HW/SW Development of Cloud-RAN in 3D Networks: Computational and Energy Resources for Splitting Options

The continuous increase in demanding for availability and ultra-reliability of low-latency and broadband wireless connections is instigating further research in the standardization of next-generation mobile systems. 6G networks, among other benefits, should offer global ubiquitous mobility thanks to the utilization of the Space segment as an intelligent yet autonomous ecosystem. In this framework, multi-layered networks will take charge of providing connectivity by implementing Cloud-Radio Access Network (C-RAN) functionalities on heterogeneous nodes distributed over aerial and orbital segments. Unmanned Aerial Vehicles (UAVs), High-Altitude Plat-forms (HAPs), and small satellites compose the Space ecosystem encompassing the 3D networks. Recently, a lot of interest has been raised about splitting operations to distribute baseband processing functionalities among such nodes to balance the computational load and reduce the power consumption. This work focuses on the hardware development of C-RAN physical (PHY-) layer operations to derive their computational and energy demand. More in detail, the 5G Downlink Shared Channel (DLSCH) and the Physical Downlink Shared Channel (PDSCH) are first simulated in MATLAB environment to evaluate the variation of computational load depending on the selected splitting options and number of antennas available at transmitter (TX) and receiver (RX) side. Then, the PHY-layer processing chain is software-implemented and the various splitting options are tested on low-cost processors, such as Raspberry Pi (RP) 3B+ and 4B. By overclocking the RPs, we compute the execution time and we derive the instruction count (IC) per program for each considered splitting option so to achieve the mega instructions per second (MIPS) for the expected processing time. Finally, by comparing the performance achieved by the employed RPs with that of Nvidia Jetson Nano (JN) processor used as benchmark, we shall discuss about size, weight, power and cost (SWaP-C) metrics related to the UAV payload design.