using With the steep rise of Bluetooth product sales and the al- the collision avoidance mechanism. ready large and growing use of wireless local area networks, there is considerable concern about mutual interference between Bluetooth-enabled and Wi-Fi devices. Both Zigbee applications occupy the 2.4 to 2.4835 GHz unlicensed band and use wideband spread-spectrum modulating techniques. They While the promoters of Zigbee aim to cover a very large will most likely be operating concurrently in the same market for those applications that require relatively low environments, particularly office/commercial but also in data rates, there will remain applications for which the the home. compromises inherent in a general specification are not Interference can occur when a terminal of one net- acceptable, and producers will continue to develop de- work transmits on or near the receiving frequency of vices with proprietary specifications and characteristics. a terminal in another collocated network with enough However, the open specification and a recognized certi- power to cause an error in the data of the desired re- fication of conformity are an advantage in many situa- ceived signal. Although they operate on the same fre- tions. For example, a home burglar alarm system would quency band, the nature of Bluetooth and Wi-Fi signals accept wireless sensors produced by different manufac- are very different. Bluetooth has a narrowband trans- turers, which will facilitate future expansion or allow mission of 1 MHz bandwidth which hops around pseudo- installers to add sensors of types not available from the randomly over an 80 MHz band while Wi-Fi (using original system manufacturer. Use of devices approved DSSS) has a broad, approximately 20 MHz, bandwidth according to a recognized standard gives the consumer that is constant in some region of the band. The in- some security against obsolescence. terference phenomenon is apparent in Figure 5.2-25. Although Zigbee claims to be appropriate for most Whenever there is a frequency an