The channel emulator for CBTC wireless communication system

A channel emulator working at 2.4 GHz ISM band related to tunnel environments for testing communication based train control (CBTC) wireless system is introduced. Based on three mechanisms, path loss, multi-path fading and Doppler frequency shift, the multi-port channel matrix is adopted to construct a multi-input and multi-output channel environment. Different from the commercial emulators with delay time of few micro-seconds due to the signals are converted into base-band and treated digitally, in the emulator, whole signal processing is conducted at the radio frequency band by using RF circuits and the time delay decreases two orders of magnitude. The channels can be programmed in terms of time-varying by setting radio propagation model of tunnels in the emulator control unit. As a test bed, several types of wireless communication system have been tested on it for CBTC system performance verifying in China subway construction.