The optimal design of Multiple-Input Multiple-Output (MIMO) antennas is significant for next-generation smartphone solutions with the appearance of further communication. This paper describes the design, simulation, and measurements of a ten-element MIMO antenna for n79 at 4.4–5.0 GHz, n102 at 5.925–6.425 GHz, and n104 at 6.425–7.125 GHz ranges that will be implemented in today’s smartphones. The proposed antenna system has a maximum dimension of 158 mm × 60 mm and will use the low-cost FR-4 as the dielectric material. The design procedure is carried out with a lot of care to ensure that it does not compromise the spatial characteristics and at the same time minimizes the mutual coupling between the nearby antenna dimensions. High isolation and low ECC values are simulated using capturing techniques on the antenna geometry and its element position for proper MIMO performance improvement. The constructed antenna system portrays good performances in the intended bands as evidenced by the reflection coefficient values, radiation patterns, and individual gains. The performance of the above proposed ten-element MIMO antenna system in terms of bandwidth efficiency, diversity gain, and channel capacity loss is discussed. It also satisfies the demands of current standards of wireless communications and provides future possibilities for higher data transmission rates and message reliability in next-generation smartphone applications. Here, the application of the FR-4 substrate is remarkable as it provides comparatively better performance with significantly easier manufacturing and less cost, and thus, the design has good possibilities to be commercially viable. This work can be understood to form part of ongoing research in enhancing the advancement of the smartphone’s antenna technology, which offers a scalable approach to the prospective spectrum altitude and the emergent surge in the data rates of mobile communication.