The Real-Time Simulation of Doppler Spread in Wireless Mobile Environment by RF Circuits

The time-varying characteristic of wireless channel under the high-speed mobile environments in tunnels causes the Doppler spread to the transmitted signals, which affects the performance of wireless communication systems. The real-time Doppler effect simulation methodology directly based on Radio frequency (RF) circuits is proposed to simulate different Doppler spread effects in real environments. Mixers and a Digital-to-analog (DA) converter circuit are utilized to spread the spectrum of RF signals. A PC platform with the interface written in C# is configured to control the spectrum spread parameters. This radio channel emulator with the proposed methodology can replace the expensive fading simulating instruments with only 25.1ns system delay. Such an emulator has been applied to test the Multi-carrier wireless information local loop (McWiLL) wireless vehicle communication system in the laboratory to meet the requirement of metro Communication based train control (CBTC) system.