There's a lot more to cell phones than just the ability to make and receive calls. Today's mobile phones come with a plethora of features that include detailed address books, built-in digital cameras, instant messaging, speakerphones, MP3 players, streaming video, and Bluetooth connectivity. Add a fully functional PDA and e-mail client, and you've got a smart phone. Phones come in a wide range of forms, from flip and candy bar styles to the slider and swivel designs. As a result, how each model performs and implements its features can differ substantially. Our testing is designed to provide a complete appraisal of the features and functionality of cell phones by examining usability (ease of use, feature sets, and so on), call quality (both subjective and comparative appraisals), and battery life. We also consider a phone's price when assigning a rating. Though the price can vary widely depending on whether you sign a service contract at the time of purchase, we still make a judgment based on the phone's overall value and how that price compares with those of similar models. Phones that are considered a good value will be assigned a higher rating than those handsets that are a poor value.

Usability

We put each phone through its paces for a minimum of two weeks, evaluating menu navigation and usability, durability, ease of use, button and keypad layout, display resolution and readability, software design, and ergonomics. We access all available features a number of times so as to gauge a mobile's performance relative to other models in its class. Usability tests are conducted in CNET Labs and outside the office in various real-world situations, such as while walking down the street. Screen visibility tests are conducted under various conditions, including at night and in broad daylight.

We test the standard features on cell phones, such as entering names in a phone book, downloading and playing games from a wireless Web connection, and sending and receiving text messages and e-mail. Phones with added features, such as built-in cameras or MP3 players, undergo additional testing of the specific features. For example, we take pictures with camera phones, then send the shots to other camera phones and e-mail addresses from the mobile's address book. We also photograph a set scene and evaluate the image quality of the captured image. If a phone has a built-in MP3 player, we put the device through similar testing we use for standalone MP3 players. Smart phones get specific tests for such features as the Bluetooth connection, the infrared port, e-mail support, PC syncing, and Internet connectivity.

In the course of testing, we also evaluate how well a phone performs in terms of audio quality and dropped calls. While this information is relatively informative, call performance is largely dependent on the quality of the network that the phone is using, as well as other variables such as the quality of the phone's antenna, the number of users currently on the network in the local area, the location of the user, and atmospheric interference. We place calls from a cell phone to a landline, and the audio quality of the call is evaluated from both ends of the connection. We place calls from multiple locations that are known for both strong and weak signals in order to test a phone under ideal and less than ideal circumstances. The performance of the speakerphone, if included, is also evaluated.

Battery life

Talk time

When we conduct our talk-time battery life test, we start with a fully charged phone. The phone's display is set to a brightness level of 50 percent, and the backlight is set to turn off after 10 seconds. The phone's volume level is set to 50 percent. We call a landline and attach an earbud to the landline's receiver. The earbud is attached to an MP3 player, which plays a set of repeating audio files. We immediately begin recording the amount of time that passes until the phone's battery drains and it shuts off. We run this test multiple times until we have at least two sets of scores that are within +/-5 percent of each other, and we report the average.

MP3 playback time

When we conduct our MP3-playback battery life test, we start with a fully charged phone. The phone's display is set to a brightness level of 50 percent, and the backlight is set to turn off after 10 seconds. All phones are set to the same volume level, which we measure electronically to ensure fairness and consistency in testing. If the phone includes an EQ setting, we set it to "flat." We play a set of repeating audio files and record the amount of time that passes until the phone's battery drains and it shuts off. We run this test multiple times until we have at least two sets of scores that are within +/-5 percent of each other, and we report the average.