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The future of global connectivity relies on the seamless integration of satellite and terrestrial networks. Recent advancements have enabled terrestrial devices to connect directly to satellites, while high-speed 5G millimeter-wave links offer a promising solution for backhauling ground station data. This paper introduces the concept of joint satellite and terrestrial networks (Jointnets), which necessitates both coexistence and backhaul. In this framework, satellites and ground stations act as relays between terrestrial base stations and devices, removing coverage barriers and providing global connectivity. However, the significant spectrum overlap between 27.5 to 30.0 GHz leads to co-channel interference degrading efficiency or causing complete link failure. Existing approaches only focus on coexistence, resulting in spectrum inefficiency and coverage gaps. We present mmSubArray: Array of Sub-band Phased Arrays, a novel solution utilizing commercial off-the-shelf phased arrays to achieve full-spectrum utilization and enable Jointnets. Through extensive simulations and real-world measurements, we demonstrate the interference challenges and evaluate the efficacy of our approach. Additionally, we have open-sourced our Python simulator and hardware implementation source codes, providing valuable tools for industrial deployment and future research. 

Modern mmWave systems have limited scalability due to inflexibility in performing frequency multiplexing. All the frequency components in the signal are beamformed to one direction via pencil beams and cannot be streamed to other user directions. We present a new flexible mmWave system called mmFlexible, which enables flexible directional frequency multiplexing. In this system, different frequency components of the mmWave signal are beamformed in multiple arbitrary directions with the same pencil beam. Our system makes two key contributions: (1) We propose a novel mmWave front-end architecture, called a delay-phased array, that utilizes a variable delay and variable phase element to create the desired frequency-direction response. (2) We propose a novel algorithm called FSDA (Frequency-space to delay-antenna) to estimate delay and phase values for the real-time operation of the delay-phased array. Through evaluations using mmWave channel traces, we demonstrate that mmFlexible achieves a 60-150% reduction in worst-case latency compared to the baselines.