T-Mobile US Inc. 's High-Speed Packet Access-Plus (HSPA+) offers download speeds around 5 Mbit/s, which means the 3G upgrade rivals the performance of the Clearwire LLC (Nasdaq: CLWR) WiMax markets and puts it within spitting distance of the promised capabilities of Verizon Wireless 's Long Term Evolution (LTE) network.

The HSPA+ upgrade promises top download speeds of 21 Mbit/s, in theory, but average download speeds tend to offer a better gauge of the actual performance users will experience. "In real-world speed tests, third party reviewers have seen the webConnect Rocket laptop stick, our first HSPA+ device, average download speeds in the 5 to 8 Mbit/s range... and peak speeds of 10 Mbit/s and higher," a T-Mobile spokeswoman tells LR Mobile.

T-Mobile is citing tests by Walt Mossberg at The Wall Street Journal, among others, for these average speeds. Mossberg found that the laptop dongle delivered average speeds of 4.88 Mbit/s and 6.15 Mbit/s in two separate locations.

Technology Business Research Inc. (TBR) analyst Ken Hyers expects that HSPA+ smartphones from T-Mobile, which are expected to start arriving this fall, will deliver average downloads of around 5 Mbit/s in city environments. T-Mobile's HSPA+ network is currently available in almost 50 major cities in the US. (See T-Mobile HSPA+ Smartphone Due in September .) "That's not bad and should give T-Mobile smartphone users the ability to have pretty speedy mobile Web experiences," Hyer says.

Indeed, a 5-Mbit/s average download speed puts T-Mobile's HSPA+ amongst the very top performing networks in the US. Clearwire claims average mobile download speeds of 3 to 6 Mbit/s, with bursts of up to 10 Mbit/s, for its mobile WiMax service. Verizon is promising average downloads of 5 to 12 Mbit/s for its LTE service, which is due to be launched later this year. (See Clearwire Coverage Tops 50 Million People and Verizon Breathing Down Sprint's 4G Neck.) — Dan Jones, Site Editor, Light Reading Mobile