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Multi-Antenna Cell Phones

Building wireless gadgets with multiple antennas could extend battery life.
October 27, 2010

Source: “Directional antenna diversity for mobile devices: characterizations and ­solutions” Ardalan Amiri Sani et al.
ACM International Conference on Mobile Computing and Networking (MobiCom), September 20-24, 2010, Chicago

Saving energy: Three antennas (yellow squares), arranged in a triangle, broadcast signals in specific directions.

Results: Multiple directional antennas that transmit signals in specific directions conserve power in a wireless device as it connects to its nearest base station. The transmitter selects a certain antenna so that energy is used only to send the signal in the optimal direction. Rapidly rotating the device, forcing it to switch between its antennas, did not interrupt a movie being streamed over the wireless link.

Why it matters: Today, gadgets like cell phones beam a signal in all directions, but only a small part of it reaches the receiver. Sending out all that unused energy needlessly runs down their batteries. Directing the signal toward the base station would conserve battery life and reduce interference for other users.

Methods: Researchers at Rice University in Houston connected a wireless transmitter to three patch antennas, which resemble Band-Aids, and mounted the prototype gadget on a spinning platform to see if it could cope with the changes in orientation that affect portable devices. They compared its power consumption with that of a single-antenna device that beams a signal in all directions. They also tested the system’s ability to rapidly switch antennas if the one being used was rotated away from the base station.

Next steps: The researchers are hacking a commercial smart phone to validate the approach on a real phone. They also plan to test whether a phone with one directional antenna on its rear and one on its face would have better signal quality and battery life.

Maintaining Privacy

How to keep information hidden when analyzing network traffic

Source: “Differentially-­Private Network Trace Analysis” Frank McSherry and Ratul Mahajan
ACM SIGCOMM Conference, August 30-September 3, 2010, New Delhi, India

Results: Researchers at Microsoft created a tool kit that makes it possible to analyze real data sets gathered from traffic over a network without compromising the privacy of the information itself. They found that in most cases the analysis was accurate enough to yield useful results.

Why it matters: Scientists who want to improve computer networks need access to real-world data so that they can study things like the behavior of malicious software. However, they do not want to accidentally gain access to passwords, private e-mails, and other sensitive information that is sent over the networks they’re studying.

Methods: Researchers developed tools that add noise to small packets of data to mask records that can easily leak private information. The researchers had to be sure the tools introduced just enough noise to preserve privacy while keeping results accurate and calculations simple.

Next steps: Even with these techniques, a small amount of private information can still leak. The researchers say more work needs to be done to predict and minimize the leaks that will result from repeated analysis of a data set.

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