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M2M comunications Thin and flexible Bluetooth LE beacons operate battery-free By FJulien Happich ujitsu Laboratories Ltd announced a Bluetooth LE beacon weighing only 3 grams and only 2.5mm thick, that does not require battery replacement or any other maintenance. The beacon is flexible enough to be wrapped around round objects, corners, and curves and it is solely powered by an integrated solar cell. Previously, beacons that did not require battery replacement needed power-supply components, such as power-management ICs and secondary batteries, as control circuits to ensure adequate power on activation. These components, which are relatively thick and occupy a large area, make the beacons themselves rigid and large, limiting locations to which they can be attached, explain the researchers in a press release. Such thin beacons could be attached to fluorescent bulbs in a ceiling, or to the surface of an LED light, hence doubling lights as information points, for guidance or any other purpose (for example when installed in parking lots together with sensors to detect available space). For this flexible autonomous beacon, Fujitsu Laboratories has developed power-control technology that temporarily deactivates the power monitor once it has detected that enough energy has been accumulated. The saved power makes it possible to supply the power needed to activate the wireless-communications module using a small storage element connected to a solar cell, only one-ninth the size of those used with previous technologies, according the Japanese lab. Reducing the power consumed just before starting communications also has the effect of reducing voltage fluctuations when power is being used, obviating the need for a power-management IC. Fujitsu is currently conducting field testing to establish the beacon’s reliability and continuous operation, hoping to have a commercial product by 2016. Bi-directional RF doubles cellular capacity By R. Colin Johnson In electrical engineering school you were taught that full-duplex (sending and receiving) had to be done on different frequencies or at different times (technically half-duplex). That is, either transmitting or receiving at the same time, but on different frequencies, or at different times on the same frequency. But that is a lie, according to researchers at Columbia University in New York City. Columbia researchers recently demonstrated a complementary metal oxide CoSMIC Lab full-duplex transceiver IC that can be implemented in nanoscale CMOS. Source: Jin Zhou and Harish Krishnaswamy/Columbia University. semiconductor (CMOS) chip called CoSMIC (Columbia high-Speed and Mm-wave IC) for doing full-duplex on the same frequency at the same time, thus doubling wireless communication’s speed. Electrical engineering professor Harish Krishnaswamy told EE Times: Full duplex at the same frequency has been thought to be impossible until today because if you transmit and receive at the same time at the same frequency, the receiver will get drowned out by the interference from the transmitter, which can be one billion times more powerful than the signal that one is trying to receive. But we have devised an echo- or selfinterference cancellation scheme that can do away with the transmitter’s interference with one part per billion accuracy, so that after cancellation, the received signal can be easily detected. Without Krishnaswamy’s team’s circuitry, full-duplex would be like trying to hear someone whisper while someone next to them was shouting at the top of their lungs, according to Krishnaswamy, who performed the work with doctoral candidate Jin Zhou. “But if you could somehow cancel or block out the screaming next to you, and note that you would need to cancel it nearperfectly, you could then hear the whisper,” Krishnaswamy said. “And we have found a way to do this for electromagnetic wireless signals using a tiny silicon chip.” What Krishnaswamy calls an “echo canceler or self-interference canceler”--CoSMIC--is installed at the receiver’s input port, silencing the louder transmission signal so that the quieter receiver signal can be heard. The key innovation is that to cancel the transmitter self-interference with one part per billion accuracy, the chip needs to make a near-exact replica of the transmitter selfinterference. This is hard to do especially because the transmitter self-interference or echo will distort and change as it reflects off objects in the nearby environment. In principle, all RF communications are amenable to this technique, Krishnaswamy noted, adding that his team have devised a circuit that can do this with a single silicon chip. The researchers will begin by trying to double the speed of wireless signals--in particular WiFi and cellular communications for smartphones and tablets. Diagram of traditional RF communication (left) versus two-way full-duplex on same frequency at the same time (right) thus doubling speed. Source: Columbia University. 36 Electronic Engineering Times Europe April 2015 www.electronics-eetimes.com


EETE APR 2015
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