Inside Sprint's cell phone testing labs (photos)

OVERLAND PARK, Kan.--Earlier this week, I joined a small group of tech reporters to tour Sprint's headquarters and its network and device testing labs outside Kansas City, Mo. The tour offered a fascinating look into not only the "mother ship" of one of the country's third largest wireless carriers, but also how it develops its wireless infrastructure and evaluates new handsets for network compatibility. In fact, over the course of the two-day visit, I learned more about how a carrier really does business than I have in my seven years at CNET.

Our first stop was Sprint's Technology Integration Center in nearby Lenexa, Kan. Inside an unremarkable building straight out "Office Space" is a 15,000-square-foot facility that holds a vast array of sophisticated equipment. Here, technicians evaluate new phones to confirm that they operate properly on Sprint's network and don't interfere with the carrier's other handsets and devices. Existing devices would also be brought in if their designs are revamped or they receive a major software upgrade (like a new Android OS).

Of course, the biggest attraction is this RF (radiofrequency) chamber. Lined on all sides with foam spikes, the anechoic (an-echoic or non-echoing) room blocks all external noise, wireless signals, and radio waves from entering and disrupting the tests. On the central pillar is one of several "heads" that serve as the first test subjects for a phone. After a handset is secured to the left side of the head, a signal is pumped into the room to test its network performance while technicians monitor the results from outside. Each phone is tested under different scenarios and the signal strength is adjusted several times. So in other words, it's just how you might interact with the network throughout a typical day.

Voice quality is not tested here (that comes later), but Sprint uses a dummy head to simulate real-world use. The head's shell is plastic, but inside it's filled with gel to resemble the density of a human brain. The phone is then positioned a set distance to one side. Though Sprint has unique criteria for its tests, handset manufacturers and other carriers use a similar process when evaluating devices. You'd even find such an arrangement at the Federal Communication Commission's labs in Columbia, Md., where the agency tests the Specific Absorption rate (SAR) of handsets sold in the United States.

The small yellow crosses on the ring surrounding the head are the points where the signal enters the room.

The RF chamber measures 15 feet in each direction. I could barely resist the urge to start bouncing off the walls and floors.

As we backed out the door, we took in the full expanse of the RF chamber and the testing equipment.

Though every other surface of the RF chamber was blue, the foam spikes on the door were yellow. I neglected to ask why.

A heavy metal door with a prominent handle sealed the chamber. In this facility, Sprint tests network compatibly for CDMA, EV-DO, and WiMax devices. The iDEN devices are tested at an RF chamber in Reston, Va.

Outside is a room where technicians operate the tests and track results. Issues will be addressed as they arise, and a phone will repeat the process until it passes. Later, the phone will undergo additional network testing in the field to evaluate, among other things, the hand-off process between the 3G and 4G networks.

Here is a closeup of the dummy hand that's used to secure the phone next to the head in the RF chamber.

New cell phones also are evaluated for the GPS signal reception.

Signal performance for streaming video is analyzed as well. The computer on the table will monitor and tabulate the results.

Back at the main Sprint campus in Overland Park, Sprint operates additional RF chambers for M2M equipment and other wireless devices that don't necessarily make calls. Though this RF chamber is smaller, it's equally adept at blocking out wireless signals thanks to the foam walls and Styrofoam panels.

Sometimes the tests are so sensitive that even the monitoring equipment can interfere with them. That's why this RF chamber uses two walls. As the new device is tested in the inner room, the equipment in the outer room tracks the results. What's more, the design allows a technician to enter the router room without disturbing the test.

Unlike the other RF chambers we saw, the inner room is not lined with foam. The moose head plays no role in the testing.

This RF chamber is used to test voice quality. As calls are placed to the phone, the audio is recorded and analyzed.

Outside the room are three dials that technicians use to change the testing parameters. For example, they could simulate a hand-off from one cell phone tower to another or between Sprint's home and roaming network.

This Ercisson E-node is an example of Sprint's Network Vision Initiative. Instead of offering a separate base station for each of its three incompatible technologies--iDEN, CDMA, and WiMax--the E-node can accommodate all three networks in one base station unit. Each network is handled through a series of cards that can be inserted in the slots in the center.

Besides using 60 percent less power, the E-node base stations are much smaller than the current base stations shown here.

Nearby is a station for testing how phones play multimedia software at various codecs and resolutions.

A few feet away, more technicians evaluate handset battery life by running multiple tests for both single use scenarios (Wi-Fi, streaming video, single calls, etc.) and multi-use scenarios (such as simulating an hour spent in an airport where a user might make a call, use the browser, play music, and use an app). What's more, signal strength is varied to affect power drain, the network is switched between 3G and 4G, and a simulation is run to evaluate how a device performs when it's off the network. Unfortunately, we weren't allowed to take photos of the battery-testing area.

At 50,000 square feet, the Mobile Technology Lab is a big place. Indeed, it showed that it takes a lot of wires to power a wireless network including 5 miles of fiber cable alone. On the campus as a whole there are 1,200 miles of fiber cable and 2,100 miles of copper cable.

Across the campus, Sprint evaluates custom user interfaces. Volunteers from outside the company sit at a computer monitor (left) where a camera tracks how their eyeballs interact with the menu design.

The monitor displays a graphical representation of a phone's menu. Subjects are then invited to watch the screen while they use an actual handset attached by a cable. In this photo, Sascha Segan, the lead analyst for PCMag.com, serves as a test subject.

As the camera tracked his eye movements, the red dots on the monitor to the left showed where his eyes were landing.

Next door is a room where volunteers are asked to use phones and talk about their experience while observers watch from behind a one-way mirror.