# Different output with same input

• This topic has 3 replies, 2 voices, and was last updated 1 year ago by John.
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• #14478
Guilavogui
Participant

Hello,
I am trying to show the impact of the high velocity (HST, 500km/h) on the 5G output (User Throughput, SINR):
– But every time I run the same scenario (@scenarios.basicScenario) with same parameters I get different output (User Throughput, SINR)
– I am also struggling to find out the “Calculation formula” related to my scenario (@scenarios.basicScenario).

Could you support me with these two points?

Kind regards,

Pema

#14791
John
Participant

Did you seed your random variable? You should.

LTE_config.seedRandStream = true;
LTE_config.RandStreamSeed = 64;

#14799
Guilavogui
Participant

I have added these two lines but the output still keeps changing. Now I decided to define UE and BS Positions by myself. And the problem comes back in another way, instead of changing, the Throughput stays the same for different user’s speeds and different distances between UE and BS.
SO I decided to check the SINR calculation formula.
Please could you help to figure out the Throughput the SINR calculation formula?
Please have a look at this (I don’t understand this part):

if obj.fastBlerMapping

iSinr = round((sinr-obj.sinrMin)/obj.sinrResolution)+1;
nSinr = length(obj.sinrList);
iSinr(iSinr>nSinr) = nSinr;
iSinr(iSinr<1) = 1;
iBler = cqi+size(obj.blerCurves,1)*(iSinr-1);
bler = obj.blerCurves(iBler);
else
bler = zeros(size(cqi));
for i = 1:length(cqi)
if sinr(i)<obj.sinrList(1)
bler(i) = 1; % very low sinr
elseif sinr(i)>obj.sinrList(end)
bler(i) = 0; % very high sinr
else
bler(i) = interp1(obj.sinrList,obj.blerCurves(cqi(i),:),sinr(i));
end

Thank you!

#15041
John
Participant

Sorry Guilavogui, I found your question during a broad search, so the answer I gave is related to the LTE SL simulator (not 5G).
To answer your question, truly I have not found that feature in the 5G simulator but I can recommend forcing a random variable seed using the rng function.
Try this:
rng(64);

The line needs to be included before the result=…; line. It’s safe to add it right after the opening clear all, clc initializations. It maintains the random number generator’s seed value (64).

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