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The ability to see through walls is no longer a subject. science fiction, thanks to new "radar" technology developed at MIT's Lincoln Laboratory.
Just as humans and other animals see through visible light waves that bounce off objects, so does radar, sending out radio waves that bounce off the target and return to the receivers. But just as light cannot pass through walls in sufficient quantities to be perceived by the eyes, it is difficult to build a radar that can penetrate solid objects well enough to show what is happening behind. Now Lincoln Lab researchers have created a system that allows you to see through walls from a distance, giving you an instantaneous picture of activity on the other side. Scientists developed their device for military use within the country.
The researchers' device is a set of antennas arranged in two rows - eight receiving elements on the top row, 13 transmission elements on the bottom, as well as some elements computer science, all attached to a movable cart.
Waves through the walls
The researchers tested their systems on four- and eight-inch-thick concrete walls.
At first, their radar functions like any other: transmitters emit waves of a certain frequency in the direction of the target. But in conventional radars, every time the waves hit the walls, 99% of them don't penetrate them. But that's only half the battle: after the waves bounce off any targets, they have to travel back through the walls to the radar receiver - and again, 99% don't. By the time the wave hits the signal receivers, it has been reduced to about 0.0025% of its original strength.
But, according to Charvat, eliminating the loss of signal from the wall is not even the main task. What was most challenging was achieving speed, resolution and range, which is especially useful in real time. "If you are in high degree risk in a combat environment, you don't want to see the same image every 20 minutes, but you also don't want to stand next to a potentially dangerous building,” Charvat says.
The Lincoln Lab team system is designed to be used up to 60 meters from a wall. (such a distance, according to Charvat, is realistic for an urban combat environment) and gives a real-time picture of the movement behind the wall in the form of video at a speed of 10.8 frames per second.
Filtering for frequencies
For good passing longer waves are needed through walls and back, but they require correspondingly larger radar equipment to address individual human targets. The researchers settled on S-band waves, which are about the same wavelength as wireless Internet—that is, quite short. This means that the signal loss will be greater, hence the need for amplifiers. But a real working radar reaches eight and a half meters in length. “This is, in our opinion, a normal size for installing the device on any car,” Charvat says.
Even when the problem of signal strength is solved by amplifiers, walls - be it concrete, adobe, or any other solid substance - will always look like a bright spot today. To get around this problem, the researchers use an analog crystal filter that uses the frequency difference between the modulated waves bouncing off the walls.
"It's a very capable system, mainly because of the real-time imaging capability," said Robert Burkholder, a professor at the Ohio State Department of Electrical and Computer Engineering, who was not involved with the work. “The device also has very good resolution thanks to digital processing and advanced image processing algorithms. But the system is a little unwieldy to move around on your own,” he says, but agrees that mounting it on a truck would be both worthwhile and useful.
Motion monitoring
In a recent demonstration, Charvat and his colleagues, John Peabody and Tyler Ralston, showed how radar was able to show an image of two people moving behind cast-in-place concrete, as well as a person swinging a metal pole in free space.
Since the processor uses a subtraction method - comparing each new picture with the previous one, the radar can only detect moving targets, and not inanimate objects such as furniture. However, even a person standing still moves slightly, and the system can detect these small movements by displaying the person's location.
For now, people can only appear as "blobs" that move across the screen. The researchers are currently working on algorithms that automatically convert the blob to a pure character to make the system more user-friendly and understandable.
With further improvement, the radar can be used internally by way to help in emergency situations. The researchers say they were developing the system primarily for military applications: "This device is designed for such tense situations where it would be great to know what is behind this wall."
The term "teleportation", which means instantaneous movement from one place to another, was coined by the American writer and paranormal researcher Charles Fort. According to his observations, most people immediately before moving experienced discomfort - weakness, dizziness, nausea, after which they lost consciousness.
Only one person felt great both before and after the teleportation - Pole Janusz Kwalezhek. Janusz was born in 1880 in Warsaw. His father worked in a mine, his mother raised four children. Janusz did not give his parents much trouble.
Everything changed when the boy was 10 years old. He played ball with his friends near railway when suddenly the ball flew off to the side and rolled onto the rails. Janusz ran after the ball and found himself in front of a locomotive flying right at him. The driver desperately slowed down and honked, but Janusz was so confused that he froze right on the rails.
It was as if he was paralyzed, he could not move his arm or leg. The boys mentally said goodbye to him, and he was already enveloped in a cloud of steam and smoke, when suddenly he took a step forward and disappeared.
In the next second, Janusz was in the shop, which was kept by the old Jew Chaim. The boys ran to him for tasty toffees once a month, when the miners' fathers received a salary. Chaim stood behind the desk and counted on large wooden abacus. When Janusz unexpectedly appeared before him, the shopkeeper looked up, straightened his pince-nez and asked: “Well, son, did Pan Tadeusz give the folder a salary a week earlier?”
At the age of 12, Janusz excelled again. On weekends, my father liked to sit with a fishing rod on the banks of the Vistula. Early on Sunday morning, he called Janusz and asked menacingly: “Where are my fishing rods? Confess in a good way! Waking up, the boy did not understand anything: he did not take fishing rods. The father did not believe and punished his son - he locked him in a closet for the whole day.
Janusz was furious, this injustice hurt him the most. He walked up and down the closet and imagined how the boys were gathering in a crowd near the old oak, as had been agreed the day before, to go to the Vistula to bathe. And Schesni promised to show his grandfather's gift - a new penknife.
Grandfather Schesni came from distant America, where he went to work and from where he brought gifts to his relatives, including a knife for his beloved grandson. The parents allowed Schesney to show the boys the knife once. Oh what a dream! The day is gone, Janusz decided. He remembered his favorite book, "David of Sasun," in which a certain Megr the Younger went through a rock in a fit of anger.
This was followed by a memory from the recent past, when two years ago he himself inexplicably escaped death on the railroad. And then the teenager decided to repeat his “feat”. He exerted all his strength and threw himself against the wall. The blow was such that the boy for a moment forgot himself, and when he woke up, the Vistula calmly rolled its blue waters in front of him.
At the beginning of the 20th century, Poland was unsettled. The global industrial and financial crisis of 1901-1903 hit the poorest sections of the population hardest. In response to widespread cuts, rising unemployment and declining wages began mass demonstrations of the workers of Lodz, Czestochowa, Warsaw.
In the autumn of 1904, the Poles rose up against the mobilization into the army announced by the government in connection with the Russo-Japanese War. Janusz Kwalezhek already worked, like his father, at the mine. And when in 1905 the Poles organized a general strike that engulfed enterprises and universities, Janusz joined it.
The authorities did not stand on ceremony with the rebels, and Janusz Kwalezhek ended up behind bars in the same cell with students who went on a hunger strike against the actions of the authorities. Janusz joined the starving. The result is a punishment cell.
And suddenly a strange entry appeared in the prison reports: “For bad behavior, Janusz Kwalezhek was taken to a punishment cell. disappeared inexplicably." The police quickly found young man who had no intention of hiding.
Janusz again ended up in prison and again immediately in a punishment cell for trying to escape. But soon the jailers were forced to state that Janusz Kwalezhek was gone. Reporters heard about the Kvalezek phenomenon, and many newspapers came out with headlines: "Penetrating through walls." So for Kvalezek this nickname stuck.
Prison played a big role in Kvalezek's life. Thanks to her, he became famous throughout the country, and also met a man who became interested in his unusual talent. Polish theoretical physicist and university lecturer Heinrich Shokolsky ended up behind bars for participating in student unrest. His cellmate was Janusz Kwalezhek.
Shokolsky was called "an eccentric of science": he was interested not only in physics, but in everything that science could not explain. He has long tried to understand the nature of paranormal phenomena, such as poltergeist, transmigration of souls, telekinesis, and so on. Janusz Kwalezhek became a gift of fate for Shokolsky.
Watching Janusz, Shokolsky theorized that during times of stress, Kwalezhek released a large supply of energy, which allowed him to penetrate walls. According to the physicist, approximately the same thing happens with other people caught in extreme situation. That is why a person can jump over a tall fence, lift a multi-ton truck, walk on burning coals.
But theory is one thing and practice is another. Janusz Kwalezhek and Heinrich Shokolsky decided to experiment right in prison. It turned out to be much more difficult for Janusz to demonstrate his abilities than usual: the cell in which the prisoners were located did not border on the outer wall. Janusz already knew from experience that it would be more difficult to leave such a room, because he had to go through two adjacent cells. However, the experiment was successful.
Janusz Kwalezhek and Heinrich Shokolsky continued their collaboration in freedom. The scientist kept a kind of diary, displaying the parameters of the "ward" - body temperature, which at the time of passing through the walls slightly increased and the heart rate (also changed). Otherwise, Kvalezhek remained in the same physical form, as usual, only experienced extreme excitement and sweated profusely.
Shokolsky tried with the help of special devices to catch electromagnetic waves emanating from the subject, but he did not succeed. But the physicist managed to find fingerprints on the wall through which Kvalezhek passed.
At some point, Shokolsky attracted his laboratory assistant Adam Stankevich to conduct experiments. Either something went wrong with the experimenters, or for another reason, but one day Janusz Kwalezhek passed through the wall and disappeared forever. This experiment cost scientists dearly. Adam Stankevich lost his place at the university, and Shokolsky ended up in a psychiatric hospital. Subsequently, Stankevich wrote in his memoirs:
Heinrich Shokolsky was the last person to talk to Janusz. Nothing foreshadowed the loss, and what happened is beyond all understanding. Perhaps Janusz stumbled (of course, in his own way), stumbling in the “portal” on the edge between the worlds he knew only, and remains on the other side of both our world and our understanding.
About a hundred years have passed since that time. AT new Age humanity has entered with many mysteries, one of them is still teleportation. Although, I must say, scientists are very close to unraveling this phenomenon. So, in the USA, serious tests are being carried out on the teleportation of complex molecules. After that, it will take several more decades to develop a method for teleporting DNA.
An American physicist of Japanese origin Michio Kaku is sure that “against the teleportation of a person, just like in science fiction films, there are also no fundamental objections, but technical problems that must be overcome on the way to such an achievement are amazing.”
Materials of the article by Sergey Shapovalov were used
Charles Fort, who coined the term "teleportation", noted in his writings side effects teleportation. Most people who have experienced this phenomenon said that immediately before moving they felt weak, dizzy, nauseous, after which they lost consciousness.
However, in the history of the study of the phenomenon, there is one amazing person who seemed to be unfamiliar with such side effects. We are talking about Janusz Kwalezek, a man known to very few.
Kwalezhek is a Pole, born in 1880. He became famous already at the beginning of the 20th century, and his fame was ambiguous. He incredibly surprised the prison administration by disappearing inexplicably from the most reliable punishment cells.
When the boy was ten years old, he played football near the railway, and the ball flew onto the rails. Janusz ran after him and found himself in front of a locomotive, desperately slowing down in a cloud of steam and smoke, but inevitably advancing. This cloud had already engulfed the boy entirely, then, as it were, bypassed, separating him from his comrades and, as it were, even from life. Being in this cloud, Janusz, realizing in a fraction of a second the inevitability of his own death, even took a counter step towards the locomotive, and then ... something seemed to pass around him and let the boy out.
Then he said that some kind of force seemed to be released inside him, opposing himself to the inevitability of meeting with the oncoming train, and he simply ... disappeared in front of the locomotive, finding himself on the railway embankment at a safe distance. Over time, this inexplicable ability to disappear from one place and appear in another did not pass from him, moreover, nature seemed to even undertake to nurture this ability.
She kept ordering the boy to be locked up somewhere, and even for offenses that he did not commit. And this repeated injustice has taken its toll. After the boy was once again locked in a bathhouse for stealing fishing rods, which he had never seen in his eyes, little Janusz suddenly went berserk. And who locked something! Favorite grandfather! And at this time, nearby, in the Vistula, the boys were swimming.
The boy's anger grew. For the first time he was so angry: at his grandfather with his rod, and at himself for his bad luck, and at the guys, and at the bathhouse with thick walls that fenced him off from them ... He remembered the book "David of Sasun", in which a certain Megr The younger one, in great anger, entered the rock, immediately found himself behind it. I also remembered the locomotive in a cloud of steam, and everything that he unconsciously did at that terrible moment. And it seemed to Janusz that he, too, could pass through the barrier - no worse than some literary character Megr.
Janusz imagined "his" cloud and tried to evoke that power of overcoming in himself. And then - for the first time consciously - he overcame the obstacle and ended up behind the bathhouse. And fate more than once provided him with opportunities to "hone" such an ability. And he, in front of the obstacle, having "revived" in himself that embracing the cloud with the approaching steam locomotive, walked towards him, and the "cloud", and the "locomotive", and the obstacle itself were already behind him.
Kvalezhek is a living illustration of the statement that you have to pay for everything in this life. Having received an amazing gift from nature, Janusz suffered all his life: he was constantly detained, mistaking either for a pickpocket or a robber. He joked that in this way he paid off. As a result, Janusz was already very tired of being behind bars for no reason. But each time it was necessary to somehow get out, and Janusz got out.
In the prison annals they wrote: "For bad behavior he was taken to a punishment cell. He disappeared inexplicably." According to the newspaper "police reports" he became already quite famous as "Wall Walker". And right there, i.e. behind bars, by the will of fate, Janusz met in 1922 with the theoretical physicist Genrikh Shokolsky, who began to investigate this unusual phenomenon. Shokolsky had by that time the reputation of "an eccentric of science." The scientist ended up behind bars after the well-known student unrest of 1922, and Kvalezhek - because he was detained all the time.
Kvalezhek was far from demonstrating his abilities to a cellmate, but in response to his questions about why he was running away, he mentioned that in the eerie conditions of the punishment cell he involuntarily goes berserk, and besides, there are no witnesses in the punishment cell. Shokolsky, being a researcher of everything unusual, knew, of course, that in a stressful situation a person sometimes releases energy reserves, which manifests itself in an amazingly huge one-time force (for example, a woman lifted a truck that ran over her child). But to inexplicably disappear in a stressful state ... He had never seen such a thing.
Imagine this scene: two people are sitting on the floor in a cell. One is a little over forty - that is. not a boy anymore to tell stories, but the second one is a scientist, albeit an eccentric, and in all seriousness they talk about how to pass through walls. And Janusz informs the interlocutor that, if he wants, then without difficulty pass the wall with the help of natural force. In response to this bold statement, Shokolsky smiled incredulously and suggested an experiment. Kvalezek agreed. He will leave the prison, please, it is not difficult for him, and later, when Heinrich is released, they will meet at the agreed place and continue the conversation.
But this time, Janusz faced special difficulties: the chamber did not border on the outer wall. He had to go through two adjacent cells. It was, in general, also not difficult, if not for one "but": they had to be passed so quickly that the prisoners simply did not have time to understand anything.
Before delving into miracles and somehow explaining them to himself, Shokolsky, as a man of science, decided to fix them on paper. "Upper and lower bunk beds were located along the walls. Everyone fell asleep, Janusz peered between the bunk beds. From his gaze, as if penetrating into the wall itself, it seemed that he was already somewhere with something important in himself, and that he only needed to move , as if catching up with himself, he must, as it were, pull himself up - from the cell, in which some part of him seemed to remain due to an oversight.
And Janusz moved - approaching the wall. And it became clear that the wall could not stop him. And approaching the bunks, Janusz for a moment - as if cut in the upper shoulders - passed them (the sleepers shuddered at the same time) and plunged into the wall before my eyes, "the scientist wrote. Having met Janusz in the agreed place - in the laboratory at the department, the physicist asked to tell how he managed to get through the walls of several cells.And this turned out to be not easy - all the time, as it were, "pushing away" an imaginary engine, but also keeping it at a short distance in order to walk towards itself.
After listening to the story, the scientist invited him to participate in new experiments and asked him to tell how Janusz discovered an unusual gift. Then Janusz told about the locomotive. Thanks to Shokolsky's notes, descendants had at their disposal information about what Kvalezhek felt when he passed through the walls. Passing, for example, a concrete wall, "Janusz felt the reinforcement, but - like cool jets in warm water," the scientist wrote. "And in general, any material was fixed by him only in temperature regime, not density.
But for some reason Janusz could not walk through the glass. It was also unexpected for Pan Shokolsky that none of the devices in the laboratory recorded Kvalezhek's "field" in any way, when, having passed through the room, he plunged from one side of the wall and, having passed it, appeared from the other. It was also unexpected that in time it did not differ from the passage of the same distance without an obstacle.
Curious was the fact that Kvalezhek, "leaving" through the walls, left on the inside of the wall a lapidary, an imprint of the physical body - like a fingerprint. Lapidaria consisted of sweat and fat secretions from the skin. These lapidaries were repeatedly recorded by both the prison authorities and Shokolsky.
The experiments went on and on, and the scientist literally got lost in the jungle of hypotheses. He assumed that at a certain moment an energy field suddenly arose around Janusz, giving him the opportunity to find himself on a certain line between the material world and the so-called. thin. This field deprived ordinary properties either matter or Janusz himself.
Only a special energy barrier could stop such a subject. "Experiments on the transformation of the X-field into matter and vice versa," as Shokolsky called them, continued in the presence of laboratory assistant Adam Stankevich, who took notes and gave his word to remain silent for the time being.
And the experiments ended unexpectedly: Janusz did not come out from the other side of the wall. He passed this wall more than once and suddenly - he didn’t come out, he disappeared. And tapping, and then the destruction of the wall did not give anything. After some time, Stankevich stopped keeping the secret, and so it became known to some scientists and acquaintances of the researcher. “Shokolsky was the last one who talked with Janusz,” Stankevich recalled. “Nothing foreshadowed the loss, and what happened surpasses all understanding. Perhaps Janusz stumbled (of course, in his own way), stumbling in the “portal” on the only known edge between the worlds, and remains on the other side of both our world and our understanding ... "
Many articles were written about the Kvalezek phenomenon; scientists rushed to put forward various hypotheses. The most reasonable is the hypothesis that explains the passage through the wall by a person's conscious use of his astral double - after all, esotericists have long known that a person, in addition to his physical body, has several more "thin" bodies, incl. the astral is a soliton, a double of the physical body.
Scientists who have studied teleportation note that this anomalous and extremely rare phenomenon becomes possible only if the entire variety of properties of an organism is converted into an elementary particle - a wave moving in the microwave range accessible to it. The same quantum mechanism explains the cases of body transfer through barriers without their destruction. The body is transformed into its impulse twin, which, like a wave, moves in its waveguide.
It turns out we are talking not about the dematerialization of the body, but about its transformation from the complex to the simplest, up to the tunneling elementary particle - the quantum model of the body. As for Kwalezhek, when the information structures of the soliton were already outside the barrier, Janusz tried to force the private consciousness of the soliton to pull the information structures of the physical body into place of the information structures of the astral body, i.e. forced his superconsciousness to swap the soliton for the physical body.
And in this Janusz was helped by the identification of his physical body with a cloud of steam and a locomotive approaching him. And it is possible that one fine (more precisely, not fine) day he failed to do this. As a result, his physical body disappeared without a trace. Perhaps these scientific explanations not entirely clear, but plain language expressing this idea is extremely difficult. Just like explaining any miracle.
However, according to Helena Blavatsky, "A miracle is not a violation of the laws of nature." Levitation, telekinesis and teleportation are not a miracle, but just a paranormal ability of people to control their force field and act on bodies and objects. The biogravitational psycho-effects of a person are a miracle, but only for those people who do not own the forces of their own body.
About portable radars Range R, which are used by the American police and other government agencies. The system "sees through walls", or rather: registers movement in the room. The high sensitivity of the radar can detect the breath of a person hiding inside a building, behind several walls.
The existence of such a device surprised many journalists who were supposed to write about the capabilities of the Range-R. These radars are mass-produced for the army and intelligence and are used, for example, FBI- during the rescue of hostages, firefighters- when searching for the wounded in destroyed buildings, US cops- to catch fugitives.
Previously, this technology was only available for some government services, however, technological advancement has contributed to falling prices, which has allowed a wider range of users. The Range-R radar costs about $6,000 while the prototypes new radar systems are built from readily available low-cost Wi-Fi modules.
How to see through walls
The Range-R device has sensors that can "look" behind the walls (Through-the-Wall Sensors, TTWS). The principle of operation is the same as in other radars: the sensors scan the area being viewed with radio waves, which, when an obstacle is detected, return to the receiver, and it registers the reflected radiation.
Unfortunately, this is only in theory. The creators of TTWS had to combine several technologies and advanced data processing methods in one device. Radar operators must pass long-term training to understand how to read data from it.
The higher the frequency, the less penetration of radiation through the walls. In turn, higher frequencies increase the accuracy in determining object size and distance. Moreover, some materials selectively absorb radio waves in a narrow range. Because of this, additional scanners have the ability to switch the frequencies used, or they can be used for a wide range of the radio frequency spectrum.
With short pulses, the user can estimate the distance to an object by measuring the time it takes for a wave to travel the distance to an obstacle and back. Motion detection is based on the Doppler effect: a wave reflected from a moving object gently changes its frequency, which makes it possible, for example, to detect small movement chest breathing person.
There is no doubt that TTWS devices have many restrictions. One of them is the fact that radio waves do not penetrate metal. Because of this, they cannot identify a person in a closed car or in a building covered with a layer of aluminum. Water has metal-like properties: wet porous concrete is also a very good shield against TTWS radio waves.
The signal level is weakened by a thick layer of concrete or brick, and if the sum of the thickness of the walls separating the radar from the desired object exceeds 30 centimeters, it will be impossible to detect it.
Most devices can detect obstacles at a distance of 15-20 meters, and devices with large antennas and powerful power supplies can reach up to 70 meters. As a rule, there are many moving objects in the house, for example, animals or curtains. Although radars are generally used to detect people, the interpretation of the object is not always correct, especially if the measurement takes too long. a short time(less than a minute).
Most radars portable. To eliminate vibrations, the operator must press the device against the wall of the building being checked. However, there are situations when you can not get close to the wall, so some models are equipped with tripods, mounted on robots or drones.
Most simple TTWS radars show whether someone is still alive and / or moving the building. More complex ones determine the distance to the object and the direction of movement, allow you to determine the approximate design of the building and its interior in two or three dimensions.
Experimental solutions look promising (at least in laboratory conditions). For example, a mobile Wi-Fi system installed on robots generated a map of a completely unfamiliar house with an accuracy of 2 centimeters. So far, this technology, however, is a sham when it comes to mass production.
How to prevent. The best defense against TTWS is building shielding, simply reinforcing your home with a thick concrete structure. A good solution is also to cover it with a layer of aluminum or paste it with metallized wallpaper. Or start three dogs- Their constant and erratic movements will confuse most radars.
This is a terrible (but not very) terahertz
If you follow popular science information, you have certainly heard that terahertz radars can see through any walls and feel bombs from afar. This topic appears periodically on the Internet after some laboratory announces in its press release that it has achieved great success in this area.
The fact is that terahertz radars are already being used to control passengers at airports. They started to be talked about loudly when it turned out that they show a very detailed image of the human body, without regard to clothing.
Most other uses for terahertz waves (operating in the 300GHz-10THz region of the spectrum) remain in the realm of science fiction. In fact, there many more unresolved issues: from the disappearance of the signal when it penetrates through various barriers to the problem of creating compact high-power emitters.
Another urban legend: IR cameras that look over the wall. Contrary to popular belief, thermal detectors cannot do this. The IR detector cannot even pass through the layer frosted glass or plywood.
How to prevent. Whether to take off your tinfoil hat is up to you.
Science fiction films sometimes show installations that allow you to see people behind walls and shelters. Thanks to the efforts of specialists from the MIT Artificial Intelligence Laboratory, this possibility is slowly becoming a reality. This is not about thermal imagers and not about x-rays. Regular Wi-Fi now helps to determine the number of people in a room behind a wall or a closed door.
The ability to detect a person behind an opaque barrier has always interested the military, special forces and rescuers. Camero-Tech has gone the furthest with the introduction of last years several serial variants of such equipment.
Each of these devices worked on the principle of radar. The area under study was illuminated by electromagnetic waves of the length that allowed them to penetrate obstacles. By the nature of their reflection, the number of objects in the path of radio wave propagation, their speed and direction of movement were judged.
Such methods are already being used by special services, but still do not allow achieving the desired result. The devices are expensive and complex, large-sized or inefficient. but the main problem not even in this. Inactive targets (for example, hostages) are practically invisible, and the very fact of electronic intelligence becomes obvious and can betray the task force with its head. Of course, everything goes perfectly in the demos.
Professor Dina Katabi of the Department of Electrical Engineering and Computer Science and her PhD student Fadel Adib took a slightly different route and got closer to solving one of two key problems. The device they created uses the widespread Wi-Fi band, which is unlikely to respond to a slight increase in activity.
In the IEEE 802.11 standard, fourteen channels are allocated with a wavelength from 121 to 124 mm. The decimeter range and typical power up to one hundred milliwatts lead to the fact that the quality of communication largely depends on the presence of any obstacles in the signal propagation path. The movement of people has a noticeable effect, which is used in this case.
In real conditions, there are practically no solid walls. They have voids, joints, technological holes and strobes, so a weak Wi-Fi signal passes even through barriers that seem to be monolithic.
In a Wi-Vi (abbreviation for Wireless Vision) device, a low-power signal is emitted out of phase by two antennas simultaneously. Reflections of radio waves are recorded by one receiver. The main part of reflections arises from walls and other fixed objects inside the studied room. Such radio waves arrive simultaneously and cancel each other, and the remaining minimal noise is filtered out by software. As a result, only radio waves reflected from moving objects - people - are taken into account.
The above video demonstrates not only the ability to determine the presence of people in the area of the Wi-Fi signal source, but also to find out the direction of their movement. When a person moves away from the device placed behind the wall, a Doppler shift occurs, the angle of reflection of the radio waves changes, and the graph goes down. Accordingly, movement in the direction of the antenna causes a sharp rise on the graph, and stomping on the spot is marked by weak bursts in the background level from a static environment.
Previously, such results could be achieved only with the help of an array of antennas spaced over a large area, individual receivers for each, and complex processing algorithms.
The Wi-Vi prototype uses only two antennas and one receiver, which significantly reduces the size and cost of the device. According to the developers, using the first version of the device, it is already possible to track the movement behind the wall of both individuals and groups of up to three people.
For the first time, Wi-Vi technology was presented at the SIGCOMM conference held in Hong Kong. As examples of practical use, the speakers cited scenarios for the work of search and rescue teams, the detection of an ambush by police officers, as well as the assessment of enemy forces and the search for hostages by anti-terrorist units.
A similar concept was reached last year at University College London. The prototype Wi-Fi scanner created there is notable for the fact that it does not give out the very fact of reconnaissance. This is a passive device that analyzes the change in signal characteristics at a frequency of 2.4 GHz from initially working Wi-Fi access points.
The described technologies also have completely different potential areas of application. For example, on their basis, you can create systems for constantly counting the number of people in public place and regulate its operation. It becomes possible to automatically change the parameters of the climate system and ventilation, the speed of escalators, the frequency of transport, receive timely messages about the need for additional personnel and apply other adaptive control schemes.
