]. bandwidth of 2.16 GHz and enables four channels in Europe; three channels in the United States, Canada, South Korea, and Japan, and two channels in China. The requirements and regulations concerning the EIRP for 60 GHz vary by geographic areas and are different from the ones in 5 GHz. For example, the requirement for peak EIRP is 43 dBm in the United States and 40 dBm in Europe where the maximum PSD is also required to be 13 dBm/MHz. The main challenge of operation in 60 GHz band is excessive path loss and blockage relative to operation in 5 GHz band. However, the large propagation loss at 60 GHz can be mitigated by increasing the antenna array gain obtained by large array sizes. Fig. 8.1 summarizes the worldwide availability and channelization of 60 GHz spectrum. The US FCC established Citizen Broadband Radio Service (CBRS) for shared commercial use of the 3.5 GHz (3550-3700 MHz) band with the incumbent military radars and fixed satellite stations in 2015. Dynamic spectrum sharing rules have been defined to make additional spectrum available for flexible wireless broadband use while ensuring interfer- ence protection and uninterrupted use by the incumbent users. Under the plan, a three-tier sharing framework coordinates spectrum access among the incumbent military radars and satellite ground stations and new commercial users. The three tiers are as follows: incum- bent, priority access license (PAL), and general authorized access (GAA) users, as shown in Fig. 8.2. The incumbent military radar systems, satellite ground stations, and wireless ISPs are always protected from possible interference from the lower-tier PAL and GAA users. Tier-2 PAL users have the next highest priority access and are protected from GAA users. 852 Chapter 8 3550MHz 3600MHz 3650MHz 3700MHz US military radars (on-ground, ship-borne) Tier-1 (Incumbents) Fixed satellite stations Primarily in the coastal areas and some inlands Wireless ISPs to transition to Tier-2/3 Wireless ISPs Tier-2 (PAL) Priority access license (PAL) Up to 7x10 MHz ch