A Day in the Life of 3G
What Do Bars Say About Your Connection?
If you've ever wondered why your phone was showing five out of five bars and yet your service was poor, you're not alone. In one of the most surprising findings of our study, we discovered that the number of bars showing on our phones was by no means an accurate predictor of our connection speed or of network service reliability. In most cases the bars were useful only for telling whether we had some signal or no signal.
Phoenix is the only city we tested where the bars-of-service reading did a good job of predicting service quality. There we saw a correlation between bars and service quality in more than 70 percent of our tests, across all carriers. In the other 12 cities where we tested, bars of service were far less meaningful. In San Francisco, for example, only 13 percent of our tests showed any correlation between bars and service quality.
Our test results suggest that the bars-of-service readings tend to be a more accurate predictor of service quality on networks that have enough capacity to handle all of the devices connected to them. Overall, the bars on Verizon devices did the best job of predicting service quality in our testing. We saw at least some correlation between number of bars and Verizon's network performance in 11 of 13 cities. Bars were a moderately useful predictor of Sprint service in our tests in only two cities--San Diego and Phoenix.
In our tests of AT&T's networks in four cities (New York, San Diego, San Francisco and San Jose), the number of bars was not predictive of the service quality we saw; in the other nine cities in our study, the number of bars proved marginally useful in predicting how well our test experience would turn out.
The Problem of Backhaul
Backhaul refers to a wireless operator's method of moving data back and forth from the cell tower to the wireline Internet backbone. Bars of service measure your phone's connection to the cell tower, but that's just the first part of the trip. Bars offer no clue as to how smoothly and quickly the backhaul network is connecting with the Internet. That's why your phone may show the optimum five bars even though your service seems to be taking forever.
Let's suppose that you have keyed in ‘www.nytimes.com' on your smartphone. Your phone shows five bars, indicating that it has connected very quickly to the nearest cell tower. The cell tower then sends your request over the backhaul network, which connects to the system of fiber-optic and copper lines constituting the backbone of the Internet. Over this system, your request reaches the server that contains the New York Times content. But again, if the backhaul system is slow or overloaded, it creates a bottleneck in the system, lengthening your response time even though your device connects to the cell tower quickly.
Understandably, wireless carriers are investing heavily in more-efficient networks and technology to backhaul wireless data, which is rapidly increasing in volume. Perhaps the fastest and most reliable backhaul strategy uses fiber-optic cable to route wireless data back and forth between the cell tower and the Internet backbone. The carrier leases, buys, or builds new fiber-optic lines. To reach cell towers that are far away from existing fiber-optic infrastructure, mobile operators will increasingly use wireless approaches such as ethernet over microwave technology as a less expensive alternative to fiber for backhauling traffic.