The report was written by Chetan Sharma Consulting, who worked closely with Root Wireless to collect and analyze millions of data points collected from February to November. (PDF can be found here.) The data looks at the performance of all four major U.S. carriers—AT&T, Verizon Wireless, T-Mobile USA, and Sprint (NYSE: S)—in San Francisco, Seattle, Los Angeles/Orange County, Washington DC, Chicago, Dallas and New York City. Root Wireless tracks network performance by installing software on smartphones and judging signal quality, average download and upload speeds, 3G availability and connection error rates.

While the study found inferior 3G speeds, results varied by carrier, market and time of day. For instance, Dallas performed best with 275 kbps download average speeds and 112 kbps upload average speeds and New York City performed the worst with 205 kbps for download. Los Angeles was the only city that fell below 100 kbps.

The good news is that while the connection may have been slow, it was fairly reliable. The tests showed that there is only a 5 percent likelihood that a smartphone data connection would not go through as expected. Dallas ranked the best and Seattle was the worst. Unfortunately, the report did not break that information down by carrier, but it did report how large each carrier’s 3G footprint is. Sure enough, Verizon Wireless covers the biggest territory with 91 percent of the U.S., while AT&T covers only 76 percent. Sprint follows Verizon closely with 87 percent coverage, and T-Mobile trails in last place with 58 percent.

While 3G blankets most of the U.S., and failure rates are low, there’s a huge middle area where people can still experience poor service. The report tries to provide this information by collecting data on the likelihood of a particular signal strength. For example, nationwide it found that there is a 45 percent chance of a strong signal; a 24 percent chance of a good signal; a 26 percent chance of an average signal; and a 5 percent chance of a poor signal. Interestingly, NYC fared the best with 84 percent strong or good signal (despite common complaints there) and the rest of the cities were more or less in line with each other.

So, what should speeds really be? Let’s take a look at AT&T, which claims to have the nation’s fastest U.S. network. It says on its website that it “has engineered its network so that most users experience typical downlink throughput rates of 700 kbps to 1.7 Mbps, with bursts over 1 Mbps.” But it says, typical uplink rates are 500 kbps to 1.2 Mbps. As you can see that’s way above the 245 kbps and 645 kbps download rates that the average consumer is experiencing across all carriers. (For the record, the report’s findings are closer to AT&T’s stated UMTS speeds, which are between 220 to 320 kbps.) But it’s no wonder all of the carriers are racing to upgrade their networks to higher-speed 3G technologies, and ultimately 4G. They need it.