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

# 56 bits out of Binary Input Reed Solomon Encoder

Started by ●November 29, 2007

Reply by ●November 29, 20072007-11-29

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

Reply by ●December 3, 20072007-12-03

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

Reply by ●December 6, 20072007-12-06

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/FFTlength>> > 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 outof>> > 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 theBinary>> > 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 > >