dwidth of the IEEE 802.11b radio signal is 11 MHz, and there is only enough space for three nonoverlapping channels at the 2.4-GHz band. This places a severe limit on the data capacity when the number of users increases. Higher capacity WLAN technologies, such as IEEE 802. 11a operat- ing at the 5-GHz frequency band, have been developed to solve this problem. WLAN networks are available in airports, hotels, and conference cen- ters to provide Internet access to customers. WLAN technology is also becoming more popular in the educational and office environments. WLAN technologies may be a solution for high-data-rate short-haul data services when integrated with third generation systems. 5.4.9 Bluetooth Bluetooth technology allows for the replacement of proprietary cables that connect one digital device to another with a universal short-haul radio link. Mobile computers, cellular handsets, printers, keyboards, and many other devices can be embedded with Bluetooth radios. Bluetooth was developed by the Bluetooth Special Interest Group (SIG, http://www.bluetooth.com), founded by Ericsson, IBM, Intel, Nokia, and Toshiba. A small wireless Bluetooth network connecting, for example, a user's computer to its peripherals is called a personal area network (PAN). PAN con- tains one or more piconets. One Bluetooth piconet contains a single master and up to seven active slaves. The master polls slaves and orders each of them to transmit in turn. For voice applications Bluetooth specifies a synchronous channel that transmits at a bidirectional 64-Kbps constant bit rate between a master and a slave. This can be used to implement cordless telephones or hands-free sets for a cellular telephone. Bluetooth systems use the same 2.4-GHz license free frequency band as WLANs and they can coexist in the same area. The wideband WLAN signals and narrowband Bluetooth signals do not interfere much. Introduction to Telecommunications Network Engineering Bluetooth uses frequency hopping spread-spectrum (FHSS) technology, in which data are trans