[ath9k-devel] Bringing up More Than Two Station Mode Virtual Interfaces

I've been having a problem using the ath9k_htc driver and was hoping someone here might have some advice.

I'm trying to connect (on a single channel) to a single AP multiple times simultaneously using one physical wireless adapter. I haven't been able to bring up more than two virtual interfaces so far.

Here's my setup.
Linux Distribution:??? Kali Linux 2016.2
Kernel Version:??? 4.6.0Wireless Adapter:??? TP-Link TL-WN722NAdapter Chipset:??? Atheros AR9271Driver: ath9k_htc
Firmware version: 1.4.0

Here's what I've tried:
Disable network-manager.????root at kali:~# /etc/init.d/network-manager stop
????[ ok ] Stopping network-manager (via systemctl): network-manager.service.
Disable hardware encryption, because I've read this adapter won't support virtual interfaces with hardware encryption enabled. 
??? root at kali:~# echo "options ath9k_htc nohwcrypt=1" >/etc/modprobe.d/ath9k_htc.conf??? root at kali:~# modprobe ath9k_htc
??? root at kali:~# cat /sys/module/ath9k_htc/parameters/nohwcrypt
????1
Create three virtual interfaces with unique MAC addresses.??? root at kali:~# iw dev wlan0 interface add wlan1 type station
????root at kali:~# iw dev wlan0 interface add wlan2 type station
????root at kali:~# iw dev wlan0 interface add wlan3 type station
????root at kali:~# macchanger -r wlan1
????Current MAC:?? [redacted] (unknown)
????Permanent MAC: [redacted] (unknown)
????New MAC:?????? ea:4c:bc:e0:8b:36 (unknown)
????root at kali:~# macchanger -r wlan2
????Current MAC:?? [redacted] (unknown)
??? Permanent MAC: [redacted] (unknown)
????New MAC:?????? 52:3a:02:22:4d:4a (unknown)
????root at kali:~# macchanger -r wlan3
????Current MAC:?? [redacted] (unknown)
????Permanent MAC: [redacted] (unknown)
????New MAC:?????? da:05:ce:1e:d0:41 (unknown)
Attempt to bring the new virtual interfaces up.??? root at kali:~# ifconfig wlan1 up
????root at kali:~# ifconfig wlan2 up
????root at kali:~# ifconfig wlan3 up
????SIOCSIFFLAGS: Device or resource busy
The third interface fails to come up. 

On?this page, they say, "We have successfully tested more than 200 stations and up to 4 APs per radio/NIC using ath9k and our code trees." They don't mention ath9k_htc, but I was hoping it also would also allow more than two station mode virtual interfaces. Or perhaps it's a firmware or hardware limitation causing my problem.

Is there anything else I can try? If not, is there another chipset and driver combination that would allow me to use at least 20 simultaneous station interfaces?
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