um absolute time alignment error between any pair of eNBs that are on the same frequency with overlapping coverage area, as outlined in Table 10-5. Table 10-5 Synchronization Requirements for ICIC and eICIC Application Type of Coordination Phase Accuracy Reference Inter-cell interference coordination eICIC Enhanced inter-cell interference coordination 3 us 3GPP TS 36.133 10.3.1 Coordinated Multipoint While eICIC reduces the level of interference for the UEs at the edge of the cell, the throughput of the UE is still limited to the frequency and time partitioned resources available from a single eNB or BS. But what advantage could arise if the UE were able to operate with multiple eNBs at the same time? Coordinated Multipoint (CoMP) transmission and reception, a technique defined in 3GPP Release 11, enables multiple eNBs to coordinate their transmission and reception to enhance the service quality for the UEs at the edge of the cell. CoMP improves coverage, cell-edge throughput, and sys- tem efficiency. 3GPP defines several types of CoMP as illustrated in Figure 10-18. Coordinated scheduling (CS) and coordinated beamforming (CBF) are enhanced versions of ICIC where frequency resource partitioning happens dynamically, and changes are applied every time scheduling is performed. Coordinated scheduling allocates different frequency resources to UEs located at the edge of cells. As shown on the left of Figure 10-18, UEA is receiving frequency f2 from eNB A, while UEB is receiving frequency f3 from eNBB. With coordinated beamforming, eNBA and eNBB can use the same frequency resource, f2, as shown, and coordinate and schedule spatially separated re- sources to UEs at the cell edge, thereby avoiding interference. eNBA could serve as master eNB for UE A, and eNBB could serve as the master eNB for UEB. Coordinated scheduling Coordinated beamforming Joint processing (190) (from) (100) contain Cell A Cell B Cell A Cell B Cell A Cell B Figure 10-18 Coordinated Scheduling, Beamforming, Joint Processing and Joint Transmission Use