The major wireless carriers are currently upgrading their 3G networks to 3.5G (HSPA+) or 4G (LTE or WiMax). Whether a specific smartphone supports these new network technologies (and their faster speeds) should be stated in the device's specifications.
Sprint and Verizon are in the process of rolling out new 4G networks, capable of delivering speeds that may be up to 10 times as fast as those possible on the carrier's older 3G networks. Verizon says that its LTE network offers download speeds of between 5 and 12 megabits per second (mbps). Sprint says that its WiMax network has average download speeds of between 3 and 6 mbps.
AT&T and T-Mobile are upgrading their 3G GSM networks to a 3.5G technology called HSPA+ (Evolved High-Speed Packet Access), which can match the speeds of current 4G networks. T-Mobile even refers to its HSPA+ service as "4G." AT&T makes no such claim, but it says that it has already converted 80% of its network to the new HSPA+ technology and plans to begin rolling out its 4G LTE network in 2011.
In our tests, both T-Mobile's and AT&T's HSPA+ networks delivered download speeds of around 4 mbps in about half our testing locations.
When deciding on a carrier, it's important to determine whether the service's faster 4G or HSPA+ network is available your area. Consult the coverage maps at the carriers' Websites for this information.
"Noise cancellation" in smartphones might be better termed "noise suppression." The phrase refers to isolating the sound of the speaker's voice while suppressing background sounds; noise suppression depends on having the design of a phone's voice microphone (or microphones) work in concert with sound-shaping technology in the phone's chip set.