Nokia Siemens Networks has successfully squeezed 1.6 Gbps of bandwidth out of its LTE test networks outside of Chicago. You have to take these speed record proclamations, with a grain of salt since they often use technologies and spectrum configurations that could never be conceivably implemented in the real world. But this network might actually see the daylight shining outside of a lab.
NSN’s tests were performed on LTE variant called time division-LTE (TD-LTE), which has already been deployed in India and the Middle East and is on the roadmaps of Clearwire(s clwr) and China Mobile. Instead of splitting the uplink and downlink between two different frequency channels, like regular LTE systems, on TD-LTE uploads and downloads split time on the same airwaves. In its tests, NSN said it managed to download a 3 GB HD movie while simultaneously uploading 1.7 GB of data, all within 24 seconds.
NSN accomplished this in part by piling a lot of spectrum onto its network – 60 MHz to be exact. In comparison, Verizon’s LTE network uses 20 MHz of spectrum. But tripling the frequencies available to a network isn’t unreasonable. In fact, Clearwire has more than 100 MHz of spectrum in all of its major markets, and it’s been playing around with fat channels 40 MHz wide. By 2014, Clearwire plans to have offer speeds of 168 Mbps.
But NSN is talking about providing 10 times that speed. How will it do it? Well, in addition to packing in the big laundry list of capacity boosting technologies available in LTE Advanced, NSN is using a new smart antenna technique called multiuser multiple input multiple output (MU-MIMO) that isn’t even in the LTE standards.
MU-MIMO is a mouthful of Ms, but you may already be familiar with the second half of the acronym. MIMO is the engineering term for bunches of antennas, and it’s already used in 4G and Wi-Fi networks today. Instead of transmitting on a single path, MIMO transmits over multiple parallel paths, greatly increasing the amount of data we can pack into a single connection.
Today LTE networks use two antennas. In LTE-Advanced, that number will grow to four. But NSN is proposing eight antennas. What’s more, those eight antennas are capable of transmitting and receiving signals from multiple radio sources. It’s complex stuff, but think of it this way: Today your device connects to the network as if your phone was tethered to a single tower. In the future your device will connect to the network through a spider web of links.
Of course, I use “device” loosely here. It’s going to be difficult to pack four LTE antennas into any gadget you can carry in your pocket, much less eight. So the devices that would enjoy these gargantuan speeds are going to laptop-sized, if not car-sized. But then again it’s larger gadgets that would make the best use of that bandwidth. A bus distributing 1 Gbps of capacity to dozens of passengers makes a lot more sense than a single smartphone using a 1 gigabit pipe to stream video.