WiFi for Voice & WLC

[fred.oosterhuis1]

Hello

I need a heads up

we did a site survey carrying around an AP1602 to do radio measurements. We thus have made a map of where to position the APs so as to have minimal signal strength of -70 dBm anywhere wifi voice terminals will be used.

OK so far.

We will have the APs managed by WLC.

I need the WLC to manage the APs in such a way that the minimum radio signal level of -70dBm is maintained at the border/overlap of different APs' radio fields.

That is:

with

AP1 ----- radio field1 ------------- | --------- radio field2 ------- AP2

the site survey determined that at the cell boundary  |  we have -70dBm with AP1 and AP2 in specific positions where they will be installed.

1. What do I need to configure/check on WLC to make this -70 dBM happen at cell boundary?

2. Do both WLC2504 and CT5508 support this?

3. Does the virtual WLC support this?

Thanks a lot,

Fred

Thanks

Fred

[Freerk Terpstra]

Hi Fred,

In your pre-deployment survey you should verify the following things:

• Are there sources of interference on the 802.11b/g/n/ and/or 802.11a/n/ac frequency (whatever your client device is going to use, for voice this is most of the times 802.11a/n/ac)
• Where is coverage needed? (It is voice, so don't forget stairways for example!)
• What is the power output of your client device? (Use this value as the maximum power on the access-point to protect against one-way audio)
• Minimal RSSI (for voice most of the times at least -67dBm, from two access-points for roaming)
• Minimal SNR (for voice most of the times at least 25dBm)
• Minimal datarate (for voice most of the times 12Mbit/s on the 802.11a/n/ac)

If you use software like Ekahau you can specify all of the above settings and select the client device so that the software can use this information in it's calculations.

All Cisco WLC's use the RRM algorithm to automatically configure and tune channel and power settings. Make sure that you configure the maximum power settings for RRM to match the power of your client device (again against one-way audio) and also tune the datarates. Last but not least do a survey when the network is operational to check all of the above and make changes when needed.

[abwahid]

Hi,

Actually the controller uses the quality of client signal levels reported by the APs to determine if the power level of that AP needs to be increased.

If clients SNR drops below the configured threshold value on the controller, the AP increases its power level to try to compensate for the client. The SNR threshold is based on the transmit power of the AP and the coverage profile settings on the controller.

You can configure the RSSI in RRM section of the WLC

[George Stefanick]

My curious you built your cells at 70. What device did you do to measure that ? Also what power was your ap at ? How much cell overlap did you use ? Something doesn't sound right here .. 

[gohussai]

You just config the RSSI as if clients SNR drops below the configured threshold value on the controller, the AP increases its power level to try to compensate for the client.