 and enable the receiving device to detect and correct certain fraction of bit errors that occur during transmission. The fraction of original data bits in the final transmitted stream is called the coding rate. Frequency Reuse Factor: The frequency reuse factor is a measure of the degree to which a certain frequency can be used throughout the network, and therefore is a measure of the extent to which the full RF transmission bandwidth is available to carry data. For a large-scale 802.11b/g WLAN, with 3 non-overlapping channels patterned across adjacent access points, the frequency reuse factor is 1/3, as each channel is only used in 1/3 of the operating area of the network. Glossary Frequency Hopping Spread Spectrum (FHSS): Frequency Hopping Spread Spectrum is a spread spectrum technique, used in Bluetooth devices, in which the centre frequency of the modulated carrier hops peri- odically between a number of predetermined frequencies. The sequence of frequencies used is determined by a hopping code which is also known to the receiver. Fresnel Effect: A phenomenon in radio wave propagation in which an object that does not directly obstruct the line-of-sight from transmitter to receiver still causes attenuation of a transmission. The impact depends on how close the object is to the line-of-sight. Gateway: A gateway is a network component that connects one network to another, typically to the Internet. The gateway performs routing and pro- tocol translation (e.g. NAT, VPN passthrough), and may also provide addi- tional functions such as acting as a DHCP server. Hub: A hub is a network device that provides a central connection point for other devices. In contrast to a switch (q.v.), a hub broadcasts each data packet to every connected device, sharing the available bandwidth among all devices in the network. Infrastructure Mode: Infrastructure Mode is a mode of operation of a wireless network in which communication between devices takes place via an access point rather than directly between devices, as occurs in peer