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Author Topic: Experiences with wifi stability and range  (Read 341 times)

fluxDev

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Experiences with wifi stability and range
« on: January 07, 2019, 04:48:00 PM »
Hi,

I'm experimenting with an OLIMEX A13-OLinuXino-WIFI and its wifi functionality. The board is run by a v4.19.9 mainline Linux kernel with a Debian Stretch user space. The network connections are handled through NetworkManager. The board in question is of revision 'H' and has a "Bus 001 Device 005: ID 0bda:0179 Realtek Semiconductor Corp. RTL8188ETV Wireless LAN 802.11n Network Adapter".

Unfortunately the network connection does not seem to be entirely stable. It seems to happen that every now and then after a group rekeying the connection is lost. I would post some exemplary log lines below:

Dec 19 21:37:40 wpa_supplicant[285]: wlan0: WPA: Group rekeying completed with 7c:ff:4d:ef:f6:ac [GTK=TKIP]
Dec 19 21:38:04 kernel: R8188EU: linked_status_chk(wlan0) disconnect or roaming
Dec 19 21:38:06 kernel: R8188EU: indicate disassoc
Dec 19 21:38:07 wpa_supplicant[285]: wlan0: CTRL-EVENT-DISCONNECTED bssid=7c:ff:4d:ef:f6:ac reason=0
Dec 19 21:38:07 NetworkManager[4357]: <info>  [1545251887.1222] device (wlan0): supplicant interface state: completed -> disconnected
Dec 19 21:38:07 NetworkManager[4357]: <info>  [1545251887.1434] device (wlan0): supplicant interface state: disconnected -> scanning

Afterwards NetworkManager reconnects and everything seems to be fine. Did anyone encounter similar behaviour or has ideas how to resolve this?

Furthermore my wifi range seems to be pretty short. I get only about half as far as with my mobile phone in the same environment (about six to seven meters in my flat). My OLIMEX A13 board is mounted in a metal case where I cannot remove it easily due to further peripheral devices. Does anybody have experiences concerning the wifi range without cases?

Kind regards,

fluxDev

JohnS

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Re: Experiences with wifi stability and range
« Reply #1 on: January 07, 2019, 05:56:20 PM »
A metal case is almost bound to reduce the signal (see Faraday cage) and  also a modern phone has years more recent tech in it.

John

LubOlimex

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Re: Experiences with wifi stability and range
« Reply #2 on: January 08, 2019, 11:55:05 AM »
This seems to be a very wide spread problem that happens with a lot of WIFI modems. There are a number of possibilities on how to fix it but even if you can't fix it there are workarounds. To find possible solutions and suggestions make sure to search online for the following strings "WPA: Group rekeying completed" and "linked_status_chk(wlan0) disconnect or roaming".
Technical support and documentation manager at Olimex

stokes

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Re: Experiences with wifi stability and range
« Reply #3 on: January 23, 2019, 09:39:04 AM »
FYI the Realtek hardware is rock solid under 3.4.90+ kernel.

I'm not sure if there are different firmware revisions, etc.

fluxDev

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Re: Experiences with wifi stability and range
« Reply #4 on: January 23, 2019, 11:44:28 AM »
@stokes: Thank you for this bold statement. That was kind of what I was looking for ;) Then this strongly hints that something is wrong with our setup.

Currently we are trying with an external power supply soldered directly on the wifi chip to rule out if it's a problem with the other devices attached to our board.

stokes

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Re: Experiences with wifi stability and range
« Reply #5 on: January 29, 2019, 12:02:09 AM »
@stokes: Thank you for this bold statement. That was kind of what I was looking for ;) Then this strongly hints that something is wrong with our setup.

Currently we are trying with an external power supply soldered directly on the wifi chip to rule out if it's a problem with the other devices attached to our board.

Personally I would suspect a kernel or firmware problem because the 802.11 stack got broken a few times over the last 5 years and there are lots of different firmware versions out there...  also check the chipset over for a version number, often the later chipsets are el cheapos that aren't reliable.