Integrated sensing and communication with optical wireless (ISAC-OW) is a potential 6G enabling technology. Leveraging visible light and infrared spectrums, high-precision sensing and positioning, and high-speed mobile communication can be realized in a single system, enabling advanced solutions for future 6G scenarios, such as smart hospitals and industrial automation. The retro-reflective optical uplink is a promising emerging solution to ISAC-OW that offers several favorable features including hassle-free alignment, minimal interference to adjacent links, microwatt power consumption, low hardware complexity, glaring-free and sniff-proof, and enables simultaneous sensing, positioning and communication with a compact-size tag under a single luminaire. However, the potential of retro-reflective link-based ISAC-OW technology is tempered by basic theoretical and technology development challenges that require a cross-disciplinary approach. The project will investigate fundamental design trade-offs in a retro-reflective uplink enabled ISAC-OW system for large-scale networks. The expected project results advance the state-of-the-art of basic theory and practical design strategies for ISAC-OW system. The project provides cross-disciplinary training opportunities for under-represented students spanning communication theory and signal processing, optical wireless system and circuit design, and wireless networking.<br/><br/>The proposed research develops a new cross-domain framework for integrated design of efficient and scalable retro-reflective uplink enabled ISAC-OW networks. The project is anchored on four key research goals: 1) Modeling the retro-reflective optical link and investigating the hardware design of light reader and retro-reflective tag to convey as much luminous flux as possible from the emitter to the receiver; 2) Investigation of MAC protocols to fully exploit the physical (PHY) layer capabilities and address concurrent transmission challenges; 3) Development of an efficient and flexible spectrum allocation strategy for joint sensing and communication; and 4) Integrated system modeling and assessment for performance-complexity-energy optimization and testbed-based experimental validation of hardware and protocols. The proposed research features investigation of several key operational requirements, including analytical optical models of ISAC-OW, dynamic hardware reconfigurability and scalability, concurrent transmission mechanism and new spectrum allocation methods for ISAC in different use cases. The proposed research acts as a catalyst for cross-disciplinary design and analysis of emerging ISAC-OW system in industry and academia to meet the connected intelligence and application requirements.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.