Energy-Aware RAN x-Haul over ONaaS-Enabled Metro-Access Networks

Disaggregated radio access network (RAN) ar- chitectures require metro-access transport networks that can satisfy stringent fronthaul (FH) and midhaul (MH) constraints while improving energy efficiency under time-varying traffic. This paper evaluates an Optical Network as-a-Service (ONaaS) enabled converged metro-access optical network for flexible RAN x-haul provisioning using Digital Subcarrier Multiplexing (DSCM) coherent transmission. A 400G DSCM transceiver (TRx) employing DP-16QAM with 16 digital subcarriers is considered, providing fine granularity for optical resource allo- cation. The proposed evaluation framework combines a realistic 24-hour mobile traffic profile with physical-layer-aware routing, wavelength, and spectrum assignment (RWSA), accounting for FH/MH latency, quality-of-transmission (QoT), Distributed Unit (DU) capacity, and residual C-band availability. Two DU operation strategies are compared: a dynamic scheme that activates or hibernates DUs according to hourly traffic demand and reachability constraints and a static baseline where all candidate DUs remain continuously active. Results show that dynamic DU operation reduces the active DU set from five DUs at peak load to three DUs during off-peak periods, achieving 13.2% DU-energy savings and 15.4% higher DU power efficiency at equal delivered load. However, the static scheme carries 40.0% more daily traffic, highlighting the trade- off between energy efficiency and service capacity. Blocking remains close to the 1% target and is dominated by spectrum exhaustion, indicating that residual optical spectrum is the main limiting factor in the considered ONaaS scenario.