I am running cognitive radio (whitespace) network simulation in NetSim (http://www.tetcos.com/). However, as I increase the number of secondary users, I see that the throughput of the network is constant. Would anybody know why ?
Hi Sai, I have used NetSim. Can you tell me what is the operation time and interval you have set, and the Operational Frequency (start / end) for both the incumbents ?
The reason the throughputs are the same is because you are using the same Operation Time & Operational Interval (10, 10) for both incumbents and they are operating in the same frequency band. This means that both incumbents come on every 10 seconds and stay for ten seconds. The timing would be
Incumbent 1 --- 0s to 10 s (OFF), 10s to 20 s (ON), 20s to 30s (OFF), 30s to 40s (ON) ... and so on
Incumbent 2 --- 0s to 10 s (OFF), 10s to 20 s (ON), 20s to 30s (OFF), 30s to 40s (ON) ... and so on
Since both incumbents are on & off at the same time, it is as-if only one incumbent is operating. So you would not notice a change in throughput when you increase the number of incumbents
You could set the operation time for one of the incumbents as say 7 seconds and operational interval as 10 for both. This would lead to the following timing
Incumbent 1 --- 0s to 10 s (OFF), 10s to 20 s (ON), 20s to 30s (OFF), 30s to 40s (ON) ... and so on
Incumbent 2 --- 0s to 7 s (OFF), 7s to 17 s (ON), 17s to 24s (OFF), 24s to 34s (ON) ... and so on
Then you will notice a reduction in throughput as you move from 1 incumbent to 2 incumbents
Here is a link to a deeply technical presentation on NetSim source code and features available
http://tetcos.com/File_Exchange/CR_Code_Walkthrough_10_Steps.pptx
- Badges
- Science topic