"The laws of physics can be bent but never broken."
The way signals propagate through the atmosphere/space, hit and pass through, are absorbed, and bounce along a reflected path, as the discussion exposes, is complex. At lower frequencies a wavelength is longer, making it more difficult to design antennas to fit into small devices. The signals travel farther which makes coverage easier and less costly. However, that also causes signals to interfere unless signals that cross into a common area/space are differentiated in some fashion so that the interfering signals can be filtered by use of analog means or digital signal processing.
At higher frequencies, wavelengths become shorter, making the job of packing antennas into small devices less of a challenge and allowing capturing a higher level of the signal reaching the antenna. However, signals also are absorbed more in common building materials, foliage, and other objects. Signals tend to bounce more, causing multiple reflected signals to occur in areas where the signal is non-line-of-sight (NLOS). These are prominent design considerations among others.
Wireless technologies including signal processing and fractional-wavelength antenna design are being increasingly used to counter the negative impacts of signal propagation in order to become practical for communications. negative impacts, such as multiple-path propagation of signals is taken advantage of by signal processing so that signals are combined to raise the received signal to a higher SNR, signal to noise ratio, compared to analog methods that may try to filter out all but the stronger signal. Rather than use narrow-band antennas, for example, MIMO, multiple-input, multiple-output, signaling methods receive the multi-path signals and differentiate them in time-space, an analog function, digitize them and use signal processing to align for time differentiation caused by signal travel.
The issue of how signals travel is complex and must often be confined to a use-case in order to weigh the impacts or else it becomes unwieldy. However, a broad grounding in both the theoretical models and evolving methods to counter or take advantage of how signals travel, how absorption reduces interferences as well as impedes signal reception, and how reflection can multiply bandwidth by multiple frequencies reuse all must be considered.
Bringing this understanding into the world of applications requires practical considerations of component (antennas, chips, etc.), device and equipment availability and cost relative to alternatives. And, lastly, using multiple-frequency-carrier signaling methods to increase reliability and combined bandwidth of wireless communications and how that impacts the cost equations must be taken into account within a competitive applications environment.