A Real-Time Hardware Emulator for 3D Non-Stationary U2V Channels

Channel emulator is an important tool to evaluate communication system performance at the physical link, and network levels. In this paper, a new discrete 3D non-stationary geometry-based stochastic model (GBSM) for UAV to vehicle (U2V) channels is proposed, which considers 3D scattering space, 3D trajectory, and 3D antenna array. And a tailed channel emulator is developed on a field programmable gate array (FPGA) platform. All channel parameters, i.e., the power, delay, and phase are calculated by FPGA hardware for the first time instead of software or pre-storage method. Meanwhile, a Greedy CORDIC-based exponential calculation method for generating massive complex sinusoids is designed and implemented. The latency is reduced by 50% than traditional CORDIC method. By further utilizing the compact architecture with time division scheme, the hardware resource is significantly reduced from 16.51% to 7.55% for 16-bit data width. Meanwhile, the fixed-point output statistical properties are also derived for quantitatively validation. Finally, the U2V channel under the campus scenario is reproduced by the proposed emulator. The generated results demonstrate that the statistical properties are consistent well with the theoretical and ray tracing ones, which verifies the correctness of both proposed channel model and emulator.