Research On Single Carrier Frequency Domain Equalization Technology For OQPSK Modulation

Now people want to watch high definition video in real time,play virtual reality games,which need a high demand for data communication rates.It can get high transmission rates by increasing the transmission bandwidth in communication technology.But now frequency bands below 5GHz have been very crowded,it is difficult to meet the bandwidth requirements,so some technologies such as wireless personal area network(WPAN)technology gradually use the 60 GHz bandwidth which is free and bountiful.It is essential to select the appropriate communication method to increase the efficiency of transmission when the signal is transmitted at the frenquency of 60 GHz.Single carrier frequency domain equalization(SC-FDE)system not only has the ability of anti-inter-symbol interference which likes orthogonal frequency division multiplexing(OFDM)system,but also overcomes the shortcoming of OFDM's high peak-to-average ratio,which can improve the transmission performance of the signal.OQPSK modulation with quasi constant envelope property through nonlinear amplifier will not have a significant expansion of the spectrum,and the sidelobe is very small,its performance is better than QPSK,which is widely used in modern wireless communication.This paper studies the single carrier frequency domain equalization technology for OQPSK modulation.The traditional algorithm uses only one UW sequence for channel estimation,in order to obtain more accurate channel estimation,a new frame structure using two UW sequences is proposed.Considering the characteristics of the new frame structure,this paper improves the traditional sliding window algorithm,and further accurates the channel estimation.And then this paper uses the adaptive decision feedback equalization algorithm and the noise reduction based on decision feedback algorithm to recover the original signal.Finally,this paper proposes a new algorithm using the maximum expectation algorithm(EM)to estimate the expectation and variance of the sequence to be judged,which optimizes the decision rules and improves the performance of the equalization algorithm.Finally,the computer simulations show that the proposed algorithms have some performance gains compared with the traditional algorithm.