Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Portable devices' built-in motion sensors improve data rates on wireless networks

14.04.2011
For most of the 20th century, the paradigm of wireless communication was a radio station with a single high-power transmitter. As long as you were within 20 miles or so of the transmitter, you could pick up the station.

With the advent of cell phones, however, and even more so with Wi-Fi, the paradigm became a large number of scattered transmitters with limited range. When a user moves out of one transmitter's range and into another's, the network has to perform a "handoff." And as anyone who's lost a cell-phone call in a moving car or lost a Wi-Fi connection while walking to the bus stop can attest, handoffs don't always happen as they should.

Most new phones, however, have built-in motion sensors — GPS receivers, accelerometers and, increasingly, gyros. At the Eighth Usenix Symposium on Networked Systems Design and Implementation, which took place in Boston in March, MIT researchers presented a set of new communications protocols that use information about a portable device's movement to improve handoffs. In experiments on MIT's campus-wide Wi-Fi network, the researchers discovered that their protocols could often, for users moving around, improve network throughput (the amount of information that devices could send and receive in a given period) by about 50 percent.

The MIT researchers — graduate student Lenin Ravindranath, Professor Hari Balakrishnan, Associate Professor Sam Madden, and postdoctoral associate Calvin Newport, all of the Computer Science and Artificial Intelligence Laboratory — used motion detection to improve four distinct communications protocols. One governs the smart phone's selection of the nearest transmitter. "Let's say you get off at the train station and start walking toward your office," Balakrishnan says. "What happens today is that your phone immediately connects to the Wi-Fi access point with the strongest signal. But by the time it's finished doing that, you've walked on, so the best access point has changed. And that keeps happening."

By contrast, Balakrishnan explains, the new protocol selects an access point on the basis of the user's inferred trajectory. "We connect you off the bat to an access point that has this trade-off between how long you're likely to be connected to it and the throughput you're going to get," he says. In their experiments, the MIT researchers found that, with one version of their protocol, a moving cell phone would have to switch transmitters 40 percent less frequently than it would with existing protocols. A variation of the protocol improved throughput by about 30 percent.

Another of the protocols governs a phone's selection of bit rate, or the rate at which it sends and receives information. Bit rate needs to be tailored to the bandwidth available: try to send too much data over a weak connection and much of it will be lost; but solving that problem by keeping the bit rate low can end up squandering data capacity.

When a device is in motion, the available bandwidth is constantly fluctuating, so selecting a bit rate becomes more difficult. Because a device using the MIT protocol knows when it's in motion, it also knows when to be more careful in choosing a bit rate. In the researchers' experiments, the gains in throughput from bit rate selection varied between 20 percent and 70 percent but consistently hovered around 50 percent.

A third protocol governs the behavior of the wireless base stations rather than the devices that connect to them. Ordinarily, a base station knows that a device has broken contact only after a long enough silence. In the meantime, the base station might try to send the same data to the device over and over, waiting forlornly for acknowledgment and wasting time and power. But with information about the device's trajectory, the base station can make an educated guess about when it will lose contact.

Since Balakrishnan and Madden are two of the three primary investigators on MIT's CarTel project, which seeks to use information technology to make driving safer and more efficient, the fourth protocol uses motion data to determine routing procedures for networks of wirelessly connected cars, whose relative positions are constantly changing.

Balakrishnan adds that he and his colleagues have identified at least another half-dozen communications protocols that could benefit from information about device movement. "What we are really hoping is that this opens up a really exciting direction for work in the community," he says. "Other people will come up with more creative ideas, now that you know that you can get these sensor hints in a fairly robust way."

Written by Larry Hardesty, MIT News Office

Caroline McCall | EurekAlert!
Further information:
http://www.mit.edu

More articles from Information Technology:

nachricht Deep Learning predicts hematopoietic stem cell development
21.02.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Sensors embedded in sports equipment could provide real-time analytics to your smartphone
16.02.2017 | University of Illinois College of Engineering

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Positrons as a new tool for lithium ion battery research: Holes in the electrode

22.02.2017 | Power and Electrical Engineering

New insights into the information processing of motor neurons

22.02.2017 | Life Sciences

Healthy Hiking in Smart Socks

22.02.2017 | Innovative Products

VideoLinks
B2B-VideoLinks
More VideoLinks >>>