How can I tell whether a USB WiFi adaptor supports the Infrastructure mode?

Question

I need a USB WiFi adaptor which supports the Infrastructure mode (not Ad-Hoc) - (i.e. I want to use a laptop as a WiFi access point).

How can I tell which WiFi adaptors support the Infrastructure mode and which do not from their specifications? What features should I look for?

For example, here is a specification of a USB WiFi chip, but it does not say anything about the Infrastructure mode explicitly.

Solution 1

Infrastructure mode is kind of redundant these days - hostapd works fine without it with any adaptor with kernel support (which is quite a lot of them), and I'm semi certain being. I know specifically that many ralink chips with the official ralink/mediatek drivers work as an AP or as a hybrid AP/Clinet (Its both at the same time) - using either the virtual router functionality in windows 7 or better, or some other mechanism in XP.

Virtualrouter uses the same mechanisms as the realtek driver I suspect and they use "Windows Virtual Wifi and Wireless Hosted Network features." - they have a list of hardware thats supported here.

TLDR - Infrastructure mode is not needed for use as a software AP - In linux, any driver with kernel support will work, and windows has a different set of required features.

Solution 2

If you already bought it or can try it in the store, this should tell you (under Windows 7 or higher):

netsh wlan show drivers

    ...
    Radio types supported     : 802.11a 802.11b 802.11g 802.11n
    FIPS 140-2 mode supported : Yes
    Hosted network supported  : Yes     ← ← ← 
    Authentication and cipher supported in infrastructure mode:
    ...

Solution 3

Almost all USB adapters support Infrastructure as this is the standard when using a home router or a business infrastructure. Adhoc is computer-to-computer without a router or dhcp in the middle, which are rare nowadays.

Just buy any off-the-shelf adapter. TPLink are pretty good.

Solution 4

One WiFi (or any network adapter) interface cannot connect your laptop as well as other devices to a network (yes, there are exceptions($), but on some level, they're still multiple interfaces). Connection-sharing must be done with a system with two adapters. Commonly, this is done with Ethernet and WiFi, but it can be done with two WiFi adapters, though they'd have to have separate BSSIDs and IP addressing. Other than differences in antennae configuration, there's little difference in the transmitter/receiver of any standard Wifi adapter: the infrastructure/ad-hoc modes are performed by software.

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Comments

[Thalys]

What OS? Infrastructure mode isn't needed in hostapd

[Alexey]

Thanks for the reply! I think, I did not explain my problem properly. I want to use a laptop as an access point. Not other way round. I'll correct my question.

[Kinnectus]

Ok. Update your question to add this so it can help people in future. The answer to your question is, again, pretty much all wifi adapters can be used an access point. What you're trying to do is turn your wifi into a router so you can connect multiple devices and either share your Internet or let your devices share resources. You can, in this case, turn on an adhoc network. Look up Windows 7 Internet connection sharing.

[Alexey]

I am trying to get an answer to this question, but before buying a device. Ad Hoc network is not what I need (I cannot connect my Android phone to it). I have two laptops, and neither of them seem to have an "Infrastructure" mode capable WiFi.

[Kinnectus]

Quick lookup a TpLink TL-WN721N has AP mode. You will need to install a DCHP server application to bind to the wifi device and then you may be able to turn on Internet connection sharing through Windows to bridge the ethernet to the wifi. Or you may need to install a proxy server application that points all requests to your ethernet card so they can use the Internet.

[Kinnectus]

Would it be easier to just buy a cheap router? Plug it between your laptop's ethernet and your Internet connection and then configure the wifi on that? All your devices will be able to communicate with each other...

[Alexey]

TL-WN721N looks like a good device. It seems to work with no additional drivers in Linux. I'll consider buying it. But my original question is more general :)

[Alexey]

Thanks! Probably, the list of hardware from the Virtualrouter website is what I am looking for. Even if I cannot use one of those devices in Linux, I will be able to use it in Windows with Virtualrouter.