What will that mean? The 4G service will very likely speed up your consumption of Web-based content, and smooth the operation of services such as streaming video. In fact, 4G speeds are likely to let you do things with your mobile device that you simply couldn't do with a 3G connection, applications such as video chatting, online gaming, and VoIP calling. 4G is the first incarnation of wireless broadband that might finally free people from the desktop, allowing us to manage our online lives whenever and wherever we want.
How We Test
In each city, we tested from 20 locations situated in a grid over the center of the city. These locations are roughly 2 miles apart, allowing us to measure service levels among and between numerous cell towers. At each testing location, we subjected the networks to industry-standard stress-testing using laptops, and we put the networks though Internet-based testing using smartphones.
Our laptop-modem tests use a direct TCP connection to the network to test the network's capacity--that is, the speed and performance that the network is capable of delivering to subscribers. To connect the laptop to the various networks, we used the fastest USB modem available, as suggested by the carriers themselves. We used the LG VL600 4G USB modem to test Verizon, the ZTE WebConnect Rocket 2.0 USB modem to test T-Mobile, the Sierra Wireless 250U AirCard to test Sprint, and the Sierra Wireless USBConnect Shockwave to test AT&T. Using the Ixia Chariot 4.2 testing tool on our laptop PC, we tested both the speed and the latency of the network.
To measure download speed, Chariot requests a number of large, uncompressible files from a server in the San Francisco Bay Area, then from another server in Northern Virginia. For each server, the software measures the speed of each transfer during a 1-minute period, and then creates an average of the results.
To measure upload speed, Chariot sends a number of files from the Chariot client on the laptop to the local and distant network servers, again timing each transfer during a 1-minute period. We report the average of all of these transfers, both from the local and distant server, at each location as the average for that location.
During the speed tests, the Ixia testing software also measures latency, or the time it takes for a packet to move from the client laptop to the network servers and back again. This metric, expressed in milliseconds, can reveal delays or bottlenecks in the flow of data through the network, and can foretell how well real-time applications such as voice calling and video chatting--which require nearly instantaneous packet transfer to work smoothly--will work on the service being tested.