arrier aggregation (con) Unlicensed Licensed Unlicensed Licensed Figure 10.5 LTE-unlicensed operation modes LTE Unlicensed FDD/TDD aggregation ((a)) Figure 10.6 LTE-advanced aggregation between FDD and TDD bands the unlicensed spectrum. Once the connection is activated to use the unlicensed band also, the existing channel quality information (CQI) feedback will allow the eNodeB to determine what kind of quality could be achieved on unlicensed band compared to the licensed band. The downlink-only mode is especially suited for such a scenario where the data volumes are dominated by the downlink traffic. The uplink transmission (full TDD operation) from a terminal operating on the unlicensed band requires more features both in the terminal side and in the LTE eNodeB compared to the existing licensed band operation. Those extra features are needed to meet especially the specific requirements on the type of transmission on the unlicensed band, including enabling the LBT feature and radar detection in the terminal side. In the actual specification work the support for LAA shall be phased in such a way that first only downlink aggregation (supplemental downlink) with 5 GHz band will supported in Release 13 and in Release 14 the full TDD operation will be enabled including uplink functionality. The LTE-Advanced carrier aggregation allows aggregating between FDD bands as well as between TDD bands from Release 10 onwards. With the Release 12 version of LTE-Advanced specifications, aggregation between FDD and TDD bands is also possible as shown in Figure 10.6, thus providing further flexibility for selecting the band that should be used together with the unlicensed band with LAA operation. LTE Performance on the Unlicensed Band The first-phase LTE networks provide up to 150 Mbps data rate and the latest chip using LTE-Advanced support up to 300 and 450 Mbps peak data rate. The LTE capabilities are evolving continuously to later enable higher data rates of up to 1 Gbps or even more, but the next steps after 450 Mbps is the s