Is weak-looking actually better?

[jpjeffery]

Hi

We're implementing MR36 APs to replace our old Ruckus ZoneFlex 7982 APs.

I've been doing some Wi-Fi Surveys (with Visiwave) with the intention of a before and after comparison, but I've found that the maps I'm getting show a much cooler signal from the new Meraki APs compared to the Ruckus.

AP location shown slightly inaccurately by blue circle, lower left (it's slightly further to the right)

You can see from the photo that the Ruckus AP is at desk height, while the Meraki is mounted high on the wall.  So, despite the fact that the Ruckus AP's position is sub-optimal, it seems to be putting out a better signal than the Meraki.

But is the Meraki performance still likely to be better despite the apparent coolness? What's the best way of performing and A/B comparison?

[alemabrahao]

Both APs are interfering each other. It's not a valid test. You should have power of one of those, and perform a test.

[jpjeffery]

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@alemabrahao wrote:

Both APs are interfering each other. It's not a valid test. You should have power of one of those, and perform a test.

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Oh that's hard, as the Ruckus units are in production, and across all floors of our building (9 floors). 😞

[GreenMan]

They may or may not be interfering, depending on what channels they have adopted and the Tx power adopted - but certainly, in it's default configuration,the MR AP will be taking the visibility of that Ruckus AP (and any other WiFi transmitters) into account in determining its own settings.

[jpjeffery]

Well, @GreenMan  I'll check the channels in a mo', but as per @alemabrahao 's suggestion I turned off the nearby Ruckus and appear to have got an improved heatmap as a result:

[jpjeffery]

On this floor, the Ruckus AP is on Channels 8 (b/g/n) and 36 (a/n), the Meraki is 1 (2.4 GHz) and 48 (5 GHz)

[GreenMan]

The Ruckus AP being on 8 isn't great:   there are only three non-overlapping channels (generally 1, 6 & 11) and 8 impinges on both 6 & 11. 🙄

[jpjeffery]

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@GreenMan wrote:

The Ruckus AP being on 8 isn't great:   there are only three non-overlapping channels (generally 1, 6 & 11) and 8 impinges on both 6 & 11. 🙄

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Okay, this is new to me. How does 8 overlap 6 and 11? 11 is three away from 8. What about 7, 9, and 10?

I thought it was only the same channel number with, say, a neighbour's Wi-Fi, that was an issue.

[GreenMan]

No - the channel number assigned should better understood as the central channel in a spread spectrum system.     So, if you are nominally on channel 6, you are actually transmitting across 4 & 5 (and 6) + 7 & 8.     The same for channel 1   (-1, 0, 1, 2, 3) and 11 (9, 10, 11, 12 & 13)

Take a look here at the non-overlapping channels diagram :https://en.wikipedia.org/wiki/List_of_WLAN_channels

It's fairly widely accepted that for proper separation / avoidance of co-channel interference, you need to be 5 channels away.   A quick glance reminds me though that some vendors try to squeeze 4 non-overlapping channels out of 13, by using 4-channel separation:  1, 5, 9, 13   but this does still involve some channel overlap and channels 12 and 13 aren't available (or at least, not available without further restrictions) in some jurisdictions - notably the US.

As per my first comment, an AP on 8 and a nearby AP on 6 will definitely be interfering with each other, to some degree, even if you're using the looser 4-channel separation model (which Meraki does not recommend).

Notice too they took a different approach with 5 GHz, though it works much the same:   you can only select 40, 44, 48 etc.   You cannot even choose to configure APs for (say) channel 41 - at least, not in any of the vendors' kit I've worked with.

[jpjeffery]

Okay, interesting, thanks. That must make things difficult for consumers in roads like where I live where the houses are narrow and terraced!

Similarly, though, we have 8 floors in our office building. Floors 1, 2, 3, and 4, all will (at the moment) have APs in the same, or very similar, location on each of those floors. The Red Stars are the AP locations.

So we've got up and down as well as sideways signals to deal with.

[alemabrahao]

In an ideal wireless network design, the ideal is not to overlap the APs on each floor, so I suggest you to change the positioning of the APs between the floors.

Something like this.

[cmr]

@GreenMan if you use 13 then 8 is okay.

[jpjeffery]

Just as an experiment we tried suspending an AP from the ceiling in the middle of our floor (with the wall-mounted AP switched off):