n 3GPP language (transmit/reception point or TRP), and the DU/RU components from the previous figure are eliminated for ease of comprehension. Radio Unit Primary Secondary Buffer Buffer Central Distributed Radio Unit Network interface Transfer of downlink User Data (38.475) Radio Unit Distributed FIGURE 7-11 High-level view of an O-RAN CU/DU/RU system implementation. CU, control unit; DU, distributed unit; O-RAN, Open Radio Access Network; RU, radio unit. Repeater I Repeater III TRP V TRP a Repeater Il FIGURE 7-12 System-level scheduling challenge. 256 Open Radio Access Network (O-RAN) Systems Architecture and Design In this example, there are multiple paths to connect to a UE. Take the Mid(dle) UE in the figure, which can be connected through the following paths: from TRP a: via Repeater I-path A via Repeater path B directly from the TRP-path E from TRP 3: directly from the TRP-path C from TRP Y: via Repeater III-path D Intuitively, we can understand that, given that TRP a is servicing both UEs "Low" and "Top," the most optimized system solution including communication to all UEs would likely involve UE "Middle" to be accessed through either TRP 3 or TRP Y-or both! To analyze more formally, assume an idealistic system model: 1. CSI is known for all paths across UEs, gNBs, and repeaters. 2. The carrier width (i.e., frequency spectrum) and MCS allocated for communication between gNB and UE is defined a priori, outside of the scheduler algorithm. This decision considers path loss and related parameters to optimize channel width, transmit power, and other parameters. 3. Multiple users do not share a single subchannel-no MU-MIMO taken into consideration. 4. Control channel signaling overheads are ignored. 5. Only downlink traffic (gNB- > UE) is considered only simplify the model rather than imposing a fundamental limitation. 6. Assume only a single user is served per slot. 7. Each repeater is uniquely associated with a single TRP (uplink) but can be associated with multiple UEs. 8. The data that is to be transmitted 