[DD-WRT] Reducing WiFi power drain
I have two WRT-54G-TM routers with DD-WRT firmware build 12874 installed. One is an AP the other is set up as a repeater and both are rock solid and have been working great for almost two years.
The primary use is to provide wifi service for my cell phones as I cannot get any T-Mobile network signal inside my home. The new HTC Sensation 4G I purchased in June will drain the battery down in about 6 hours with wifi on (that's after some improvements).
I recently went out of town for 6 days and turned wifi off the whole time. The difference in power drain was remarkable. Instead of draining down in 6 hours the battery would have about 60% charge remaining after 12 hours.
Prior to purchasing the Android phone I was using a Blackberry and had a great deal of trouble getting the phone to connect using UMA. I finally discovered that reducing the beacon interval to 50 from the default of 100 and setting the DTIM interval to 3 from a default of 5 resulted in a good stable connection.
I've been doing some research and learned that a low beacon interval setting can result in more power consumption by the cell phone radio. As a test I started raising the beacon interval and went all the way to 1,000 with a DTIM setting of 5.
I've been keeping good records and my results seem to be mixed. At a beacon interval of 300 to 500 the power consumption was about 6% per hour. At a beacon interval of 1,000 the power consumption is 16% per hour. With a beacon interval of 50 the power drain was 15% per hour. I have switched back and forth between 500 and 1,000 three times and the results are very consistent - 6%/hr at 500 and 16%/hr at 1,000.
I see no difference in wifi performance at either setting. The phone connects just as quick and is stable. But I wonder why there is such a large difference in power drain.
I'm not a router expert and I wonder if anyone has any insight into what might be going on?