Frequency spectrum is a limited natural resource. It is impossible to artificially cram any new frequencies into it or into its ranges, even in quotation marks. You can use the spectrum more efficiently by applying new modulation and signal coding techniques. Encoding is not in the sense of protection from someone, but in the sense of the effectiveness of "packaging" the original signal and protection from interference. In this case, you can "play" with the parameters, for example, you can "cram" more, but either the quality or the service area will suffer, or there will be restrictions on movement. For example, for stationary broadcast reception, we can accommodate 10-15 TV channels of standard quality in the 8 MHz band, but if we want to receive a signal in motion up to 100 km / h, then it will be 2-3 channels. Moreover, if we transmit a signal through a closed waveguide system (cable, waveguide, optical system), then 20-30 channels in the 8 MHz band is not the limit only due to the fact that, due to the absence of interference, we can use more efficient methods of signal modulation ... For data transfer, everything is approximately the same.
But everything has its own limitations, everything has a limit. The modern European standard for terrestrial television DVB-T2 is already so close to the limit of spectrum use that there will be no DVB-T3 anymore. But there is no limit in signal coding, although now we want to transmit an HD signal, and soon ultra-HD. So there are interrelated processes going on. Most of all, the spectrum is needed for data transmission, so they even began to "clamp" the spectrum for television for the sake of data transmission. Telephony, even with a large population, is not such a big problem due to the low demand for bandwidth and the availability of other opportunities to improve the use of the spectrum (for example, the time division of the communication channel between subscribers), but data transmission is growing at a catastrophic pace. Moreover, it is growing primarily due to the same video traffic. And if no one needs hundreds of TV channels on the air (technically, this is not so difficult to implement), then video traffic continues to grow.
But back to the spectrum. On the one hand, it seems that there is still a lot of spectrum in the region of ultrahigh frequencies, but, on the other hand, it is more and more difficult to use them with increasing frequency for a number of reasons. But below, almost everything that can be effectively used is densely packed, so the spectrum, one might say, is now exhausted. There is only a redistribution of frequencies between different services, for example, as I said, TV people are being ousted, forcing them to abandon analog broadcasting. So what you are afraid of has already arrived.
But it's not all bad. Good frequency planning can help you use the same frequencies far apart without interference. Modern devices also "teach" to work effectively side by side, without interfering with each other. You can also shorten service areas, for example by placing telephone "cells" more often. But at the same time, in fact, there is an almost bottomless barrel nearby: up to 80%the spectrum is militarized, that is, reserved by the military. And how many do not try to push them, all this is very difficult. In Russia, this is just a misfortune - since the 90s I have heard that it is necessary to demilitarize the spectrum, but things are still there. Recently, this has also calmed down, but the spectrum is still being released a little. So, abandoning "plans for war" can not only save material resources, but also the frequency spectrum. At the same time, the use of the spectrum by the military, I must say, is extremely ineffective.
But in spite of everything, your fear is hardly justified: you personally will not feel the limited spectrum on yourself, in the coming decades for sure (if only because and now you don't feel it :)). One way or another, but consumption is also of course: we don’t need 1000 TV channels, a million radio stations, we don’t watch ultra-HD videos on our phone around the clock, and every person doesn’t need 1 GHz / sec speed in constant mode. Therefore, even in overpopulated countries, they do not yet experience a particular shortage of spectrum (although, of course, it does not do without administrative restrictions), which, by the way, cannot be said about data transmission via cables: due to the ever-increasing world data exchange, scientific and technical work is constantly underway to increase the amount of information transmitted over optical fiber.
Do you mean telecommunications? Theoretically possible, but unlikely, since the resolution of the transmitting and receiving equipment is improving all the time. That is, more and more "frequencies" fit into the same range (after all, it is clear that, from a formal point of view, frequencies are infinite in any range and the only question is how much they should differ from each other so as not to interfere) .
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