Wireless communications have undeniably shaped our everyday lives. We expect ubiquitous connectivity to the Internet, with increasing demands for higher data rates and low lag everywhere: at work, at home, on the road, even with massive crowds of Internet users around us. Despite impressive breakthroughs in almost every part of our wireless devices—from antennas and hardware to operating software—this demand is getting increasingly challenging to address. The large scale of research efforts and investment in the fifth generation (5G) of wireless communications reflects the enormity of the challenge.1 A valuable and seemingly unnoticed resource could be exploited to meet this goal.
A common denominator in related research efforts is that the wireless environment—the set of physical objects that stand between two wireless communicating devices—remains a passive spectator in the data-exchange process. The ensuing effects on the data communication quality are generally degenerative: First, a transmitting device emits electromagnetic energy—carrying encoded information—which dissipates astoundingly fast within the environment. This path-loss phenomenon can be envisioned as distributing the same power over an ever-growing sphere. The power of the intended signal quickly diminishes, making its reception progressively more difficult. Second, as this ever-growing sphere reaches objects, such as walls, doors, desks, and humans, it scatters uncontrollably in multiple directions. This creates the multipath phenomenon where many, unsynchronized echoes of the original signal reach the receiver at the same time, making it difficult to discern the original. Third, the scattered signals naturally reach unintended recipients, increasing their noise levels (and allowing for eavesdropping). Finally, mobile wireless devices acquire a false perception of the frequency of electromagnetic waves, a phenomenon known as the Doppler effect. Notice that the hunt for higher data rates in 5G pushes for very high communication frequencies, at 60GHz for example, where the described effects become extremely acute.1
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