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(6G) will use millimeter wave, THz (terahertz) frequency band, "optical wireless" communication, but the big challenge for these three is "very high frequency selective path loss" - in LOS (line of sight communication) In the case of a distance of a few meters, the signal power loss easily exceeds 100 dB; under NLoS (non-line-of-sight communication) conditions, the situation will get worse. Thus, it is necessary to use a high gain directional panel antenna to complete the communication.

Similarly, in a mobile communication system using a lower frequency, an antenna array can be utilized to implement MMO communication, which can extend the communication distance by beam forming, or achieve a larger data transmission rate by spatial multiplexing. In the past few years, the concept of Massive MIMO has been introduced and has been extensively studied as a potential 5G core technology. In such an approach, a very large antenna array with tens to hundreds of antenna elements is utilized to increase spectral efficiency to enable large distance communication. This method has been proven to be "very useful for millimeter-wave 5G communication systems."

When the future 6G mobile communication system uses a higher frequency terahertz band, the single antenna unit will become smaller, so that more antenna units can be embedded in the same area of the bottom plate.

 However, linearly increasing the number of antenna elements is not sufficient to overcome the "larger path loss" challenge in the terahertz band. In this context, the industry has recently proposed the concept of "Ultra-Massive MIMO" from very dense plasma nano-antenna arrays.