5ghz coverage & disconnects

Unanswered Question
Oct 14th, 2009


I have a wlan that uses both the 5ghz an 2.4ghz radios in our 1131ag's. I'm having some issues configuring the 5ghz radio so it is someone useful.

These ap's were installed after a survey using the 2.4ghz radio of an 1131, so the building was surveyed for G not A. I have turned on the A radio and enabled the ssid to broadcast on both. I can see that some notebooks are connecting to the A radio and have a good or decent connection of -60 to -75. What I have done is disable all of the data rates below 36mbit so that clients don't connect slower than 36.

What is happening is that the clients will connected at 36 or better on the A radio, but then move around the room where there might be less signal for the A radio, but still good signal for the G radio, and lose there connection because they initially connected on A.

I'm running a 5508 controller with the latest version. Is there a better way to make the 5ghz radios useful even though they don't have the same coverage as the G radios?

Also, I have replaced some of the 1131's with 1142's and I was wondering if I enable N on the 5ghz, will I get better coverage than 5Ghz on A?



I have this problem too.
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jeff.kish Wed, 10/14/2009 - 13:07

Hi Dan,

Unfortunately, 5GHz just doesn't propagate as far as 2.4GHz. So a 2.4GHz may work fine, but the 5GHz may well fall short of what's needed for solid connectivity.

One of the best fixes for this is to install new APs in dead-zones, and disable the 2.4GHz. This will prevent extra noise in that spectrum that's unneeded while filling the holes in the 5GHz.

802.11n is more robust than 802.11a, but it tends to simply provide better data rates than to actually increase coverage. There may be a small increase, but only your 802.11n clients will see it.

dan.letkeman Wed, 10/14/2009 - 15:10

So would it be best for me to just turn off 5ghz instead because I only have full coverage with 2.4ghz? Or is there a way to make the 5ghz less attractive to the clients?

How does the controller choose what frequency the client should connect on? Or does the client choose?


nelson.garcia Wed, 10/14/2009 - 16:45

Dan, I'm no expert, but I would assume that it's up to the clients to choose what frequency they connect on based on their capabilities.

I know that with laptops and desktop wireless NICs, you can configure them to communicate on a particular frequency, channels, etc, etc.

Don't take my word for it though, Jeff is the expert :)

jeff.kish Thu, 10/15/2009 - 04:35

Haha, thanks Nelson, but I'm only an expert when it comes to Nintendo :)

You're spot-on, the client makes the decision. +5 for that. I've heard that Cisco has a function in beta that will push a client to use one or the other, but that might only work for 802.11n. I'm sadly not a Cisco insider.

As for your other question, Dan, if your 2.4GHz is robust then there's really no need to use the 5GHz, especially if it will cost a lot of money to 'patch' those holes up. However, if you (for example) have neighbors or business devices that produce a lot of 2.4GHz interference, then 5GHz is the way to go. Very few companies have the ability for all devices to use 5GHz, but when it can be used it's generally a cleaner wireless environment.

I'll say this at least. 802.11n is designed to be run in the 5GHz space. It can be run in 2.4GHz, but it's a lot less effective. So you'll likely want to patch those 5GHz holes at some point, but that might be way in the future.


Peter Nugent Fri, 10/16/2009 - 09:18

The function is availabe in software version 6.0.182 via the cli

config band-select probe-response enable

ALso turning off the data rates below 36mbps will make the 5GHz cell sizes smaller so it may be worth experimenting and also pushing the power up to see if it helps


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