Research On Interference Cancellation Technology Of The OFDM Signal Based On Cyclic Prefix

The purpose of every modulation technology’s improvment is to enhance the bandwidth efficiency and the performance of the interference cancellation, To combat the multipath delay spread,a cyclic prefix is added in front of an OFDM signal. This scheme guarantees the transmission reliability, but has an influence to the bandwidth efficiency. Shorten the cyclic prefix might cause new interferences.The main researches of this paper are analyze the bandwidth efficiency under the insufficient CP and the interference cancellation of the OFDM signal based on the CP. The main works of this paper are as follows:1:Analyzed the bandwidth efficiency of the OFDM system and proposed a formula of the bandwidth efficiency of the OFDM system with insufficient CP.The simulation results showed that the bandwidth efficiency is a monotone increasing function of the CP length and a monotone decreasing function in the high and low SNR respectively. Between the high and low SNR, the bandwidth efficiency is optimal while the CP length is among its’minima and maxima.2:Analyzed the interference cancellation based on the CP-OFDM system under the insufficient CP. Anlyzed the rationale of the ZF-DFE and MMSE-DFE interference cancellation technology. The simulation results showed these two interference cancellation schemes will optimize the BER while the SNR is larger than certain values. The complexity research indicates the computation complexity is based on the process of ICI cancellation. 3:To enhance the transmission rate and to enhance the bandwidth efficiency, we proposed a cyclic prefix overlapped OFDM signal. This signal keeps the whole CP, and overlapped with the previous signal. This scheme is able to combat the ICI efficiently,keeps the ISI and brings in the overlap interference. Meanwhile, we proposed the algorithms to cancel the ISI and the overlap interference. The simulation results and the complexity analysis show that this algorithm could cancel the interferences,meanwhile the computation complexity is low compared with theZF-DFE and the MMSE-DFE. We pointed out that the bandwidth efficiency after the interference cancellation has advantage compare with the CP-OFDM after the interference cancellation with similar computation complexity.