## 2 Related Work  
This section explores the existing literature on DoA estimation methods in the context of satellite communication systems, considering various factors that may affect efficient communication. It also discusses the crucial aspects of accurately modeling the satellite channel and compares the findings of this study with the literature. The estimation of DoA is a topic of considerable interest in the field of satellite communication systems. Its investigation has been extensive, with researchers exploring a variety of scenarios and confronting a multitude of practical challenges. Among these challenges are accurate angle of arrival (AoA) estimation, optimization of positioning accuracy in the presence of system failures, resolution of phase measurement ambiguities, and geolocation accuracy for moving objects. Each of these challenges has been tackled by researchers, who have provided valuable insights and potential solutions. For instance, in [9], the researchers introduced a method for precisely estimating the AoA of wideband signals that impinge on localized hybrid antenna arrays mounted on satellites. To tackle system failures, the authors in [6] performed a novel satellite altitude determination method using the DoA estimation of a ground source for three-axis stabilized communication satellites. To optimize the positioning accuracy of satellites, the authors in [8] utilized receiver antenna beamforming and improved receiver sensitivity. Consequently, to improve the ambiguity resolution of phase measurements and positioning accuracy with AoA estimation, the authors in [11] deployed instruments across multiple flying satellites and performed data link synchronization and channel estimation. In addition, to address issues with mobile objects that affect the accuracy of location, the authors of [7] studied two nonlinear optimization (NLO) algorithms, namely, velocity and time delay, which enhance the geolocation accuracy and confidence intervals for moving objects. The challenges are broader than the above discussions. For instance, the outdoor scenarios surpluses complexity was addressed by the authors in [12] through AoA-assisted GNSS collaborative positioning that reduced computational complexity and improved the accuracy of collaborative positioning and AoA measurements. Appropriate geometry selection for target localization problems is also a big challenge, as mentioned in [10], so the authors employed triangulation using a spherical Earth model and a satellite observer over the spherical surface utilizing spherical trigonometry and singular value decomposition (SVD). The literature review recognized that the DoA estimation method is challenging in satellite communication systems due to the numerous factors involved in establishing effective communication. It also requires accurate channel-phase estimation. The problem of phase estimation has been studied extensively in various contexts. An example is provided in [15], where the authors conducted a statistical analysis to detect bias problems in phase tracking and provided solutions for correcting these biases. Furthermore, the literature review identified spatial correlation in multiple input multiple output (MIMO) communication channels as a prevalent issue arising from channel properties, antenna patterns, or inadequate spacing between the antennas at the transmitter or the receiver. In general, the influence of spatial correlation on system performance has been widely studied under different contexts. The authors in [16] considered whitening transformations at both the transmitter and the receiver and eliminated spatial correlations to enhance the error performance of LEO Satcom systems based on MIMO-orthogonal time frequency space (OTFS). Consequently, the authors in [17] quantified the effects of fading correlations in multi-element antenna (MEA) systems using a spatial Rayleigh-fading correlation model (MIMO)-based receiver diversity system.