Compaq CQ50-139WM Bluetooth Wireless Technology Basics - Page 3

How Bluetooth wireless technology works BWT-enabled devices operate in the unrestricted 2.4-gigahertz (GHz) Industrial, Science, Medical (ISM) band. The ISM band ranges between 2.400 GHz and 2.483 GHz. BWT-enabled devices use seventy-nine 1-megahertz frequencies (from 2.402 to 2.480 GHz) in the ISM band as shown in Figure 1. BWT-enabled devices use a technique called frequency hopping to minimize eavesdropping and interference from other networks that use the ISM band. With frequency hopping, the data is divided into small pieces called packets. The transmitter and receiver exchange a data packet at one frequency, and then they hop to another frequency to exchange another packet. They repeat this process until all the data is transmitted. BWT devices randomly hop between frequencies up to 1600 times per second-much faster than other types of devices that use the ISM band. This means that if another device, such as a 2.4-GHz cordless phone, interferes with a BWT network at a particular frequency, the interference only lasts for about 1/1600 of a second until the BWT devices hop to another frequency. This gives BWT networks a high immunity to interference from other 2.4-GHz devices. There are three classes of BWT radio devices, each with a different maximum range: Class 1 (100 meters); Class 2 (50 meters); and Class 3 (10 meters). HP notebooks feature Class 3 BWT radios, and HP printers feature Class 1 radios. Figure 1. BWT-enabled devices hop between frequencies up to 1600 times per second. 3