This article presents compact wideband four elements Many-Input Many-Output (MIMO) antenna using Defect Ground Structure (DGS). The proposed structure is dedicated to cover 4G-LTE/Sub 6 GHz bands in the 2.5/3.5/5.5 GHz frequency range and WLAN, Wi-Fi, and (LTE bands 41, 42, 43, 46, and 48). It also includes new radio (NR) technology which has different bands for 5G and (sub-6 GHz bands 47, 48). The designed antenna is very compact in size having dimensions of 28 mm x 29.58 mm x 0.8 mm. Isolation is achieved with square ring resonators (SRR). Isolation is further enhanced by inserting slots and SRRs between antennas. MIMO antenna characteristics such as high isolation (45 dB), low envelope correlation coefficient (0.01), and high diversity gain (10 dB) are measured. Furthermore, a wide impedance bandwidth of 8 GHz is measured. MIMO antenna is verified with a Software-Defined Radio (SDR) platform.