Radio Transmit Power Control (TPC) Settings - Power Threshold

[kfarrington]

Hello all,

Reading the following document

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a008072c759.shtml#tpca

Can some explain to me a little better what the "Power threshold does"

Dont know if its me, but I am finding the text below a little hard to understand?

It says it is only for downward power control? Man, im confused?

Power Threshold-This value (in dBm) is the cutoff signal level at which the TPC algorithm will adjust power levels downward, such that this value is the strength at which an AP's third strongest neighbor is heard. In certain rare occasions where the RF environment has been deemed too “hot”, in the sense that the APs in a probable high-density scenario are transmitting at higher-than-desired transmit power levels, the config advanced 802.11b tx-power-control-thresh command can be used to allow downward power adjustments. This enables the APs to hear their third neighbor with a greater degree of RF separation, which enables the neighboring AP to transmit at a lower power level. This has been an un-modifiable parameter until software release 3.2. The new configurable value ranges from -50dBm to -80dBm and can only be changed from the controller's CLI.

Many thx indeed,

Ken

[Aaron · Accepted solution]

Ken,

You might think of the power threshold as the "master fader" in AutoRF that

controls, overall, how "hot" the radios in the given band will be.

The way this works, is that AutoRF tries to set the APs' radios' transmit

power levels such that each radio can hear exactly three other radios

at or above the threshold value.

For example, if I set the threshold to -65dBm, then, at each AP,you will

be able to hear three *other* APs at -65dBm or hotter. But if you set the

threshold down to -75dBm, then AutoRF will turn down the radios' power

levels, such that, at each AP, all but three other APs will be below -75dBm.

If you didn't quite follow that, then perhaps it will suffice to say that

higher values (such as "config advanced 802.11b tx-power-control-thresh -65")

will make your APs overall transmit at higher power, and lower values

(such as "config advanced 802.11b tx-power-control-thresh -74") will make

them transmit at lower power (assuming that you have sufficient density.)

[Rob Huffman]

Hi Ken,

Aaron, great description of this feature! +5 points for sure.

I always relate this to a Temperature "Set Point" or Trigger. When you reach the Set Point the AC kicks in to cool things off (hahaha).

Take care,

Rob

[kfarrington]

Aaron,

That is a excellent way of looking at it :))

Very helpful mate!

cheers fella

Ken