2.4 Ghz Backhaul for outside AP

[mlsc]

Hello

We are looking to implement three AP (1530 with 2504 WLC) in an outside open space and have a quick question on the backhaul. We don't want to use any of the 5.8 Ghz backhaul frequencies. As of WLC 8.2, i believe we can use the 2.4 Ghz as a backhaul. Does this mean that the APs use the 2.4 Ghz for both client access and backhaul at the same time. Will it be the same radio, or will it use two different radios at the same frequencies. Has anyone used this with good success, is it a viable option? What would be the normal distance between any two APs?

Thanks, Michael

[Ric Beeching · Accepted solution]

Hi Michael,

I think this answers your question; although it is in the 8.5 deployment guide it does say from 8.2.

https://www.cisco.com/c/en/us/td/docs/wireless/technology/mesh/8-5/b_mesh_85/Mesh_Network_Components.html

The 802.11ac indoor access points are two-radio Wi-Fi infrastructure devices for select indoor deployments. One radio can be used for local (client) access for the access point and the other radio can be configured for wireless backhaul. If Universal Backhaul Access is enabled, the 5-GHz and 2.4–GHz radios in rel 8.2 can be used for local (client) access as well as a backhaul.

The Cisco indoor mesh access points are equipped with the following two simultaneously operating radios:

• From rel 8.2 2.4 GHz radio used for data backhaul and client access if UBA is enable

I think that covers the backhaul Q though one consideration is that at each end the APs could suffer or cause high levels of interference from using the 2.4 band which you're probably aware of.

Distance - That depends on a number of factors that can't easily predicted such as line of sight, humidity/weather, antenna height and alignment and, very importantly, what external antenna you are using (if you're not using the internal models). The antenna gain will have a huge affect on distance and could take you from a limited distance of say 100m up to kilometers.

What also counts regarding stability would be traffic type / throughput / usage etc. If you just need a basic link of 1Mbps you could get a much further distance but as soon as you want to up that and have more clients on the far side etc, that distance for a reliable connection is reduced. 

As all the experts will say on this forum, you'll need to perform link budget calculations to try and theoretically work out your distance and do some testing / site surveying / tweaking to come up with the best config, alignment and speeds for your deployment.

I find this free too quite handy for providing estimates on distance but take into account the gains on the various APs that ubiquiti use and compare to your 1532 AP gain.

https://link.ubnt.com/#

Thanks,

Ric

[mlsc]

Hi Ric

Thanks for your answer and the various links; that's what I was looking for.

My specific use case is fairly simple, 1-5 clients, with the APs about 150 meters apart.

Thanks, Michael 

[Ric Beeching]

I still recommend using 5 GHz at that distance unless you have a specific reason for it. Again, depends on your antennas in use. I've setup 1532s to a distance of 800m - 1km with that many clients behind them on 5GHz. I used the 14dBi antenna on each to achieve that however.

Cheers,

Ric

[mlsc]

Unfortunately, the 5 Ghz is not available to us (long story). Do you think that the 2.4 Ghz backhaul will have such a performance hit over the 5 Ghz? It should be able to cover 150m with the right antennae?

thanks, michael

[Ric Beeching]

Sorry for the slow response.

Look you should be fine but I'd try and tweak your power levels so you have a nice mix of good signal versus not interfering with everything else around the bridge. You can't do much about other devices interfering with your link though so you may see dropouts. Make sure you disable the lower data rates (anything below 12) on the bridge link.

Ric