Paper Reduction And Total Inter-Carrier Interference Cancelled Multiuser Detection In CFO Corrected CDMA-OFDM With Elliptic Curve Cryptography

摘要

The Code division multiple accesses with Orthogonal Frequency Division Multiple Modulation (CDMA-OFDM) system has been considered as a strong communication system for the next generation wireless communication performs excellent in noisy multipath channel because of low Peak to Average Power Ratio (PAPR) and interference cancellation of the transmitted signal at the receiver. In CDMA-OFDM, Multiuser detection (MUD) is the most important process. In this paper, the MUD process can be achieved by applying Elliptic Curve Cryptography (ECC) with high gain, low computational complexity peak to average power ratio (PAPR) reduction scheme on interference cancelled multipath fading channel in CDMA OFDM system with different modulation schemes is proposed. The proposed CDMA OFDM wireless communication consists of M-QAM that can provide better performance when the system is focused to AWGN and multipath fading channel. During the transmission, the inter-carrier interference occurs due to different carrier frequency offsets (CFO) of different users at the receiver. The CFO error and the Channel Impulse Response (CIR) can be minimized by applying Expectation Maximization (EM) algorithm with the channel condition calculated by Linear Minimum Mean Square Error (LMMSE) equalizer. Also the LMMSE with symbol timing offset (STO) equalizer helps to reduce the BER (Bit Error Rate in) and crease the Signal to Noise Ratio (SNR) in the CDMA OFDM system. The proposed CDMA-OFDM with ECC reduces BER and increases SNR of more than 30dB and using EM and LMMSE algorithm with STO reduces the PAPR up to 8 dB with significant reduction on inter carrier interference and channel impulse response.