vation beams: (a) cell splitting (vertical), (b) Tx/Rx tilting, (c) carrier-specific tilting, (d) operator-specific tilting and (e) technology-specific tilting applications, as shown in Figure 11.11, include cell splitting (vertical), separate Tx/Rx tilting, carrier-specific tilting, operator-specific tilting and technology-specific tilting [3]. Cell splitting (vertical) allows spectral efficiency gains by reusing system resources; carrier-specific tilting allows operators to manage the load in each carrier; operator-specific tilting allows network sharing among multiple operators; technology-specific tilting allows managing link budgets, load and SO on according to the different technologies. 11.5 Massive-MIMO Supported by LTE The support of multiple antenna techniques (MIMO) has been one of the cornerstones of the LTE physical layer specifications since the first release (Rel-8). LTE Rel-8 was designed to provide MIMO support of up to four antenna ports for downlink transmission. This was extended to eight antenna ports in Rel-10 which is also the maximum number of ports supported in Rel-12. Massive-MIMO arrays as described above may offer the flexibility of achieving baseband control of over 16-64 antenna ports for a base-station. In this section, we describe the opportunities for Massive-MIMO deployments that are enabled with the existing Rel-8- Rel-12 specifications. This is important both from an early deployment perspective as well as from the perspective of supporting legacy mobile devices in the network. LTE Rel-8-Rel-12 specifications can be used to support a Massive-MIMO base-station with an arbitrary number of ports even though it is not designed or optimized for such operation. In the following, we focus on the capacity performance of the shared downlink data channel which is of primary interest in the deployment scenarios described above. The restriction to four or eight antenna ports in the specifications limits the mobile devices to the measurement and feedback of channel state information (CSI) c