Effect of Doppler Shift on the MIMO-OFDM Systems in Troposcatter Fading Channels

Abstract

In troposcatter communication systems based on multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM), both channel estimation error and Doppler shift exist inherently. To investigate the Doppler shift effect, an improved time-varying multipath channel model is built. Zero-forcing (ZF) detection and approximation method of Wishart distribution are adopted to calculate the signal to interference plus noise ratio (SINR) of the system and its probability distribution. Then, SINR is used to analyze the average error rate in the presence of both channel estimation error and Doppler shift. The simulated results show that, in troposcatter fading channels, Doppler shift has little influence on the performance of the bite error rate (BER) in the presence of relatively small estimation error. However, with larger estimation error, a slight Doppler shift influences the system performance significantly, and a large Doppler shift has little effect on the system. Moreover, the BER performance is also investigated when low density parity check (LDPC) channel codes are used.