adjustment of tx power for APs with external antennas

[merilcerpos]

hello everyone,

i have a question regarding access points with external antennas.

Let's say a typical client is sending at max 14 dBm, when planning with Access Points with external antennas in Ekahau with antenna gain of e.g. 4 dBi, the EIRP is increasing. In order to have an equal transmit power bidirectional from both sides the values should match (or the AP should be even set lower than 14 dBm)

The antenna gain needs to be set as parameter on the WLC in the AP's radio manually.

Is it required to plan in Ekahau with 10 dBm Access Point transmit power (14 dBm - 4 dBm Antenna Gain) so that effectively the Access Point is sending with 14 dBm and the client can send with 14 dBm?

Can someone give me more information ideally with a link for more deep dive.

Thank you.

[Flavio Miranda]

TX power is not a protocol that must match between client and AP  in order to work. It is much more simple. What can not happen is you to put an Access Point antenna whith a high gain in the way that the signal travels so far that the client can´t reply with enough quality. This is would be problem.

 Signal power Tx or RX is one part of the equasion. The most important parameter is SNR and that´s why Configure parameters manually is a bad decision. You can prevent TX power by configuring manually but you can´t prevent noise and them you SNR will degradate.

 Best advise:  Position your AP the best way you can, let the WLC take decision and use good client adapter. 

[ammahend]

Agree with some of the points Flavio mentioned, although not sure the best thing to do is "Position your AP the best way you can, let the WLC take decision. ", if this was true, then wireless survey seems like a waste of time. Although lot of people do that, and might be OK with your 10 AP deployment, but for not for critical infrastructures.

If you are doing survey, keeping client's receive sensitivity in mind is a good idea, it basically is a representation of how week signal a client can receive and still process frame at a certain speed (data rate), you can use this as a baseline for your survey. for e.g. say your client can operate at 24 mpbs data rate even if it got the AP signal at -72dBm and if you are ok with this (which seems like a decent value), then keep -72dBm as your cutoff for cell edge and now see how much TX power you need on AP to have a -72dBm cutoff covering your desired area.

having said that, every engineer has their own way of approaching it, because every environment is different and information available from customer can be limited, but this approach above has worked well.