T-Mobile rolls out dual-carrier HSPA+ as Verizon expands LTE

T-Mobile USA’s (NYSE:DT) pending acquisition by AT&T (NYSE:T) hasn’t halted the operator’s aggressive expansion of mobile broadband one whit. Today T-Mobile rolled out dual-carrier high-speed packet access plus (HSPA+) and services in 58 markets, doubling the theoretical speeds of its mobile data network to 42 Mb/s.

Meanwhile, Verizon Wireless (NYSE:VZ, NYSE:VOD) is sitting idly by while T-Mobile achieves a new benchmark in so-called 4G speeds. It is expanding its long-term evolution (LTE) network in June to bevy new markets large and small as well as increasing coverage in its existing metro footprint.

Unlike Verizon, which is building a new mobile broadband network, T-Mobile is upgrading its current HSPA+ network through software taking advantage of technology in the 3GPP standards that allows it to bond HSPA carriers together to create a single 10 MHz downlink carrier. Only devices embedded with dual-carrier chips can take advantage of the increased speeds. T-Mobile announced the first of these today: a USB modem made by Chinese vendor ZTE, available on Wednesday for $200 without contract.

T-Mobile won’t charge any more for the extra bandwidth, offering its same 4G data plans ranging from $30 to $85 a month, but its throttling policies will remain in place (Unfiltered: T-Mobile fully implements ‘throttle down’ caps). That means customers using the faster dual-carrier connection might find themselves using up their 200 MB to 10 GB monthly data allotments more quickly, resulting in T-Mobile reining in bandwidth to sub-4G speeds for the remainder of the billing period.

The majority of T-Mobile’s modems and all of its smartphones don’t yet support dual-carrier, but they’ll still benefit from increased overall network capacity. In order to launch dual-carrier in a market, T-Mobile must implement two HSPA+ carriers at every cell. Though single-carrier HSPA+ devices can only access one of those 5 MHz carriers at any given time, collectively they’ll have twice as much capacity at their disposal. All devices also benefit from the queuing principle: dual-carrier devices, by virtue of their faster speeds, will perform their transactions on the network faster, thus clearing up capacity for HSPA+ and 3G devices and relieving overall network congestion.

T-Mobile originally turned up dual-carrier in three trial markets, New York City, Las Vegas and Orlando (CP: Can T-Mobile’s dual-carrier HSPA+ match Verizon’s LTE?), but due to a lack of dual-carrier devices wasn’t able to offer the increased speeds to its customers. With the introduction of the T-Mobile Rocket 3.0, however, T-Mobile will be able to offer near-LTE speeds in those three markets as well as the 55 new markets announced today. Atlanta, Ga.; Chicago, Ill.; Denver, Colo.; Detroit, Mich.; Dallas and Houston, Texas; Los Angeles, Calif.; Miami, Fla.; New Orleans, La.; Phoenix, Ariz.; Pittsburgh, Pa.; Portland, Ore.; and San Francisco, Calif.; are the major metros to receive the service, while the remaining 47 are primarily mid-sized and small markets (a full list is at the bottom of the story). T-Mobile didn’t reveal the total population covered by the deployment, but it said that by the end of the year it plans to have a dual-carrier footprint covering 150 million pops, about three-quarters of its current HSPA+ footprint.

Meanwhile Verizon Wireless is aggressively expanding its LTE footprint, announcing the June launch of another batch of small and mid-sized LTE markets (Unfiltered: Verizon revs up LTE engine). Verizon’s goal is to have 185 million pops covered by year end, which would exceed the coverage of its T-Mobile’s dual-carrier network and Sprint (NYSE:S) and Clearwires’ (NASDAQ:CLWR) WiMAX networks, but not T-Mobile’s 4G-branded single-carrier HSPA+ footprint. AT&T also has launched a mobile broadband service under the 4G banner, but its rollout is impeded by the lack of fiber and Ethernet backhaul to its cell towers, which limit the speeds it can offer to customers. AT&T has enhanced backhaul in place in a only a handful of HSPA+ markets but has said it will expand that footprint significantly this year.

While T-Mobile is positioning dual-carrier as a challenger to the primacy of Verizon’s LTE network, it will likely fall well short of LTE’s average speeds and consistency. Technically the dual-carrier and LTE deployments use the same amount of bandwidth, 10 MHz on the downlink, and theoretically can support similar capacities. But unlike T-Mobile, Verizon is using dual-path smart antenna technology, which boosts the network’s performance at the cell edge and in dense urban areas. That in turn will boost Verizon’s average LTE speeds over T-Mobile average dual-carrier speeds.

Wireless connection testing firm RootMetrics on Monday released the first in-depth (using hundreds of thousands of data points) study of how Verizon’s LTE network performed against its 4G counterparts. Verizon spanked the competition soundly, delivering average download speeds of 9.2 Mb/s compared with 3.0 Mb/s for T-Mobile’s HSPA+ network, 3.2 Mb/s for Sprint’s WiMAX and 1.9 Mb/s for AT&T’s HSPA+. Even if T-Mobile were to fully double its average speeds with dual-carrier, it would still be several megabits per second shy of Verizon’s LTE network, though it would likely blow the other two 4G networks out of the water (See CP’s full analysis of dual-carrier versus other 4G flavors).

Furthermore, Root believes Verizon’s network may be a lot faster than its tests let on. Verizon suffered a nationwide LTE outage in late April, during Root’s testing period, knocking out both EV-DO and LTE services for 4G customers (CP: IMS bug caused Verizon LTE outage). For 15% of the trial period, Root’s LTE phones were recording only 1X speeds, which had a big impact on its overall averages, Root said.