something like that which would work just fine
> and the performance would increase drastically. u
> can also goahead and design some other kiind of
> simple adaptive filter to countaertact the effect of
> the noise .......
>
> lemme know if any further quiries ..........
> Tarang Dadia <> wrote:
>
> Sairamesh,
>
> What channel coding schemes are you using?? wht is
> the code rate.??
>
> I would recommend you to first check your channel
> coding scheme in
> AWGN channel and compare with your BER perf obtained
> for uncoded case
> in AWGN channel. Doing that u can atleast be sure
> that your channel
> coding algorithm works well.
>
> Hope this helps.
> Tarang > On Fri, 15 Oct 2004 02:33:27 -0000, sairamesh90
> <> wrote:
> >
> >
> > Hi,
> > I am implementing a channel coding scheme,
> and i got the standard
> > BER plots in AWGN chanels, now i am testing the
> coding scheme in
> > Rayleigh flat fading channels. But I did not got
> any performance
> > improvement compared to the uncoded system(BPSK)
> in flat fading channels.
> > Now I am wondering whether to I have to design an
> interleaver to get
> > good performance(Is it essential??).
> > Does any one simulated any coding scheme(BCH,
> Conv. code, etc) and
> > tested the performance with/without interleaver in
> flat fading
> > chanenls(Rayleigh)??
> > Help in this regard is highly appreciated!
> > Regards,
> > -SaiRamesh.
> >
> >
> >
> >
> >
> >
> >
> >
> > _____________________________________
> > /groups.php3
> >
> >
> >
> > Yahoo! Groups Sponsor
> >
> > ADVERTISEMENT
> >
> >
> > ________________________________
> > Yahoo! Groups Links
> >
> > To > _____________________________________
> /groups.php3 > Yahoo! Groups SponsorADVERTISEMENT > ---------------------------------
> Yahoo! Groups Links
>
> To > Yahoo! India Matrimony: Find your life
partneronline.

_______________________________






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Re: channel coding in flat fading - Karthik Subramanian - Oct 26 3:46:00 2004


Hi Sairamesh,

Most practical wireless systems will use *both* error
control coding (WITH an interleaver) and an (adaptive)
equalizer.

No basic book tells you to use adaptive equalizers,
you're right - but it kind of makes common sense, if
your channel changes, so should your equalizer! So you
can either choose to periodically estimate the channel
and keep the equalizer constant till the next time you
estimate the channel, or to use an adaptation
algorithm to update your equalizer between channel
estimates.

Most practical wireless systems also have training
symbols for training the equalizer. For instance, the
preamble in 802.11b has a nice periodic structure and
can be used to train the equalizer.

You never ever get complete CSI in any practical
system. You have to make do with what you get!

I don't think it's wise to hope to beat the channel
with just error control coding, even if it's just a
one-tap channel. You need both coding *and*
equalization. Think of it this way - the equalization
helps you bring the equivalent channel at the receiver
as close as possible to an AWGN channel, and the
coding performs better than it would in the
unequalized channel.

Regards,
Karthik.

--- nammi sairamesh <> wrote: > Raja,
> Thanks for your suggestion! This is a flat
> fading channel! so the channel is just a single tap!
>
> I found few claws in your ideas, as
>
> 1. Adaptive filter needs training?? who is going to
> train symbols?
> 2. Implementation of adaptive filter is costly.
> 3. No book on digital comunication specifies that we
> have to use adaptive filter to mitigate the effects
> of
> fading!!!
> But , i can understand we have to use one kind of
> filtering (Equlaizer) to mitigate the effects of
> frequency selective fading (number of taps in the
> channel >1). That too the system is perfect only
> with
> the full CSI(channel state information).
> I don't think it is a good option than using an
> interleaver!
> Regards,
> -SaiRamesh. > --- raja venkat <>
> wrote:
>
> >
> > hi;
> >
> > i dont think that an interleaver would perform in
> an
> > dynamic enviroinment which i guess u r tryin to
> > simulate. i would advice u to go for an LMS filter
> > or something like that which would work just fine
> > and the performance would increase drastically. u
> > can also goahead and design some other kiind of
> > simple adaptive filter to countaertact the effect
> of
> > the noise .......
> >
> > lemme know if any further quiries ..........
> > Tarang Dadia <> wrote:
> >
> > Sairamesh,
> >
> > What channel coding schemes are you using?? wht is
> > the code rate.??
> >
> > I would recommend you to first check your channel
> > coding scheme in
> > AWGN channel and compare with your BER perf
> obtained
> > for uncoded case
> > in AWGN channel. Doing that u can atleast be sure
> > that your channel
> > coding algorithm works well.
> >
> > Hope this helps.
> > Tarang
> >
> >
> > On Fri, 15 Oct 2004 02:33:27 -0000, sairamesh90
> > <> wrote:
> > >
> > >
> > > Hi,
> > > I am implementing a channel coding scheme,
> > and i got the standard
> > > BER plots in AWGN chanels, now i am testing the
> > coding scheme in
> > > Rayleigh flat fading channels. But I did not
> got
> > any performance
> > > improvement compared to the uncoded
> system(BPSK)
> > in flat fading channels.
> > > Now I am wondering whether to I have to design
> an
> > interleaver to get
> > > good performance(Is it essential??).
> > > Does any one simulated any coding scheme(BCH,
> > Conv. code, etc) and
> > > tested the performance with/without interleaver
> in
> > flat fading
> > > chanenls(Rayleigh)??
> > > Help in this regard is highly appreciated!
> > > Regards,
> > > -SaiRamesh.
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > _____________________________________
> > > /groups.php3
> > >
> > >
> > >
> > > Yahoo! Groups Sponsor
> > >
> > > ADVERTISEMENT
> > >
> > >
> > > ________________________________
> > > Yahoo! Groups Links
> > >
> > > To
> >
> >
> >
> >
> >
> > _____________________________________
> > /groups.php3
> >
> >
> > Yahoo! Groups SponsorADVERTISEMENT
> >
> >
> > ---------------------------------
> > Yahoo! Groups Links
> >
> > To
> >
> >
> > Yahoo! India Matrimony: Find your life
> partneronline. >
>
> _______________________________
> ">http://mail.yahoo.com





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