Monthly Archives: June 2017

Artificial Intelligence Lab speeds data transfer

There are few things more frustrating than trying to use your phone on a crowded network. With phone usage growing faster than wireless spectrum, we’re all now fighting over smaller and smaller bits of bandwidth. Spectrum crunch is such a big problem that the White House is getting involved, recently announcing both a $400 million research initiative and a $4 million global competition devoted to the issue.

But researchers from MIT’s Computer Science and Artificial Intelligence Lab (CSAIL) say that they have a possible solution. In a new paper, a team led by professor Dina Katabi demonstrate a system called MegaMIMO 2.0 that can transfer wireless data more than three times faster than existing systems while also doubling the range of the signal.

The soon-to-be-commercialized system’s key insight is to coordinate multiple access points at the same time, on the same frequency, without creating interference. This means that MegaMIMO 2.0 could dramatically improve the speed and strength of wireless networks, particularly at high-usage events like concerts, conventions and football games.

“In today’s wireless world, you can’t solve spectrum crunch by throwing more transmitters at the problem, because they will all still be interfering with one another,” says Ezzeldin Hamed, a PhD student who is lead author on a new paper on the topic. “The answer is to have all those access points work with each other simultaneously to efficiently use the available spectrum.”

To test MegaMIMO 2.0’s performance, the researchers created a mock conference room with a set of four laptops that each roamed the space atop Roomba robots. The experiments found that the system could increase the devices’ data-transfer speed 330 percent.

MegaMIMO 2.0’s hardware is the size of a standard router, and consists of a processor, a real-time baseband processing system, and a transceiver board.

Katabi and Hamed co-wrote the paper with Hariharan Rahul SM ’99, PhD ’13, an alum of Katabi’s group and visiting researcher with the group, as well as visiting student Mohammed A. Albdelghany. Rahul will present the paper at next week’s conference for the Association for Computing Machinery’s Special Interest Group on Data Communications (SIGCOMM 16).

How it works

The main reason that your smartphone works so speedily is multiple-input multiple-output (MIMO), which means that it uses several transmitters and receivers at the same time. Radio waves bounce off surfaces and therefore arrive at the receivers at slightly different times; devices with multiple receivers, then, are able to combine the various streams to transmit data much faster. For example, a router with three antennas works twice as fast as one with two antennas.

But in a world of limited bandwidth, these speeds are still not as fast as they could be, and so in recent years researchers have searched for the wireless industry’s Holy Grail: being able to coordinate several routers at once so that they can triangulate the data even faster and more consistently.

“The problem is that, just like how two radio stations can’t play music over the same frequency at the same time, multiple routers cannot transfer data on the same chunk of spectrum without creating major interference that muddies the signal,” says Rahul.

Flexible traffic management

Like all data networks, the networks that connect servers in giant server farms, or servers and workstations in large organizations, are prone to congestion. When network traffic is heavy, packets of data can get backed up at network routers or dropped altogether.

Also like all data networks, big private networks have control algorithms for managing network traffic during periods of congestion. But because the routers that direct traffic in a server farm need to be superfast, the control algorithms are hardwired into the routers’ circuitry. That means that if someone develops a better algorithm, network operators have to wait for a new generation of hardware before they can take advantage of it.

Researchers at MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) and five other organizations hope to change that, with routers that are programmable but can still keep up with the blazing speeds of modern data networks. The researchers outline their system in a pair of papers being presented at the annual conference of the Association for Computing Machinery’s Special Interest Group on Data Communication.

“This work shows that you can achieve many flexible goals for managing traffic, while retaining the high performance of traditional routers,” says Hari Balakrishnan, the Fujitsu Professor in Electrical Engineering and Computer Science at MIT. “Previously, programmability was achievable, but nobody would use it in production, because it was a factor of 10 or even 100 slower.”

“You need to have the ability for researchers and engineers to try out thousands of ideas,” he adds. “With this platform, you become constrained not by hardware or technological limitations, but by your creativity. You can innovate much more rapidly.”

The first author on both papers is Anirudh Sivaraman, an MIT graduate student in electrical engineering and computer science, advised by both Balakrishnan and Mohammad Alizadeh, the TIBCO Career Development Assistant Professor in Electrical Engineering and Computer Science at MIT, who are coauthors on both papers. They’re joined by colleagues from MIT, the University of Washington, Barefoot Networks, Microsoft Research, Stanford University, and Cisco Systems.