AP RF configuration fo site survey?

[-alx-]

Hi!

Who can explain proper AP RF configuration for use with Site Survey tool (Ekahau SS for example)?

I need to configure two parametes for SS tool - IR Power and Antenna gain.

And we knew: IR_Power + Antenna_gain =< Regulatory_Domain_Restriction

For example, I use 2602I AP. Lets look for "show command"

sh controller dot 0 powerr

### Tx Power: Dot11 Config
Serving Channel 3 (Type 0)
Active Level Index 1 (Unitless)
Active Level 16 dBm (OFDM 16 dBm)
IEEE MIB format TRUE
Metric unit dBm
HD Active 127
Low Power Mode Set High (Active: Set High)
Cookie max 17
Client Power Max 32767, Active Max 16 (Asymmetric)
Regulatory Limit 20
Modulation Index 0
Antenna Selection Internal, Rx: 4 active in [ABCD] Tx: 3 active in [ABC ]
Antenna Gain Reported:Configured:InUse = [0:8:8] (2 x dBi)
Allowed Power Levels Total 5 levels in TPO [16/13/10/7/4] Per-ant [11/8/5/2/-1]

Who can explain "Active Level 16 dBm (OFDM 16 dBm)" is IR_Power or EIRP?

Not so easy. Here used default antenna selection scheme - "4 active in [ABCD] Tx: 3 active in [ABC ]". And we see "Per-ant [11/8/5/2/-1]". Does 11 dBm proper IR_Power? At that configuration I receive a signal ~ -34dBm. If I chose antenna configuration to "a-antenna" my received signal increased by 10 dB to ~ - 26dB. Per-ant power level increased to +5 dB for every level [Per-ant16/13/10/7/4/1]. What antenna type should I use for site survey? And why increased power for antenna by +5 dB gives me +10 dB signal strength in physical?

Next question. For passive Survey my tool "hear" for beacon frames (I suppose). But "sh controller dot 0 powerr" command lists that:

Max per-path TxPower at modulation (at operation condition)
1.0 to 54.0 , 11 dBm
6.0bf to 54.0bf, 6 dBm

etc...

Does bf == Beacon Frame? If I disable DSSS data-rates, beacon frames will transmit at +6dB tx_power?

Should I disable stbc and other channel improvement technology while site survey?

And what I should to configure at "antenna gain" if I have pre-installed antenna?  Value from Datasheet or some offset?

[Flavio Miranda]

Hi,

 If you are using a omni-directional Access Point antenna don´t make sense worry about gain. As you may know, omni-directional spread the signal equally in all direction. 

 The power can be change considering your weaker client. Keep in mind that not only the AP need to reach the client but also the client need to reach the AP. However, most of client is able to do that just fine in a office environment. I´d worry more about it in a open space area. 

"Does bf == Beacon Frame? If I disable DSSS data-rates, beacon frames will transmit at +6dB tx_power?"

 I think you are over-complicating a quite simple task. 

 Hope that helps.

-If I helped you somehow, please, rate it as useful.-

[Haydn Andrews]

Hi Alx

In Ekahau if for a predictive you should select the AP and antenna model you are planning to use. By setting the TX power you will then be able to see the EIRP of that AP - based on the antenna gain and the TX power (note this is relevant to the TX power).

If you have any attenuators between the AP and the Antenna like RF extension cabling, you need to do the RF Maths to calculate the EIRP of the desired power, RF Loss and Gain and then alter the TX power to you get that EIRP.

For the passive survey your adapters will hear the APs, now if you have an device that is less/more sensitive to the adapter you are using, you can use offsets to show the expected signal coverage for those devices:

https://support.ekahau.com/hc/en-us/articles/115005259648-Visualization-Options

Around turning off TPC/DPC, if the environment is stable then its half a dozen of one half a dozen of the other, but if the environment is likely to be changing power or channels whilst you are surveying then best to disable during the survey.

Haydn