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In this paper, a joint power and beam-level beamwidth control scheme is proposed for full duplex (FD) millimeter wave (mmWave) indoor wireless systems. Energy efficiency of the proposed scheme is investigated considering various system parameters, such as maximum transmit power level, level of self-interference cancellation and pilot transmission overhead. With this analysis for a realistic indoor wireless communication scenario, the feasibility of FD is studied for mmWave links, considering their specific propagation characteristics, namely, narrow transmission and reception beam-level beamwidths and high absorption losses, as well as massive bandwidth which is much larger than the existing sub 6 GHz bands. We evaluate the performance of the proposed FD mmWave system for three power budget schemes (low, moderate and high) in terms of average total energy efficiency. Our simulation results show that, for currently available state-of-the-art self-interference cancellation levels, FD mmWave with proposed joint power and beam-level beamwidth control outperforms the smart half duplex (HD) mmWave with joint transmission slot and beam-level beamwidth control by a factor of up to four times and improves FD mmWave with only power control by up to 33.92 %. If higher (close to ideal) selfinterference cancellation can be achieved, the net average total energy efficiency improvements over existing abovementioned schemes, are up to 4.8 times and 26.45 %, respectively. It is concluded that with the proposed joint power and beamwidth control, the current FD mmWave technology promises a good potential for indoor wireless networks.

Terahertz band (0.1-10 THz) communications is one of the candidates for 6G systems due to intrinsic massive bandwidth and data rate support. Having demonstrated the significant potential of THz band at various atmospheric altitudes, in this article, we discuss the prospects of THz communications for drone networks, more specifically, for Drone Sensor Networks (DSNs). For 6G non-terrestrial communication scenarios, drones will not only serve as on-demand base-stations, as supporting alternatives or backhauls for the terrestrial base stations, but they will also provide seamless connectivity for distributed monitoring and surveillance applications, which require an ultra-reliable low latency service for carrying multimedia data. THz band sensing will also provide additional sensing capabilities from the sky to THz-enabled DSNs. Presenting this vision, in this paper, we first discuss possible use cases of THz-enabled drone networks considering communication, sensing and localization aspects. Then, for revealing the capacity potential of THz-enabled drone networks, we provide motivating channel capacity results for communication of drones at different altitudes, under ideal channel conditions with no fading and realistic channel with beam misalignment and multipath fading. We further present major challenges pertaining to employing the THz band for DSNs, addressing physical layer issues, followed with spectrum and interference management, medium access control and higher layers and security, while reviewing some prominent solutions. Finally, we highlight future research directions with Artificial Intelligence (AI)/Machine Learning (ML)-based approaches and mobile edge computing.

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