Is dualband WiFi at all logically possible?

Installing and Using OpenWrt Network and Wireless Configuration
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I have set up dualband on my TP-LINK Archer C7 v4 router. 2,4GHz ( 802.11bgn) and 5 GHz ( 802.11nac). Same SSID, same passwort, 802.11r active, FS over the AIR, dtim 3, and so on. And it works. I can switch between both networks instantly without interruptions (I will explain later why I know that).

The problem are my WiFi Clients, which are a state of the art Samsung Galaxy smartphone or a Lenove ThinkPad Laptop. It seems like the logic of every dualband device is pretty simple: "pick the stronger signal"

So even if I am 1 meter away from my router, they always stay in the 2,4Ghz frequency (-59dBm), even if the 5GHz is strong enough (-62dBm). Because of those 3dBm difference.

I don't want to disable the 2,4GHz signal, because if I am 30 meters away and the 5GHz signal is poor, the device should roam into the better signal. But if I return closer, it seems like there is no logic "Ok, now 5GHz is strong enough, I will roam back from 2,4 to 5"

I just wonder if dualband makes sense at all, if the logic of every device will always pick 2,4GHz as it will be always stronger.

(I can test roaming by restarting just the 2,4GHz signal, by removing the antennas or by a second device just running 5GHz connected by LAN 20 meters away, so i can confirm that roaming is working)

config wifi-device 'radio0'
        option type 'mac80211'
        option hwmode '11a'
        option path 'pci0000:00/0000:00:00.0'
        option htmode 'VHT80'
        option country 'US'
        option legacy_rates '1'
        option channel '60'

config wifi-device 'radio1'
        option type 'mac80211'
        option hwmode '11g'
        option path 'platform/qca956x_wmac'
        option htmode 'HT20'
        option country 'US'
        option legacy_rates '1'
        option channel '11'

config wifi-iface
        option device 'radio1'
        option mode 'ap'
        option ssid 'myssid'
        option network 'lan'
        option encryption 'psk-mixed'
        option key 'mypassword'
        option wpa_disable_eapol_key_retries '1'
        option macfilter 'deny'
        list maclist '40:B4:CD:15:CF:90'
        list maclist 'FC:A6:67:7C:69:11'
        option ieee80211r '1'
        option mobility_domain '12FE'
        option ft_over_ds '0'
        option ft_psk_generate_local '1'
        option wps_pushbutton '0'
        option dtim_period '3'

config wifi-iface
        option device 'radio0'
        option mode 'ap'
        option network 'lan'
        option encryption 'psk-mixed'
        option key 'mypassword'
        option ieee80211r '1'
        option ft_psk_generate_local '1'
        option wps_pushbutton '0'
        option ssid 'myssid'
        option mobility_domain '12FE'
        option dtim_period '3'
        option ft_over_ds '0'
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Btw. here is a confirmation of my theories:

3

yeah, you found out, how WiFi works.

you need extra software for active band steering, try „dawn“

1 Like
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I consider 2.4 only as support for legacy devices. A high performance network will use 5 GHz only. It is a lot faster.

If you need wider coverage, add more APs. Any client operating in fringe coverage requires a lot of AP airtime due to slow MCS rate and retransmits, which slows the whole AP down. Also the "hidden node problem" occurs.

2 Likes
5

use not the same ssid

2.4 GHz -> WIFI
5 GHz -> WIFI_5GHz

6

I guess thats a compliment :wink:

Already installing it. But how can it affect the decisions of the Client?

No matter how many AP's, there will be always a boundery. 2,4GHz will always go further. An I will not place AP's outside the house.

But that is not roaming. And I will still have the same issues that my devices will pick the stronger signal.

7

if it's for the phone see if there is an Android utility that automatically switches to the fastest speed

8

Probably best to tone down the 2.4 GHz so that it is just strong enough to allow FT between APs.

With the same SSID they’ll then quickly FT you to the 5GHz band on the currently active AP.

9

Solved it, thank you. Works like a charm. Here is my HowTo:

It can't be if the phone is not rooted. You can not control WiFi connections with an app.

Then I will not have the bigger distance advantage. Perfect solution is:
distance: 1m------10m------20m------50m------100m
bandwith: 5GHz--5GHz----5GHz----2,4GHz--2,4GHz

10

Interesting!

It seems you turned off FT between APs and rely on unassisted roaming?

Also, how stable is the band steering - I didn’t see threshold limits set in your config?

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To be honest, I just followed the (two) instructions and combined them.

I just can confirm, it works amazingly. Getting closer will switch my smartphone to 5GHz. Sometimes it takes up to 1 minute, but as it is real roaming, there is no interruption at all. As I backup my smartphone by WiFi every evening and larger files (e.g. Videos or my messanger "Signal" backup which is 6 Gigabyte ) are copied for a longer period, the switch to 5GHz is immediately boosting the speed. So I had no reason to play with the config settings.

And going to the garage will roam me to 2,4 Ghz and so I have a stable connection even outside the house.

1 Like
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For save my smartphone i have this box + adapter Realtek USB-3 gigabits ( USB\VID_0BDA&PID_8153 )

It cost me about 50 euros in France

Speed is fine -> gigabits !!!

I use also HDMI with my TV , charge the smartphone , USB/HDD , Logitech keyboard + mouse ...

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But thats wire. I could also use USB or remove my microSD. WiFi is more comfortable. I can move and use my smartphone without any inconvenience. 5GHz is fast enough and DAWN works great. Also with my Laptop.

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