Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

Thread Subject:
tblen parameter in vitdec function

Subject: tblen parameter in vitdec function

From: C?sar Ghali

Date: 9 Jan, 2009 15:08:03

Message: 1 of 2

Dear friends,

I am developing a frame-based simulation that uses a viterbi decoder. I found that the vitdec function takes tblen as a parameter and I didn't know what to put as a best value for this parameter. I noticed that changing the value of this parameter will affect the result BER curve, in other words, I got different SNRs for BER = 1e-3. Is this logical and what is the best value for tblen?

Thanks in advance for your help.


Cesar Ghali

Subject: tblen parameter in vitdec function

From: Idin Motedayen-Aval

Date: 9 Jan, 2009 15:24:36

Message: 2 of 2

C?sar Ghali wrote:
> Dear friends,
>
> I am developing a frame-based simulation that uses a viterbi decoder. I found that the vitdec function takes tblen as a parameter and I didn't know what to put as a best value for this parameter. I noticed that changing the value of this parameter will affect the result BER curve, in other words, I got different SNRs for BER = 1e-3. Is this logical and what is the best value for tblen?
>
> Thanks in advance for your help.
>
>
> Cesar Ghali

That's the traceback depth of your Viterbi algorithm. There is no exact
theoretical answer to this question. Clearly, the longer the traceback
depth, the better performance you will get, but then the VA needs more
memory and will add more latency to your system.
The rough rule of thumb for traceback depth is 5-7 times the constraint
length of the code. The idea is that at that depth all your surviving
paths will have merged (in most cases), so there isn't much to be gained
by setting the traceback depth longer that this. You can experimentally
determine the best value for your particular code and application.

HTH,
Idin

--
Idin Motedayen-Aval
The MathWorks, Inc.
zq=[4 2 5 -15 -1 -3 24 -57 45 -12 19 -12 15 -8 3 -7 8 -69 53 12 -2];
char(filter(1,[1,-1],[105 zq])), clear zq

Tags for this Thread

No tags are associated with this thread.

What are tags?

A tag is like a keyword or category label associated with each thread. Tags make it easier for you to find threads of interest.

Anyone can tag a thread. Tags are public and visible to everyone.

Contact us