Adaptive Terahertz Beam Steering for Enhanced Deep Space Communication Links

Abstract: Adaptive Terahertz (THz) beam steering is a promising and energy efficient technology which has the potential to enhance signal strength, link reliability and signal rate in deep space communication systems where conventional fixed-beam THz links experience severe path loss, atmospheric attenuation and degradation of the pointing error. Under deep space long-distance propagation conditions and a stable high-gain communication link, the problem of maintaining a stable high-gain communication link becomes one of the most critical issues. Conventional fixed-beam THz systems, based on fixed radiation patterns and mechanical steering, have limited pointing error rejection and high misalignment sensitivity, and are infeasible with spacecraft vibration and relative motion. This piece of work proposes a low-complexity adaptive beam steering scheme of the THz deep space communication links where closed-loop beamforming algorithm dynamically adapts the phased array radiation pattern [13], [15] in response to received signal strength feedback with no full channel state information required. The steering issue is formulated as an optimization of beamforming weights in real-time and is solved with the assistance of an adaptive algorithm which is scalable in nature and is less burdensome in terms of processing. To model more realistic deep space conditions, the system model is further developed to include distance-varying SNR degradation and dynamics of the pointing error. The characteristics of the channel capacity [1], [5] and the bit error rate of the adaptive THz beam steering is analyzed as the distance and pointing offset increase and displays the resilience of adaptive THz beam steering against non- adaptive fixed-beam systems. The simulation results, obtained by a full implementation in MATLAB, confirm the proposed strategy leads to the reduction of the sensitivity to pointing errors by a significant margin, high integrity of link maintenance, and spectral efficiency at the deep space propagation conditions. The presented framework offers a viable and scalable next generation deep space communication system solution to future lunar, Mars and interplanetary missions. The simulation results in MATLAB confirm that adaptive THz beam steering is always better than conventional fixed-beam steering in all the measures considered, such as cumulative distribution of channel capacity [1], [5], signal-to-noise ratio over long distance and the ability to tolerate normalized pointing errors. This work provides a solid base on which it is possible to implement intelligent and self-aligning THz communication terminals onboard deep space probes, eliminating the need to rely on bulky mechanical gimbals and allowing autonomous maintenance of links without necessarily ground-based intervention. The further development of this framework can include predictive beam steering with orbital dynamics and channel prediction made by machine learning to achieve even greater efficiency in deep space communication networks.

Keywords: Terahertz communication, deep space, beam steering, adaptive beamforming, phased array, MATLAB simulation, high-data-rate links.