O-RAN enabled Physical Layer hardening for 5G and Beyond

Abstract

This thesis investigates what forms of physical-layer resiliency can be practically demonstrated in standards-based 5G systems using open-source radio access network software, Open Radio Access Network control interfaces, software-defined radios, and experimentally characterized sub-terahertz hardware. The work combines platform analysis, protocol modification, and radio-frequency front-end design to study three complementary problems: the present control authority of open-source O-RAN platforms, protection of 5G control signaling through an underlay channel, and frequency-agile operation of a D-band fixed-intermediate-frequency super heterodyne transceiver. First, the thesis analyzes FlexRIC, O-RAN Software Community, and SD-RAN and muONOS to determine what E2 service-model support and runtime control authority are currently available for physical-layer-aware adaptation. This analysis shows that current open-source platforms provide useful telemetry and limited standardized control, but they do not yet expose a complete, validated path for xApp-driven in-service carrier retuning. Second, the thesis implements and evaluates underlay-assisted obfuscation of Downlink Control Information in a standards-based 5G New Radio air interface using modified srsRAN and USRP X310 hardware. Over-the-air results show that an authorized receiver can maintain operation while an unauthorized commercial receiver is denied usable control-channel decoding. Third, the thesis designs and characterizes a frequency-agile dual-conversion fixed-intermediate-frequency D-band front end and derives a master spurious-product framework for predicting carrier-dependent degradation. Comparative measurements at 1.8 GHz and 118 GHz show closely aligned block error rate and error vector magnitude behavior under controlled line-of-sight conditions, indicating that the 5G New Radio physical layer can remain viable at D-band when the radio-frequency front end is carefully designed. Additional retuning experiments confirm that the carrier can be retuned in real time while the modem remains fixed at the intermediate frequency, that connection can be maintained while sweeping across broad carrier ranges, and that the resulting signal-to-interference-plus-noise ratio structure is repeatable across independent runs, with localized degraded carrier regions tied to deterministic front-end impairments. Taken together, the results show that open-source 5G and O-RAN platforms already enable meaningful physical-layer resiliency experiments, even though standards-based control of real-time RF retuning remains future work. The thesis therefore contributes both validated mechanisms and bounded design studies toward secure, adaptive 5G and beyond-5G systems.