uch as car ignition, power distribution and transmission systems, industrial equipment, consumer products, distant electrical storms and cosmic sources. Incidental noise - the aggregate background noise from localised man-made sources. The ambient noise floor is generally "white noise", with constant power per unit bandwidth, while incidental noise may be either broadband or narrow band. In implementing local or metropolitan area wireless networks, the ambient noise floor will be established during an RF site survey, and should be explicitly included in the link budget if it is above the receiver sensitivity of planned equipment. For example, in the link budget calculation above, if an ambient noise floor of -85 dBm was measured, using this in place of the receiver sensitivity of -90 dBm would result in a required transmitter power of 11 dBm. This type of environmental noise will limit the range that can be achieved for a given equipment configuration (transmitter power, antenna gains, etc.), but will not degrade the performance of wireless networks when operating within that limit. Narrow band incidental noise, from nearby man-made sources such as a microwave oven or a narrow band transmitter, is more likely to result in unpredictable and unreliable network performance. Interference Mitigation Techniques Wireless networking specifications are increasingly including a range of measures to mitigate the effect of interference on network performance. Wireless USB, covered in Chapter 10, is a good example of the approach which starts with establishing information about the quality of the RF link and then provides measures to control various link characteristics. Radio Communication Basics Table 4-20: Wireless USB Interference Mitigation Controls Control Description Transmit power (TPC) Host can control its own transmit power level as well as querying and controlling transmit power of devices in the cluster. Transmitted bit rate Host can adjust the transmitted bit rate for both outward (host to device) and inward (dev