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OndrejHolas
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Audience 5GHz - channel limitation

Fri Jan 03, 2020 12:05 pm

Hi all,

I am considering replacing current office AP (hAP ac) with more powerful one. Since there are multiple SSIDs (including one for VoIP), I'd prefer to distribute SSIDs to different channels, thus looking for an AP with multiple 5GHz radios and Audience meets this.

Although in specs on the web ( https://mikrotik.com/product/audience#f ... ifications ) there's no information about frequency ranges, quick guide mentions disjunct frequency ranges ( https://i.mt.lv/cdn/rb_files/1568200626 ... -%20qg.pdf ), even if there's no info, which range applies to which radio. In the forum I've found only one post mentioning real experience ( viewtopic.php?t=152628#p754422 ) but it is three months old and for such a new product this may have changed in recent ROS releases.

Has anyone here experience with channel limitations on Audience's 5GHz radios? In the case the one radio is limited to channels 100 and above, it is unusable for me - channels 100-140 (for outdoor use in local regulation) is quite busy due to usage by WISPs, so I'd like to stay on indoor channels 36-64. In that case, I'd go another way - possibly RB922UAGS-5HPacD with additional ac card.

Ondrej
 
heidarren
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Re: Audience 5GHz - channel limitation

Fri Jan 03, 2020 1:24 pm

The Audience do have 2 5GHz band, 5GHz1 which is 2x2:2 support channel 36~64, 5GHz2 is 4x4:4 support channel 100~165
 
OndrejHolas
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Re: Audience 5GHz - channel limitation

Fri Jan 03, 2020 2:11 pm

The Audience do have 2 5GHz band, 5GHz1 which is 2x2:2 support channel 36~64, 5GHz2 is 4x4:4 support channel 100~165
Thank you for clear information. So Audience does not meet my requirements and I'll go to RB922UAGS-5HPacD + R11e-5HacD.

Hope the information about supported bands/channels will be clarified in specs on the Audience's product page as well. Nevertheless, such a hard separation of bands between multiple 5GHz radios does limit use cases of the product. Could someone from MikroTik explain intentions for this limitation? I can only imagine prevention of interfering configuration - both radios on the same channel or on different but overlapping wide channels, although such configurations can be easily prevented in software as well.

  1. Is it technically impossible to use for example 2x2 radio on channel 48 and 4x4 radio on channel 64 (assuming 20MHz channels, that don't overlap)?
  2. Why 4x4 radio, obviously intended primarily for meshing (double throughput and in many European regulations channels 100-140 have allowed transmit power up to 1W e.i.r.p.), also supports channels up to 165 (5825MHz), which falls (in Europe) into low-power SRD range? This makes no sense at all.

Brgds,

Ondrej
 
r00t
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Re: Audience 5GHz - channel limitation

Fri Jan 03, 2020 2:39 pm

I think band split is caused by hardware filters to make sure both 5GHz radios are well separated and not interfering each other. You can only use ch 36-64 on first radio and 100-165 on second. So 48 + 64 will not work.
Max frequency is limited by used radio chipset, there is no specific reason to have support for ch 165 (that's just highest legal channel you can use), radio simply works from 4.8 to 6.2GHz, but on Audience the band split filters limit frequencies you can use.
Would be interesting to actually plot the filter shape, where exactly it falls and by how much for both radios. If only it supported the secret feature Mikrotik wants you to forget about, the magic spectral scan...
 
mkx
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Re: Audience 5GHz - channel limitation

Fri Jan 03, 2020 3:23 pm

  1. Is it technically impossible to use for example 2x2 radio on channel 48 and 4x4 radio on channel 64 (assuming 20MHz channels, that don't overlap)?

It is technically possible, but under one strict condition: that both radios are synchronized in Tx/Rx periods. If they aren't, then they would interfere with each other massively and no SW processing could do anything about it (adjacent channel interference with level of +70dB to +100dB compared to own Rx signal is unbearable). Mikrotik so far failed to develop synchronization between radios (which is wanted by some WISPs).
BR,
Metod
 
WeWiNet
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Re: Audience 5GHz - channel limitation

Thu Jan 09, 2020 5:03 pm

- You want to "distribute" SSID on 2 AP--> Why need for 2 AP??? You can create as many SSID as you want on one,
the advantage if it is on one AP that they are "synchronised" and actually no interference is created between them.
The limit is overall frequency system capacity only. And the capacity is best used/served by one AP taking care of all the clients
that are close!
- If you plan to use 2 x 5GHz RF AP at the exact SAME LOCATION you will create interference and lot of issues.
Ok you can use it with 20MHz channels, and fix frequency on both AP, but what if another AP comes in on exactly that frequency?
The throughput is also pretty limited with 20Mhz channels on 5Ghz, I would not do that neither.
- If you want to use 2 x 5GHz AP at different location each, no filters needed, use ethernet link and any device will do it.
or 2 x Audience for wireless interconnect.

Conclusion: When someone co-locates channels or omnidirectional AP physically, you need filters!
From that perspective Audience is a well designed product. The decision to use 4x4 on 100+ channels is because those channels can be up
to 160MHz and a couple of them are available. Also the output power (depending on regulations) is often higher, so they reach further.
This allows to "interconnect" two audience over Wifi and have the 2G and 5G band for client connections (MESH system/Range extender).
If you want 4x4 5GHz in channel 36 onwards, you can use RB4011. This one has no filters as it has only one 5GHz Radio and it can cover
the whole frequency range.
Instead of 2 small AP, better to use one "big one"... (if you want to put them at the same spot)
WeWiNet

**
MTCNA
hapac2, map, hap-lite, ltap-mini, RB4011 (good!), Audience (better) :-) !!!

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