Motion detection enhances wireless network switching

MIT researchers have presented a set of new communication protocols that uses information about a portable electronic device's movement to improve performance when switching between wireless networks

In experiments on MIT's campus-wide Wi-Fi network, the researchers discovered that, for users moving around, the protocols could often improve network throughput -- the amount of information that devices could send and receive in a given period -- by about 50 per cent.

The researchers used motion detection to improve distinct communications protocols. One is said to govern the smartphone's selection of the nearest transmitter.

"Let's say you get off at the train station and start walking toward your office" said the researcher. "What happens today is that your phone immediately connects to the Wi-Fi access point with the strongest signal. But by the time it is finished doing that, your have walked on, so the best access point has changed. And that keeps happening."

By contrast, he added, 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,’ said Balakrishnan.

In their experiments, the MIT researchers found that, with one version of their protocol, a moving mobile phone would have to switch transmitters 40 per cent less frequently than it would with existing protocols. A variation of the protocol improved throughput by about 30 per cent.

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, given that data can be lost when sending too much data over a weak connection. Solving that problem by keeping the bit rate slow can lead to wasted 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 per cent and 70 per cent but consistently hovered around 50 per cent.

A third protocol governs the behaviour of the wireless basestations rather than the devices that connect to them.

Ordinarily, a basestation knows that a device has broken contact only after a long enough silence. In the interim, the basestation might try to send the same data to the device repeatedly, waiting for acknowledgment and wasting time and power. With information about the device’s trajectory, the basestation can make an educated guess about when it will lose contact.

The MIT team presented its work at the Eighth Usenix Symposium on Networked Systems Design and Implementation, which took place in Boston in March.

Read more: http://www.theengineer.co.uk/sectors/electronics/news/motion-detection-enhances-wireless-network-switching/1008290.article#ixzz1JgWA6Vod

参考：http://www.theengineer.co.uk/sectors/electronics/news/motion-detection-enhances-wireless-network-switching/1008290.article

The power gird of the future

参考：http://www.guardian.co.uk/smart-revolution/the-power-grid-of-the-future#

Eye-fi Launches 8GB Wireless SD Card with Direct Mode for iOS & Android Right Behind

Eye-fi is launching a new 8GB SD card called Eye-Fi Mobile X2 that takes advantage of the Direct Mode capability announced at CES 2011. With the new higher capacity wireless SD card photographers can instantly and automatically transfer their full-resolution photos from their camera directly to a Wi-fi enabled iOS or Android device so long as the device has the app running.

The SD card is a fast class 6 SDHC card fast enough to keep up with most digital cameras on the market today, even if they are shooting in burst mode. The built-in Wi-fi capability supports 802.11n networks for fast wireless transfer. The new direct Wi-Fi transfer mode will be much faster than the old model of uploading to a web page and then downloading to the computer.

I have an Eye-fi card and have been frustrated because I cannot use it at a hotspot that uses proper security. My card cannot communicate with my computer due to the Wi-Fi security in place. Ninety-nine percent of the time that is a good thing because it also means that a criminal at the next table is going to have a hard time connecting to my laptop too. You can pay for the Eye-Fi hotspot service for an extra $30/year if you don’t have an X2 card already. But that won’t help with hotspots that have a click-through page. A click-through page is the page that loads when you first log onto many Wi-Fi hotspots. It requires you to click a log-on button or link. With Direct Mode, I can bypass the Wi-fi at the hotspot altogether. I can also connect directly even if there is no hotspot or Wi-Fi nearby.

To use Direct Mode you will have to have an Eye-Fi X2 card and a supported device that runs either iOS (iPhone, iPod Touch, iPad) or Android. The apps will be available in their respective stores.

The 8GB Eye-Fi Mobile X2 is be $79.99 available for order at Amazon and will be in Best Buy stores on April 17. TheEye-Fi Pro X2, which has geotagging, support for RAW files and an 8GB capacity, will drop in price from $150 to just $99.99. All previously available X2 cards will support the new Direct Mode with a forthcoming firmware update which should be out this week.

Check out our review by editor Josh Smith at Notebooks.com of the previous generation 8GB Eye-Fi X2 card.

In the video below an Engadget editor talks to an Eye-fi representative who explains the new Direct Mode.

参考：http://www.gottabemobile.com/2011/04/12/eye-fi-launches-8gb-wireless-sd-card-with-direct-mode-for-ios-android/

TABLETS QUICKLY BECOMING THE NEW TV

As if the Cable TV companies didn’t have enough to worry about, there comes a new global survey to suggest that tablets are rapidly becoming the entertainment device of choice ahead of televisions and PCs. The survey, conducted by Google Mobile, found that 77% of those asked reduced usage of their PCs after buying a tablet computer. Of that 77%, 43% say a tablet has replaced their computers altogether. Additionally, a full 1/3 of those surveyed stated that they use their tablets more often for entertainment than their televisions. Further, 84% state they use their tablets to play games.

The results of the global survey only underscores what we already knew … that mobility and choice of when to watch what we want has been pushing the industry for awhile now. And with more people “cutting the cable” and getting rid of cable TV and satellite in favor of streaming television solutions via the Internet, the need to keep an open internet is even more vital. Viewers are turning to online portals such as Hulu, Netflix, and even Amazon to rent movies and TV Shows to what when they want. And iTunes shows no signs of slowing down with video downloads.

Hollywood has been keen to pick up on the trend, offering digital copies of movies with DVD purchases. But if these numbers truly hold, that measure was nothing more than a stop gap at best and as tablets become more popular and cheaper, the number of people using them as their primary entertainment tool will certainly climb. Then again, TV sales were brisk the last few years as America underwent the digital TV turnover. And when it comes right down to it, would users rather watch the Super Bowl on their tablet or that 60″ plasma in the living room? Guess it depends on if you’re home.

参考：http://androidcommunity.com/tablets-quickly-becoming-the-new-tv-20110410/