Comments on: Convolutional code

By: sundar kharvi

sundar kharvi — Wed, 08 Feb 2012 05:15:42 +0000

hi,
I m doing project on implementation of turbo encoder using VHDL . Can i get information about turbo encoder?

By: Krishna Sankar

Krishna Sankar — Mon, 09 Jan 2012 01:09:16 +0000

@Gheorge: I think that might be a typo. From Digital Communications by John Proakis, Table 8.2.1 , the generator polynomial in octal for constraint length 7, rate1/2 codes are: a) 133_octal = 10000101_binary b) 171_octal = 10101011_binary

By: Gheorghe M.Panaitescu

Gheorghe M.Panaitescu — Sun, 08 Jan 2012 18:04:30 +0000

I found in various places a table containing generator polynomials for convolutional encoding, specifically Table 1-”Generator Polynomials found by Busgang for good rate ½ codes” posted at http://www.complextoreal.com/convo.htm.
That table contains on the line Constraint length = 7 two identical polynomials, G1 = 110101 and G2 = 110101.
I guess this is not possible. The two polynomials must be different.
Does anybody knows the correct polynomials?

By: Krishna Sankar

Krishna Sankar — Tue, 24 May 2011 00:22:53 +0000

@Citra: How are you converting to 2/3 code – by puncturing?

By: Citra

Citra — Sun, 08 May 2011 09:29:31 +0000

Hi Krishna
I’ve seen the program about the convolutional code. What if the rate is replaced 2 / 3 with constraint length 3, kira2x parameters which must be changed? listings that you make there is the theory of maximum likelihood or not? If there is where do? Why should use the AWGN in the form of the complex?
Thank you for your attention.
I look forward to your assistance.

By: Krishna Sankar

Krishna Sankar — Sat, 03 Apr 2010 23:48:08 +0000

@hina: Plz refer Digital Communications by Proakis

By: Krishna Sankar

Krishna Sankar — Mon, 29 Mar 2010 23:26:56 +0000

@manisha: Some relevant links which I picked up from a quick Googling.
(a) Tone reservation : where some of the unused subcarriers in an OFDM system is modulated to reduce the PAPR.
(b) MERL has a paper on PAPR reduction by oversampling, soft clipping and filtering.
PAPR Reduction for WiMAX OFDM Systems
http://www.merl.com/projects/papr/
(c) Nice comp.dsp thread on this topic
Has The peak-to-average ratio problem of OFDM been solved?
http://tinyurl.com/6jn9ql