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Expectation propagation (EP) has been recently proposed as a low-complexity algorithm for symbol detection in massive MIMO systems, where its performance is evaluated on the premise that perfect channel state information (CSI) is available at the receiver. However, in practical systems, exact CSI is not available due to a variety of reasons including channel estimation errors, quantization errors, and aging. In this paper, we study the performance of EP in the presence of imperfect CSI due to channel estimation errors and show that in this case, the EP detector experiences significant performance loss. Moreover, the EP detector shows a higher sensitivity to channel estimation errors in the high signal-to-noise ratio (SNR) regions, where the rate of its performance improvement decreases. We investigate this behavior of the EP detector and propose a modified EP detector for colored noise, which utilizes the …