Short-range and indoor propagation

There is an increasing expectation that radio systems will work seamlessly as the user moves in and out of buildings. Furthermore, an increasing number of industrial and consumer devices incorporate a radio interface of some kind for portability or convenience of installation. Examples of such systems include wireless LANs, the Bluetooth and ZigBee standards, industrial telemetry, wireless microphones, smart metering networks, baby monitors and cellular picoand femto-cells. In addition to such short-range technologies, a greater or lesser degree of indoor coverage will be provided by cellular macroand microcells and by broadcast networks. A wide range of frequency allocations are in use for such services, often on a licence-exempt basis, ranging from low VHF to around 6 GHz. The lower limit tends to be set by bandwidth limitations, ambient noise and considerations of antenna efficiency, while the upper limit is dictated by acceptable path loss.