OpenWrt Forum Archive

Topic: bottleneck with internal and external USB Wifi dongle

The content of this topic has been archived on 5 Apr 2018. There are no obvious gaps in this topic, but there may still be some posts missing at the end.

Maybe someone can give me a hint:

I have one TP-Link wr703n set up as a repeater for my LAN.
No NAT, no firewall, just plain IP routing from one /24 net to another.
The internal Wifi-module is configured as a client as well as an AP, where the client (STA) Interface acts as the uplink.

Now, in order to improve performance, I added an USB Wifi-Adapter and configured this one to be the client Interace. Surprisingly, the performance is really very bad with this setup - a lot slower than with just one Interface acting as both - client and ap. Even though signal levels are just fine (actually better since there is an external antenna) and the AP Channel is more than 5 channels apart from the uplink. I already tried a number of different USB-Wifi-devices with different chipsets (ath9_htc and rtl81xx) but they all give poor results. Watching CPU load during transfers does not show any significant values, system is over 90% idle most of the time.

Any ideas how to troubleshoot this?

Try to get the antennas as far apart as possible, like using an usb cable. Also, try to use channel 1 on one device and the highest possible channel on the other one.

Thank you very much.
Separating the antennas is the only thing I haven't tried yet.
And it seems to do the trick.
So, after placing the antennas approx 1.5m apart, I get an improvement of approx. 25% (approx. 6 minutes for 70MB compared to 8 minutes without the additional usb device).

Well, I just ordered an 802.11abgn Adapter to shift the uplink to 5GHz.

Today, the ordered 802.11abgn USB Adapter arrived. Setup was easy and the performance improvement was well worth it. Preliminary tests show, that the performance is drastically improved! No more interference with the 2.4GHz Uplink.

So if anyone wants to upgrade his wr703n (or whatever running openwrt) to a dual-band device, this seems to be a good
choice. Here are some more details:


Advertised as RT5572N Chipset, it actually anounces itself as follow:

[    9.500000] usb 1-1: reset high-speed USB device number 2 using ehci-platform
[    9.650000] ieee80211 phy0: rt2x00_set_rt: Info - RT chipset 5592, rev 0222 detected
[    9.690000] ieee80211 phy0: rt2x00_set_rf: Info - RF chipset 000f detected
[    9.700000] ieee80211 phy0: Selected rate control algorithm 'minstrel_ht'
[    9.710000] usbcore: registered new interface driver rt2800usb

Note, that it says 5592 instead of 5572. Not sure if this is an error, since the 5592 is supposed to be a PCIe Chipset
whereas the 5572 is the USB variant. As you can see, it is supported by the RT28xx driver.
Easy installation:
$ opkg install kmod-rt2800-usb


available 5GHz Channels - regulatory domain germany:
root@OpenWrt:~# iw reg get
country DE: DFS-ETSI
        (2400 - 2483 @ 40), (N/A, 20)
        (5150 - 5350 @ 80), (N/A, 20), NO-OUTDOOR
        (5470 - 5725 @ 80), (N/A, 27), DFS
        (57240 - 65880 @ 2160), (N/A, 40), NO-OUTDOO

$ iw list
...
        Band 2:
                Capabilities: 0x2f2
                        HT20/HT40
                        Static SM Power Save
                        RX Greenfield
                        RX HT20 SGI
                        RX HT40 SGI
                        TX STBC
                        RX STBC 2-streams
                        Max AMSDU length: 3839 bytes
                        No DSSS/CCK HT40
                Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
                Minimum RX AMPDU time spacing: 2 usec (0x04)
                HT RX MCS rate indexes supported: 0-15, 32
                TX unequal modulation not supported
                HT TX Max spatial streams: 2
                HT TX MCS rate indexes supported may differ
                Frequencies:
                        * 5180 MHz [36] (20.0 dBm)
                        * 5190 MHz [38] (20.0 dBm)
                        * 5200 MHz [40] (20.0 dBm)
                        * 5210 MHz [42] (20.0 dBm)
                        * 5220 MHz [44] (20.0 dBm)
                        * 5230 MHz [46] (20.0 dBm)
                        * 5240 MHz [48] (20.0 dBm)
                        * 5250 MHz [50] (20.0 dBm)
                        * 5260 MHz [52] (20.0 dBm)
                        * 5270 MHz [54] (20.0 dBm)
                        * 5280 MHz [56] (20.0 dBm)
                        * 5290 MHz [58] (20.0 dBm)
                        * 5300 MHz [60] (20.0 dBm)
                        * 5310 MHz [62] (20.0 dBm)
                        * 5320 MHz [64] (20.0 dBm)
                        * 5500 MHz [100] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5510 MHz [102] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5520 MHz [104] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5530 MHz [106] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5540 MHz [108] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5550 MHz [110] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5560 MHz [112] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5570 MHz [114] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5580 MHz [116] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5590 MHz [118] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5600 MHz [120] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5610 MHz [122] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5620 MHz [124] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5630 MHz [126] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5640 MHz [128] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5650 MHz [130] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5660 MHz [132] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5670 MHz [134] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5680 MHz [136] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5690 MHz [138] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5700 MHz [140] (27.0 dBm) (radar detection)
                          DFS state: usable (for 2149925 sec)
                        * 5745 MHz [149] (disabled)
                        * 5755 MHz [151] (disabled)
                        * 5765 MHz [153] (disabled)
                        * 5775 MHz [155] (disabled)
                        * 5785 MHz [157] (disabled)
                        * 5795 MHz [159] (disabled)
                        * 5805 MHz [161] (disabled)
                        * 5825 MHz [165] (disabled)
                        * 4920 MHz [184] (disabled)
                        * 4940 MHz [188] (disabled)
                        * 4960 MHz [192] (disabled)
                        * 4980 MHz [196] (disabled)
...

$ iw reg set US
$ iw list
...
                Frequencies:
                        * 5180 MHz [36] (17.0 dBm)
                        * 5190 MHz [38] (17.0 dBm)
                        * 5200 MHz [40] (17.0 dBm)
                        * 5210 MHz [42] (17.0 dBm)
                        * 5220 MHz [44] (17.0 dBm)
                        * 5230 MHz [46] (17.0 dBm)
                        * 5240 MHz [48] (17.0 dBm)
                        * 5250 MHz [50] (disabled)
                        * 5260 MHz [52] (23.0 dBm) (radar detection)
                          DFS state: usable (for 1 sec)
                        * 5270 MHz [54] (23.0 dBm) (radar detection)
                          DFS state: usable (for 1 sec)
                        * 5280 MHz [56] (23.0 dBm) (radar detection)
                          DFS state: usable (for 1 sec)
                        * 5290 MHz [58] (23.0 dBm) (radar detection)
                          DFS state: usable (for 1 sec)
                        * 5300 MHz [60] (23.0 dBm) (radar detection)
                          DFS state: usable (for 1 sec)
                        * 5310 MHz [62] (23.0 dBm) (radar detection)
                          DFS state: usable (for 1 sec)
                        * 5320 MHz [64] (23.0 dBm) (radar detection)
                          DFS state: usable (for 1 sec)
                        * 5500 MHz [100] (disabled)
                        * 5510 MHz [102] (disabled)
                        * 5520 MHz [104] (disabled)
                        * 5530 MHz [106] (disabled)
                        * 5540 MHz [108] (disabled)
                        * 5550 MHz [110] (disabled)
                        * 5560 MHz [112] (disabled)
                        * 5570 MHz [114] (disabled)
                        * 5580 MHz [116] (disabled)
                        * 5590 MHz [118] (disabled)
                        * 5600 MHz [120] (disabled)
                        * 5610 MHz [122] (disabled)
                        * 5620 MHz [124] (disabled)
                        * 5630 MHz [126] (disabled)
                        * 5640 MHz [128] (disabled)
                        * 5650 MHz [130] (disabled)
                        * 5660 MHz [132] (disabled)
                        * 5670 MHz [134] (disabled)
                        * 5680 MHz [136] (disabled)
                        * 5690 MHz [138] (disabled)
                        * 5700 MHz [140] (disabled)
                        * 5745 MHz [149] (30.0 dBm)
                        * 5755 MHz [151] (30.0 dBm)
                        * 5765 MHz [153] (30.0 dBm)
                        * 5775 MHz [155] (30.0 dBm)
                        * 5785 MHz [157] (30.0 dBm)
                        * 5795 MHz [159] (30.0 dBm)
                        * 5805 MHz [161] (30.0 dBm)
                        * 5825 MHz [165] (30.0 dBm)
                        * 4920 MHz [184] (disabled)
                        * 4940 MHz [188] (disabled)
                        * 4960 MHz [192] (disabled)
                        * 4980 MHz [196] (disabled)
...

Not sure though, how much power it will actually emit on channels with 30dBm specified.

So if it proves stable over the next few days, I'll connect it with an USB extension cable to my WR703N and
mount it over the roof on the antenna-mast.

Just in case anybody cares, this is, what I bought: http://www.ebay.de/itm/121320710061

The discussion might have continued from here.