Air-interface emulation for wireless broadband communications applied to OFDM

This paper presents a hardware platform that enables the realistic emulation of wide-band air interfaces at low cost. Real-time base-band algorithms for the modulator and demodulator are implemented on separate-and thus independent-DSP evaluation boards. A channel simulation sub-system is suggested, consisting of another DSP board for multipath channel simulation and of analog I/Q-modulators and -demodulators for emulating carrier frequency offsets. The latter allows assessment of frequency synchronization techniques. Reduced speed (bandwidth -40 kHz) tremendously reduces implementation difficulties. The advantages and limitations compared to full-speed hardware and pure computer simulation are elaborated on. The system is used by the authors to assess real-time algorithms for OFDM air-interfaces, but it can be used for other modulation schemes as well. Another possible application is in the education of electrical engineers.