Terahertz (THz) integrated sensing and communication (ISAC) systems promise ultra-high data rates and precise sensing capabilities, enabled by narrow and directional beams. However, such beams are susceptible to beam misalignment (BM) fading caused by platform instability. While statistical models for BM fading exist for communication links, their extension to sensing applications, especially in drone-to-drone (D2D) scenarios, remains unexplored. In D2D ISAC networks, misalignment effects from the aerial platforms impact both the forward and return paths. This paper presents closed-form statistical models for BM fading in THz ISAC, addressing both monostatic (co-located transceivers) and bistatic (separated transceivers) sensing configurations, and considering both the spot-filling regime (target larger than beam) and the spot-limited regime (target smaller than beam). The proposed models facilitate the extension of BM fading analysis to sensing in drone-to-drone THz ISAC systems and have been validated through Monte Carlo simulations.

Even though Terahertz (THz) band is promising for Drone-to-Drone (D2D) communication, there exists significant challenges, primarily high path loss and the sensitivity of directional links to mobility-induced beam misalignment. In this paper, we propose a novel adaptive beamwidth control system for THz D2D communication by activating rows of the designed 8×8 microstrip patch antenna array operating at 272.5 GHz. The proposed row-selective activation mechanism provides dynamic adjustment of the elevation beamwidth by activating different combinations of antenna rows (from 1×8 to 8×8 configurations). The proposed mechanism offers a flexible trade-off in its beam characteristics, utilizes narrow, high-gain beams to maximize performance in stable links, and dynamically switches to wider, more robust beams to ensure connectivity during drone maneuvers. The performance of the reconfigurable array is evaluated through real drone mobility traces. Simulation results reveal that during periods of misalignment, the adaptive beamwidth strategy maintains link capacity that is up to three orders of magnitude higher than fixed-beam configurations, promising a practical solution for resource-constrained THz D2D communication.

In this work, 0.75-10 THz band is explored for non-terrestrial communications, by leveraging the improved atmospheric conditions at various altitudes. A channel model for aerial communications at THz band is proposed to calculate the common flat bands for frequency-selective path gain and the colored noise spectrums, both of which are highly affected by the atmospheric conditions. With capacity computation based on common flat bands, we consider aerial vehicles at different altitudes and distances, under realistic weather and channel fading conditions, due to beam misalignment and also multi path fading. An extensive capacity analysis is presented, considering equal and water-filling power allocation. It is shown that, when there is no fading, capacity for aerial links is several orders of magnitude larger than the sea-level capacity. When ergodic capacity is computed for the fading scenarios, it is shown that the impact of fading vanishes with altitude. Sea-level ergodic capacity is increased by an order of magnitude for drone-to-drone communications, providing several Tbps at 10 m range, while 10s of Tbps is achievable among jet planes and UAVs, and several 100s of Tbps is possible for satellites/cubesats at 1 km under fading, suggesting that THz band is a promising alternative for aerial communications.

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) self-interference 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.