Wi-Fi is a family of wireless network protocols based on the IEEE 802.11- standard. It is the most common wireless network in the world and is practically ubiquitous in private homes and enterprises alike. The range of radio transmission can be up to 250 m outdoors, depending on the IEEE standard that is applied. Indoors, walls and furnishings greatly reduce the range. Wi-Fi most commonly uses the 2.4 gigahertz (120 mm) UHF and 5 gigahertz (60 mm) SHF radio bands; these bands are subdivided into multiple channels. Channels can be shared between networks but, within range, only one transmitter can transmit on a channel at a time. The data transmission rate depends on the mobile communications infrastructure, the number of antennas and the number of receiving devices.