D-MIMO, 10 dB threshold D-MIMO, 20 dB threshold Number of cells that can serve each user Figure 10.46 Number of cells that can serve the user in a macro environment. Relative uplink data rates Single cell Intra-site MIMO Inter-site MIMO Inter-site MIMO reception (10 dB) (20 dB) Figure 10.47 Relative uplink user throughputs with distributed MIMO options. be received by multiple cells. Inter-site dMIMO can further improve the data rates by 40-100%. The relative gain in the cell edge data rates is even higher. It is an expected result that cell edge users benefit more from dMIMO than average users. Figure 10.48 illustrates the potential downlink spectral efficiency gains with dMIMO. The studied case is small cells with 200 m distance, and each user is connected to a max- imum of seven cells. The following cases are studied: Single cell transmission where each cell operates independently by using multi-user MIMO with four antennas. Seven site fixed disjoint clusters. Precoding coefficients are determined within each non-overlapping cluster. 10 5G Performance Relative downlink data rates Single cell 7-site fixed 7-site flexible Ideal transmission clusters cluster coordination Figure 10.48 Relative downlink user throughputs with distributed MIMO options. Seven site clustering per user. Each user connects to sites within 26 dB of the strongest access, but to a maximum of seven sites. Precoding coefficients are determined cen- trally. The results show that it is possible to even double the spectral efficiency by using per-user clustering compared to single cell transmissions. Packet Scheduling Algorithms 3GPP does not define beamforming or packet scheduling algorithms. There are a number of options for configuring and optimizing scheduling algorithms in 5G radio. This section briefly illustrates two scheduling aspects which are different from LTE: low latency scheduling and mini-slot scheduling. 10.8.1 Low Latency Scheduling The packet scheduler is responsible for enforcing Quality of Service (QoS) differen- tiation in t