Answer Description
Infrared (IR) light requires line of sight in order to properly function. Infrared is most commonly used in TV remotes. WiFi, Bluetooth and Radio Frequencies (RF) do not requires LoS and can penetrate physical objects such as walls and ceilings.
Wikipedia
Infrared radiation, or simply infrared or IR, is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore invisible, although it is sometimes loosely called infrared light. It extends from the nominal red edge of the visible spectrum at 700 nanometers (frequency 430 THz), to 1000000 nm (300 GHz) (although people can see infrared up to at least 1050 nm in experiments). Most of the thermal radiation emitted by objects near room temperature is infrared. …
Infrared - Wikipedia, the free encyclopedia