  The open-radio access network (O-RAN) embraces cloudification and network
function virtualization for base-band function processing by dis-aggregated
radio units (RUs), distributed units (DUs), and centralized units (CUs). These
enable the cloud-RAN vision in full, where multiple mobile network operators
(MNOs) can install their proprietary or open RUs, but lease on-demand
computational resources for DU-CU functions from commonly available open-clouds
via open x-haul interfaces. In this paper, we propose and compare the
performances of min-max fairness and Vickrey-Clarke-Groves (VCG) auction-based
x-haul and DU-CU resource allocation mechanisms to create a multi-tenant O-RAN
ecosystem that is sustainable for small, medium, and large MNOs. The min-max
fair approach minimizes the maximum OPEX of RUs through cost-sharing
proportional to their demands, whereas the VCG auction-based approach minimizes
the total OPEX for all resources utilized while extracting truthful demands
from RUs. We consider time-wavelength division multiplexed (TWDM) passive
optical network (PON)-based x-haul interfaces where PON virtualization
technique is used to flexibly provide optical connections among RUs and
edge-clouds at macro-cell RU locations as well as open-clouds at the central
office locations. Moreover, we design efficient heuristics that yield
significantly better economic efficiency and network resource utilization than
conventional greedy resource allocation algorithms and reinforcement
learning-based algorithms.
