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56 bits out of Binary Input Reed Solomon Encoder

Started by Rohith November 29, 2007
Hello,

  I am trying to implement a COFDM System which has an IFFT/FFT length
of 64. Out of 64 carriers, 8 are set aside for nulls and pilots (56
remaining).

   So, out of Reed Solomon encoder I want to get 56 bits which will
then be convolutionally encoded and modulated using QPSK before
presenting them as inputs to the IFFT. So, in order to 56 bits out of
the Reed Solomon Encoder, I was planning on using a coding structure
of (7,3,2).

  But when I implement this in simulink, the number of samples per
frame that I can present as the input to the RS Encoder has to be a
multiple of 9.

  My question is: Is there any way I can get 56 bits out of the Binary
Input RS Encoder?

Thanks,
Rohith


Rohith wrote:

> Hello, > > I am trying to implement a COFDM System which has an IFFT/FFT length > of 64. Out of 64 carriers, 8 are set aside for nulls and pilots (56 > remaining). > > So, out of Reed Solomon encoder I want to get 56 bits which will > then be convolutionally encoded and modulated using QPSK before > presenting them as inputs to the IFFT. So, in order to 56 bits out of > the Reed Solomon Encoder, I was planning on using a coding structure > of (7,3,2). > > But when I implement this in simulink, the number of samples per > frame that I can present as the input to the RS Encoder has to be a > multiple of 9. > > My question is: Is there any way I can get 56 bits out of the Binary > Input RS Encoder?
n^(n-1) ~ 2^56 If you insist on RS code in GF(2^n), then the closest block size would be 15 symbols in the GF(16) Homework? VLV
Actually assuming shortended RS codes are acceptable, then pretty
much any length code and symbol size that can generate a 56-bit
output can be used.


Arash Partow
__________________________________________________
Be one who knows what they don't know,
Instead of being one who knows not what they don't know,
Thinking they know everything about all things.
http://www.partow.net



On Nov 29, 6:52 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
wrote:
> Rohith wrote: > > Hello, > > > I am trying to implement a COFDM System which has an IFFT/FFT length > > of 64. Out of 64 carriers, 8 are set aside for nulls and pilots (56 > > remaining). > > > So, out ofReed Solomonencoder I want to get 56 bits which will > > then be convolutionally encoded and modulated using QPSK before > > presenting them as inputs to the IFFT. So, in order to 56 bits out of > > theReed SolomonEncoder, I was planning on using a coding structure > > of (7,3,2). > > > But when I implement this in simulink, the number of samples per > > frame that I can present as the input to the RS Encoder has to be a > > multiple of 9. > > > My question is: Is there any way I can get 56 bits out of the Binary > > Input RS Encoder? > > n^(n-1) ~ 2^56 > > If you insist on RS code in GF(2^n), then the closest block size would > be 15 symbols in the GF(16) > > Homework? > > VLV
Hello,

   Well...I was able to get it by using different primitive and generator
polynomials. The thing is, my shortened code version had the same numbers
as an actual RS code (7,3). So, I had to use different polynomials. 

  Thanks for the replies.

-Rohith

>Actually assuming shortended RS codes are acceptable, then pretty >much any length code and symbol size that can generate a 56-bit >output can be used. > > >Arash Partow >__________________________________________________ >Be one who knows what they don't know, >Instead of being one who knows not what they don't know, >Thinking they know everything about all things. >http://www.partow.net > > > >On Nov 29, 6:52 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com> >wrote: >> Rohith wrote: >> > Hello, >> >> > I am trying to implement a COFDM System which has an IFFT/FFT
length
>> > of 64. Out of 64 carriers, 8 are set aside for nulls and pilots (56 >> > remaining). >> >> > So, out ofReed Solomonencoder I want to get 56 bits which will >> > then be convolutionally encoded and modulated using QPSK before >> > presenting them as inputs to the IFFT. So, in order to 56 bits out
of
>> > theReed SolomonEncoder, I was planning on using a coding structure >> > of (7,3,2). >> >> > But when I implement this in simulink, the number of samples per >> > frame that I can present as the input to the RS Encoder has to be a >> > multiple of 9. >> >> > My question is: Is there any way I can get 56 bits out of the
Binary
>> > Input RS Encoder? >> >> n^(n-1) ~ 2^56 >> >> If you insist on RS code in GF(2^n), then the closest block size would >> be 15 symbols in the GF(16) >> >> Homework? >> >> VLV > >