lgated, 5-GHz although the mask is somewhat more complex and ap- radios implemented in standard silicon processing were parently narrower than the old 802.11 mask (Figure 5.1-8), not widely available, SO this choice implied relatively high in practice both signals end up being around 16-MHz costs for hardware. The motivation for the change was wide at 10 dB down from the maximum intensity at the the realization that a successful commercial imple- center of the transmitted spectrum. This design choice mentation of 802.11 classic and/or 802.11b devices, was made to allow the same analog-to-digital conversion combined with the other proposed and existing occu- hardware to be used for the baseband in either standard, pants of the 2.4-GHz band (Bluetooth devices, cordless which is beneficial in those cases where a single baseband/ Wireless local area networks CHAPTER 5.1 max. xmit power (6 dBi antenna) 5.805 5.785 800 mW 5.765 outdoors max. xmit power -5.745 (6 dBi antenna) 6 GHz 6 GHz -5.700 -5.805 5.680 -5.785 -5.825 800 mW 5.825 5.660 U-NII upper 5.765 U-NII upper -5.640 -5.725 -5.745 5.725 5.620 200 mW U-NII mid -5.600 indoor or -5.580 outdoor 5.320 5.470 -5.560 5.350 -5.300 200 mW 5.350 -5.540 U-NII middle 5.280 U-NII mid 5.520 5.250 -5.260 5.250 U-NII lower U-NII lower -5.500 -5.150 -5.240 5.150 5.220 5 GHz -5.200 40 mW 5 GHz 5.320 -5.180 5.300 200 mW indoor or 5.280 outdoor 5.260 5.240 5.220 40 mW 5.200 indoor -5.180 FCC 03-287 11/03 2004+ Figure 5.1-15 UNII band in the United States, then and now. MAC design is to serve both 802. lla and 802.11b radio allowances, SO that in practice fewer channels might be chips. This important fact allowed the 802.11a PHY to be used. In the new band assignment, there is room for up to kidnapped and transported whole into the ISM band in 19 nonoverlapping channels in the lower and middle the 802.11g standard, as we discuss in section 5.1.3.7. bands alone. Recall that the ISM band allows only three Nonoverlapping channels in the old band definition, nonoverlapping 802.11 channe