A new wideband compact slot antenna array with cavity back for indoor wireless local area network (WLAN) access points (AP) is described, covering several wireless communication services from 2.4 to 4.8 GHz, that is especially designed to enhance multiple-input-multiple-output (MIMO) system performance. Despite very close packing of the array elements, these exhibit very low mutual coupling (<;-60;-23 dB) and low cross-polarization (<;-60;-14 dB). Each element of the array produces a unidirectional radiation pattern with a steady gain increase vs frequency from 5.5 to 8 dBi. Results are confirmed with measurements.