GPU-Accelerated Real-Time Software Defined Radio-Based Orthogonal Time Frequency Space Network-Coded Cooperation System: Hardware Implementation

While Orthogonal Time Frequency Space (OTFS) modulation offers robust reliability for 6G vehicular networks, standalone links suffer from blockages, and existing Software-Defined Radio (SDR) testbeds are bottlenecked by complex Delay-Doppler (DD) equalizers. This paper presents a real-time Decode-and-Forward Network-Coded Cooperation OTFS (OTFS-NCC) prototype implemented on consumer hosts and USRP B210 SDRs. Operating over a five-node TDD (Time-Division Duplexing) topology, our framework improves spectral efficiency by 33% over conventional relaying while mitigating error propagation via an enhanced Gaussian Approximate Message Passing Algorithm (GA-MPA). To support a 2 MHz baseband rate, we devise a hardware-algorithm decoupled GPU (Graphics Processing Unit) architecture using 1D memory mapping and transcendental function clipping, compressing the simulated Real-Time Factor (RTF) from 4.37 to 0.89. RF-conducted Hardware-in-the-Loop validation under 3GPP EVA70 (Extended Vehicular A model) fading confirms sustained zero-packet-drop real-time demodulation over 60-second test runs across a large 112-by-64 DD grid.