This work presents a miniaturized quad-element multiple-input multiple-output (MIMO) antenna with low mutual coupling, inherent isolation, and easy upgradability for an Internet of Things (IoT)-based high-speed smart digital entertainment network using ultrawideband (UWB) technology. UWB technology is anticipated to play a significant role in the future IoT-based smart systems due to its ability to provide high precision location information, low power consumption, high data rates, and secure communication. An elliptical quadrant-shaped radiator with a C-shaped protuberant ground plane is conceptualized as a quasi-monopole UWB antenna following the half-cut miniaturization approach with very compact dimensions of $18\times11$ mm 2. The elliptical quadrant radiator in combination with C-shaped ground plane introduces multiresonance characteristic in addition to providing better impedance matching with miniaturization and inherent high isolation for MIMO configuration. The single element antenna is then organized in an orthogonal arrangement with an edge-to-edge distance of 5 mm to develop a quad-element MIMO antenna system. The MIMO antenna structure realizes a wide bandwidth of 3.14–11.23 GHz (center frequency at 7.19 GHz), peak gain of 7.2 dBi, and radiation efficiency of above 60% with good isolation (−20 dB) between the adjacent elements without employing any dedicated decoupling structure. The diversity performances of the proposed MIMO antenna are relatively good, with a very low envelope correlation coefficient (ECC) of less than 0.35 and diversity gain (DG) nearly at 10. Further, the total active reflection coefficient (TARC) <−10 dB and channel capacity loss (CCL) <0.4 bit/s/Hz, parameters are witnessed to be within acceptable limits. The simulated and measured results agree well, testifying that the proposed four-element MIMO antenna is suitable for UWB applications.