Explain what the input variables represent to the following program in MATLAB. f

Question

Explain what the input variables represent to the following program in MATLAB.

function impulse_response=ht_mp_ch(max_delay,L,decay_base,t_step)

t_vector=0:t_step:max_delay;
mp_tmp=0*(t_vector);

path_delays=[0 sort(rand(1,L-1)*max_delay)];
impulse_positions=floor(path_delays/t_step);
mp_tmp(impulse_positions+1)=exp(j*2*pi*rand(1,L));
mp_tmp=mp_tmp.*(decay_base.^(t_vector/max_delay));
impulse_response=mp_tmp/sqrt(sum(abs(mp_tmp).^2));

The program outputs the sampled version of the impulse response hmp(t) of the multipath fading channel as a vector.

Explanation / Answer

Hello Student!

I am happy to help you.

Function - ht_mp_ch(max_delay,L,decay_base,t_step)

Use of max_delay and t_step

These are normal integer values.

It is used for computing t_vector.

If we take a value of 20 for max_delay and 2 for t_step

The t_vector becomes - 0 2 4 6 8 10 12 14 16 18 20

It will form a vector with updation as t_step and max_delay as terminating condition.

Now, for the value of L, it is used for computing path delays. (also an integer value)

For L = 20 and max_delay = 20

Path delays comes out to be - 0 , 3.9319, 4.8705, 5.0217, 5.7168, 6.9997, 7.0332, 9.4658, 10.9945, 11.7053, 12.3209, 16.2857, 16.6166, 18.3439, 18.5853.

These delays will be used for determining the impulse positions.

Now, decay_base.

Now, for mp_tmp it stores exp(j*2*pi*rand(1,L))

Now, the impulse is prone to decay.. For which decay_base is utilised.

For, the value of 5 decay base comes out to be -

-0.8156 + 0.5786i 0.4739 + 1.0748i 0.0870 + 1.3770i -1.4066 + 0.8050i 1.8118 + 0.5843i -2.2324 + 0.1283i

-2.6205 + 0.1772i 0.0000 + 0.0000i 2.9325 - 2.1291i -2.8992 + 3.1168i 0.0000 + 0.0000i

Impulse response for function values - 20, 15, 5, 2 are -

ans =

Columns 1 through 6

0.0649 + 0.1164i -0.0179 - 0.1555i -0.1752 + 0.0558i -0.0620 + 0.2069i -0.0085 - 0.2536i 0.1115 + 0.2763i

Columns 7 through 11

0.0000 + 0.0000i -0.1591 - 0.3791i 0.1959 + 0.4414i -0.3996 - 0.4027i 0.0000 + 0.0000i

Thank you. Feel free to ask anything. Please upvote the answer, if you like it.

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