The increased demand for mobile network connectionshas lead to the establishment of RF interface standardsfor Wireless Local Area Networks (WLANs). Theunlicensed ISM frequency band, 2.4–2.5 GHz, has beendesignated for WLAN usage.Table 1[1] displays frequencyallocations in different parts of the world for WLAN. In theUS, IEEE 802.11 specifies two RF physical layerinterfaces for WLAN, Direct Sequence Spread Spectrum(DSSS), and Frequency Hopped Spread Spectrum(FHSS).DSSS uses an 11-bit Barker code where each bit ofinformation is spread within a single channel. The IEEEstandard allocates 11 channels, each 22 MHz wide, with5 MHz spacing between center frequencies in the83.5 MHz band.This creates channels whose frequenciesoverlap.