Why could iPhone 3G fast access to the Internet and email around the world? A technology protocol called HSDPA (High-Speed Downlink Packet Access) is used by iPhone 3G to download data fast over UMTS (Universal Mobile Telecommunications System) networks. Download speeds of email attachments and web pages on 3G networks are twice than that on 2G EDGE networks. You could get the best speeds possible since iPhone 3G seamlessly switches between EDGE, faster 3G, and even faster Wi-Fi.
You can make calls and surf the web from practically anywhere around the world because iPhone 3G meets worldwide standards for cellular communications. And if you are in an area without a 3G network, you will be connected by iPhone via GSM for calls and via EDGE for data.

iPhone already gives you mobile multitasking. However, 3G technology makes it possible to surf the web, download email, get directions, and watch video even when you’re on a call since 3G networks enable simultaneous data and voice.
Intelligent iPhone power management technology gives you up to 5 hours of talk time over 3G networks. That’s some of the best in the business.
iPhone 3G delivers UMTS, HSDPA, GSM, Wi-Fi, EDGE, GPS, and Bluetooth 2.0 + EDR in one compact device — using only two antennas. Clever iPhone engineering integrates these antennas into a few unexpected places, such as the metal ring around the camera, the audio jack, the metal screen bezel, and the iPhone circuitry itself.