Hah, I wish I had a proper thermometer or a thermal imaging camera for these kind of things!
My reference is of course touch, under heavy load it gets really hot, feels like the >80ºC I experienced with Amlogic S905X android tv boxes. Since this is a device that is supposed to be on 24/7, it worries me. I wish lm-sensors worked on this device.
Regardless of that, and even if the device wasn't hot, I'd still like to know if there are packages which may improve energy consumption, or any general tips like reducing tx power.
At least last I recall, the "guideline" was that if you could touch the device for a few seconds, it was somewhere below 60° C / 140° F, which was then generally well below the "safe limit" for transistors or early ICs.
If you think you've got a thermal problem with the device, with standard caveats around voiding warranties and possibility of damage to the device, the first thing I'd try would be a heat sink on the SoC. Not completely sure if this is the correct device, but they look like bare chips in the photo at Xiaomi WiFi Router 3G
That, of course, assumes you've got good airflow around the device, have blown out or vacuumed any dust you can from inside the case, and don't have it sitting on top of your 500 W stereo system, or the like
How much power does it draw from the mains or from its power supply? There's no more than 2 W of RF output (30 dBm = 1 W) from a dual-band radio, and it typically doesn't run at anywhere near full duty cycle. Many devices already only put out 1/2 or 1/4 W at "max" output (27 dBm and 24 dBm, respectively). I'd be surprised if reducing the RF output dramatically reduced the total power consumption.
What, if anything, do you have running on it other than the wireless, routing, DNS, and DHCP functionality? Are you running a VPN on it?
I've just started using the 3G and notice the same thing with temperature. I was looking for a little fan or similar to help increase airflow. Not noticing any issues with the temperature, just that it gets rather hot.