Clearwire: You want fast 4G?? How’s 168 Mbps?

Source: Shutterstock / Sashkin

The Big 4 carriers took a lot of swipes at one another at CTIA Wireless, arguing over which had the faster mobile broadband service and whose networks were and weren’t really 4G. Clearwire stayed out of the debate, but according to CTO John Saw the carrier is putting together an LTE network to shame all four of them. In 2014, Saw said Clearwire will have a 4G network capable of supporting peak speeds of 168 Mbps.

Clearwire may not have the most ideal spectrum in the world for a nationwide launch – its higher frequency 2.5 GHz airwaves don’t propagate as far as the low-frequency licenses everyone else owns – but it is certainly blessed with a lot of it. Consequently, Clearwire can string those frequencies together to build some enormously fat pipes, Saw said.

Saw said Clearwire plans to use the LTE-Advanced technique know as carrier aggregation to deploy an LTE pipe — which in wireless speak is called a carrier — 40 MHz in width. Verizon and AT&T’s largest carrier size is 20 MHz. (Clearwire’s TD-LTE is a different technology than its competitors, but in terms of speed and data capacity those differences come out in the wash).

Theoretically at least, Clearwire’s network will support peak speeds of 168 Mbps, twice as fast as anything Verizon, AT&T, Sprint and T-Mobile can throw at us, Saw said. Still, Clearwire has to wait for the technology to be ready. While carrier aggregation is already being used widely in HSPA+ — and is, in fact, the secret sauce in T-Mobile’s dual-carrier 42 Mbps service – it will take a few years for the technology to percolate into commercial LTE gear. Saw says he expects it to be ready for Clearwire’s network by 2014.

“We’re going to start with 20 MHz carriers,” he said. “When carrier aggregation comes along we will go to 40 MHz, which will essentially leave the competition in the dust.”

Clearwire doesn’t have to stop there. Technically it can keep stacking carriers on top of one another to create 60 MHz and even 80 MHz pipes. It certainly doesn’t lack the spectrum. At CTIA, Nokia Siemens Networks had rigged up a demo that squeezed 1 Gbps out of Clearwire’s spectrum by not only piling on the carriers but using multiple antennas and several other technologies in LTE-Advanced’s bag of tricks. Saw said Huawei has accomplished similar feats using Clearwire’s airwaves, but he also acknowledged that such outsized throughput demos are really intended to be proofs of concept. Sixty MHz or 80 MHz carriers “would be overkill,” he said — at least in the near term.

Why don’t Verizon and AT&T do carrier aggregation as well? They have the technical capability, and they have unused spectrum to play with. The problem is their spectrum isn’t in the right places. For carrier aggregation to work initially all of the frequencies involved need to be contiguous, but most of the spectrum holdings of the Big 4 are scattered across the airwaves. Eventually the LTE standards will allow for non-contiguous aggregation – splicing together bands from all over the electromagnetic spectrum – but that’s a few steps further along the LTE roadmap.

At the end of the day, all of this speed talk is a bit silly. It’s great for bragging rights, but at today’s mobile data prices, no one could actually make regular use of such enormous throughputs without going broke. The near-term goal here isn’t to provide 500 Mbps or 1 Gbps to a single customer, but rather a consistent 5-10 Mbps to 100 different customers in the same cell. To hit that goal operators will need lots of spectrum and they’ll need to deploy lots of carriers, but it won’t matter if those carriers are bound together.

Speedometer image courtesy of Shutterstock user Sashkin

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