In this year’s wireless speed tests, TechHive and its testing partner OpenSignal focused on getting real-world results. That’s why we used ordinary, readily available smartphones and tested in the physical spaces where real people use such devices, both inside and outside buildings.
Drive test metrics are great to have, and they help mobile carriers improve service and target problem areas on their networks. However, with over 34 percent of households in the United States claiming a mobile phone as their only phone, we know that most smartphone users are either at home or at work, presumably somewhere inside a building.
The results
In our tests, outdoor service was usually better than indoor service, but not by much. Both 4G and 3G service suffered an average speed loss of less than 0.7 megabits per second (700 kilobits per second), but that small difference turned into a big one for services where download speeds were less than 1 mbps to begin with.
Overall, 3G service showed marginal speed decreases when we used it indoors. Sprint, T-Mobile, and Verizon 3G speeds degraded by 5 to 9 percent in indoor usage. AT&T was an anomaly: Its 3G service produced download speeds that were 5.28 percent faster indoors than outdoors.

Full Story: Is 3G/4G slower indoors? Not as much as you might think | TechHive.