This paper explores the implementation of a 4K-element massive MIMO antenna array to support 1,000 simultaneous users in a Direct-to-Cell (D2C) framework for Low Earth Orbit (LEO) satellite communication. Key challenges, including beamforming, spatial multiplexing, and interference management, are addressed using advanced signal processing techniques like adaptive beamforming and user tracking. A detailed link budget and performance analysis highlight the system’s feasibility and scalability under dynamic conditions such as satellite motion and Doppler effects. The findings offer a roadmap for robust, high-capacity LEO satellite systems, bridging the digital divide and advancing connectivity in the 5G/6G era.