Multistage detection for OFDM signals under phase noise

In orthogonal frequency-division multiplexing (OFDM) transmission system, phase noise from oscillator instabilities in the receiver is a potentially serious problem, especially when bandwidth efficient, high order signal constellations are employed. There are two carrier phase noise effects in the OFDM receiver. One is the common phase error (CPE) which is caused by the own carrier phase noise, another is the inter carrier interference (ICI) which is caused by the phase noise of all other carriers. The orthogonality of the sub-carriers has been broken due to the ICL So the conventional detection implemented by an FFT and a decision is not the good choice. The optimum detection is based on maximum likelihood sequence estimation. But the computational complexity of the optimum detection depends exponentially on the number of sub-carriers. Multistage detection for OFDM signals is proposed in this paper. The computational complexity of the multistage detection is linear in the number of sub-carriers. The performance of the multistage detection is compared with that of the optimum detection. Some simulation results show that the proposed multistage detection improves BER remarkably under the heavy carrier phase noise circumstances