AWGN channel in VHDL testbench

Question

I want to create AWGN channel in VHDL testbench. Is it possible? and how can I proceed? I searched online but not many related posts.

Regards

Have you noticed that **all** of your questions at StackOverflow have received a negative voting average? You should really improve your question quality. Please read ["How to ask a good question"](https://stackoverflow.com/help/how-to-ask). — JHBonarius, Jul 31 '17 at 09:59
I don't know what is wrong in this question :) It's a valid question, and I think didn't asked before. — Taimur Wajad, Jul 31 '17 at 14:22
To begin, you don't explain what a "AWGN channel" is. And then: what did you try so far? What sources did you check? Where do you want to use it for. And so on, and so on: there are many more things. Did you read my link? — JHBonarius, Jul 31 '17 at 17:27

score 2 · Answer 1 · answered Jul 31 '17 at 09:34

Yes, you can.

How to generate a uniform distributed value in VHDL is described here. Quote (original by "Vipin Lal"):

library ieee;
use ieee.math_real.all;

entity rand_gen is end rand_gen;

architecture behavior of rand_gen is 
    signal rand_num : integer := 0;
begin
    process
        variable seed1, seed2: positive;               -- seed values for random generator
        variable rand: real;   -- random real-number value in range 0 to 1.0  
        variable range_of_rand : real := 1000.0;    -- the range of random values created will be 0 to +1000.
    begin
        uniform(seed1, seed2, rand);   -- generate random number
        rand_num <= integer(rand*range_of_rand);  -- rescale to 0..1000, convert integer part 
        wait for 10 ns;
    end process;
end behavior;

Then you have to scale the output of the uniform function to a AWGN distribution. An example in C is given here. Quote(summarized from original by "Dr Cagri Tanriover")

temp2 = ( rand() / ( (double)RAND_MAX ) );
temp1 = cos( ( 2.0 * (double)PI ) * rand() / ( (double)RAND_MAX ) );
result = sqrt( -2.0 * log( temp2 ) ) * temp1;

Just correctly convert this to VHDL. The math_real library contains all functions and constants required.

AWGN channel in VHDL testbench

1 Answers1