Simulating interference between two PHY Layers

[Gaurang Naik]

Hi,

I am trying to simulate a network  which have nodes operating on two different PHY Layers, 802.11p and 802.11a. So, for starters I want the two operating in the same frequency band. I set the frequency to be the same using 

wavePhy.Set ("Frequency", UintegerValue (5900)) and 

wifiPhy.Set("Frequency", UintegerValue (5900)); 

Here wavePhy is an object of class YansWavePhyHelper and wifiPhy is an object of class YansWifiPhyHelper.

The code seems to work fine - I do not get compile time or run time errors. But I am not observing any interference between the two sets of nodes. At the Wave Receiver, I print the received SNR. This SNR remains the same whether or not there is a 802.11a transmission present. I also observed that this received SNR is not varying with the frequency (which is strange as path loss must depend on the frequency). Am I missing something? Is this the right way to set the frequency of operation? 

Another basic question I have is - would making the frequency of the two sets of nodes be sufficient to make them interfere with each other? For instance, I assumed that when there is an 802.11a node operating in the vicinity on same frequency, the 802.11p node will detect a fall in the SINR and there will be an effect on the delivery rate of 802.11p. But this isn't happening right now. Could someone tell me if there is a better way to do this? 

Any help is sincerely appreciated.

Thanks. 

[Konstantinos]

Hi,

We have discuss it several time and I think it is also in the manual.

The current implementation of WifiPhy does not support inter-channel interference.

https://www.nsnam.org/bugzilla/show_bug.cgi?id=986

By creating two independent PHYs, without proper care, you have created two channel objects, even though they might operate in the same frequency. Hence there is no interference among them.

Solutions:

a) Try to use a single Channel object

b) Try to use the ns-3-laa tree where the WifiPhy uses the Spectrum model and can support interchannel interference. This is still under-development so it might not be completely working.

Regards,

K

[Gaurang Naik]

Hi, 

Thanks for your reply. I had indeed used two different YansWifiChannel objects, but now I changed that to just one channel object for both type of nodes. Yet, I do not seem to observe any interference. 

Do the channel bandwidths matter? In reality 802.11p would use 10 MHz bandwidth, while 802.11a does not. So the channels don't really overlap even if the center frequencies are the same. Does this come into picture? I'm not sure how this is implemented in ns3. Could you provide some insights?

Thanks,

Gaurang.