equen- cies in low, medium, and high spectrum bands, but some of those frequencies are yet to be specifically defined by 3GPP and ITU-R. It can be assumed that most of the bands currently being used for 4G networks will be ultimately re-allocated to 5G technologies. Meanwhile, worldwide activities have already begun to explore a number of bands between 24.25 and 86 GHz that are being studied for the 2019 World Radiocommunication Conference (WRC), as well as on bands not included in the WRC agenda item. In the United States, the FCC is planning to make 64-71 GHz band available for unlicensed use based on the same rules applicable to the unlicensed 57-64 GHz band. In addition, FCC is studying several other bands in 24 GHz and above. It further plans to make some bands available for unli- censed applications using the same rules applicable to the unlicensed 57-64 GHz band. However, it has been asked to reconsider allocating the entire 64-71 GHz band to unli- censed operations. 3GPP also has a study item on 5G in unlicensed bands below and above 6 GHz. Unlicensed bands above 52.6 GHz covering the FCC 64-71 GHz frequency range will be considered to the extent that waveform design principles remain unchanged relative to that in below 52.6 GHz bands. The FCC has allowed access to spectrum for next- generation wireless broadband in the 28 GHz (27.5-28.35 GHz), 37 GHz (37-38.6 GHz), and 39 GHz (38.6-40 GHz) bands, as well as an unlicensed band at 64-71 GHz. The new rules make available almost 11 GHz of spectrum consisting of 3.85 GHz of the licensed spectrum and 7 GHz of the unlicensed spectrum [31]. As shown in Fig. 8.1, 60 GHz unli- censed spectrum comprises up to four non-overlapping channels, where each channel has a Operation in Unlicensed and Shared Spectrum Channel Channel 2 Channel 3 Channel 4 (57.24-59.40 GHz) (59.40-61.56 GHz) 61.56-63.72 GHz) (63.72-65.88 GHz) US (57.05-64 GHz) Europe (57-66 GHz) Korea (57-64 GHz) Japan (59-66 GHz) China (59-64 GHz) Figure 8.1 Worldwide 60 GHz unlicensed spectrum allocation [26