Scarcity of available spectrum resources imposes limits on wireless system performance, as spectrum has to be shared by multiple users across time, space, and frequency dimensions. Increasing spectrum efficiency at all layers and developing a common framework with significant efficiency gains, will be very useful. IAI proposes to develop Spectrum Efficient Communications and Advanced Networking Technology (SECANT), a novel multiuser communication system that integrates advanced physical (PHY) layer techniques for dynamic multiple access and interference management, and supports spectrum efficiency gains through a clean slate design of medium access control (MAC). SECANT combines dynamic interference management, including interference avoidance/cancellation and interference alignment (IA) with spectrum-aware multiuser detection (MUD) at PHY layer to increase spectrum efficiency in a distributed wireless network. A new adaptive MAC scheme is proposed to enable PHY layer gains by allowing concurrent transmissions in a collision domain and dynamically controlling interference and channel access with local spectrum information. SECANT is supported by reliable spectrum sensing and adapts to spectrum dynamics by optimizing transmission and sensing times. Multi-layer design is realistic in terms of cost-effectiveness and network performance, and allows practical SDR deployment for prototyping and testing under real radio hardware performance. Theoretical analysis, protocol design, software-defined-radio (SDR) implementation with Universal Software Radio Peripherals (USRPs), and experiments based on high-fidelity wireless network emulation will be undertaken on IAI’s SDR test bed platform, CREATE, with full network protocol stack implemented for fast prototyping. Spectrum efficiency gains will be compared with traditional SISO QPSK TDMA schemes under realistic channel conditions and real hardware performance. This design allows wireless nodes to adaptively utilize local information and optimally exploit PHY layer resources to achieve increased spectrum efficiency.