A luminaire is disclosed comprising an optical stack (200) transparent to radio waves, the optical stack comprising a first surface (210) including a light exit window (211) and a further surface (220) opposing the first surface, the optical stack including a planar light guide (300) having a first major surface facing or defining the first surface, an opposing second major surface facing or defining the further surface and at least one edge surface (310) extending between said opposing first and second major surfaces; and a frame (700) around the optical stack, the frame carrying at least one light source (100) optically coupled to one or more of said edge surfaces of the light guide, wherein the frame delimits the light exit window and an exposed portion (221) of the further surface opposing the light exit window, said light exit window and the exposed portion delimiting a conduit (230) for said radio waves through the optical stack.