Scientists twist radio beams to send data: Transmissions reach speeds of 32 gigibits per second

Graphic showing the intensity of the radio beams after twisting.
Credit: Courtesy of Alan Willner / USC Viterbi

Building on previous research that twisted light to send data at unheard-of speeds, scientists at USC have developed a similar technique with radiowaves, reaching high speeds without some of the hassles that can go with optical systems.

The researchers, led by electrical engineering professor Alan Willner of the USC Viterbi School of Engineering, reached data transmission rates of 32 gigabits per second across 2.5 meters of free space in a basement lab at USC.

For reference, 32 gigabits per second is fast enough to transmit more than 10 hour-and-a-half-long HD movies in one second and is 30 times faster than LTE wireless.

"Not only is this a way to transmit multiple spatially collocated radio data streams through a single aperture, it is also one of the fastest data transmission via radio waves that has been demonstrated," Willner said.

Faster data transmission rates have been achieved -- Willner himself led a team two years ago that twisted light beams to transmit data at a blistering 2.56 terabits per second -- but methods to do so rely on light to carry the data.

"The advantage of radio is that it uses wider, more robust beams. Wider beams are better able to cope with obstacles between the transmitter and the receiver, and radio is not as affected by atmospheric turbulence as optics," Willner said.

Willner is the corresponding author of an article about the research that will be published in Nature Communications on Sept. 16. The study's co-lead authors Yan Yan and Guodong Xie are both graduate students at USC Viterbi, and other contributors came from USC, the University of Glasgow, and Tel Aviv University.

To achieve the high transmission rates, the team took a page from Willner's previous work and twisted radio beams together. They passed each beam -- which carried its own independent stream of data -- through a "spiral phase plate" that twisted each radio beam into a unique and orthogonal DNA-like helical shape. A receiver at the other end of the room then untwisted and recovered the different data streams.

"This technology could have very important applications in ultra-high-speed links for the wireless 'backhaul' that connects base stations of next-generation cellular systems," said Andy Molisch of USC Viterbi. Molisch, whose research focuses on wireless systems, co-designed and co-supervised the study with Willner.

Future research will focus on attempting to extend the transmission's range and capabilities.

The work was supported by Intel Labs University Research Office and the DARPA InPho (Information in a Photon) Program.

Source: University of Southern California

A smart fluorescent antenna for Wi-Fi applications

A charged argon gas in the fluorescent lamp emits Wi-Fi signals. Credit: Faculty of Electrical Engineering, Universiti Teknologi MARA

A new invention uses ionized gas in fluorescent light tubes to transmit Internet wireless frequency signals throughout a building with the aid of already existing electrical wiring.

Due to continuously evolving applications, the electronic communications industry requires high performance and speed efficient systems. However, the physical limitations of microwave devices limits further improvements in current technology. This predicament has led to growing interest in the use of plasma as a conductive element in microwave devices due to their unique and innovative properties, which corresponds with traditional metallic antennas.

Matter exists in four different states: solid, liquid, gas and plasma. Plasma is a type of gas in which the atoms are ionized -- they have both free negatively charged electrons and positively charged ions. These charged particles can be controlled by electromagnetic fields, allowing plasmas to be used as a controllable reactive gas.

This invention employs an ionized gas enclosed in a tube as the conducting element of an antenna. When the gas is electrically charged or ionized to plasma, it becomes conductive and allows radio frequency signals to be transmitted or received. When the gas is not ionized, the antenna element ceases to exit.

The invention features a smart fluorescent antenna with a 3G/3.75G/4G router for Wi-Fi applications. The antenna operates at the 2.4 GHz frequency band, which is suitable for Wi-Fi applications. A commercially available fluorescent tube, measuring 0.61 metres in length by 0.25 metres in diameter, is used as the plasma antenna. The gas inside the tube is a mixture of argon and mercury vapour, in the ratio 9:1. The tube is energized by a 240 V current, provided by a standard AC power supply. A glowing tube indicates that the gas inside the tube has been ionized to plasma and forms a plasma column. In this state, the plasma column becomes highly conductive and can be used as an antenna.

A coupling sleeve is positioned at the lower end of the tube, which is used to connect the plasma tube to the router. The function of the coupling sleeves is to store the electrical charge. When the gas inside the tube is sufficiently ionized into a plasma state, it becomes conductive and allows radio frequency signals to be transmitted or received.

Measurements indicate that the plasma antenna yields a return loss over 10 dB in the 2.23 GHz to 2.58 GHz frequency band. The antenna's ability to operate as either a transmitter or receiver in this particular frequency band was verified through a series of wireless transmission experiments.

The performance of this antenna was measured using the Wi-Fi Received Signal Strength 
Indicator (RSSI) technique. The product was tested for a month in the Universiti Teknologi MARA's High Frequency Antenna Laboratory. Our results show that the signal is stronger and more stable compared to others signals.

One advantage of this product is its low cost. The Wi-Fi signal can be transmitted into other rooms using only one router with a splitter cable. The fluorescent tube has dual functionality, thereby reducing the cost of buying additional antennas. Commercial antennas are made from metal elements while this invention uses plasma element as its source of material. Normal antennas can only transmit and receive radio frequencies, while this product not only can be used for transmitting and receiving radio frequency signals, but as a light emitting device as well.

Source: Universiti Teknologi MARA (UiTM)

World's first ZigBee-based inter-satellite comms system

This image depicts VELOX-I before and after deployment and a picosatellite. Credit: Shuanglong Xie, Guo Xiong Lee, Kay-Soon Low, Erry Gunawan, 2014

Engineers at the Nanyang Technological University in Singapore have successfully piloted the world's first ZigBee-based inter-satellite communication system.

The team at the Satellite Research Centre launched the VELOX-I, which consists of a nanosatellite weighing 3.5 kg and a piggyback picosatellite weighing 1.5 kg, from the two highest points on campus. Both miniature satellites were configured with a ZigBee wireless network and equipped with small sensor nodes that perform functions such as local sensing, distributed computing and data-gathering.

Designed to evaluate the performance of wireless sensor networks (WSNs) in space, the experiment marks a breakthrough in aeronautical engineering. After conducting Received Signal Strength Indicator tests on the satellites' radio frequency modules, a maximum range of 1 km was found to be achievable for inter-satellite communication in the campus environment. An even longer communication range can be expected in free space, due to the absence of signal attenuation caused by fading and diffraction.

To estimate the range of inter-satellite communication in free space, the team applied a link budget analysis based on the Friis transmission equation, deriving an average theoretical distance of 4.186 km and a maximum of 15.552 km. Published in the special issue of Unmanned Systems, these findings present a compelling case for further studies into inter-satellite communication systems with more complex designs.

In addition to their high performance in inter-satellite communication, WSNs are also remarkably suitable for intra-satellite communication. The team found that by replacing internally wired connections with wireless links, a satellite's mass could be reduced by as much as 10%. With the twin pressures of minimising development costs and maximising risk diversification imposing major constraints on satellite design, the production of comprehensive yet lightweight systems could benefit significantly from WSNs.

Although WSNs have been used in a wide range of applications in recent years, their use in space applications has, until now, remained limited. The Singaporean team's data-driven survey has established a sound platform for future formation-flying satellite missions, and seems poised to create subsequent revolutions in space.

Source: World Scientific

A new wireless energy transfer device can charge any device without using cables

Researchers have designed a new device for wireless energy transfer that will charge mobile phones or laptops without the need for wires. Credit: UPV

Researchers at the Universitat Politècnica de València (UPV) have designed a new device for wireless energy transfer that will, for example, charge mobile phones or laptops without needing wires.

The system, patented by the UPV, is based on the use of resonators designed with radial photonic crystals; one of them would act as an energy transmitter and the other would be set on the device that needed to be charged. Between them a phenomena known as resonant coupling is produced, which is what finally produces the charging or recharging of the equipment.

"This phenomena is produced when a resonant object is moved closer to a second resonant element and both resonance frequencies are equal or quite similar. This physical proximity produces an energy coupling from the first device, that acts as the source, to the second one, that acts as the charge," says José Sánchez-Dehesa, researcher at the Wave Phenomena 

Group of the Universitat Politècnica de València.

The device could also be used as a power supply system for equipment such as keyboards and wireless mice, speakers, etc. Besides consumer electronics, it could also be used in an industrial environment as power supply for robots or guided vehicles, and bioelectric devices (cardiac pacemakers, defibrillators, etc.)

The UPV researchers' study was released last June in the Annals of Physics magazine. After the first laboratory simulations and calculations of the system's performance, the engineers of the Wave Phenomena Group are now working on the development of the first prototype.

Technology implementation

With regard to the implementation of these devices, UPV researchers say that, "although it may seem futuristic, it is foreseeable that they become universal due to the spread of charging infrastructure in many settings. This technology could follow the same path as WIFI networks," explains Jorge Carbonell, researcher at the Wave Phenomena Group.

Source: Asociación RUVID

Sensors that improve rail transport safety

Cloud-supported sensor network for the condition-based maintenance of rail vehicles.
Credit: © Fraunhofer IZM

A new kind of human-machine communication is to make it possible to detect damage to rail vehicles before it's too late and service trains only when they need it -- all thanks to a cloud-supported, wireless network of sensors.

A train running on damaged wheels could easily be heading for serious trouble. This is why German national rail corporation Deutsche Bahn continuously monitors the wheelsets of its intercity express trains -- a process that costs a considerable amount of time and money. 

Researchers at the Berlin-based Fraunhofer Institute for Reliability and Microintegration IZM are collaborating with industry partners to develop a solution that ensures a great safety while reducing effort and cost. "We want to root out any damage early on and move away from maintenance at set intervals in favor of condition-based maintenance," explains Dr. Michael Niedermayer, microsystems engineer and head of the IZM's Technology-Oriented Design Methods working group. He is also project coordinator for "Mobile Sensor Systems for Condition-Based Maintenance," or MoSe for short.

Seamless monitoring

It's all based on a cloud-supported, wireless network of sensors. Every axle and undercarriage on a train is fitted with small radio sensors, which collect data on the condition of wearing parts. These data are then transferred to the online maintenance cloud, where the measurement and analysis data are encrypted and stored ready for use. The sensors can detect even the tiniest scratch on a ball bearing. As Niedermayer says, "Here we have sensor nodes that can capture even the slightest variations in vibration. We call this in-depth diagnosis." As a result, repairs can be made before anything works its way loose and causes damage.

"What's remarkable about this approach is that it allows everything to be monitored with the train in service, rather than having to inspect it at the rail yard. And in any case, visual checks are not 100 percent reliable," says Manfred Deutzer from project partner Deutzer Technische Kohle GmbH. Although there are wired sensors out there that can be used to examine rail vehicle chassis for wear and tear, these fail to match the high diagnostic quality standards the MoSe developers are striving for.

Using the new method, it is possible to get precise data on, say, whether an axle bearing will have to be replaced three months down the line, which avoids the need to replace it prematurely just in case. The latter is just as uneconomical as the custom of overhauling wheels at preset intervals with a view to resolving any wheel flats that could damage rails. 

"Wheels can tolerate such repairs no more than three times before they have to be scrapped," Deutzer reports. "It would make more sense and cost less to grind only those wheels we know actually turn poorly. The problem is that there has never been a suitable way of checking for wheel flats." MoSe is to change all that and much more besides.

"Not only do we intend to improve diagnostics, a top priority is also to process the data collected in as detailed and tailored a manner as possible," says Niedermayer. The idea is to provide train drivers with all relevant data (for instance about critical wheel damage), diagnostic technicians with detailed measurement data so they can assess how fast gear damage is progressing, and designers with measurement statistics covering wear to all parts, enabling them to improve the technical design of the next product generation. Making sure everyone involved receives the data they need in a form they can work with right away involves developing some clever diagnostic algorithms. "Yet another advantage is that wireless sensors can be easily retrofitted," adds Niedermayer.

What's also new is that the system can adapt to the different rotational speeds of the parts being examined -- such as the wheels on a train -- and in doing so, deliver incredibly precise data at whatever speed the train happens to be traveling. It used to be that sensors were designed to work at constant rotational speeds. Although this setup may be easier to manage, it means that the diagnostic quality suffers. Thanks to analysis algorithms, this is set to change. But developing these algorithms is a balancing act: "Since the system is intended to work without batteries, the algorithms mustn't drain unnecessary energy by using up excessive computing power," explains Niedermayer. As MoSe uses energy harvesting, it can tap energy from the vibrations and heat generated as the parts rotate.

Over the next couple of years a prototype will be developed that will be tested in a tram run by the German city of Brandenburg an der Havel. The system could then be used for monitoring purposes in suburban or long-distance trains.

Source: Fraunhofer-Gesellschaft

Li-fi protocol allows use of the Internet at the speed of light

Sisoft Company in Mexico has developed a technology that can illuminate a large work space, an auditorium or an office, while providing full mobile internet to every device that comes into the range of the light spectrum. Credit: SISOFT

Sisoft Company in Mexico has developed a technology that can illuminate a large work space, an auditorium or an office, while providing full mobile internet to every device that comes into the range of the light spectrum.

The Mexican group managed to transmit audio, video and Internet across the spectrum of light emitted by LED lamps. This new technology, called Li-Fi or light fidelity, is presented as an alternative to Wi-Fi because it will maximize the original provided speed of the internet to offer safer data transfer and a transfer rate of up to 10 gigabytes per second.

The Li-Fi device circulates data via LEDs that emit an intermittent flicker at a speed imperceptible to the human eye. "As Wi-Fi uses cables to spread our connections, wireless transmission Li-Fi uses LED lamps that emit high brightness light," said Arturo Campos Fentanes, CEO of Sisoft in Mexico.

Another advantage in comparison to Wi-Fi is that there is no way to hack the signal since the internet is transmitted by light, there is no way to "steal it." Furthermore, it can be installed in hospitals areas that use radiation apparatus and generally block or distort internet signal, Campos Fentanes said.

With this new technology expansion through the market is seeked, with lower costs and a service increased by five thousand percent internet speed. Currently in Mexico the highest transfer rate is 200 megabytes per second. Just to get an idea, with Li-Fi you could quickly download an entire HD movie in just 45 seconds.

Also known as visible light communications (VLC), this technology began with an internet speed of two Gigabits per second, but Sisoft along with researchers from the Autonomous Technological Institute of Mexico (ITAM) adapted the system to be multiplied five times.

Campos Fentanes explained that the first experiments were conducted with audio, in which a cable is connected via 3.5 mm audio Jack from a smartphone to a protoboard table to transform the auditory signal in optical waves. That way a special emitter transmits data across the spectrum of light generated by an LED lamp and is captured by a receptor located in a speaker that reproduces sound.

For wireless internet transmission, the mechanics is similar. The station developed by Sisoft of Mexico stands above the router device that distributes the internet signal and a lamp-LED is incorporated to maximize the speed of data transfer. Light will emulate an antenna, but only the electronic apparatus that has the receptor for the "optical audio" signal and is inside the range of the halo of light will have a connection. 

Source: Investigación y Desarrollo