ndustry to increase the amount of spectrum available for unlicensed use. In the United States, the Federal Communications Commission (FCC) made 300 MHz of spectrum available in 5.15-5.25 GHz (UNII-1), 5.25-5.35 GHz (UNII-2A), including 5.725-5.825 GHz (UNII- 3), for use by a new category of unlicensed equipment. The latter band is partially over- lapped with the ISM band (5.725-5.875 GHz), hence, is sometimes referred to as Unlicensed National Information Infrastructure (U-NII)/ISM. The FCC further made avail- able additional 255 MHz spectrum in 5.47-5.725 MHz (UNII-2C) band. This aligns the U- NII frequency band in the United States with other parts of the world, thereby allowing the same product to be used in most parts of the world. The frequency ranges 5.250-5.350 and 5.470-5.725 GHz in U-NII-2 are used by radar systems worldwide; thus the use of these bands requires DFS techniques to avoid adverse effects on radar operation [20]. In certain geographical regions, such as the European Union and Japan, support of LBT rule is manda- tory to reduce the interference to other users operating in the same band. The LBT medium access rule prevents a transmitter from continuous transmission and dominating the commu- nication channel, rather it requires the transmitter to check for other radio activities in the channel prior to transmission. In the United States, the use of 5 GHz unlicensed spectrum is subject to FCC regulations. At present, unlicensed wireless systems can access bands 5.15-5.25 GHz (UNII-1), 5.25-5.35 GHz (UNII-2A), 5.47-5.725 GHz (UNII-2C), and 5.725-5.85 GHz (UNII-3). In addition, bands 5.35-5.47 GHz (UNII-2B) and 5.85-5.925 GHz (UNII-4) are also being Bluetooth Special Interest Group: https://www.bluetooth.com/ ZigBee Alliance: https://www.zigbee.org/ Wi-Fi Alliance: https://www.wi-fi.org/ Table 8.1: 5 GHz unlicensed band designations worldwide [18]. 5 GHz UNII-1 UNII-2A UNII-2B Region 100 MHz 100 MHz 120 MHz UNII-2C 255 MHz UNII-3 125 MHz UNII-4 75 MHz (Total Bandwidth) 5.15-5.25 GHz 5.25-5.35 GHz 