I ran a Skype test call so that I would make sure that both the AP and the iPhone would transmit plenty of frames. I wanted to check out an example using my iPhone (which, from what I gather, transmits at 10 dBm) connecting to an AP in a small office (which probably transmits at 17 dBm or 18 dBm). goes on to add that most traffic is downstream, thus making it all the more important to maintain high from-AP data rates. I have found this to be incorrect, so double-sorry, G.T.) His theory is that even if your client stations transmit at low power levels, having a high AP power level at least allows the from-AP data rates to stay as high as possible. G.T.’s primary point is that is is borderline mentally handicapped (politically correct term) to turn your AP’s power down. Now I’m going to tell you why his blog post is bullshit. Hill (of Ruckus Wireless) recently wrote a blog post discussing why this post is bullshit. One of those things is lowering your AP transmit power to a level that more closely matches your client station’s transmit power. The vagaries of iPhones and other station devices are the most difficult part of managing a WiFi network, but there are some things that can be done on the infrastructure to try to make your stations work better. Can’t live with ’em, can’t keep your job without ’em. I let my iPad send Probe Requests for while. The first device I checked was a 3rd generation iPad, which has 1 stream 802.11a/b/g/n radio.
I used the received signal strength in those Probe Request messages to see if my WiFi devices were changing power levels. Then I let the device send Probe Request frames looking for nearby WiFi networks. I sat the device directly adjacent to my 2012 MacBook Air (which has a 2-stream 802.11a/b/g/n WiFi radio) running in monitor mode. I decided to do a quick, unscientific test of device transmit power levels while on a non WiFi-equipped plane. The unanswered question is, “just how vast are these ranges of transmit power levels?” Can a smartphone or tablet go as low as half power? 10% power? 0.0001% power? Those differences could have a major effect on a WLAN infrastructure’s ability to handle a variety of devices. A typical implementation would force a device to lower its transmit power when receiving a strong signal from the AP and raise its transmit power when the AP’s signal is weak. Over the past year or so, more and more client/station devices have started using adaptive power levels. In the “Mighty iPhone Power Ranges” blog post, I wrote about the value of setting AP transmit power levels to approximately the same level as client/station device power levels. And possibly the biggest change (to iPhones, at least) is how aggressive iPhones are in modifying transmit power levels. About a year and a half ago, yours truly wrote about WiFi transmit power levels in iPhones.
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