Release 14 there may be as many 64 transceivers. Figure 16.13 shows the assumptions for the physical antenna structures in 3D beamforming studies. 3D beamforming will bring efficiency gains for the downlink transmissions as shown in Figure 16.14: 16x pro- vides a 2.5-fold gain in spectral efficiency compared to 2x2, and 64x1 shows a 3.0-fold gain. The gain available from 64x2 compared to 8x2 is +50%. Note that the 8x2, 16x2, and 64x2 transceiver configurations are each associated with four columns of cross-polarized antenna elements of approximately the same physical dimensions, while the 2x2 transceiver configuration is associated with only one column of cross-polarized antenna elements. In all cases, the total transmission power is the same. The uplink efficiency can be enhanced with multiantenna reception at the eNodeB, and this has been widely deployed in the field by aggregating the signals received from four, eight, or even more transceivers in the form of the Centralized Radio Access 16 LTE-Advanced Evolution Figure 16.13 Antenna assumptions in 3D beamforming studies. Antenna for Antenna for 8 X 2, 16 X 2 4 x 2 simulations and 64 X 2 simulations Average Spectral Efficiency 2 x 2 8 x 2 16 X 2 64 X 2 Figure 16.14 Gain of 3D beamforming in spectral efficiency. Network (CRAN). These uplink improvements are mostly transparent to user devices and can be implemented with Release 8 devices, without requiring any LTE-Advanced feature support. The introduction of a large number of transceivers is made possible with active antenna arrays, which consist of passive radiating elements, RF amplifiers, filters, and digital processing integrated into the array. The use of such active arrays effectively moves the radio closer to the radiating elements, reducing feeder loss, and this integration reduces the footprint of the tower-top structure. The spectral efficiency is often limited by the inter-cell interference. Therefore, the efficiency can be improved by using inter-cell interference cancelation at the UE. A rel- ative