The advent of 6th Generation (6G) wireless systems and the increasing demand for spectrum to accommodate a growing number of users and diverse services have necessitated novel ap- proaches to spectrum sharing. Among these approaches, distributed spectrum sharing offers the most flexibility by allowing real-time spectrum use based on user demand and network con- straints. However, this approach presents significant challenges due to the probabilistic nature of system dynamics and the autonomous behavior of each incumbent, which require advanced strategies to predict and manage spectrum usage effectively. Listen-Before-Talk (LBT) is the most widely adopted method for distributed spectrum sharing in unlicensed bands. While LBT has been extensively studied in the context of Wireless Fidelity (Wi-Fi), providing key insights into its performance under various conditions, its application in synchronized, slot-scheduled sys- tems like New Radio (NR) Unlicensed (NR-U) remains underexplored. This gap exists primarily due to the lack of hardware testbeds and system-level simulation platforms that are essential for evaluating the effectiveness of LBT in NR-U and for developing improved methods for operating in shared spectrums with deterministic worst-case delays. This thesis addresses the existing gap by proposing a reference architecture for spectrum sharing based on 5th Generation (5G) NR-U to facilitate further research and experimentation in distributed spectrum sharing. The approach taken in this thesis is threefold: (i) the establishment of a system architecture for an end-to-end 5G NR-U system based on existing work in hardware and simulation models; (ii) the realization of this system model on the Network Simulator 3 (ns-3) discrete-event simulator by leveraging developments from the 5G Long-Term Evolution (LTE) Enhanced Packet Core (EPC) Network Simulator (LENA) (5G-LENA) system architecture; and (iii) the conceptual design for implement- ing the Physical (PHY) layer of a 5G NR-U system using Software-Defined Radios (SDRs) and the OpenAirInterface (OAI) 5G software platform. A key novelty of this reference architecture is the proposed mitigation of LBT latency in split architectures with SDRs and General-Purpose Processors (GPPs). The LBT block is designed for implementation within the Field Program- ming Gate Array (FPGA) of Universal Software Radio Peripheral (USRP) SDRs, thereby enabling heterogeneous coexistence experimentation with Common Off-the-Shelf (COTS) Wi-Fi Access Points (APs). The thesis presents a simulation-based experiment that optimizes traffic manage- ment to improve the ability to serve delay-critical traffic in NR-U systems operating under ho- mogeneous coexistence conditions. The thesis then outlines a reference design for exploring heterogeneous coexistence between Wi-Fi and NR-U in the sub-7 GHz spectrum. This concep- tual framework leverages a proposed hardware experimentation platform with SDRs. The in- frastructure supporting these simulations and proposed hardware experiments is envisioned as virtualized resources over the Commonwealth Cyber Initiative (CCI) xG Testbed, with potential extensions for advanced spectrum sharing use cases across indoor and outdoor testbed sites. The thesis outlines potential enhancements to this testbed, specifically toward spectrum sharing with scheduled-access systems. / Master of Science / As wireless communication demand grows with the development of 6G, finding efficient ways to share the limited available spectrum has become increasingly important. One promising ap- proach is distributed spectrum sharing, which allows dynamic use of the spectrum based on real-time demands. However, this method faces challenges due to the unpredictable behavior of different users and devices, requiring sophisticated strategies to manage spectrum usage effec- tively. Currently, the most common method for distributed spectrum sharing is LBT, widely used in Wi-Fi networks. Although LBT has been well-studied in these environments, its use in systems like NR-U – a variant of 5G designed for unlicensed spectrum—has not been thoroughly explored. This gap exists mainly because there are few hardware testbeds and simulation platforms avail- able to study how LBT and other methods might work in real-world systems. This thesis aims to address this gap by developing a standardized platform for testing and experimenting with 5G NR-U technologies. The work involves three key steps: (i) designing a comprehensive system architecture for 5G NR-U; (ii) implementing this system in a simulation environment to study its performance; and (iii) proposing a design for key components using SDR and open-source soft- ware, creating a foundation for future hardware-based testing. To demonstrate the capabilities of this new platform, we conducted a simulation-based experiment focused on optimizing traffic management in NR-U systems to better handle delay-sensitive communications. Although no hardware experiments were conducted, the thesis provides a conceptual framework for future studies exploring how Wi-Fi and NR-U could coexist in the same frequency bands using the pro- posed hardware platform. The thesis concludes with suggestions for future improvements to the testbed, particularly in advancing spectrum sharing techniques with scheduled-access systems.