Line of Sight Requirement in Indoor Positioning | Marvelmind

0:01 Hello colleagues. I would like to address a very peculiar issue of line of sight and non-line of sight. We have covered this already in the previous presentation, but it covered many topics, and I would like to address one more time about line of sight and non-line of sight summary. Line of sight is required for any precision navigation system, any particularly for industrial applications. Why? How the system works: the system is measuring their the distance between stationary beacons and the mobile beacon using time of flight. In our case, time of flight of ultrasonic. So it means that if there is any obstacle which is not sound transparent, then the sound will not be able to propagate. If, for example, you are not using our system—for example, using

1:01 ultrawide band, which is a great system—ultraviolet band is using time of flight of radio pulses. But there is one major underlying assumption, and that underlying assumption is that if you are measuring the time of flight, you assume that the propagation speed is the same, which is the same in vacuum. But if you have a wall—even radio transparent wall in the middle—then within this wall, their propagation distance will not be equal to the thickness of the wall because the properties of the wall is completely different than properties of air or vacuum. So it means that the real distance will not be the same as the thickness. So it means that when you measure a few nanoseconds between these points, you don't know how much actually was this. Because in air, this was passed—I don't know—for one nanosecond,

2:00 but if it was a concrete wall, it could be two nanoseconds. So it means that effectively distance was like this. So you'll have already this kind of additional time of flight, which means that you will not be able to make any precise navigation system if it's not direct line of sight. So direct line of sight is a must. Second, it's more warning because it's easy to assume like in this office when you have a very basic walls that could be radio transparent—for example, for ultra red band. For our case, for ultrasonic-based system like Marvelmind navigation system, it doesn't matter because even this would be not line of sight. My cloth is line of sight. So it's line of hearing the sound would go through it. But even this or even basic, you know, carton would be blocking their ultrasonic signal. So you must provide their line of sight. But when you are dealing with radio, you can

3:00 easily fall into the assumption that it can go through the walls without problem because if you measure in the office, it looks kind of okay. But then you go to the real environment—real means warehouses, assembly plans, and all other places where you have real thick walls, concrete or brick or metal. Or if you have shelves full of metal, the radio will not be able to propagate through, and you'll be getting all kind of reflections. You'll be getting all kind of dispersed radio waves from different directions, and you will not have a precise tracking. So just a summary and warning and recommendation is actually: don't try to build precise indoor navigation system without line of sight. Sooner or later, it will not work, particularly in industrial applications when you have

3:58 thick walls, metal walls, or something which is not letting you to go through. And majority of walls or majority of obstacles that you have in real environment—not in the office environment, but in the real industrial environment—are like this. So they are not letting to propagate through radio waves. And of course, ultrasonic. Ultrasonic is more, let's say, demanding from this respect. So we are not even trying to build non-line of sight. This is why the only recommendation that you can see in our placement manual is how to place the beacon so that you would have all the time the best coverage from the beacons. And the best coverage is usually when you have the beacon somewhere high and the mobile beacon is also high—for example, on your helmet or on top of your robot or on top of your drone—like in this case. So, for example, this is your drone's, and in order to provide the best coverage,

4:58 the mobile deck inside meeting like this and the stationary beacon meeting like this, and you don't have anything in the middle. If you have anything in the middle, then you install additional stationary beacon so that if this is blocked, that would be still serving you. That's the approach: N plus 1 or 2N redundancy. But again, summary—key summary: don't try to build precise indoor navigation system without direct line of sight. Thank you very much.