• Good afternoon everyone,

    Would any of you all have a lead to resources that would perhaps list common materials and their RF absorption ratings? I know there is a small table in the CWNA book, but I was wondering if maybe there is a larger list.

    I tried searching the web, but most of the results that I found had information pertaining to MRIs and other medical oriented material.

    I did find something from the IEEE, but the link that I was taken to must be dead as nothing came up on the page but the IEEE banner.

    Also, I have one other question about this. When the material states that it has an absorption of say, 15dB, would you use the power of 3s and 10s rule? Or would it be a clear cut case where you would just subtract that amount from the received signal strength if you were doing a pre-construction survey?

  • I don't have a list per say, but predictive modeling programs such as Motorola LAN Planner have built in losses, although that does need to be tuned somewhat. I prefer to find attenuation ratings on site because even if you know the exact loss of a wall, it is more difficult to find losses of desks, chairs, filing cabinets etc.

    Once you have your object attenuation ratings, you don't need to do RF math. Here is how it works (just examples):

    Transmit power: 20dBm
    Free Space path loss: 65dB
    Wall and other object attenuation: 19dB

    STA device RSSI: 20dBm - 65dB - 19dB = -64dBm

    We usually don't do this in an indoor environment, but this is the basics of how predictive modeling works.


  • Ok got it. So when studying for the CWNA, I need to think on a much larger scale and not think of it on an indoor wifi scenario for SoHo or SMB right?

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