Most people have experienced the frustration of not being able to receive a mobile phone signal while indoors; it’s even more irritating when there’s a perfectly usable signal just outside the door.The situation is usually caused by the structure of the building; the signals just can’t penetrate through the walls. Ironically it’s often modern insulating materials such as foil-backed insulation that prevent the ingress of signal and makes it necessary to go outside in the cold to make a call.Nowadays of course mobile devices aren’t just phones; they perform a vast range of other functions, some of which rely on the reception of GPS satellite signals which are usually only available outside the building.