Figure 16.9. Licensed 3GPP Releases 8-9 paired and unpaired coverage LTE-Advanced Licensed 3GPP Releases 10-12 paired and unpaired capacity LTE-Advanced Pro Licensed Unlicensed 3GPP Releases 13 paired and unpaired unpaired and beyond Figure 16.8 Spectrum usage evolution for licensed and unlicensed bands. 16.3 LTE-Advanced Pro Technologies United = 580 MHz States Europe = 455 MHz Japan China = 325 MHz Figure 16.9 Spectrum resources at 5 GHz unlicensed bands. 5 GHz Carrier LTE licensed Wi-Fi unlicensed Wi Fi Reliable Higher data rates and connection more capacity Figure 16.10 Aggregation of licensed and unlicensed bands. LTE-Advanced Pro can utilize unlicensed band spectrum through two techniques: LAA or by integrating Wi-Fi more closely with the cellular network via LTE-Wi-Fiaggre- gation (LWA). The two solutions are shown in Figure 16.10. LAA combines the use of licensed and unlicensed spectrum for LTE using carrier aggregation. LAA is an efficient solution for traffic offloading since the data traffic can be split, with millisecond resolu- tion, between licensed and unlicensed frequencies. The primary cell on a licensed bands can provide reliable connectivity, mobility, signaling, and guaranteed data rate services, while the secondary cell(s) on unlicensed band can significantly boost the data rates. Unlicensed spectrum operation involves various regulatory rules which aim at facili- tating fair and equal spectrum usage for different devices and radio access technologies, such as Wi-Fi. Before being permitted to transmit, a user or an access point (such as eNodeB) may need to monitor the given radio frequency for a short period of time to ensure the spectrum is not already occupied by some other transmission. This require- ment is referred to as Listen-before-talk (LBT). The requirements for LBT vary depend- ing on the geographic region: for example, in the United States, such requirements do not exist, whereas in, for example, Europe and Japan, the network elements operating on unlicensed bands need to comply w