Example2 / Experiments: How to modify Noise and SINR?

Asked by Sebastian on 2009-04-16


a very basic question: in the UsersGuide, Example2 is altered in the Experiments subsection. It says one should try to modify noise and SNR. Unfortunately, after spending some time searching the source code, I still don't know how this is done or where to find the appropriate methods.

Furthermore, is there a good strategy so that I can find the answers on my own next time?

Greets, Sebastian

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Sebastian Max
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Best Sebastian Max (smx-comnets) said : #1

Hi Sebastian,

Where did you find any indication that one should "try to modify noise and SNR" during the experiment 2? The experiments subsection says, quote:

   1. Calculate (roughly) the maximum distance for which a reception is possible using
         1. The pathloss function from the config.py in experiment 1.
         2. A background noise N = -95dBm
         3. A minimum Signal to Noise Radio (SNR) of 6 dB.
   2. How does the saturation point change when varying the distances between the AP and the STA?
   3. Validate the calculation by simulating distances near to the calculated maximum distance (e.g. +- 10m).

(end quote, see also http://docs.openwns.org/usersGuide/modules/dll/wifimac/experiment2.html)

In the simulator, it is not possible to directly set the noise (N) and the SNR of a reception. The noise depends on the channel bandwith and the receiver noise figure; the SNR depends on the received signal strength (which depends on the transmission power, the distance, the pathloss function, the shadowing inbetween), and the noise.

A simple way to have different SNR values is to use different distances between transmitter and receiver during the simulation, like it is indicated in task 2 and 3.

Sebastian (heglmeie) said : #2


maybe I should have read that part of the UsersGuide more precisely. I was completely barking up the wrong tree, believing that I could

a) artificially introduce some higher constant interference to the system by changing the background noise
b) globally alter the minimum SNR for successful reception, i.e. a different receiver sensitivity

Thanks a lot for the rapid and detailed answer!

Sebastian (heglmeie) said : #3

Thanks Sebastian Max, that solved my question.