T-Mobile’s 42 Mbps HSPA+: Fast, but it’s still no LTE

T-Mobile USA likes to talk up the capabilities of its souped-up 42 Mbps HSPA+ network, claiming it can rival even the new LTE networks deployed by Verizon Wireless(s VZ)(sVOD) and AT&T(s T). Well, over the last few weeks, mobile network tester RootMetrics has been holding T-Mobile to its claims, pitting the carrier’s new 42 Mbps smartphones against their LTE equivalents in real-world environments. Root found T-Mobile’s network can support some truly astonishing speeds, but they still don’t match up to the raw bandwidth of LTE.

Root tested the HTC Amaze 4G in five markets: Columbus, Ohio; Orlando, Fla.; Providence, R.I.; Richmond, Va.; and Tuscon, Ariz. Root found T-Mobile’s 42 Mbps HSPA+ network averaged download speeds between 6.2 Mbps and 7.7 Mbps and upload speeds between 1 Mbps and 1.4 Mbps. (You can see the full reports on Root’s website.) T-Mobile handily beat out AT&T’s (s t) HSPA and Sprint’s(s S) WiMAX services — in most cases more than doubling their speeds — though Root hasn’t yet tested Ma Bell’s recently released LTE smartphones. But in four of those markets (Verizon hadn’t yet offered LTE in Providence), Root pitted the Amaze against Verizon’s LTE HTC Thunderbolt, which averaged download speeds between 9.6 Mbps and 11.4 Mbps and upload speeds between 3.8 Mbps and 6.7 Mbps. It’s not hard to pick a winner.

These tests are important, because they’re the first apples-to-apples comparisons of rivaling network technologies. To say LTE is inherently faster than HSPA+ based on older tests simply isn’t fair because LTE networks like those deployed by Verizon and AT&T are using double the spectral bandwidth – 10 MHz on both the downlink and uplink – compared to a typical HSPA+ network. T-Mobile’s new 42 Mbps network, however, bonds two 5 MHz-by-5 MHz HSPA+ carriers together. For the first time in the U.S., we’re able to compare two networks, megahertz for megahertz.

That LTE still comes out on top may not seem like a surprise, but in truth, as an air interface, LTE is not that much more spectrally efficient than the latest generation HSPA technologies. The likely reason Verizon’s – and presumably AT&T’s – network is so much faster is the multiple input-multiple output (MIMO) smart antenna technologies used in LTE. MIMO sends two parallel data transmissions, allowing LTE in many cases to double up on capacity. HSPA+ can support MIMO as well, along with a host of other upgrades that can send its theoretical ceiling of 42 Mbps into the stratosphere. T-Mobile has simply elected not to deploy those upgrades – at least not yet.