capability is mandatory for all UEs, except the category 1 devices. With the introduction of LTE Advanced in Release 10, the additional UE categories 6, 7 and 8 were added. Currently, the most advanced devices in the market are Release 11 category 9 devices that can provide up to 450 Mbps peak data rate when network is able to have three downlink 20 MHz carriers aggregated with Release 10 carrier aggregation. Category 8 is rather theoretical one with all the possible features enabled. The latest categories in Release 11, categories 9 and 10, were added to the specifications as recently as in June 2014. While they are based on otherwise Release 10 principles, they are using three-carrier aggregation in downlink direction, thus enabling up to 450 Mbps when using three 20 MHz carriers and two-stream MIMO transmission. Category 9 devices, enabling 450 Mbps downlink peak data rate, have become available during 2015 in the field. The use of carrier aggregation was in the market first realized with Class 4 type of devices, which could aggregate 10 + 10 MHz of downlink spectrum, before the Class 6 type of devices entered the market in 2014, allowing more than 150 Mbps which was possible with Release 8-based baseband capabilities. Table 2.4 UE categories introduced in Release 11 to further enhance carrier aggregation capabilities UE category Class 9 Class 10 Class 11 Class 12 Peak rate DL/UL (Mbps) 450/50 450/100 600/50 600/100 RF bandwidth (MHz) Modulation DL 64QAM 64QAM 64QAM 64QAM Modulation UL 16QAM 64QAM 16QAM 64QAM Rx diversity MIMO DL 2x2 or 4x4 2x2 or 4x4 2x2 or 4x4 2x2 or 4x4 MIMO UL LTE Small Cell Optimization The Release 12 new UE categories accommodate further higher data rates as well as new functionality such as 256-QAM downlink modulation. Release 12 UE categories are covered in Chapter 3. 2.5 Conclusions In the previous sections, we have covered the LTE standards from the first LTE Release 8 standard to the LTE-Advanced Release 10 and 11 standards. These form the basis currently deployed in the field at th