Problem about multi-interface multi-channel in WLAN

[Max]

Hi, everyone！

I write a script to simulate multi-interface multi-channel WLAN based on example/wireless/ht-wifi-network.cc file. In my script, there has a STA and an AP  both installing two wifiNetDevices to transmission(as shown in the uploaded picture). I set the same ip address to the two wifiNetDevice, but their channel frequency are different(one is 1th channel and another one is 6th channel on 2.4GHz spectrum).  but the simulation result indicates that first wifiNetDevice receives 5478 packets and second wifiNetDevice just receives 203 packets. And then my question is：

1)  why the number of packet received on the wifiNetdevice is different?

2) or some attribute value i set are incorrect?

3)How do the packets UdpClient generated forward to lower layer(or how to decide to distribute to which wifiNetdevice)

I hope somebody could help me,thanks. 

    Best regards

[Tommaso Pecorella]

Hi,

Let's suppose you have two PCs with two Ethernet NICs each. You connect both Ethernets through a simple Ethernet cable (nowadays it is not even necessary to use a cross-cable). Then you assign manually to each Ethernets the same IP address. Well, a different one for each PC of course, but the same one for both Ethernets of both PCs.

Now, do you expect that the throughput between the two PCs will be double ?

Well, of course no. Just one of them will be used.

Why ? For the exact same reason. Think about it.

If you want a hint... routing. A packet wants to be sent to an IP address. At one point your PC will have to choose:

1) the sender address (it's not that obvious)

2) the outgoing interface

Have fun,

T.

[Shi Su]

Hi, thanks for your reply.As My English is not good, my point does not express well. But I indeed need to realize multi-interface multi-channel on the wifi node to increase the throughput. I am not familiar with ns-3 tool so far. Therefore,i just simply realize the two channels on the node as i mentioned earlier. If i set the different ip addresses on the wifiNetDevice, will it work?  

    In fact, i want to realize that one control channel which just transmit control frame ，i.e Beacon, and at least one data channel which transmit data frame on the node. so could you tell me some detailed suggestion?Thank you very much!

      Best Regards

--
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 post to this group, send email to ns-3-...@googlegroups.com.
Visit this group at http://groups.google.com/group/ns-3-users.
For more options, visit https://groups.google.com/d/optout.

[Tommaso Pecorella]

Hi,

don't worry about your English, it0's good enough to be understood. Well, improving is always good, but I can't say mine is perfect either, so...

In order to do what you're thinking you need to have two Wi-Fi interfaces acting as a single one. The IP layer should not be aware that there are two or more Wi-Fi radios down there, otherwise it will become a routing problem (and you'll not be able to send beacons on one channel and data on the other).

Unfortunately there's no simple way to do what you described You'll need to heavily modify all the wifi module, in order to have two (or more) WifiPhy and one WifiMac instance. 

Split the data between two NetDevices just below the IP layer could be more feasible, but each one will behave separately, each one with its own beacons, data, associations, etc.

Anyway, I'd suggest to study the idea from an architectural point of view first. Then, when you have a clear picture of the layers and who is communication with who, you can move to coding.

Hope this helps,

T.

[Shi Su]

Hi,

Thank you for your quick response. Does it mean that it is very difficult to realize my idea about MIMC? To be honest, this is a project i try to study. So the whole algorithm and simulation purpose had been finished. Then my current work is to realize it with ns-3. 

Of course, i do know there will be much difficulty.  So i plan to do it step by step. So sorry for that i do not understand the mean of "an architectural point of view". Does it mean the framework of software or program or something else? Would you tell me where to start in detail？like what classes in API?what documentation or book?Thanks again. 

      Best Regards

 

[Tommaso Pecorella]

Hi,

I meant that you should study who's talking with who.

The Wi-FI standard (better, 802.11) is based on a layer design, i.e., MAC, PHY and so on. Usually there is one PHY and one MAC, and you plan t have one MAC and two PHY, or two PHY and two MAC, but the two MAC will have to act like one.

You need to fully understand and design all the interactions between the various entities, since in ns-3 they are (mostly) following the standard guidelines.

About what to read, I'd grab one of the countless books on Wi-Fi standard, if not the standard itself (but it's very difficult to read). Moreover, check the ns-3 wifi module documentation.

Good luck,

T.