How to connect to multiple APs at the same time? - Page 1
Forum section: electronics / general

author: Logan
author_rank: Frequent Contributor
timestamp: August 13, 2021, 04:34:41 pm
content: Hi.Is it possible for a client with single WLAN adapter to connect to 2(or more) different WLAN APs at the same time? (from PC or phone, any OS possible)Not to combine the bandwidth, just because they have different purpose.Thanks.

author: magic
author_rank: Super Contributor
timestamp: August 13, 2021, 08:40:15 pm
content: There was some talk about getting this to work on Linux some years ago, I don't know how far it went. Maybe it works.There are some challenges involved. The main problem is that if the APs are on different channels and you are tuned to receive from one of them, all packets from the other are transmitted into the void and not received. This generates unnecessary radio traffic due to inevitable retransmissions and increases latency somewhat unpredictably.However, there are power management features which allow a station to go to sleep and notify the AP that it is temporarily unavailable and any incoming packets are to be queued until the station comes back. So the idea was to use that functionality to schedule RX transmissions from different APs.

author: Logan
author_rank: Frequent Contributor
timestamp: August 14, 2021, 05:41:34 pm
content: Thank you!Can you give the link of the discussion you refered?I googled but cannot find it.

author: magic
author_rank: Super Contributor
timestamp: August 14, 2021, 06:12:38 pm
content: I don't remember, it was many years ago.Some documentation of relevant system utilities is available here:https://wireless.wiki.kernel.org/en/users/documentation/iwhttps://wireless.wiki.kernel.org/en/users/documentation/iw/vifYou need to run:Code:iw dev wlan0 interface add wlan1 type stationiw dev wlan1 del # when you are done with itIt works on my laptop, but I get "SIOCSIFFLAGS: Name not unique on network" when I try to bring wlan1 up with ifconfig. YMMV. It's gonna depend on kernel version and wireless driver (i.e. what hardware you have). It also depends on interface type, because creating a monitor interface (used for network debugging) works just fine on the same system.You will also need to get wpa_supplicant, NetworkManager or whatever other softtware to work with it, unless you are content with joining unencrypted or WEP networks.Alternatively, a USB dongle, of course.editI found solution to "name not unique on network". I just needed to change the MAC address on the virtual interface and now I can bring it up.https://superuser.com/questions/592296/using-iw-to-add-a-virtual-wireless-interface-getting-the-error-no-such-deviceI also found a screenshot of virtual interfaces working in Ubuntu with their GUI tools and everything.https://askubuntu.com/questions/488588/how-do-i-connect-to-multiple-wifi-networksedit editI started wpa_supplicant on the virtual interface and it connected to my AP. However, it doesn't seem to work if I try to connect simultaneously on 2.4GHz and 5GHz bands. I have no means of testing different channels on the same band or different APs on the same channel. Have fun.My hardware is Atheros, by the way. They have long been known for decent Linux drivers.

author: Logan
author_rank: Frequent Contributor
timestamp: August 15, 2021, 03:30:44 pm
content: Thank you so much magic.May I know if it's possible in Windows as well?

author: magic
author_rank: Super Contributor
timestamp: August 15, 2021, 03:49:29 pm
content: I used to be a bit into wardriving years ago so I have some familiarity with that stuffSorry, I haven't used M$ Wind0z€ since XP

author: DiTBho
author_rank: Super Contributor
timestamp: August 15, 2021, 04:02:44 pm
content: Quote from: magic on August 14, 2021, 06:12:38 pmYup, that's on kernel >= 5.4 also depends on the quality of support for the new "mac80211".

author: Ian.M
author_rank: Super Contributor
timestamp: August 15, 2021, 04:18:57 pm
content: Under Windows, I don't believe its possible. Its bad enough if you *DO* have multiple real WiFi adapters.Windows 10 (and IIRC earlier versions as well) are a total bitch and even if you have multiple WiFi adapters, when you choose a network to connect to in the Win10 wireless network list, it connects *ALL* your adapters to the same network but only uses the lowest latency one!There is a workaround - use third party software to configure and connect one or more of your wireless adapter. Usually the device or WiFi chipset manufacturer has a usable tray utility for this purpose.

author: Halcyon
author_rank: Unknown
timestamp: August 17, 2021, 09:59:32 am
content: Two different access points on the same channel... *maybe* it's possible with a normal consumer WiFi card. On different channels at the same time? You can almost forget about it.I've never seen it done. It sounds like it would have the potential to cause all kinds of problems.What's your application? Sounds like something that can be just dealt with via routing.

author: magic
author_rank: Super Contributor
timestamp: August 17, 2021, 11:03:49 am
content: Quote from: Halcyon on August 17, 2021, 09:59:32 amIf you can get promiscuous mode and monitor interfaces to work (and you often do) then everything could be implemented in software. It shouldn't be a problem in principle unless you hit some crippled firmware or half-baked driver. I imagine some features like crypto offload may or may not be available if the firmware is not designed for multi-station operation.Many cards also support managing multiple networks in AP mode. Because they are the same hardware which the vendor wants to sell to AP manufacturers too.Quote from: Halcyon on August 17, 2021, 09:59:32 amAnything involving stuff on some LAN when you want to stay connected to other networks. Could be as simple as turning on a "smart" lightbulb which you control by joining its SSID - there are devices working like that.

author: Logan
author_rank: Frequent Contributor
timestamp: August 17, 2021, 01:57:41 pm
content: Quote from: magic on August 17, 2021, 11:03:49 amYes, actually the network are internet + network camera. The network camera can only work in Ad-hoc mode, it cannot join existing network.

author: magic
author_rank: Super Contributor
timestamp: August 17, 2021, 05:25:44 pm
content: Ad-hoc is a different mode altogether but I see no reason why it wouldn't work if both networks are on the same channel.So I suppose you have that camera which you are now trying to bridge to some other network? That ought to be doable with any semi-decent router running OpenWRT.

author: Logan
author_rank: Frequent Contributor
timestamp: August 18, 2021, 01:44:19 pm
content: Quote from: magic on August 17, 2021, 05:25:44 pmYes but I just want to try without additional hardware.

author: magic
author_rank: Super Contributor
timestamp: August 18, 2021, 01:55:22 pm
content: Nope, I'm lost. If you only want to connect to it from some laptop or whatnot without losing net access then you don't need to bridge any networks, you simply connect to it.Instructions for Linux above, instructions for Windows given by Ian.M: buy a second WiFi dongle and pray for a utility smarter than Microsoft's built-inThat being said, given a sufficiently advanced router, you could make it permanently visible on your WiFi LAN and then even Windows could connect to it through the router like to anything else.