In the latest test of future wireless bandwidth, Chinese handset maker ZTE and carrier China Mobile last week described achieving a peak download speed of 223 megabits per second in experiments involving a network technology known as LTE Advanced.
Users’ appetite for mobile bandwidth seems insatiable. Cisco Systems estimates that mobile data traffic will grow by a factor of 18 by 2016, and Bell Labs predicts it will increase by a factor of 25. “Data traffic has been growing,” says Michel Peruyero, senior director of product evolution strategy at Alcatel-Lucent, which is developing small base stations, called small cells, that include the new LTE Advanced features. “If you stay with only LTE, you can only support a certain number of users. With LTE Advanced, you have significant increase in data rates, or the same data for many more users.”
LTE Advanced has been in the works for a few years and will be tested by carriers in parts of North America later this year. In essence, the technology stitches together streams of data from as many as five different frequencies—a trick known as “carrier aggregation.” In addition to that, it can transmit and receive from as many as eight antennas, known as multiple-input, multiple-output, or MIMO, technology. Actual wireless bandwidth changes constantly depending on your location and the number of devices connecting to a base station at any given moment.
The new technology promises to bring high-bandwidth applications like video streaming, gaming, and video conferencing to phones and tablets. But it does not come without cost: devices using it—which are expected to proliferate in the next few years—will need more powerful processors, as well as more antennas inside. Current phones generally use only one antenna taking one stream of data at a time. LTE Advanced devices will also need more energy storage to do the necessary onboard computation. Without new breakthroughs in batteries or reductions in power consumption by other means (see “Efficiency Breakthrough Promises Smartphones that use Half the Power”), phones will simply get larger.
Devices using the new technology are not available yet, but the chips that will power them are coming. At the Consumer Electronics Show in Las Vegas last month, chipmaker Qualcomm announced that it will come out with a chipset that provides for carrier aggregation and will provide bandwidth of 150 megabits per second.
Meanwhile, many carriers haven’t even finished rolling out the latest standard, known as LTE. So while AT&T, for example, says it plans to test LTE Advanced later this year, it adds that it is mainly focused on completing the underlying rollout of LTE to reach 300 million people in North America by the end of 2014.
LTE Advanced could also bring about a powerful new way to deliver wireless broadband to homes. In theory, optimal use of the channels and antennas could lead to download speeds of one gigabit per second, the same rate as the hardwired cutting-edge fiber-to-the-home speeds that Google is installing in Kansas City (see “When Will the Rest of Us Get Google Fiber?”). “We know, practically, you won’t be able to have eight antennas in all the devices—especially small ones like netbooks and laptops. But fixed devices in the home could have an array of eight antennas, leading to a greater opportunity to deliver broadband Internet wirelessly, rather than through copper or fiber,” says Peruyero.
In many ways the wireless industry is betting on a continuation of the trend toward smaller, cheaper, and more powerful microelectronics to make LTE Advanced feasible and affordable. “The whole ecosystem, from materials to the chipsets, will need to work together to bring prices down while computational complexity is going up,” says Hossam Hmimy, director of technology strategy and principal consultant at Ericsson, a leader in developing LTE technology.
While base stations might send signals from eight antennas, it is likely that phones and tablets would stop at four antennas, at least for now. But the need for additional hardware components to put four antennas in phones or tablets could still change the design and form factor of those gadgets.
Because LTE Advanced merges signals from different channels and antennas, it makes for a more complex and ever-changing use of spectrum—and one benefit is that it will make signals more robust and able to withstand interference.
Right now, blocking one of several tiny parts of the LTE signal with a battery-operated jammer could block access across a city, researchers have found (see “One Simple Trick Could Disable a City’s 4G Network”). Aggregating many different channels makes that harder to do, says Jeff Reed, who heads the wireless research lab at Virginia Tech. “It will help with that problem, because it’s basically coordinating base stations together. That coordination will help reduce the jamming issues.”
Overall, Reed says, LTE Advanced “is going to certainly provide a much higher data rate, give a lot more spectrum flexibility, and let everyone use spectrum more efficiently.”
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