Sunday, January 19, 2014

LTE-Advanced, the Next Big Thing

LTE-Advanced is the next step in the evolution to true 4G. More network capacity, faster data speeds, and better coverage will come from LTE-Advanced mobile technologies. So now, four years after the first networks using LTE went live, operators are looking to its successor.

Already, more than a dozen carriers, including AT&T, Korea’s SK Telecom, Australia’s Telstra, Japan’s NTT DoCoMo, and Telenor Sweden are testing LTE-Advanced technologies, and analysts expect commercial rollouts to start this year. By 2018, according to ABI Research, global LTE-Advanced connections will approach 500 million — about five times as many as LTE can claim today.

Wireless specialists are calling LTE-Advanced “true 4G” because, unlike ordinary 4G LTE, it actually meets the International Telecommunication Union’s specifications for fourth-generation wireless systems.

One of these criteria is speed. LTE-Advanced can theoretically achieve data download rates as high as 3 gigabits per second and upload rates as high as 1.5 Gb/s. By comparison, current implementations of LTE top out around 300 Mb/s for downloads and 75 Mb/s for uploads.

LTE-Advanced isn’t just about faster rates. It also includes new transmission protocols and multiple-antenna schemes that enable smoother handoffs between cells, increase throughput at cell edges, and it can stuff more bits per second into each hertz of spectrum. The result will be higher network capacity, more consistent connections, and cheaper data.

As its name implies, LTE-Advanced is meant to enhance LTE (Long Term Evolution … to “4G”). The two standards are mutually compatible, which is great for consumers. New LTE-Advanced phones will still work on LTE networks, and old LTE phones will connect to LTE-Advanced networks. Operators will benefit as well. Those wishing to upgrade to LTE-Advanced won’t need to scrape together new radio spectrum or build out new infrastructure as they did to make the leap from 3G to LTE.

But there is a catch: Carriers won’t roll out all of LTE-Advanced’s capabilities at once. Like LTE before it, the new standard isn’t a single technology but rather a grab bag of many technologies, and operators will pick and choose items as they’re needed. The new technology that will likely be adopted first is “carrier aggregation.”

Carrier aggregation increases the bandwidth available to a mobile device by stitching together frequency channels, or “carriers,” that reside in different parts of the radio spectrum. Ordinary LTE can deliver data using a contiguous block of frequencies up to 20 megahertz wide. But as more and more companies and devices bid for radio spectrum, such wide swaths are increasingly scarce. Most operators, having bought bits and pieces of spectrum wherever they could, have fragmented collections.

Carrier aggregation solves that problem. It allows operators to combine their narrow, disjointed channels into “one very big pipe.” To deliver its LTE-Advanced service, for example, a company can combine two separate 10-MHz-wide channels, at 800 MHz and 1.8 gigahertz, into a single 20-MHz-wide channel, essentially doubling the data rate available to each user.

Besides carrier aggregation, four other key features distinguish LTE-Advanced from its predecessors. The first of these is called “multiple input, multiple output” (MIMO), which allows base stations and mobile units to send and receive data using multiple antennas. LTE already supports some MIMO, but only for the download stream. And it limits the number of antennas to four transmitters in the base station and four receivers in the handset. LTE-Advanced allows for up to eight antenna pairs for the download link and up to four pairs for the upload link.

MIMO serves two functions. In noisy radio environments — such as at the edge of a cell or inside a moving vehicle — the multiple transmitters and receivers work together to focus the radio signals in one particular direction. This “beamforming” boosts the strength of the received signal without upping transmission power (and reducing battery life).

If signals are strong and noise is low — such as when stationary users are close to a base station — MIMO can be used to increase data rates, or the number of users, for a given amount of spectrum. The technique, called spatial multiplexing, permits multiple data streams to travel over the same frequencies at the same time.

Another important cell phone technology is “relaying,” which extends coverage to places where reception is poor. Wireless network architects have long used relays to extend a tower’s reach, such as into a train tunnel or a remote area. But traditional relays, or repeaters, are relatively simple. They receive signals, amplify them, and then retransmit them.

LTE-Advanced supports more advanced relays, which first decode the transmissions and then forward only those destined for the mobile units that each relay is serving. This scheme reduces interference and lets more users link with the relay.

Yet another LTE-Advanced feature will help alleviate network congestion. Known as “enhanced inter-cell interference coordination,” or eICIC, it will be used for so-called heterogeneous networks, in which low-power base stations, or small cells, overlay the “macro” network of traditional towers. Many carriers have already begun using variously sized small cells (also called metro-, micro-, pico-, or femtocells) to expand data capacity in busy urban centers. These compact boxes are cheaper, less obtrusive, and easier to install, and analysts see a bright future for them. But as operators cram more and more cells into the same spaces, they will have to find ways to lessen the inevitable crosstalk, a form of interference between transmitters.

The last major item on LTE-Advanced’s broad menu helps further improve signals and increase data rates at a cell’s edge, where it can be tough to get a good connection. The technique is called “coordinated multipoint,” or CoMP. Essentially, it enables a mobile device to exchange data between multiple base stations at the same time.

While the positive improvements from implementation of all of these new features will be a big jump in cell phone quality and performance, it will take years for telecommunications companies to implement all of these features across the country. And there’s even more exciting news waiting in the wings. There is talk of a new standard promoted by The 3rd Generation Partnership Project. This international body originally worked to make mobile phone system specification based on Global System for Mobile Communications (GSM) specifications. They were responsible for the EDGE (Enhanced Data Rates for GSM Evolution) standard. They plan to release the next iteration later this year.

Cell phones will get faster and the quality of service will improve. Companies are rushing to fulfill the demand for more and more speed and bandwidth to a growing customer base. Evolution takes time. We’ve already seen the shift from dinosaurs to small mammals. Next thing you know these creatures will grow wings and start to fly. It will take some time. Not geological time, but a few years. Hope I’m around to see it.

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