Scientists create wireless network with LED room light

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Summary: German researchers have demonstrated how regular LEDs can be turned into an optical WLAN with only a “few additional components.”

Lights are no longer just for lighting up.

Scientists from the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute (HHI) in Berlin, Germany, have developed a new kind of optical WAN with enough throughput to allow four people in a room to watch a film from the Internet on their laptops, in HD quality.

The technology can potentially be used on both laptops and mobile telephones.

Credit: Fraunhofer HHI

The researchers say they’ve achieved a transfer data rate of 100 megabits per second (Mbit/s) without any losses, using LEDs in the ceiling that light up more than ten square meters (90 square feet). This area also marks the radius in which the receiver — a simple photo diode on the laptop — can be placed before it is out of range.

In lab tests, the team pushed speeds even further using red-blue-green-white light LEDs. Those transmitted data at a blistering 800 Mbit/s, setting a record for VLC or visible light communication.

Klaus-Dieter Langer, the project leader said:  “For VLC the sources of light – in this case, white-light LEDs – provide lighting for the room at the same time they transfer information. With the aid of a special component, the modulator, we turn the LEDs off and on in very rapid succession and transfer the information as ones and zeros.”

The system works because the modulation of the light is imperceptible to the human eye. Langer explains: “The diode catches the light, electronics decode the information and translate it into electrical impulses, meaning the language of the computer.“

While rigging a system to turn LEDs into a transfer medium may not require many components, sending data over light waves is not without challenges. The key one is that whenever on object (like a hand) comes between the light and the photo diode the transfer is impaired.

The HHI scientists stress that the optical WAN is not intended to replace other networks, but rather serve as an additional and low-invasive option in environments where radio transmission networks are not desired or not possible, such as hospital surgical rooms.

“Combinations are also possible, such as optical WLAN in one direction and PowerLAN for the return channel. Films can be transferred to the PC like this and also played there, or they can be sent on to another computer,” notes a release.

The scientists will demonstrate how videos are transmitted by light at the International Telecommunications Fair IFA (Internationale Funkausstellung IFA) in Berlin from September 2-7, 2011.

Related:

MIT: built-in motion sensors in devices improve wireless data rates

A wireless radio that can send and receive signals at the same time

‘Microring’ wireless devices could nix wires in homes, offices

Christopher Jablonski is a freelance technology writer.

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A wireless bicycle brake with 11 nines reliability

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Summary: Computer scientists at Saarland University have developed a wireless bicycle brake that is 99.999999999997 percent safe.

Computer scientist Holger Hermanns with the wireless bicycle brake. Credit: Saarland University

A day in the life with wireless technologies is sprinkled with connectivity hiccups. Bluetooth keyboards momentarily disconnect, mobile calls drop and WiFi networks unexpectedly go dark.

Given this reality, consider the idea of accelerating down a steep hill on a bicycle with a wireless braking system. Would you trust it?

Now what if the system was designed by German computer scientists and tested with equipment used in control systems for aircraft and chemical factories; and it worked with 99.999999999997 percent reliability.

That’s exactly what a group at Saarland University demonstrated with a wireless brake installed on a cruiser bicycle.

The bike does away with a brake lever on the handlebars and cable snaking down the frame, and instead has a rubber handle that only needs to be squeezed and some electronics mounted on the handlebar and fork, the part which attaches the wheel to the frame. The tighter a rider squeezes the handle, the harder the disk brake presses on the wheel to slow the bike.

According to Professor Holger Hermanns, who holds the chair of Dependable Systems and Software at Saarland, the system is not perfect but “acceptable,” registering three failures out of a trillion braking attempts.

“Wireless networks are never a fail-safe method. That’s a fact that’s based on a technological background. Nonetheless, the trend is to set up wireless systems that, like a simple bicycle brake, have to function all the time,” he said.

The wireless connection between sender and receiver is accomplished with TDMA, MyriaNed wireless nodes, and the 2.4 GHz ISM band. It takes roughly 250 milliseconds for the cruiser bike to brake once a rider squeezes the rubber grip (150 ms for wireless communication between the components).

The brake is engaged when the pressure sensor activates a sender if a specified pressure threshold is crossed. Then, the sender–contained within a blue plastic box attached to the handlebar–transmits radio signals to a receiver attached at the end of the bicycle’s fork. The receiver forwards the signal to an actuator, transforming the radio signal into the mechanical power by which the disk brake is activated.

To give the system a reliability boost, additional senders attached to the bicycle repeatedly send the same signal. In this way, Hermanns and his team of scientists hope to ensure that the signal arrives at the receiver in time, even if the connection causes a delay or fails. They note that simply increasing the number of senders does not result in increased reliability. “If it is not configured correctly, it is possible that three out of five braking attempts fail,” Hermanns said.

The functionality can be further improved with an integrated anti-lock braking system and traction control, and that would only take a few adjustments, according to Hermanns.

The next step is for the scientists to bring their wireless bicycle brake concept to bicycle brake manufacturers and find engineers who will help realize it.

If wireless bicycle brakes take off, similar technology can potentially be applied to the derailing systems for bicycles with gears. In addition to delivering comparable or improved performance than the status quo, the weight and size of the electronics and power supply would have to be minimized to beat or match that of cable controlled components before most bicyclists give it serious consideration.

Sources: ScienceDaily, IEEE: A Verified Wireless Safety Critical Hard Real-Time Design (PDF)

Christopher Jablonski is a freelance technology writer.

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New full-duplex technology doubles wireless capacity

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Summary: Rice University engineers have developed technology that allows for wireless devices like cell phones and tablet PCs to both “talk” and “listen” to wireless cell towers on the same frequency, paving the way for 5G networks.

Rice University engineering researchers have demonstrated a new device that could allow wireless phone companies to double throughput on their networks without adding a single cell tower, and they’ve shown that it could work on a real network.

Current wireless technologies rely on two frequencies to send and to listen. Full-duplex allows communication in both directions simultaneously, such as in land-line telephone networks. Long thought impossible for wireless networks, Rice’s team overcame the full-duplex hurdle by employing an extra antenna and some computing tricks.

“Our solution requires minimal new hardware, both for mobile devices and for networks, which is why we’ve attracted the attention of just about every wireless company in the world,” said Ashutosh Sabharwal, professor of electrical and computer engineering at Rice. “The bigger change will be developing new wireless standards for full-duplex. I expect people may start seeing this when carriers upgrade to 4.5G or 5G networks in just a few years.”

As I’ve reported last February, Stanford researchers have also developed a system that allows wireless signals to be sent and received simultaneously on a single channel, but Rice has taken it a step further with a demo (see paper) that produced a signal quality about 10 times better than any previously published result.

Jade Boyd, associate director and science editor at Rice, told me over email: “We’re also the first to demo asynchronous full-duplex. Our people have published the first experimental work on full-duplex with directional antennas, and they’ve offered a theoretical analysis to explain their experimental results.”

While Rice and Stanford teams are attacking the same problem and using the same research platform, WARP (Wireless Open Access Research Platform–an open-source development platform developed by Dr. Sabharwal’s group a few years ago), they’re using different technologies. For instance, Rice’s technology would allow wireless device makers to add full duplex as an additional mode on existing hardware by repurposing most of the components that are already used in current systems. “I believe that’s also a first — and a key one for device makers,”  said Boyd.

“Device makers love this because real estate inside mobile devices is at a premium, and it means they don’t have to add new hardware that only supports full-duplex,” said Sabharwal.

In the video below, you can learn more about the full-duplex test device and the technology behind the breakthrough:

Christopher Jablonski is a freelance technology writer.

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