wlan0/wlan1 hotspot performance issue

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wlan0/wlan1 hotspot performance issue

Postby adulescentulus » Wed Apr 27, 2016 4:13 pm

Hi there,

the arch linux community was recommended to me, because I am stuck with a problem, which exists also on raspbian wheezy/jessie as well on arch linux, all tested on a pi1, pi2 and now pi zero.

I want to have a thin mobile hotspot, for connecting my devices at places where I only have one single (and perhaps unsecure) wifi internet account, so my setup looks like this:
technical setup
$this->bbcode_second_pass_code('', '
public/hotel wifi (192.168.178.x) <--A--> [pi/wlan1 (192.168.178.82), pi/wlan0(192.168.12.1)] <--B--> all my clients (192.168.12.x)')

I am not very familiar with arch linux but after lots of reading I got it up running, getting a dynamic IP address for wlan1 and creating a hostapd hotspot:
  • wlan1 with netctl-auto set to 192.168.178.82
  • wlan0 with the script create_ap (GitHub) (on raspbian I configured dnsmasq, hostapd, iptables on my own)
  • 1 usb wifi dongle Ralink 3570
  • 1 usb wifi dongle Ralink 3572
  • I also tested different combinations (2 Ralink 3570, 2 Ralink 3572, also one Realtek RTL8188CUS)

Problem
When I create traffic on a hotspot client, e.g. downloading a 100 mb file, the speed drops to unusable 60 KB/s!
I find no solution, neither do I find a cause. I do not know where to look for problems.
When I test the download on the pi itself, i.e. only creating load on connection A, everything is performant.
I also tested the connection A with iperf: everything good as expected
I also tested the connection B with iperf: everything good as expected
When I test connections A and B concurrently with iperf: wifi speed drops to nearly nothing

And here is the final surprise: when I replace connection A with a usb connection mobile phone (using also wifi connection) it all works like a charm

Theory
It seems the pi cannot handle two wifi dongles very well and they disturb each other in some way.

Questions
$this->bbcode_list('1')
  • has anyone an equal setup running well?
  • do you have any suggestions, where to look further into it?
  • is there any solution out there?
  • adulescentulus
     
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