I just finished up with a customer of mine, using a PMP450 network to connect video cameras around an industrial site. He called needing help, last night when it rained all of the video cameras connected wirelessly went offline. Knowing a bit about the site - it is not very large, everything is inside a 1KM square plot of land with the Access Point (AP) in the top left corner if you were looking at a map. There are just 3 camera locations, and the cameras all add up to about 12 Mbps per Subscriber Module (SM), all comfortably within the limits of the system The customer gave me remote access, and I began taking a look at things. The signal level was very strong for all of the SMs, all modulating at 8x data rate. I took a closer look and found that the frequency selected had significant noise on it, so I chose a much cleaner channel I also saw that the Uplink / Downlink radio was set at the defualt value of 75% down. In thei network, there is only video coming from the cameras, a small amount of Pan Tilt and Zoom (PTZ) camera controll info, and a tiny bit of radio management traffic. We reset the UL/DL ratio for 85% of the traffic to come from the SMs, or 15% Downlink, 85% Uplink.
So...in the end it wasn't rain fade that took down the cameras. The AP logs showed that the SMs never went offline. What happened was that the rain caused a peak in visual activity in all of the cameras, over-running the throughput available in the high interfrence and very low uplink avaible configuration.
All of this serves as a reminder, that while the PMP is a very capable video backhaul solution, the default settings favor traffic down to the remote modules. It's an easy and quick fix. Just look in the Configuration / Radio settings on the AP, and adjust the "Downlink Data %".