A Novel Emulator for Discrete-Time MIMO Triply Selective Fading Channels

Hardware implementation of discrete-time triply selective Rayleigh fading channel emulators is proposed for multiple-input-multiple-output (MIMO) communications. The proposed work differs from existing ones in that it incorporates temporal correlation, intertap correlation, and spatial correlation matrices into multiple uncorrelated frequency-flat fading waveforms to obtain a triply selective fading channel. The flat fading waveforms with temporal correlation or Doppler spectrum are generated using a sum-of-sinusoid method. The intertap correlation matrix associated with multipath delay spread is computed according to the channel power delay profile and transmit/receive filters. The spatial correlation matrices are predefined inputs associated with transmit and receive antenna arrangements. The square roots of the three correlation matrices are computed via singular-value decomposition and then combined in real time with the flat fading waveforms. Several fading channel examples are implemented on an Altera Stratix III EP3SL150F field-programmable gate array (FPGA) DSP development kit with fixed-point arithmetics. A 4-by-4 MIMO triply selective channel with ten correlated delay taps per subchannel utilizes one-third of the hardware resource of the FPGA chip. The statistical properties of the emulated fading waveforms match those of the software-based simulators and the theoretical ones. The proposed method achieves good balance between computational complexity and resource utilization.