Digital twins are becoming an important tool for designing, developing, testing, and optimizing next-generation wireless communication systems. Over the past decade, system softwarization has become a reality, and wireless communication systems are no exception. Software-Defined Radios (SDRs), in general, and Universal Software Radio Peripherals (USRPs), in particular, are often used for prototyping and testing advanced wireless systems. Unfortunately, there is currently no end-to-end, software-based, general-purpose testing environment for SDR-based systems: developers often rely on benchtop setups or even small testbeds, but those are costly and cumbersome to build. At the other end of the spectrum, simulations often rely on simplified channel/radio models and typically do not execute full-stack production code, which can increase development effort and reduce fidelity. In this paper, we propose ACHEM (A Channel Emulator), the first software-based, end-to-end wireless channel emulation environment and toolset for communication systems based on SDRs, specifically USRPs. With the proposed emulator and toolkit, any USRP-based system can be fully emulated at the I/Q level in a pure digital environment without requiring specialized hardware (e.g., vehicles, USRPs, FPGAs, or GPUs). The proposed emulator supports multiple transmitters and receivers, MIMO communications, multiple frequencies, heterogeneous sampling rates, real-time node mobility through vehicle emulation, antenna radiation patterns, and various channel models. ACHEM facilitates wireless digital twin development and deployment. ACHEM is validated with several popular open-source USRP-based wireless communication applications, including GNU Radio, srsRAN 4G/5G, and OpenAirInterface.

翻译：数字孪生正逐渐成为设计、开发、测试及优化下一代无线通信系统的重要工具。过去十年间，系统软件化已成为现实，无线通信系统亦不例外。软件定义无线电（SDR）及通用软件无线电外设（USRP）常被用于先进无线系统的原型开发与测试。然而，目前尚缺乏基于软件的全端通用测试环境：开发者往往依赖实验台搭建或小型测试平台，这些方式成本高昂且构建繁琐。另一方面，仿真通常依赖简化的信道/无线电模型，且无法执行全栈生产级代码，这既增加了开发工作量，也降低了保真度。本文提出ACHEM（信道仿真器）——首个基于软件、面向SDR（尤其是USRP）通信系统的全端无线信道仿真环境与工具集。借助所提出的仿真器与工具包，任何USRP系统均可在纯数字环境中以I/Q级精度进行全面仿真，无需专用硬件（如车辆、USRP、FPGA或GPU）。该仿真器支持多发射机与接收机、MIMO通信、多频率、异构采样率、通过车辆仿真实现的实时节点移动性、天线辐射模式以及多种信道模型。ACHEM促进了无线数字孪生的开发与部署。我们通过GNU Radio、srsRAN 4G/5G及OpenAirInterface等多个主流开源USRP无线通信应用验证了ACHEM的有效性。