Massive MIMO represents a significant departure from conventional practices by employing an extensive array of service antennas, potentially numbering in the hundreds or thousands, which are operated with full coherence and adaptability. The additional antennas facilitate the concentration of signal energy transmission and reception into increasingly smaller spatial regions. This results in substantial enhancements in both throughput and Energy efficiencyenergy efficiency, especially when paired with the simultaneous scheduling of numerous user terminals. Research areas that merit attention include detection algorithms for Multiple-Input Multiple-Output (MIMO)Massivereceivermassive MIMO receivers, performance analysis under specific channel conditions, capacity analysis for large-scale Multiple-Input Multiple-Output (MIMO)MassiveMIMO systems, precoding matrix design for Multiple-Input Multiple-Output (MIMO)Massiveprecodingmassive MIMO, resource allocation optimization within these systems, as well as simulation and implementation strategies. This chapter delineates two quintessential topics on Multiple-Input Multiple-Output (MIMO)MassiveMassive MIMO that have been incorporated into our proposed simulation tool tailored for 5G/6G networks. The initial segment addresses a solution to optimal beamforming design within Massive MIMO frameworks—covering problem formulation, derivation of analytical expressions, and implementation algorithms. The subsequent section evaluates the performance of two Modulationmethodsmodulation techniques based on Multiple-Input Multiple-Output (MIMO)MassiveMassive MIMO technology: Modulationspatialspatial modulation and Modulationspatialdifferentialdifferential spatial modulation.