Dual-band SSID Best Practices?

Installing and Using OpenWrt Network and Wireless Configuration
1

What's the best practice for setting SSIDs on a dual-band access point? For example, on a router with 2.4 GHz and 5 GHz radios, should I:

  • Set both SSIDs to the same value, and have clients connect to that SSID, leaving the choice to the client OS.
  • Set a different SSID for each band, and configure the client OS to connect to exactly one of them.
  • Set a different SSID for each band, but configure the client OS with both of them in order of preference (if the OS allows it).
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2

Good question!

Yes, this is what I suggest. I use the following scheme:

  • SSIDfoo_2.4
  • SSIDfoo_5.4

If a device is capable of 5.4 GHz, I only configure it for 5.4. In most cases, 5.4 will be less congested and have higher bandwidth.

This doesn't work on some OSes. It will see 2 BSSIDs (MAC address of the APs) and randomly select.

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3

try same ssid and see if it works well in your environment with your clients.

if you want or need the ability to switch bands quickly, use different ssid's, simple

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4

afaik it would select the one with the better signal.
it becomes interesting thou if signal strength changes; "should i switch?"

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5

Yes; but in this case, signal is relative, they're different bands.

6

This is a problem I've had in my case - I have a couple of machines that are just at the edge of the 5GHz network reach, and I can see from logs that every couple of minutes it would switch back and forth between the 2.4GHz and 5GHz networks when using a single-SSID setup. I'd like to say that it was not noticeable from the end user perspective, but it was...

The other side of the coin is that, on those same machines in a dual-SSID setup, I find myself frequently manually switching back and forth between them as the signal quality tends to vary quite a bit.

7

You may wanna think about replacing the antennas on the router with high dB antennas (a 5dB or 7dB).

8

only if there is not much other wifi around.
in an already congested (urban) environment, it may very well make things worse.
(more antenna gain -> more range -> more collisions/interference)

9

Provided one utilizes WireShark or an equivalent to determine what channels one should utilize, a higher dB antenna is unlikely to make it worse.

  • The 5.7GHz range degrades quickly as it is, and provided one is utilizing a channel not being heavily used by others in the vicinity, a higher dB antenna should not adversely affect performance.
    • If we were able to see high frequency radio waves, you'd see we're always enveloped by an extremely high amount of radio waves utilizing different band and channel widths.
10

I'm in an urban environment - lots of apartments all around me. When my router scans for access points, it can see 57 stations on the 2.4GHz band, and 29 stations on the 5.0GHz band... and that's just on the first pass. On 2.4GHz, they're evenly split between channels 1, 6, and 11. On 5GHz, they're evenly split between 36, 149, and 161.

11

How many are on 5.7GHz channels 149 - 157 & 5.8GHz 161 (this is the only channel block that would be utilized)?

  • 5.7GHz
    • 149: 5.745GHz
    • 153: 5.765GHz
    • 157: 5.785GHz

  • 5.8GHz
    • 161: 5.805GHz
12

Annotated the above.

13

157 looks as though it would work best, as I believe it only switches between 1 above and below, but it might be 1 above and 2 below (I can't recall which).

  • Depending on the strength of those 9 on 161, a 5dB or 7dB might result in those neighbors experiencing reception issues with their own routers, but a 2dB antenna chosen specifically for your current environment would likely help.
    • WiFi antennas don't operate in the way most would picture, as WiFi antennas are designed to broadcast more vertically, more horizontally, or about evenly on both axis'
14

So, when I set it to 157 with a bandwidth of 40MHz, OpenWRT shows it as broadcasting on channel 161, where if I do 20MHz, 157 shows as 157. Does this have something to do with the channel being positioned relative to the bandwidth requested?

15

I believe with VHT (40Mhz bandwidth) it will cover 1 channel above and below, but it might be 1 above and 2 below

  • I don't recall enough information to provide a technical answer, but if I recall correctly:
    • If Channel 157 is selected, it will cover 153, 157, & 161, whereas if Channel 153 is selected, it would cover 149, 153, & 157

However, if HT [20MHz bandwidth] is chosen, it would only utilize the specific channel selected.

  • HT will halve your throughput
16

How would I determine the gain of my current antennae? My router's info page at OpenWRT doesn't seem to list it: https://openwrt.org/toh/tp-link/tl-wdr3600 , nor does the manufacturer's page: https://www.tp-link.com/us/products/details/cat-9_TL-WDR3600.html#specifications

17

Great question =] WikiDevi also doesn't list it, however I'd imagine the FCC application would (or the applicable government agency if not within the US).

For WAN traffic, no... but for LAN traffic, yes. For LAN data transfers it would make an enormous amount of difference.

18

If my upstream cable internet connection is only 60 megabit, is there going to be any real difference between a 150 megabit and a 300 megabit wireless lan? I don't do any high bandwidth traffic between wireless clients, everything is going out to the internet.

19

Yes, see the chart here:

You minus the gain of the old, and add the gain of the new. Be advised, changing antennae could change Part 15 authorization in the US (even though a lot of devices came with detachable antennae).

No bufferbloat due to being on WiFi versus wired...that's all I can think of at the moment...

Hope this helps.

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20

Antenna type: Dipole antenna with 3dBi gain

https://apps.fcc.gov/eas/GetApplicationAttachment.html?id=1812724

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