A Real-Time Digital Baseband Channel Emulation System for OFDM Communications

This paper presents the design and implementation of a digital baseband channel emulator. The proposed emulator consists of several wireless channel effects and RF front-end impairments. The channel effects include an additive white Gaussian noise source and a multi-path fading channel with up to 12 faders that can have programmable delays, magnitude, and a Doppler spectrum or a flat spectrum. Other RF electronics effects such as power amplifier non-linearity, carrier frequency offset, oscillator pulling, phase noise, I/Q imbalance, DC offset, and sampling clock offset are also modeled and designed in digital logic. The whole emulator is implemented on FPGA and can run up to 40 MHz, making it suitable for most OFDM wireless systems.