One last note I should add is that a big difference in transmitted and received Retry percentages most likely means that there is a transmit power mismatch between AP and station, but there are exceptions. And if the transmitted and received Retry percentages are approximately equal? Great job! That means that you already have AP transmit power set to the level it should be at. (Unfortunately, I have an old Apple Airport Extreme wireless router that does not allow its transmit power to be reduced in the configuration GUI.) When the transmitted Retry% is lower than the received Retry% (as it often is in modern enterprises, due to the unfortunate "picocell" phenomenon), then AP transmit power should be raised to avoid a meltdown when the Wi-Fi network gets busy. When the transmitted Retry% for a station is higher than the received Retry%, then AP transmit power is too high, as it is at my place. Anything under 5% is usually considered good in a crowded residential environment.)īy comparing the transmitted Retry% with the received Retry%, you can figure out whether your AP transmit power is too high, too low or just right. (In my case, the received Retry% for my iPod was much more acceptable than the transmitted Retry%. To do that, select the "AP" tab in the Start screen of AirMagnet, then double-click on your AP to get to the Infrastructure screen of AirMagnet. First, open AirMagnet and start capturing only what your AP is transmitting and receiving. Here's how to use AirMagnet WiFi Analyzer (I'm going to call it "AirMagnet" from here on out for brevity's sake) to test whether AP and station transmit power is balanced:ġ. I've used Wireshark, OmniPeek and AirMagnet WiFi Analyzer, and they all work great. Any protocol analyzer that can use Monitor Mode will do. My technique for finding out which transmit power level works best on APs is to test connections using a Wi-Fi protocol analyzer. FCC documents can help (try searching " FCC" and you might find some leads), but the fact that a lot of devices use a transmit power level below their registered maximum makes it tough. ![]() The tough part about matching AP and station transmit power is that it is often hard to find out exactly what power level stations are using. If your applications are primarily downlink applications, then your optimal Wi-Fi infrastructure probably is going to have AP transmit power be quite a bit higher than typical transmit power levels for smartphones and tablets.) (At this point it should be noted that if the applications you support are primarily one-way applications, then you probably should ignore what I'm saying. And lots of users like to use two-way applications nowadays. Matching AP and station transmit power is great because it facilitates two-way applications. Sometimes we need really, really good Wi-Fi, and matching the transmit power levels of APs and stations can go a long way towards fulfilling that need. ![]() ![]() ![]() Most Wi-Fi deployments are not like the beaches of Normandy, where everyone had the same model of radio. Breaking the rule is understandable because Wi-Fi environments are often vendor-neutral. It has long been the recommended to have matching transmit power for devices engaging in two-way wireless communication, but with Wi-Fi that rule is often broken. And an important step in setting up a good Wi-Fi infrastructure is finding out whether the APs' transmit power is too high, too low or juuuuuuust right. But there's a difference between understanding that Wi-Fi devices have differences and creating an infrastructure that supports them. If there's one recent change in the Wi-Fi world that has brought some heat and light to your humble blogger's cold, dark heart, it's the awareness of device differences.
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