Absolute Power


iPhone Antennagate Solved


This blog originally posted on the Low Power Engineering Community 1/12/12.


Last time we looked at the relative signal strengths on the iPhone 4S vs. the iPhone 4 using field test mode to gather data in a variety of locations around Silicon Valley. The data below shows signal strengths for the 4S and 4, with and without using the “death grip” on the phone.

We saw slightly better reception on the iPhone 4S than on the iPhone 4, but the really dramatic difference was the delta in signal strength with the “death grip” applied. The iPhone 4S showed a signal strength attenuation of around -6dBm which is significant, but the iPhone 4 showed a huge drop of -17dBm, more than enough to cause dropped data and voice connections.

The next question is, what’s the relative performance of the two smart phones in our video streaming test? We’ve run quite a few tests already, so here’s a summary from the archives:

We have a couple of comparable data points. The data suggests that not only does the iPhone 4S fix the death grip problem (from the graph above) as a result of the new dual-antenna design, but it also seems to have markedly better power efficiency in communications. That’s likely due to the new and improved modem chip. Comparing the baseline numbers with the “2 to 3 bar” data, the 4S requires only an additional 500 mWh of energy to stream the movie vs. watching it locally, compared to 1500 mWh on the iPhone 4. That’s a pretty significant improvement. Plus, we don’t see the runaway energy consumption problem at very low signal strengths as was the case in our original iPhone 4 tests. This one’s a little harder to draw a conclusion, since the test conditions don’t match up too well. I’m very interested in looking at iPhone 4S performance on the Star Trek test at the edge of its signal reception capability.

It’s time to go locate another good testing spot, and watch the movie a few more times. I’ll report back next time!


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