e 3GPP LTE- Advanced and the IEEE 802.16m is a method of MIMO transmission for interference reduction which enables features such as network synchronization, cell- and user-specific pilots, feedback of multi-cell channel state information, and synchronous data exchange between the base stations that can be used for interference mitigation and to achieve macro diversity gain. The collaborative MIMO and the Downlink Coherent Combining or Dynamic Cell Selection (Joint Transmission/Dynamic Cell Selection) Downlink Coordinated Scheduling/Beamforming Uplink Coordinated Multi-point Reception (Receiver signal processing at central BS) FIGURE 10-46 Downlink multi-BS transmission schemes 10.7 Multi-BS MIMO closed-loop macro diversity schemes are optional features supported in the IEEE 802.16m standard. For downlink collaborative MIMO, multiple base stations perform joint MIMO transmissions to multiple mobile stations located in different cells. Each BS performs multi-user precoding when transmitting to multiple mobile stations and each MS benefits from collaborative MIMO by receiving multiple streams from multiple base stations. When collaborative MIMO is enabled, several mobile stations are jointly served by multiple coordinated base stations through MU-MIMO scheduling and precoding, whereas when closed-loop macro-diversity is enabled, a single MS is served jointly by multiple coordinated base stations. In terms of downlink CoMP, two different approaches are under consideration in 3GPP LTE- Advanced: coordinated scheduling and/or beamforming; and joint processing/transmission. In the first category, the downlink transmission to a single UE is sent from the serving cell, exactly as in the case of non-CoMP transmissions. However, the scheduling, including any beamforming function- ality, is dynamically coordinated between the cells in order to control/reduce the interference between different transmissions. In principle, the best serving set of users will be selected SO that the transmitter beams are constructed to reduce t