wlc - 2700i - client connection speed not dynamic

MadsLahrmann · ‎03-04-2016

Hi all

I am running a Wireless Network at a storage Facility with handheld clients (honeywell A720 and intermec devices CK3x).

I am currently seeing the clients - including laptops - not being able to change connection speed within the 802.11a datarates. It seems they are all fixed at 54Mbit and wont go to lower speeds when moving to the perimiter of the cell of a given AP.

Has anyone ever seen this sort of issue? - I have been going through the wlc configuration but cannot seem to spot any tings that should Lock the connection speeds.

Thank you,

Mads

Freerk Terpstra · ‎03-06-2016

It depends on your access-points and the data-rate configuration but the biggest part of the puzzle is the client itself. The client decides which data-rate it is going to use and in this case apparently they decide that the 54Mbit/s is fine. What you can do on your side is checking which data-rates are enabled (globally or with the help of RF-profiles) on the WLC / autonomous access-point and also on the client devices.

Do you currently have problems with the infrastructure or are you just curious?

Please rate useful posts... :-)

MadsLahrmann · ‎03-08-2016

Currently have some issues with this.

Accesspoints are 2702i's. From what I can spot, i enabled lower datarates aswell. Will doublecheck on that asap.

I cannot figure out if its due to the clients, or the wlc settings. From what I can gather, I havent set any parameteres that would lock down the clients to connect at 54mbit exclusively.

But the issue is a bit annoying seeing as my coverage cells would be smaller at 54Mbit than what they would be if the speed was dynamic and would scale back to say 24Mbit..?

Freerk Terpstra · ‎03-08-2016

A higher data-rate means more complex modulation which requires a better signal/noise ratio (SNR). This requires a certain level of signal strength which depends on your access-point placement, configured power, used antennas and the specs of the client.

If your client has "the opinion" that 54Mbit/s is still a good data-rate this means that the signal is sufficient enough or that the wireless driver makes a stupid decision (due to configuration or bug). You can easy test this by walking away from your coverage area and see if the client will ever try to use lower data-rates or just disassociate.

It really depends on your deployment, but making your coverage cells bigger is something you (most of the times) try to prohibit. A lower data-rate means that the client will "claim" the channel longer and that the other clients have to wait for this. This causes a higher channel utilization which means less throughput on the channel.

Please rate useful posts... :-)

MadsLahrmann · ‎03-08-2016

We did exactly that - walking away from the coverage area - but the connection speed didnt change untill the client got disassociated.

Throughput isnt really an issue here, the amount of data needing to be transmitted is very limited. The main issue here is coverage.

I have been checking yesterday, but i cannot for the life of me see how the controller should be limiting the datarate to 54Mbit. Due to other Things I have disabled N and AC datarates though. But that shouldnt limit it from my knowledge.

Freerk Terpstra · ‎03-12-2016

Did you already check the settings on the client device? Any (driver) software updates available?

If you can't find anything on the client side, you should make some wireless captures with a notebook next to the client. I'm curious what is going on in those beacons. I personally use "Acrylic Wi-Fi Free" to get my wireless NIC into monitoring mode and capture the virtual interface with wireshark.