International spectrum allocations are established by the International Telecommunication Union (ITU)
Domestic spectrum may differ from these allocations as long as the use results in no conflict with the international regulations
License exempt spectrum or unregulated bands are
radio spectra available to any users without charge and license.
Some restrictions are imposed by regulating agencies, e.g., limiting transmission power, which thus reduces ranges
Pro: to promote development of various devices and simulate growth of new industries.
Con: crowed RF spectrum as devices from different vendors may attempt to use the same frequency