WifiNigel

Cisco APs support a number of discrete transmit power levels which are 3dB apart. They are usually numbered levels 1 (highest) down to 7 or 6 (lowest). The numbers of levels and the transmit power values assigned vary between models and regions. The quickest way to determine the levels supported by your AP is to logon to your WLC and execute the following CLI command: show ap config 802.11b <ap-name> This will list out a whole lot of information, including a section which starts with the title: "TX Power". This contains the levels and corresponding dBm levels supported. Here is a sample: Tx Power       Num Of Supported Power Levels ............. 6       Tx Power Level 1 .......................... 16 dBm       Tx Power Level 2 .......................... 13 dBm       Tx Power Level 3 .......................... 10 dBm       Tx Power Level 4 .......................... 7 dBm       Tx Power Level 5 .......................... 4 dBm       Tx Power Level 6 .....

I often like to do a quick FSPL calculation to understand how far a WiFi signal might travel and usually have to search around to find an FSPL calculator. So, I put my own together so save me the search next time. To understand what a signal level might be over a particular distance, simply select the channel you are interested in, enter the EIRP of your AP and the distance involved. Then hit the 'Calc' button: Enter Frequency (Ghz): -- choose freq -- Ch1 - 2.412Ghz Ch2 - 2.417Ghz Ch3 - 2.422Ghz Ch4 - 2.427Ghz Ch5 - 2.432Ghz Ch6 - 2.437Ghz Ch7 - 2.442Ghz Ch8 - 2.447Ghz Ch9 - 2.452Ghz Ch10 - 2.457Ghz Ch11 - 2.462Ghz Ch12 - 2.467Ghz Ch13 - 2.472Ghz Ch14 - 2.484Ghz Ch36 - 5.180Ghz Ch40 - 5.200Ghz Ch44 - 5.220Ghz Ch48 - 5.240Ghz Ch52 - 5.260Ghz Ch56 - 5.280Ghz Ch60 - 5.300Ghz Ch64 - 5.320Ghz Ch100 -

After previously looking at the challenges we may face with 802.11ac due to the restrictions of the 5GHz band (see part 1 and part 2 of this series), in this final installment, I suggest how we may mitigate the challenges we may face, together with a possible (but no doubt controversial) solution. The Solution? I'm not aware of any "magic bullet" to solve all of the challenges outlined in this series of articles (sorry). More spectrum will certainly help things. But, time-scales for the allocation and adoption of new spectrum are not clear at this point in time, though many agencies around the world are considering ways to free up more spectrum to improve WiFi capacity. Though spectrum may become available in relatively short time-frames, there will still, no doubt, be a significant time-lag before this permeates through in to the world of vendor and consumer WiFi products (remember the issues raised around UNII-2e support?)  The best way to mitigate th