Turbo Receiver for Polar-Coded OFDM systems with unknown CSI

In this paper, a turbo receiver for polar-coded orthogonal frequency division multiplexing(OFDM) systems for frequency-selective fading channels with unknown channel state information(CSI) is proposed. The receiver iteratively exchanges soft information between an expectation-maximization(EM) symbol detector and a soft polar decoder that is based on the belief propagation(BP) algorithm. By utilizing such receiver, the error-correcting performance of the system can be significantly improved even with unknown CSI. Simulation results show that by using the proposed turbo receiver, around 5dB coding gain at a bit-error rate of 5 × 10 −2 can be obtained compared to the receiver that detects symbols and implements decoding separately with unknown CSI.