Re: Sending Beacons/Action Frames between Access Points

[Geovany Teca]

Hi,

My question is if there is any method of sending beacons/frames between two different access points in NS-3? 

I think what you want to ask is: Is any method of sending beacons/frames between two AP belonging to two different SSIDs.

Example: AP1 - SSID = "apx-wifi"

                AP2 - SSID = "apy-wifi"

AP1 sends beacons/frames to AP2?

Two points before going to the answer to helping you understand what happens in ns-3.

1. Take a look at the .pcap file that I have attached. That is wifi traffic from my house, and you can see many SSIDs in beacons, probe requests, and so on. It means that, if AP is placed close enough and their range covers each other, they will be able to hear each other's transmission. Yes, AP1 will know that AP2 sends beacons, probes responses and receives probe requests, and so on, and ns-3 is not different from reality.
2. Take a look at  ap-wifi-mac.cc (line 1013)  ==> void ApWifiMac::Receive (Ptr<WifiMacQueueItem> mpdu). That is, how AP handles received frames in ns-3, that includes frames from STA and AP in the different network.

Here is the list of the frames that are handled if you follow the function execution:

• Data
• Management frames (Probe request, Association request, Disassociation)

Those are frames that come from STA. By default, AP is designed to serve STA clients and not to talk to others AP. 

But still, if you place in your simulation two APs within the same range in two different networks, they will see what the other is transmitting, you can implement a small std::cout in this receive function and check the SSID and BSSID of all received frames, and see the beacons from different SSID, but AP only handles frames from STA. 

Back to your question,  Is any method of sending beacons/frames between two AP belonging to two different SSIDs?

My answer would be, No. According to the 802.11 standard, in the IBSS (infrastructure mode) AP is designed to connect to STA clients only.

Can you change this behavior? My answer is Yes (Remember Obama's slogan!). If you add a handler in this receive function in ap-wifi-mac you change the AP behavior, that's a matter of coding. In my opinion, you have to answer a few questions, before:

What frames from AP2, and AP1 shall handle?

How does AP1 identify the frames from AP2? (E.g: Field SSID, BSSID).

How AP1 will behave after receiving a frame from AP2? (Eg.: Change beacon interval, stop beacons, block probe responses I don't know.)

Does it impact the regular behavior of the network?

Best regards

Geovani 

'Ahmed Hasan Ansari' via ns-3-users <ns-3-...@googlegroups.com> escreveu no dia sexta, 27/05/2022 à(s) 11:21:

Hi all.

I am working on implemeting a method of coordination between two wireless Access Points in two different wireless networks. My question is if there is any method of sending beacons/frames between two different access points in NS-3? Most of the code/examples I have come across relate to sending these frames within the same network and between an AP and its associated stations. Some help would be greatly appreciated.

Ahmed Hasan Ansari

--
Posting to this group should follow these guidelines https://www.nsnam.org/wiki/Ns-3-users-guidelines-for-posting
---
You received this message because you are subscribed to the Google Groups "ns-3-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to ns-3-users+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/ns-3-users/53d2965c-6c64-4fe9-a5b6-96468cc6a279n%40googlegroups.com.

[Ahmed Hasan Ansari]

Hi Geovani,

Thanks for your detailed reply. I currently have 2 APs in my scenario. The issue is that I check whether the APs are receiving each other's beacons but they are not. I used the same code that is present in the sta-wifi-mac file that checks for a beacon. 

if (hdr->IsBeacon ())
    {
      NS_LOG_UNCOND ("Beacon received");
I added this line to the Ap-wifi-mac.cc file at the start of the receive function. But is does not print anything during simulation which gives me the indication that the other AP does not receive it. This line only prints for the stations which are present within the same BSS. I also tried placing the 2 APs very close to each other.

Just FYI, my actual goal is develop a mechanism in which APs exchange a frame between one another periodically and alter some physical channel parameters e.g. channel width to see if there is any impact on the performance KPIs while some other packet transmission is taking in place in parallel e,g, between a station and AP. 

I would greatly appreciate any further feedback.

Regards,

Ahmed

[Geovany Teca]

Hi Ahmed,

I will try to do a similar scenario just to see what happens, and let you know in this thread.

Best regards

Geovani Teca

To view this discussion on the web visit https://groups.google.com/d/msgid/ns-3-users/f28df07a-20a2-407c-a67a-1b4f4e701a06n%40googlegroups.com.

[Ahmed Hasan Ansari]

Hi Geovani,

Were you able to test the above issue? Also, just a further point I may have missed, I am trying to working in an overlapping BSS scenario. The two APs that I have are using the same frequency band and are within each other's range. I am trying to setup communication between them.

Regards,

Ahmed Hasan Ansari